Polymers

2021

Jump to: 2020, 2019, 2018, 2017

12 pages, 8509 KiB

Open AccessArticle

Use of Ionic Liquid Pretreated and Fermented Sugarcane Bagasse as an Adsorbent for Congo Red Removal

by Uroosa Ejaz, Agha Arslan Wasim, Muhammad Nasiruddin Khan, Othman M. Alzahrani, Samy F. Mahmoud, Zeinhom M. El-Bahy and Muhammad Sohail

Polymers 2021, 13(22), 3943; https://doi.org/10.3390/polym13223943 - 15 Nov 2021

Cited by 13 | Viewed by 2775

Abstract

A large amount of industrial wastewater containing pollutants including toxic dyes needs to be processed prior to its discharge into the environment. Biological materials such as sugarcane bagasse (SB) have been reported for their role as adsorbents to remove the dyes from water. [...] Read more.

A large amount of industrial wastewater containing pollutants including toxic dyes needs to be processed prior to its discharge into the environment. Biological materials such as sugarcane bagasse (SB) have been reported for their role as adsorbents to remove the dyes from water. In this study, the residue SB after fermentation was utilized for the dye removal. A combined pretreatment of NaOH and methyltrioctylammonium chloride was given to SB for lignin removal, and the pretreated SB was utilized for cellulase production from Bacillus aestuarii UE25. The strain produced 118 IU mL⁻¹ of endoglucanse and 70 IU mL⁻¹ of β-glucosidase. Scanning electron microscopy and FTIR spectra showed lignin and cellulose removal in fermented SB. This residue was utilized for the adsorption of an azo dye, congo red (CR). The thermodynamic, isotherm and kinetics studies for the adsorption of CR revealed distinct adsorption features of SB. Untreated SB followed Langmuir isotherm, whereas pretreated SB and fermented SB obeyed the Freundlich isotherm model. The pseudo-second-order model fitted well for the studied adsorbents. The results of thermodynamic studies revealed spontaneous adsorption with negative standard free energy values. Untreated SB showed a 90.36% removal tendency at 303.15 K temperature, whereas the adsorbents comprised of pretreated and fermented SB removed about 98.35% and 97.70%, respectively. The study provided a strategy to utilize SB for cellulase production and its use as an adsorbent for toxic dyes removal. Full article

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24 pages, 2632 KiB

Open AccessReview

Review on Spinning of Biopolymer Fibers from Starch

by Selamu Temesgen, Mirko Rennert, Tamrat Tesfaye and Michael Nase

Polymers 2021, 13(7), 1121; https://doi.org/10.3390/polym13071121 - 1 Apr 2021

Cited by 39 | Viewed by 6902

Abstract

Increasing interest in bio-based polymers and fibers has led to the development of several alternatives to conventional plastics and fibers made of these materials. Biopolymer fibers can be made from renewable, environmentally friendly resources and can be fully biodegradable. Biogenic resources with a [...] Read more.

Increasing interest in bio-based polymers and fibers has led to the development of several alternatives to conventional plastics and fibers made of these materials. Biopolymer fibers can be made from renewable, environmentally friendly resources and can be fully biodegradable. Biogenic resources with a high content of carbohydrates such as starch-containing plants have huge potentials to substitute conventional synthetic plastics in a number of applications. Much literature is available on the production and modification of starch-based fibers and blends of starch with other polymers. Chemistry and structure–property relationships of starch show that it can be used as an attractive source of raw material which can be exploited for conversion into a number of high-value bio-based products. In this review, possible spinning techniques for the development of virgin starch or starch/polymer blend fibers and their products are discussed. Beneficiation of starch for the development of bio-based fibers can result in the sustainable replacement of oil-based high-value materials with cost-effective, environmentally friendly, and abundant products. Full article

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18 pages, 3038 KiB

Open AccessArticle

Extraction and Characterization of Potential Biodegradable Materials Based on Dioscorea hispida Tubers

by K. Z. Hazrati, S. M. Sapuan, M. Y. M. Zuhri and R. Jumaidin

Polymers 2021, 13(4), 584; https://doi.org/10.3390/polym13040584 - 15 Feb 2021

Cited by 35 | Viewed by 5226

Abstract

This study was driven by the stringent environmental legislation concerning the consumption and utilization of eco-friendly materials. Within this context, this paper aimed to examine the characteristics of starch and fibres from the Dioscorea hispida tuber plant to explore their potential as renewable [...] Read more.

This study was driven by the stringent environmental legislation concerning the consumption and utilization of eco-friendly materials. Within this context, this paper aimed to examine the characteristics of starch and fibres from the Dioscorea hispida tuber plant to explore their potential as renewable materials. The extraction of the Dioscorea hispida starch and Dioscorea hispida fibres was carried out and the chemical composition, physical, thermal, morphological properties, and crystallinity were studied. The chemical composition investigations revealed that the Dioscorea hispida starch (DHS) has a low moisture t (9.45%) and starch content (37.62%) compared to cassava, corn, sugar palm, and arrowroot starches. Meanwhile, the Dioscorea hispida fibres (DHF) are significantly low in hemicellulose (4.36%), cellulose (5.63%), and lignin (2.79%) compared to cassava, corn hull and sugar palm. In this investigation the chemical, physical, morphological and thermal properties of the Dioscorea hispida fibre and Dioscorea hispida starch were examined by chemical composition investigation, scanning electron microscopy (SEM), particle size distribution, thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), and Fourier transform infrared (FTIR), respectively. It was found that Dioscorea hispida waste is promising alternative biomass and sustainable material with excellent potential as a renewable filler material for food packaging applications. Full article

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14 pages, 2214 KiB

Open AccessArticle

Hybrid Collagen Hydrogel/Chondroitin-4-Sulphate Fortified with Dermal Fibroblast Conditioned Medium for Skin Therapeutic Application

by Manira Maarof, Masrina Mohd Nadzir, Lau Sin Mun, Mh Busra Fauzi, Shiplu Roy Chowdhury, Ruszymah Bt Hj Idrus and Yogeswaran Lokanathan

Polymers 2021, 13(4), 508; https://doi.org/10.3390/polym13040508 - 8 Feb 2021

Cited by 10 | Viewed by 2784

Abstract

The current strategy for rapid wound healing treatment involves combining a biomaterial and cell-secreted proteins or biomolecules. This study was aimed at characterizing 3-dimensional (3D) collagen hydrogels fortified with dermal fibroblast-conditioned medium (DFCM) as a readily available acellular skin substitute. Confluent fibroblasts were [...] Read more.

The current strategy for rapid wound healing treatment involves combining a biomaterial and cell-secreted proteins or biomolecules. This study was aimed at characterizing 3-dimensional (3D) collagen hydrogels fortified with dermal fibroblast-conditioned medium (DFCM) as a readily available acellular skin substitute. Confluent fibroblasts were cultured with serum-free keratinocyte-specific medium (KM1 and KM2) and fibroblast-specific medium (FM) to obtain DFCM. Subsequently, the DFCM was mixed with collagen (Col) hydrogel and chondroitin-4-sulphate (C4S) to fabricate 3D constructs termed Col/C4S/DFCM-KM1, Col/C4S/DFCM-KM2, and Col/C4S/DFCM-FM. The constructs successfully formed soft, semi-solid and translucent hydrogels within 1 h of incubation at 37 °C with strength of <2.5 Newton (N). The Col/C4S/DFCM demonstrated significantly lower turbidity compared to the control groups. The Col/C4S/DFCM also showed a lower percentage of porosity (KM1: 35.15 ± 9.76%; KM2: 6.85 ± 1.60%; FM: 14.14 ± 7.65%) compared to the Col (105.14 ± 11.87%) and Col/C4S (143.44 ± 27.72%) constructs. There were no changes in both swelling and degradation among all constructs. Fourier transform infrared spectrometry showed that all groups consisted of oxygen–hydrogen bonds (O-H) and amide I, II, and III. In conclusion, the Col/C4S/DFCM constructs maintain the characteristics of native collagen and can synergistically deliver essential biomolecules for future use in skin therapeutic applications. Full article

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2020

Jump to: 2021, 2019, 2018, 2017

18 pages, 5091 KiB

Open AccessArticle

Synthesis and Characterization of Partially Renewable Oleic Acid-Based Ionomers for Proton Exchange Membranes

by Carlos Corona-García, Alejandro Onchi, Arlette A. Santiago, Araceli Martínez, Daniella Esperanza Pacheco-Catalán, Ismeli Alfonso and Joel Vargas

Polymers 2021, 13(1), 130; https://doi.org/10.3390/polym13010130 - 30 Dec 2020

Cited by 3 | Viewed by 2795

Abstract

The future availability of synthetic polymers is compromised due to the continuous depletion of fossil reserves; thus, the quest for sustainable and eco-friendly specialty polymers is of the utmost importance to ensure our lifestyle. In this regard, this study reports on the use [...] Read more.

The future availability of synthetic polymers is compromised due to the continuous depletion of fossil reserves; thus, the quest for sustainable and eco-friendly specialty polymers is of the utmost importance to ensure our lifestyle. In this regard, this study reports on the use of oleic acid as a renewable source to develop new ionomers intended for proton exchange membranes. Firstly, the cross-metathesis of oleic acid was conducted to yield a renewable and unsaturated long-chain aliphatic dicarboxylic acid, which was further subjected to polycondensation reactions with two aromatic diamines, 4,4′-(hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline and 4,4′-diamino-2,2′-stilbenedisulfonic acid, as comonomers for the synthesis of a series of partially renewable aromatic-aliphatic polyamides with an increasing degree of sulfonation (DS). The polymer chemical structures were confirmed by Fourier transform infrared (FTIR) and nuclear magnetic resonance (¹H, ¹³C, and ¹⁹F NMR) spectroscopy, which revealed that the DS was effectively tailored by adjusting the feed molar ratio of the diamines. Next, we performed a study involving the ion exchange capacity, the water uptake, and the proton conductivity in membranes prepared from these partially renewable long-chain polyamides, along with a thorough characterization of the thermomechanical and physical properties. The highest value of the proton conductivity determined by electrochemical impedance spectroscopy (EIS) was found to be 1.55 mS cm⁻¹ at 30 °C after activation of the polymer membrane. Full article

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20 pages, 7088 KiB

Open AccessArticle

Study of the Influence of the Almond Shell Variety on the Mechanical Properties of Starch-Based Polymer Biocomposites

by Ana Ibáñez García, Asunción Martínez García and Santiago Ferrándiz Bou

Polymers 2020, 12(9), 2049; https://doi.org/10.3390/polym12092049 - 8 Sep 2020

Cited by 23 | Viewed by 4432

Abstract

This article is focused on the development of a series of biodegradable and eco-friendly biocomposites based on starch polymer (Mater-Bi DI01A) filled with 30 wt% almond shell (AS) of different varieties (Desmayo Rojo, Largueta, Marcona, Mollar, and a commercial mixture of varieties) to [...] Read more.

This article is focused on the development of a series of biodegradable and eco-friendly biocomposites based on starch polymer (Mater-Bi DI01A) filled with 30 wt% almond shell (AS) of different varieties (Desmayo Rojo, Largueta, Marcona, Mollar, and a commercial mixture of varieties) to study the influence of almond variety in the properties of injected biodegradable parts. The different AS varieties are analysed by means of Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD). The biocomposites are prepared in a twin-screw extruder and characterized in terms of their mechanical (tensile, flexural, Charpy impact, and hardness tests) and thermal properties (differential scanning calorimetry (DSC) and TGA). Despite observing differences in the chemical composition of the individual varieties with respect to the commercial mixture, the results obtained from the mechanical characterisation of the biocomposites do not present significant differences between the diverse varieties used. From these results, it was concluded that the most recommended option is to work with the commercial mixture of almond shell varieties, as it is easier and cheaper to acquire. Full article

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14 pages, 2915 KiB

Open AccessEditor’s ChoiceArticle

Light Processable Starch Hydrogels

by Camilla Noè, Chiara Tonda-Turo, Annalisa Chiappone, Marco Sangermano and Minna Hakkarainen

Polymers 2020, 12(6), 1359; https://doi.org/10.3390/polym12061359 - 17 Jun 2020

Cited by 54 | Viewed by 8472

Abstract

Light processable hydrogels were successfully fabricated by utilizing maize starch as raw material. To render light processability, starch was gelatinized and methacrylated by simple reaction with methacrylic anhydride. The methacrylated starch was then evaluated for its photocuring reactivity and 3D printability by digital [...] Read more.

Light processable hydrogels were successfully fabricated by utilizing maize starch as raw material. To render light processability, starch was gelatinized and methacrylated by simple reaction with methacrylic anhydride. The methacrylated starch was then evaluated for its photocuring reactivity and 3D printability by digital light processing (DLP). Hydrogels with good mechanical properties and biocompatibility were obtained by direct curing from aqueous solution containing lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) as photo-initiator. The properties of the hydrogels were tunable by simply changing the concentration of starch in water. Photo-rheology showed that the formulations with 10 or 15 wt% starch started curing immediately and reached G’ plateau after only 60 s, while it took 90 s for the 5 wt% formulation. The properties of the photocured hydrogels were further characterized by rheology, compressive tests, and swelling experiments. Increasing the starch content from 10 to 15 wt% increased the compressive stiffness from 13 to 20 kPa. This covers the stiffness of different body tissues giving promise for the use of the hydrogels in tissue engineering applications. Good cell viability with human fibroblast cells was confirmed for all three starch hydrogel formulations indicating no negative effects from the methacrylation or photo-crosslinking reaction. Finally, the light processability of methacrylated starch by digital light processing (DLP) 3D printing directly from aqueous solution was successfully demonstrated. Altogether the results are promising for future application of the hydrogels in tissue engineering and as cell carriers Full article

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21 pages, 3830 KiB

Open AccessArticle

Chitosan Grafted with Biobased 5-Hydroxymethyl-Furfural as Adsorbent for Copper and Cadmium Ions Removal

by Mariza Mone, Dimitra A. Lambropoulou, Dimitrios N. Bikiaris and George Kyzas

Polymers 2020, 12(5), 1173; https://doi.org/10.3390/polym12051173 - 20 May 2020

Cited by 27 | Viewed by 3699

Abstract

This work investigates the application of 5-hydroxymethyl-furfural (HMF) as a grafting agent to chitosan (CS). The material produced was further modified by cross-linking. Three different derivatives were tested with molecular ratios CS/HMF of 1:1 (CS-HMF1), 2:1 (CS-HMF2) and 10:1 mol/mol (CS-HMF3)) to remove [...] Read more.

This work investigates the application of 5-hydroxymethyl-furfural (HMF) as a grafting agent to chitosan (CS). The material produced was further modified by cross-linking. Three different derivatives were tested with molecular ratios CS/HMF of 1:1 (CS-HMF1), 2:1 (CS-HMF2) and 10:1 mol/mol (CS-HMF3)) to remove Cu²⁺ and Cd²⁺ from aqueous solutions. CS-HMF derivatives were characterized both before, and after, metal ions adsorption by using scanning electron microscopy (SEM), as well as Fourier-transform infrared (FTIR) spectroscopy thermogravimetric analysis (TGA), and X-Ray diffraction analysis (XRD). The CS-HMF derivatives were tested at pH = 5 and showed higher adsorption capacity with the increase of temperature. Also, the equilibrium data were fitted to Langmuir (best fitting) and Freundlich model, while the kinetic data to pseudo-first (best fitting) and pseudo-second order equations. The Langmuir model fitted better (higher R²) the equilibrium data than the Freundlich equation. By increasing the HMF grafting from 130% (CS-HMF1) to 310% (CS-HMF3), an increase of 24% (26 m/g) was observed for Cu²⁺ adsorption and 19% (20 mg/g) for Cd²⁺. By increasing from T = 25 to 65 °C, an increase of the adsorption capacity (metal uptake) was observed. Ten reuse cycles were successfully carried out without significant loss of adsorption ability. The reuse potential was higher of Cd²⁺, but more stable desorption reuse ability during all cycles for Cu²⁺. Full article

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13 pages, 1848 KiB

Open AccessArticle

One-Step Synthesis of Novel Renewable Vegetable Oil-Based Acrylate Prepolymers and Their Application in UV-Curable Coatings

by Yupei Su, Hai Lin, Shuting Zhang, Zhuohong Yang and Teng Yuan

Polymers 2020, 12(5), 1165; https://doi.org/10.3390/polym12051165 - 19 May 2020

Cited by 50 | Viewed by 5959

Abstract

With the rapid development of social economy, problems such as volatile organic compound (VOC) pollution and the excessive consumption of global petroleum resources have become increasingly prominent. People are beginning to realize that these problems not only affect the ecological environment, but also [...] Read more.

With the rapid development of social economy, problems such as volatile organic compound (VOC) pollution and the excessive consumption of global petroleum resources have become increasingly prominent. People are beginning to realize that these problems not only affect the ecological environment, but also hinder the development of the organic polymer material industry based on raw fossil materials. Therefore, the modification and application of bio-based materials are of theoretical and practical significance. In this study, a series of vegetable oil-based acrylate prepolymers were synthesized by one-step acrylation using palm oil, olive oil, peanut oil, rapeseed oil, corn oil, canola oil, and grapeseed oil as raw materials, and the effect of different double bond contents on the product structure and grafting rate was investigated. Furthermore, the as-prepared vegetable oil-based acrylate prepolymers, polyurethane acrylate (PUA-2665), trimethylolpropane triacrylate (TMPTA), and photoinitiator (PI-1173) were mixed thoroughly to prepare ultraviolet (UV)-curable films. The effect of different grafting numbers on the properties of these films was investigated. The results showed that as the degree of unsaturation increased, the acrylate grafting number and the cross-linking density increased, although the acrylation (grafting reaction) rate decreased. The reason was mainly because increasing the double bond content could accelerate the reaction rate, while the grafted acrylic groups had a steric hindrance effect to prevent the adjacent double bonds from participating in the reaction. Furthermore, the increase in grafting number brought about the increase in the structural functionality of prepolymers and the cross-linking density of cured films, which led to the enhancement in the thermal (glass transition temperature) and mechanical (tensile strength, Young’s modulus) properties of the cured films. Full article

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14 pages, 3897 KiB

Open AccessArticle

Hydrophobic Modification of Cashew Gum with Alkenyl Succinic Anhydride

by Atanu Biswas, H. N. Cheng, Sanghoon Kim, Carlucio R. Alves and Roselayne F. Furtado

Polymers 2020, 12(3), 514; https://doi.org/10.3390/polym12030514 - 27 Feb 2020

Cited by 22 | Viewed by 5246

Abstract

Cashew gum (CG) shows promise of being useful as an agro-based raw material for the production of eco-friendly and biodegradable polymers. In this work, we modified this water-soluble polymer with alkenyl succinic anhydride in order to attach a hydrophobic group to it. The [...] Read more.

Cashew gum (CG) shows promise of being useful as an agro-based raw material for the production of eco-friendly and biodegradable polymers. In this work, we modified this water-soluble polymer with alkenyl succinic anhydride in order to attach a hydrophobic group to it. The modification used two reagents: octenyl succinic anhydride and tetrapropenyl succinic anhydride. Reactions were conducted at 120 °C using dimethyl sulfoxide as a solvent, with conversions better than 88%. Samples with degrees of substitution (DS) between 0.02 and 0.20 were made. The resulting polymers were characterized using ¹H NMR, ¹³C NMR, FTIR, TGA, and GPC. The addition of the hydrophobe decreased the affinity of cashew gum for water absorption. Hydrophobically modified polysaccharides are often used as polymeric emulsifiers, thickeners, and compatibilizers; we anticipate that these new hydrophobically modified CGs may be used for the same applications. Full article

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2019

Jump to: 2021, 2020, 2018, 2017

16 pages, 3248 KiB

Open AccessArticle

Impact of Crystalline Structural Differences Between α- and β-Chitosan on Their Nanoparticle Formation Via Ionic Gelation and Superoxide Radical Scavenging Activities

by Yattra Jampafuang, Anan Tongta and Yaowapha Waiprib

Polymers 2019, 11(12), 2010; https://doi.org/10.3390/polym11122010 - 4 Dec 2019

Cited by 66 | Viewed by 4863

Abstract

α- and β-Chitosan nanoparticles were obtained from shrimp shell and squid pen chitosan with different set of deacetylation degree (%DD) and molecular weight (MW) combinations. After nanoparticle formation via ionic gelation with sodium tripolyphosphate (TPP), the % crystallinity index (%CI) of the α- [...] Read more.

α- and β-Chitosan nanoparticles were obtained from shrimp shell and squid pen chitosan with different set of deacetylation degree (%DD) and molecular weight (MW) combinations. After nanoparticle formation via ionic gelation with sodium tripolyphosphate (TPP), the % crystallinity index (%CI) of the α- and β-chitosan nanoparticles were reduced to approximately 33% and 43% of the initial %CI of the corresponding α- and β-chitosan raw samples, respectively. Both forms of chitosan and chitosan nanoparticles scavenged superoxide radicals in a dose-dependent manner. The %CI of α- and β-chitosan and chitosan nanoparticles was significantly negatively correlated with superoxide radical scavenging abilities over the range of concentration (0.5, 1, 2 and 3 mg/mL) studied. High %DD, and low MW β-chitosan exhibited the highest superoxide radical scavenging activity (p < 0.05). α- and β-Chitosan nanoparticles prepared from high %DD and low MW chitosan demonstrated the highest abilities to scavenge superoxide radicals at 2.0–3.0 mg/mL (p < 0.05), whereas α-chitosan nanoparticles, with the lowest %CI, and smallest particle size (p < 0.05), prepared from medium %DD, and medium MW chitosan showed the highest abilities to scavenge superoxide radicals at 0.5–1.0 mg/mL (p < 0.05). It could be concluded that α- and β-chitosan nanoparticles had superior superoxide radical scavenging abilities than raw chitosan samples. Full article

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16 pages, 3786 KiB

Open AccessArticle

Preparation and Characterization of Superabsorbent Polymers Based on Sawdust

by Mingchang Zhang, Shaodi Zhang, Zhuoran Chen, Mingzhi Wang, Jinzhen Cao and Ruoshui Wang

Polymers 2019, 11(11), 1891; https://doi.org/10.3390/polym11111891 - 15 Nov 2019

Cited by 43 | Viewed by 6267

Abstract

Sawdust, a cheap by-product of the timber and forestry industry, was considered as a framework structure to prepare superabsorbent polymer with acrylic acid (AA) and acrylamide (AM), the synthetic monomers. The effects of initiator content, crosslinker content, AA content, AM content, degree of [...] Read more.

Sawdust, a cheap by-product of the timber and forestry industry, was considered as a framework structure to prepare superabsorbent polymer with acrylic acid (AA) and acrylamide (AM), the synthetic monomers. The effects of initiator content, crosslinker content, AA content, AM content, degree of neutralization of AA, and reaction temperature on the swelling rate of superabsorbent polymer were investigated. The synthesized polymer was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Under optimal synthesis conditions, the results showed that the swelling rate of the polymer in deionized water and 0.9% NaCl solution reached 738.12 and 90.18 g/g, respectively. The polymer exhibits excellent swelling ability, thermal stability, and reusability. After the polymer was introduced into the samples (soil or coal), the water evaporation rate of the samples was significantly reduced, and the saturated water holding capacity and pore structure were also significantly improved. Full article

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16 pages, 4527 KiB

Open AccessArticle

Demethylation of Alkali Lignin with Halogen Acids and Its Application to Phenolic Resins

by Hao Wang, Thomas L. Eberhardt, Chunpeng Wang, Shishuai Gao and Hui Pan

Polymers 2019, 11(11), 1771; https://doi.org/10.3390/polym11111771 - 28 Oct 2019

Cited by 65 | Viewed by 6008

Abstract

Lignin, a byproduct from the chemical processing of lignocellulosic biomass, is a polyphenolic compound that has potential as a partial phenol substitute in phenolic adhesive formulations. In this study, HBr and HI were used as reagents to demethylate an alkali lignin (AL) to [...] Read more.

Lignin, a byproduct from the chemical processing of lignocellulosic biomass, is a polyphenolic compound that has potential as a partial phenol substitute in phenolic adhesive formulations. In this study, HBr and HI were used as reagents to demethylate an alkali lignin (AL) to increase its hydroxyl content and thereby enhance its reactivity for the preparation of phenolic resins. Analyses by FT-IR, ¹H-NMR and 2D-NMR(HSQC) demonstrated both a decrease in methoxyl groups and an increase in hydroxyl groups for each demethylated lignin (DL). In addition, the molar amounts of phenolic hydroxyls, determined by ¹H-NMR, increased to 0.67 mmol/g for the HI-DL, and 0.64 mmol/g for the HBr-DL, from 0.52 mmol/g for the AL. These results showed that HI, a stronger nucleophilic reagent than HBr, provided a higher degree of AL demethylation. Lignin-containing resins, prepared by copolymerization, met the bonding strength standard for exterior plywood with DL used to replace as much as 50 wt.% of phenol. The increased hydroxyl contents resulting from the lignin demethylations also imparted faster cure times for the lignin-containing resins and lower formaldehyde emissions. Altogether, the stronger nucleophilicity of HI, compared to HBr, impacted the degree of lignin demethylation, and carried through to measurable differences the thermal properties and performance of the lignin-containing PF resins. Full article

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14 pages, 2622 KiB

Open AccessArticle

Improving the Hydrolysis Rate of the Renewable Poly(hexamethylene sebacate) Through Copolymerization of a Bis(pyrrolidone)-Based Dicarboxylic Acid

by Geert. J. Noordzij, Manta Roy, Natasja Bos, Vincent Reinartz and Carolus H.R.M. Wilsens

Polymers 2019, 11(10), 1654; https://doi.org/10.3390/polym11101654 - 11 Oct 2019

Cited by 5 | Viewed by 4661

Abstract

In this work, we report on the synthesis of a series of polyesters based on 1,6-hexanediol, sebacic acid, and N,N’-dimethylene-bis(pyrrolidone-4-carboxylic acid) (BP-C₂), of which the latter is derived from renewable itaconic acid and 1,2-ethanediamine. Copolymers with a varying [...] Read more.

In this work, we report on the synthesis of a series of polyesters based on 1,6-hexanediol, sebacic acid, and N,N’-dimethylene-bis(pyrrolidone-4-carboxylic acid) (BP-C₂), of which the latter is derived from renewable itaconic acid and 1,2-ethanediamine. Copolymers with a varying amount of BP-C₂ as dicarboxylic acid are synthesized using a melt-polycondensation reaction with the aim of controlling the hydrolysis rate of the polymers in water or under bioactive conditions. We demonstrate that the introduction of BP-C₂ in the polymer backbone does not limit the molecular weight build-up, as polymers with a weight average molecular weight close to 20 kg/mol and higher are obtained. Additionally, as the BP-C₂ moiety is excluded from the crystal structure of poly(hexamethylene sebacate), the increase in BP-C₂ concentration effectively results in a suppression in both melting temperature and crystallinity of the polymers. Overall, we demonstrate that the BP-C₂ moiety enhances the polymer’s affinity to water, effectively improving the water uptake and rate of hydrolysis, both in demineralized water and in the presence of a protease from Bacillus licheniformis. Full article

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14 pages, 3057 KiB

Open AccessArticle

Phase Diagrams of n-Type Low Bandgap Naphthalenediimide-Bithiophene Copolymer Solutions and Blends

by Gada Muleta Fanta, Pawel Jarka, Urszula Szeluga, Tomasz Tański and Jung Yong Kim

Polymers 2019, 11(9), 1474; https://doi.org/10.3390/polym11091474 - 9 Sep 2019

Cited by 6 | Viewed by 3963

Abstract

Phase diagrams of n-type low bandgap poly{(N,N′-bis(2-octyldodecyl)naphthalene -1,4,5,8-bis(dicarboximide)-2,6-diyl)-alt-5,5′,-(2,2′-bithiophene)} (P(NDI2OD-T2)) solutions and blends were constructed. To this end, we employed the Flory–Huggins (FH) lattice theory for qualitatively understanding the phase behavior of P(NDI2OD-T2) solutions as a function of solvent, chlorobenzene, [...] Read more.

Phase diagrams of n-type low bandgap poly{(N,N′-bis(2-octyldodecyl)naphthalene -1,4,5,8-bis(dicarboximide)-2,6-diyl)-alt-5,5′,-(2,2′-bithiophene)} (P(NDI2OD-T2)) solutions and blends were constructed. To this end, we employed the Flory–Huggins (FH) lattice theory for qualitatively understanding the phase behavior of P(NDI2OD-T2) solutions as a function of solvent, chlorobenzene, chloroform, and p-xylene. Herein, the polymer–solvent interaction parameter (χ) was obtained from a water contact angle measurement, leading to the solubility parameter. The phase behavior of these P(NDI2OD-T2) solutions showed both liquid–liquid (L–L) and liquid–solid (L–S) phase transitions. However, depending on the solvent, the relative position of the liquid–liquid phase equilibria (LLE) and solid–liquid phase equilibria (SLE) (i.e., two-phase co-existence curves) could be changed drastically, i.e., LLE > SLE, LLE ≈ SLE, and SLE > LLE. Finally, we studied the phase behavior of the polymer–polymer mixture composed of P(NDI2OD-T2) and regioregular poly(3-hexylthiophene-2,5-dyil) (r-reg P3HT), in which the melting transition curve was compared with the theory of melting point depression combined with the FH model. The FH theory describes excellently the melting temperature of the r-reg P3HT/P(NDI2OD-T2) mixture when the entropic contribution to the polymer–polymer interaction parameter (χ = 116.8 K/T − 0.185, dimensionless) was properly accounted for, indicating an increase of entropy by forming a new contact between two different polymer segments. Understanding the phase behavior of the polymer solutions and blends affecting morphologies plays an integral role towards developing polymer optoelectronic devices. Full article

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11 pages, 4025 KiB

Open AccessArticle

Synthesis of Highly Thermally Stable Daidzein-Based Main-Chain-Type Benzoxazine Resins

by Mengchao Han, Sijia You, Yuting Wang, Kan Zhang and Shengfu Yang

Polymers 2019, 11(8), 1341; https://doi.org/10.3390/polym11081341 - 13 Aug 2019

Cited by 22 | Viewed by 4015

Abstract

In recent years, main-chain-type benzoxazine resins have been extensively investigated due to their excellent comprehensive properties for many potential applications. In this work, two new types of main-chain benzoxazine polymers were synthesized from daidzein, aromatic/aliphatic diamine, and paraformaldehyde. Unlike the approaches used synthesizing [...] Read more.

In recent years, main-chain-type benzoxazine resins have been extensively investigated due to their excellent comprehensive properties for many potential applications. In this work, two new types of main-chain benzoxazine polymers were synthesized from daidzein, aromatic/aliphatic diamine, and paraformaldehyde. Unlike the approaches used synthesizing traditional main-chain-type benzoxazine polymers, the precursors derived from daidzein can undergo a further cross-linking polymerization in addition to the ring-opening polymerization of the oxazine ring. The structures of the new polymers were then studied by ¹H nuclear magnetic resonance spectroscopy (NMR) and Fourier-transform infrared spectroscopy (FT-IR), and the molecular weights were determined by using gel permeation chromatography (GPC). We also monitored the polymerization process by differential scanning calorimetry (DSC) and in situ FT-IR. In addition, the thermal stability and flame-retardant properties of the resulting polybenzoxazines were investigated using TGA and microscale combustion calorimeter (MCC). The polybenzoxazines obtained in this study exhibited a very high thermal stability and low flammability, with a T_g value greater than 400 °C, and a heat release capacity (HRC) value lower than 30 J/(g K). Full article

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21 pages, 5296 KiB

Open AccessArticle

Cellulose Fibers Hydrophobization via a Hybrid Chemical Modification

by Stefan Cichosz and Anna Masek

Polymers 2019, 11(7), 1174; https://doi.org/10.3390/polym11071174 - 11 Jul 2019

Cited by 69 | Viewed by 8011

Abstract

The following article highlights the importance of an indispensable process in cellulose fibers (UFC100) modification which may change the biopolymer properties—drying. The reader is provided with a broad range of information considering the drying process consequences on the chemical treatment of the cellulose. [...] Read more.

The following article highlights the importance of an indispensable process in cellulose fibers (UFC100) modification which may change the biopolymer properties—drying. The reader is provided with a broad range of information considering the drying process consequences on the chemical treatment of the cellulose. This research underlines the importance of UFC100 moisture content reduction considering polymer composites application with the employment of a technique different than thermal treating. Therefore, a new hybrid chemical modification approach is introduced. It consists of two steps: solvent exchange (with ethanol either hexane) and chemical treatment (maleic anhydride—MA). With the use of Fourier-transform infrared spectroscopy (FT-IR), it has been proven that the employment of different solvents may contribute to the higher yield of the modification process as they cause rearrangements in hydrogen bonds structure, swell the biopolymer and, therefore, affect its molecular packing. Furthermore, according to the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), the improvement in fibers thermal resistance was noticed, e.g., shift in the value of 5% temperature mass loss from 240 °C (regular modification) to 306 °C (while solvent employed). Moreover, the research was broadened with cellulose moisture content influence on the modification process—tested fibers were either dried (D) or not dried (ND) before the hybrid chemical treatment. According to the gathered data, D cellulose exhibits elevated thermal resistance and ND fibers are more prone to the MA modification. What should be emphasized, in the case of all carried out UFC100 treatments, is that a decrease in moisture contend was evidenced—from approximately 4% in case of thermal drying to 1.7% for hybrid chemical modification. This is incredibly promising considering the possibility of the treated fibers application in polymer matrix. Full article

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14 pages, 2576 KiB

Open AccessArticle

Mechanisms of Adsorption of Heavy Metal Cations from Waters by an Amino Bio-Based Resin Derived from Rosin

by Wanting Huang, Kaisheng Diao, Xuecai Tan, Fuhou Lei, Jianxin Jiang, Bernard A. Goodman, Yahong Ma and Shaogang Liu

Polymers 2019, 11(6), 969; https://doi.org/10.3390/polym11060969 - 3 Jun 2019

Cited by 20 | Viewed by 5301

Abstract

Rosin derived from conifer trees is used as the basis for a novel environmentally-friendly adsorbent prepared from a sustainable resource. After treatment with ethylenediamine, ethylenediamine rosin-based resin (EDAR) is produced, which possesses cation exchange capacity that is comparable to that of the best [...] Read more.

Rosin derived from conifer trees is used as the basis for a novel environmentally-friendly adsorbent prepared from a sustainable resource. After treatment with ethylenediamine, ethylenediamine rosin-based resin (EDAR) is produced, which possesses cation exchange capacity that is comparable to that of the best commercial synthetic resins. This is demonstrated by its application to the removal of Pb, Cd, and Cu from water, in single and multicomponent systems. Maximum uptake was obtained at pH 5 and in the order Pb(II) > Cd(II) > Cu(II). The maximum adsorption of Pb was ~1.8 mmol/g, but the adsorption process resembled the Freundlich isotherm, whereas the adsorption of Cd(II) and Cu(II) followed the Langmuir isotherm. In the multicomponent systems, there was direct competition between Pb and Cd for sorption sites, whereas the results with Cu indicated it had a preference for different types of sites compared to Pb and Cd. The EDAR resin could be efficiently regenerated and used repeatedly with only a small decrease in performance. Characterization of EDAR, and investigations of its adsorption mechanisms using physical, spectroscopic, and theoretical techniques, including fourier transform infrared spectroscopy (FTIR), ¹³C nuclear magnetic resonance (¹³C NMR), scanning electron microscope (SEM), Brunauer Emmett Teller (BET) method, elemental analysis, thermogravimetric analysis (TGA), and molecular dynamics calculations, showed that amino groups have a critical role in determining the cation adsorption properties. We conclude that this new adsorbent derived from an abundant natural material has the potential to make valuable contributions to the routine removal of heavy metal ions (HMs) from drinking water and wastewater. Full article

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14 pages, 2682 KiB

Open AccessArticle

Biobased Engineering Thermoplastics: Poly(butylene 2,5-furandicarboxylate) Blends

by Niki Poulopoulou, George Kantoutsis, Dimitrios N. Bikiaris, Dimitris S. Achilias, Maria Kapnisti and George Z. Papageorgiou

Polymers 2019, 11(6), 937; https://doi.org/10.3390/polym11060937 - 29 May 2019

Cited by 18 | Viewed by 4629

Abstract

Poly(butylene 2,5-furandicarboxylate) (PBF) constitutes a new engineering polyester produced from renewable resources, as it is synthesized from 2,5-furandicarboxylic acid (2,5-FDCA) and 1,4-butanediol (1,4-BD), both formed from sugars coming from biomass. In this research, initially high-molecular-weight PBF was synthesized by applying the melt polycondensation [...] Read more.

Poly(butylene 2,5-furandicarboxylate) (PBF) constitutes a new engineering polyester produced from renewable resources, as it is synthesized from 2,5-furandicarboxylic acid (2,5-FDCA) and 1,4-butanediol (1,4-BD), both formed from sugars coming from biomass. In this research, initially high-molecular-weight PBF was synthesized by applying the melt polycondensation method and using the dimethylester of FDCA as the monomer. Furthermore, five different series of PBF blends were prepared, namely poly(l-lactic acid)–poly(butylene 2,5-furandicarboxylate) (PLA–PBF), poly(ethylene terephthalate)–poly(butylene 2,5-furandicarboxylate) (PET–PBF), poly(propylene terephthalate)–poly(butylene 2,5-furandicarboxylate) (PPT–PBF), poly(butylene 2,6-naphthalenedicarboxylate)-poly(butylene 2,5-furandicarboxylate) (PBN–PBF), and polycarbonate–poly(butylene 2,5-furandicarboxylate) (PC–PBF), by dissolving the polyesters in a trifluoroacetic acid/chloroform mixture (1/4 v/v) followed by coprecipitation as a result of adding the solutions into excess of cold methanol. The wide-angle X-ray diffraction (WAXD) patterns of the as-prepared blends showed that mixtures of crystals of the blend components were formed, except for PC which did not crystallize. In general, a lower degree of crystallinity was observed at intermediate compositions. The differential scanning calorimetry (DSC) heating scans for the melt-quenched samples proved homogeneity in the case of PET–PBF blends. In the remaining cases, the blend components showed distinct T_gs. In PPT–PBF blends, there was a shift of the T_gs to intermediate values, showing some partial miscibility. Reactive blending proved to improve compatibility of the PBN–PBF blends. Full article

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14 pages, 6307 KiB

Open AccessArticle

Biosourced Disposable Trays Made of Brewer’s Spent Grain and Potato Starch

by Ana M. Ferreira, Jorge Martins, Luísa H. Carvalho and Fernão D. Magalhães

Polymers 2019, 11(5), 923; https://doi.org/10.3390/polym11050923 - 26 May 2019

Cited by 27 | Viewed by 6161

Abstract

Single-use plastic items made of non-biodegradable and fossil-based materials have been identified as a major environmental problem in modern society. Food packaging materials represent an important fraction of these, and replacement with biosourced, sustainable and low-cost alternatives, is a key priority. In the [...] Read more.

Single-use plastic items made of non-biodegradable and fossil-based materials have been identified as a major environmental problem in modern society. Food packaging materials represent an important fraction of these, and replacement with biosourced, sustainable and low-cost alternatives, is a key priority. In the present work, and for the first time, trays suitable for some food packaging applications were produced by the hot-pressing of brewer’s spent grains (BSG, a low added-value byproduct of the beer industry), bound with potato starch. Expanded polystyrene (EPS) trays were used as reference, since this material has been widely used in food packaging trays. The results demonstrated that all trays produced with varying proportions of BSG and potato starch have appropriate flexural strength, with values ranging between 1.51 ± 0.32 MPa, for 80% BSG content, and 2.62 ± 0.46 MPa, for 40% BSG content, which is higher than for EPS, 0.64 ± 0.50 MPa. Regardless of BSG content, flexural strength and modulus decreased significantly after contact with water, due to starch plasticization, attaining values below EPS. Trays produced with 60% BSG, and also with the addition of chitosan and glyoxal presented the highest flexural strength, both before and after contact with water, 3.75 ± 0.52 MPa and 0.44 ± 0.11 MPa, respectively. The latter is reasonably close to the reference value obtained for EPS. Full article

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10 pages, 915 KiB

Open AccessArticle

A Novel One-Pot Synthesis of Poly(Propylene Carbonate) Containing Cross-Linked Networks by Copolymerization of Carbon Dioxide, Propylene Oxide, Maleic Anhydride, and Furfuryl Glycidyl Ether

by Lijun Gao, Xianggen Chen, Xiangjun Liang, Xiuzhi Guo, Xianling Huang, Caifen Chen, Xiaodan Wan, Ruyu Deng, Qifeng Wu, Lingyun Wang and Jiuying Feng

Polymers 2019, 11(5), 881; https://doi.org/10.3390/polym11050881 - 14 May 2019

Cited by 14 | Viewed by 4201

Abstract

The thermoplastic poly(propylene carbonate) (PPC) containing cross-linked networks was one-pot synthesized by copolymerization of carbon dioxide, propylene oxide (PO), maleic anhydride (MA), and furfuryl glycidyl ether (FGE). The copolymers were characterized by Fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), differential scanning [...] Read more.

The thermoplastic poly(propylene carbonate) (PPC) containing cross-linked networks was one-pot synthesized by copolymerization of carbon dioxide, propylene oxide (PO), maleic anhydride (MA), and furfuryl glycidyl ether (FGE). The copolymers were characterized by Fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) measurements. The thermal and dimensional stability of the copolymers were improved. When the MA and FGE load increased from 1 mol% to 4 mol% of PO, the copolymers contained the gel contents of 11.0%–26.1% and their yields were about double that of the PPC. The 5% weight-loss degradation temperatures (T_d,-5%) and the maximum weight-loss degradation temperatures (T_d,max) increased from 149.7–271.3 °C and from 282.6–288.6 °C, respectively, corresponding to 217.1 °C and 239.0 °C of PPC. Additionally, the hot-set elongation tests showed that the copolymers exhibited elasticity and dimensional stability with the minimum permanent deformation of 6.5% which was far less than that of PPC of 157.2%, while the tensile strengths were a little lower than that of PPC because of the following two conflicting factors, cross-links and flexibility of the units formed by the introduced third monomers, MA and FGE. In brief, we provide a novel method of one-pot synthesis of PPC containing cross-linked networks. According to this idea, the properties would be more extensively regulated by changing the cross-linkable monomers. Full article

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15 pages, 3152 KiB

Open AccessArticle

Effect of Poly(styrene-ran-methyl acrylate) Inclusion on the Compatibility of Polylactide/Polystyrene-b-Polybutadiene-b-Polystyrene Blends Characterized by Morphological, Thermal, Rheological, and Mechanical Measurements

by Bocheng Wang, Zheng Tu, Chonggang Wu, Tao Hu, Xiaotao Wang, Shijun Long and Xinghou Gong

Polymers 2019, 11(5), 846; https://doi.org/10.3390/polym11050846 - 10 May 2019

Cited by 6 | Viewed by 3804

Abstract

A poly(styrene-ran-methyl acrylate) (S-MA) (75/25 mol/mol), synthesized by surfactant-free emulsion copolymerization, was used as a compatibilizer for polystyrene-b-polybutadiene-b-polystyrene (SBS)-toughened polylactide (PLA) blends. Upon compatibilization, the blends exhibited a refined dispersed-phase morphology, a decreased crystallinity with an increase [...] Read more.

A poly(styrene-ran-methyl acrylate) (S-MA) (75/25 mol/mol), synthesized by surfactant-free emulsion copolymerization, was used as a compatibilizer for polystyrene-b-polybutadiene-b-polystyrene (SBS)-toughened polylactide (PLA) blends. Upon compatibilization, the blends exhibited a refined dispersed-phase morphology, a decreased crystallinity with an increase in their amorphous interphase, improved thermal stability possibly from the thicker, stronger interfaces insusceptible to thermal energy, a convergence of the maximum decomposition-rate temperatures, enhanced magnitude of complex viscosity, dynamic storage and loss moduli, a reduced ramification degree in the high-frequency terminal region of the Han plot, and an increased semicircle radius in the Cole–Cole plot due to the prolonged chain segmental relaxation times from increases in the thickness and chain entanglement degree of the interphase. When increasing the S-MA content from 0 to 3.0 wt %, the tensile properties of the blends improved considerably until 1.0 wt %, above which they then increased insignificantly, whereas the impact strength was maximized at an optimum S-MA content of ~1.0 wt %, hypothetically due to balanced effects of the medium-size SBS particles on the stabilization of preexisting crazes and the initiation of new crazes in the PLA matrix. These observations confirm that S-MA, a random copolymer first synthesized in our laboratory, acted as an effective compatibilizer for the PLA/SBS blends. Full article

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15 pages, 3240 KiB

Open AccessEditor’s ChoiceArticle

Exploring Next-Generation Engineering Bioplastics: Poly(alkylene furanoate)/Poly(alkylene terephthalate) (PAF/PAT) Blends

by Niki Poulopoulou, Nejib Kasmi, Maria Siampani, Zoi N. Terzopoulou, Dimitrios N. Bikiaris, Dimitris S. Achilias, Dimitrios G. Papageorgiou and George Z. Papageorgiou

Polymers 2019, 11(3), 556; https://doi.org/10.3390/polym11030556 - 23 Mar 2019

Cited by 39 | Viewed by 6981

Abstract

Polymers from renewable resources and especially strong engineering partially aromatic biobased polyesters are of special importance for the evolution of bioeconomy. The fabrication of polymer blends is a creative method for the production of tailor-made materials for advanced applications that are able to [...] Read more.

Polymers from renewable resources and especially strong engineering partially aromatic biobased polyesters are of special importance for the evolution of bioeconomy. The fabrication of polymer blends is a creative method for the production of tailor-made materials for advanced applications that are able to combine functionalities from both components. In this study, poly(alkylene furanoate)/poly(alkylene terephthalate) blends with different compositions were prepared by solution blending in a mixture of trifluoroacetic acid and chloroform. Three different types of blends were initially prepared, namely, poly(ethylene furanoate)/poly(ethylene terephthalate) (PEF/PET), poly(propylene furanoate)/poly(propylene terephthalate) (PPF/PPT), and poly(1,4-cyclohenedimethylene furanoate)/poly(1,4-cycloxehane terephthalate) (PCHDMF/PCHDMT). These blends’ miscibility characteristics were evaluated by examining the glass transition temperature of each blend. Moreover, reactive blending was utilized for the enhancement of miscibility and dynamic homogeneity and the formation of copolymers through transesterification reactions at high temperatures. PEF–PET and PPF–PPT blends formed a copolymer at relatively low reactive blending times. Finally, poly(ethylene terephthalate-co-ethylene furanoate) (PETF) random copolymers were successfully introduced as compatibilizers for the PEF/PET immiscible blends, which resulted in enhanced miscibility. Full article

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16 pages, 777 KiB

Open AccessArticle

A Study of Some Mechanical Properties of a Category of Composites with a Hybrid Matrix and Natural Reinforcements

by Marius Marinel Stănescu and Dumitru Bolcu

Polymers 2019, 11(3), 478; https://doi.org/10.3390/polym11030478 - 12 Mar 2019

Cited by 22 | Viewed by 3346

Abstract

The current composite materials must meet a double challenge, one that involves obtaining mechanical properties suitable to the field of activity in which they are used and another one, equally important, that requires that they be renewable. In this paper, we have obtained [...] Read more.

The current composite materials must meet a double challenge, one that involves obtaining mechanical properties suitable to the field of activity in which they are used and another one, equally important, that requires that they be renewable. In this paper, we have obtained a category of composite materials that have natural reinforcements (fabrics of flax, cotton, hemp, cattail leaves, and wheat straw). As a matrix, we have used three types of hybrid resin, in the composition of which we used the natural resin dammar, in different majority volume proportions. The differences, up to 100%, were represented by epoxy resin and its associated reinforcement, to generate a quick process of polymerization. We have measured certain mechanical properties and the damping properties of the three types of hybrid resin and of the composite materials under study. Based on these properties, we point out a few fields of activity where these composite materials can be used. Full article

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10 pages, 2273 KiB

Open AccessArticle

Solid-State Foaming of Acrylonitrile-Butadiene-Styrene/Recycled Polyethylene Terephthalate Using Carbon Dioxide as a Blowing Agent

by Dong Eui Kwon, Byung Kyu Park and Youn-Woo Lee

Polymers 2019, 11(2), 291; https://doi.org/10.3390/polym11020291 - 9 Feb 2019

Cited by 13 | Viewed by 4813

Abstract

In this study, a single paragraph of acrylonitrile-butadiene-styrene (ABS)/recycled polyethylene terephthalate (R-PET) polymeric foams is prepared using CO₂ as a blowing agent. First, the sorption kinetics of subcritical and supercritical CO₂ are first studied at saturation temperatures from −20 to 40 [...] Read more.

In this study, a single paragraph of acrylonitrile-butadiene-styrene (ABS)/recycled polyethylene terephthalate (R-PET) polymeric foams is prepared using CO₂ as a blowing agent. First, the sorption kinetics of subcritical and supercritical CO₂ are first studied at saturation temperatures from −20 to 40 °C and a pressure of 10 MPa, in order to estimate the diffusion coefficient and the sorption amount. As the sorption temperature increases, the diffusion coefficient of CO₂ increases while the sorption amount decreases. Then, a series of two-step solid-state foaming experiments are conducted. In this process, a specimen is saturated with liquid CO₂ and foamed by dipping the sample in a high-temperature medium at 60 to 120 °C. The effects of foaming temperature and depressurization rate on the morphology and structure of ABS/R-PET microcellular foams are examined. The mean cell size and the variation of the cell size distribution increases as the foaming temperature and the depressurization rate increases. Full article

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14 pages, 3293 KiB

Open AccessArticle

Facile Isolation of LCC-Fraction from Organosolv Lignin by Simple Soxhlet Extraction

by Reza Ebrahimi Majdar, Ali Ghasemian, Hossein Resalati, Ahmadreza Saraeian, Claudia Crestini and Heiko Lange

Polymers 2019, 11(2), 225; https://doi.org/10.3390/polym11020225 - 31 Jan 2019

Cited by 13 | Viewed by 4959

Abstract

A new fractionation protocol for wheat straw organosolv lignin was developed on the basis of the dominating H-bonding orientations of its components. Acetone as H-bond accepting aprotic polar solvent and methanol as H-bond donating and accepting protic polar solvent were used in sequence. [...] Read more.

A new fractionation protocol for wheat straw organosolv lignin was developed on the basis of the dominating H-bonding orientations of its components. Acetone as H-bond accepting aprotic polar solvent and methanol as H-bond donating and accepting protic polar solvent were used in sequence. Obtained fractions were structurally and thermally analysed. The protocol allowed for the generation of purified lignin fractions and the isolation of a novel, yet unobserved lignin carbohydrate complex (LCC) fraction. This LCC fraction was found to contain exclusively phenyl glycosides and γ-esters as LCC motifs. Full article

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13 pages, 3167 KiB

Open AccessEditor’s ChoiceArticle

Flame Inhibition and Charring Effect of Aromatic Polyimide and Aluminum Diethylphosphinate in Polyamide 6

by Haisheng Feng, Yong Qiu, Lijun Qian, Yajun Chen, Bo Xu and Fei Xin

Polymers 2019, 11(1), 74; https://doi.org/10.3390/polym11010074 - 5 Jan 2019

Cited by 25 | Viewed by 5100

Abstract

An aromatic macromolecular polyimide (API) was synthesized and characterized, and used as a synergistic charring flame retardant in glass fiber reinforced polyamide 6 (GF/PA6). API and aluminum diethylphosphinate (ADP) exhibited better flame inhibition behavior and synergistic charring flame retardant behavior compared with ADP [...] Read more.

An aromatic macromolecular polyimide (API) was synthesized and characterized, and used as a synergistic charring flame retardant in glass fiber reinforced polyamide 6 (GF/PA6). API and aluminum diethylphosphinate (ADP) exhibited better flame inhibition behavior and synergistic charring flame retardant behavior compared with ADP alone. The 5%API/7%ADP/GF/PA6 sample achieved the lower peak value of the heat release rate (pk-HRR) at 497 kW/m² and produced higher residue yields of 36.1 wt.%, verifying that API and ADP have an outstanding synergistic effect on the barrier effect. The API/ADP system facilitated the formation of a carbonaceous, phosphorus and aluminum-containing compact char layer with increased barrier effect. FTIR spectra of the residue and real-time TGA-FTIR analysis on the evolved gases from PA6 composites revealed that API interacted with ADP/PA6 and locked in more P–O–C and P–O–Ar content, which is the main mechanism for improving flame inhibition and charring ability. In addition, the API/ADP system improved the mechanical properties and corrosion resistance of GF/PA6 composites compared to ADP alone. Full article

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2018

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14 pages, 3822 KiB

Open AccessArticle

Luffa Pretreated by Plasma Oxidation and Acidity to Be Used as Cellulose Films

by Ying Wang, Zhao-xuan Ding, Yan-hui Zhang, Chun-yan Wei and Zi-chang Xie

Polymers 2019, 11(1), 37; https://doi.org/10.3390/polym11010037 - 27 Dec 2018

Cited by 15 | Viewed by 3516

Abstract

Cellulose is the most abundant natural polymer on earth. With the increasing shortage of oil resources, people have been focusing more on producing natural cellulose. In this study, guaiacol was used as the model compound to investigate the degradation of lignin in luffa. [...] Read more.

Cellulose is the most abundant natural polymer on earth. With the increasing shortage of oil resources, people have been focusing more on producing natural cellulose. In this study, guaiacol was used as the model compound to investigate the degradation of lignin in luffa. A new cellulose material was extracted from natural luffa by a pretreatment based on the oxidation and acidity of glow discharge plasma in water. The produced luffa cellulose was dissolved in anhydrous phosphoric/polyphosphoric acid (aPPAC) solvent to prepare cellulose film. Results showed that the reactive species of OH·, HO₂· and H₃O⁺ were produced during the plasma discharge of water. The free radicals ·OH were useful in eliminating lignin by the destruction of aromatic structure, whereas H₃O⁺ in eliminating hemicellulose in the luffa raw material. At the conditions of luffa powder concentration of 9.26 g/L, discharge time of 20 min, and plasma power of 100W, the cellulose component was increased to 81.2%. After 25 min, the luffa cellulose was completely dissolved in the aPPAC solvent at 0–5 °C. Thus, a regenerated cellulose film of cellulose II was prepared. The aPPAC solvent was a good non-derivatizing solvent for the luffa cellulose. The regenerated film exhibited good mechanical properties, wettability and a compact structure. Therefore, plasma pretreatment was an environmentally friendly and high-efficiency method for luffa degumming. The luffa cellulose can be well used in dissolution and regeneration in films. Full article

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15 pages, 2154 KiB

Open AccessArticle

Green Processes for Green Products: The Use of Supercritical CO₂ as Green Solvent for Compatibilized Polymer Blends

by Muhammad Iqbal, Christiaan Mensen, Xiaohua Qian and Francesco Picchioni

Polymers 2018, 10(11), 1285; https://doi.org/10.3390/polym10111285 - 19 Nov 2018

Cited by 10 | Viewed by 4677

Abstract

Polycaprolactone-g-glycidyl methacrylate (PCL-g-GMA), a reactive interfacial agent for PCL-starch blends, is synthesized using supercritical carbon dioxide (scCO₂) as reaction medium and relatively high molecular weight PCL (M_w = 50,000). Higher GMA and radical initiator intakes [...] Read more.

Polycaprolactone-g-glycidyl methacrylate (PCL-g-GMA), a reactive interfacial agent for PCL-starch blends, is synthesized using supercritical carbon dioxide (scCO₂) as reaction medium and relatively high molecular weight PCL (M_w = 50,000). Higher GMA and radical initiator intakes lead to higher functionalization degrees (FD) for PCL-g-GMA samples. A mathematical model is developed to describe the correlation between monomer and initiator intake and FD values. The model shows an excellent R²-value (0.978), which implies a good fit of the experimental data. Comparison of this model with a similar one for the reaction in the melt clearly indicates a better reaction efficiency in scCO₂. Furthermore, GPC results show that less degradation occurred for samples made in scCO₂. Finally, the use of the PCL-g-GMA made in scCO₂ (as interfacial agent) in ternary blend of PCL/starch/PCL-g-GMA results in better mechanical properties with respect to those obtained by using the same graft-copolymer as prepared in the melt. Full article

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15 pages, 3895 KiB

Open AccessArticle

Synthesis of Linseed Oil-Based Waterborne Urethane Oil Wood Coatings

by Chia-Wei Chang, Jing-Ping Chang and Kun-Tsung Lu

Polymers 2018, 10(11), 1235; https://doi.org/10.3390/polym10111235 - 7 Nov 2018

Cited by 16 | Viewed by 5247

Abstract

The linseed oil glyceride (LOG) was synthesized by using a transesterification process with a glycerol/linseed oil molar ratio of 1.0. The waterborne urethane oil (WUO) wood coating was prepared by acetone process. First, dimethylolpropionic acid was reacted with hexamethylene diisocyanate (HDI) or isophorone [...] Read more.

The linseed oil glyceride (LOG) was synthesized by using a transesterification process with a glycerol/linseed oil molar ratio of 1.0. The waterborne urethane oil (WUO) wood coating was prepared by acetone process. First, dimethylolpropionic acid was reacted with hexamethylene diisocyanate (HDI) or isophorone diisocyanate (IPDI), followed by adding LOG at various NCO/OH molars of 0.7, 0.8, and 0.9, respectively, and the COOH-containing prepolymer was obtained. Then, the ionomer which was prepared by neutralizing prepolymer with trimethylamine, was dispersed by adding deionized water, and the water–acetone dispersion was obtained. Finally, the acetone was removed by vacuum distillation. In the whole synthesized process, the LOG and COOH-containing prepolymer could be steadily synthesized by FTIR analysis, and the weight-average molecular weight and polydispersity of COOH-containing prepolymer increased with an increase of NCO/OH molar ratios. During the water dispersion process of the ionomer acetone solution, the point of phase inversion was prolonged, meaning the solid content decreased with an increase of NCO/OH molar ratios. After acetone was removed, the color of WUO was milky-white, and it was weakly alkaline and possessed a pseudoplastic fluid behavior. The particle size of WUO increased with increasing of NCO/OH molar ratios, however, the storage stability was extended for HDI and shortened for IPDI synthesized with increasing of NCO/OH molar ratios. Full article

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10 pages, 4029 KiB

Open AccessArticle

Aging Properties of Phenol-Formaldehyde Resin Modified by Bio-Oil Using UV Weathering

by Yuxiang Yu, Pingping Xu, Miaomiao Chang and Jianmin Chang

Polymers 2018, 10(11), 1183; https://doi.org/10.3390/polym10111183 - 24 Oct 2018

Cited by 18 | Viewed by 4941

Abstract

The aging properties of phenol-formaldehyde resin modified by bio-oil (BPF) were analyzed using ultraviolet (UV) weathering. The variations on bonding strength of BPF were measured, and the changes on microstructure, atomic composition and chemical structure of BPF were characterized by using a scanning [...] Read more.

The aging properties of phenol-formaldehyde resin modified by bio-oil (BPF) were analyzed using ultraviolet (UV) weathering. The variations on bonding strength of BPF were measured, and the changes on microstructure, atomic composition and chemical structure of BPF were characterized by using a scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance (NMR), respectively. With the increase of aging time, the bonding strength decreased gradually, the resin surface became rougher and the O/C radio of resin surface increased. However, the loss rate of bonding strength of BPFs was 9.6–23.0% lower than that of phenol-formaldehyde resin (PF) after aging 960 h. The aging degree of BPF surfaces was smaller in comparison to PF at the same aging time. These results showed that the bio-oil had a positive effect on the anti-aging property. Analytical results revealed that with increasing the aging time, the XPS peak area of C–C/C–H decreased, while that of C=O and O–C=O increased. The intensity of methylene and ether bridges in NMR analysis decreased along with increasing the intensity of aldehydes, ketones, acids and esters. These results indicated that the aging mechanism of BPF was a process of the breakage of molecular chains and formation of oxygen-containing compounds. Full article

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17 pages, 5014 KiB

Open AccessArticle

Diels–Alder-Crosslinked Polymers Derived from Jatropha Oil

by Muhammad Iqbal, Remco Arjen Knigge, Hero Jan Heeres, Antonius A. Broekhuis and Francesco Picchioni

Polymers 2018, 10(10), 1177; https://doi.org/10.3390/polym10101177 - 22 Oct 2018

Cited by 7 | Viewed by 4971

Abstract

Methyl oleate, methyl linoleate, and jatropha oil were fully epoxidized using in situ-generated performic acid. The epoxidized compounds were further reacted with furfurylamine in a solvent-free reaction to obtain furan-functionalized fatty esters which, then, functioned as oligomers for a network preparation. Thermoreversible crosslinking [...] Read more.

Methyl oleate, methyl linoleate, and jatropha oil were fully epoxidized using in situ-generated performic acid. The epoxidized compounds were further reacted with furfurylamine in a solvent-free reaction to obtain furan-functionalized fatty esters which, then, functioned as oligomers for a network preparation. Thermoreversible crosslinking was obtained through a (retro) Diels–Alder reaction with bismaleimide, resulting in the formation of a brittle network for furan-functionalized methyl linoleate and jatropha oil. The furan-functionalized fatty esters were mixed with alternating (1,4)-polyketone reacted with furfurylamine (PK-Furan) for testing the mechanical and self-healing properties with DMTA and DSC, respectively. Full self-healing properties were found, and faster thermoreversibility kinetics were observed, compared to PK-Furan. Full article

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11 pages, 1295 KiB

Open AccessArticle

Lignin Phenol Formaldehyde Resoles Using Base-Catalysed Depolymerized Kraft Lignin

by Pia Solt, Björn Rößiger, Johannes Konnerth and Hendrikus W. G. Van Herwijnen

Polymers 2018, 10(10), 1162; https://doi.org/10.3390/polym10101162 - 17 Oct 2018

Cited by 47 | Viewed by 12291

Abstract

Lignin phenol formaldehyde (LPF) resols were produced using depolymerized lignin fractions at various levels of phenol substitution (50 to 70 wt %). To produce monomeric-rich (BCD-oil) and oligomeric (BCD-oligomers) bio-based phenolic compounds, softwood kraft lignin was base-catalysed degraded. These base-catalysed depolymerized (BCD) building [...] Read more.

Lignin phenol formaldehyde (LPF) resols were produced using depolymerized lignin fractions at various levels of phenol substitution (50 to 70 wt %). To produce monomeric-rich (BCD-oil) and oligomeric (BCD-oligomers) bio-based phenolic compounds, softwood kraft lignin was base-catalysed degraded. These base-catalysed depolymerized (BCD) building blocks were further used to substitute phenol in the synthesis of phenolic resins and were characterized in detail (such as viscosity, free formaldehyde and phenol content, chemical composition, curing and bonding behaviour). The adhesive properties were compared to a phenol formaldehyde (PF) reference resin and a LPF with untreated kraft lignin. The resins synthesized with the two depolymerized lignin types differ significantly from each other with increasing phenol substitution. While with LPF-BCD-oligomers the viscosity increases and the bonding strength is not effected by increasing lignin content in the resin, a reduction of these properties could be observed with LPF-BCD-oil. Furthermore, LPF-BCD-oil showed similar curing behaviour and ultimate strength as the reference LPF. Adhesive bonds made using LPF-BCD-oligomers exhibited similar strength to those made using PF. Compared to the reference resins, it has been demonstrated that modified renewable lignin based phenolic components can be an equally performing alternative to phenol even for high degrees of substitution of 70%. Full article

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12 pages, 2966 KiB

Open AccessArticle

Improve the Performance of Soy Protein-Based Adhesives by a Polyurethane Elastomer

by Yecheng Xu, Yantao Xu, Wenjie Zhu, Wei Zhang, Qiang Gao and Jianzhang Li

Polymers 2018, 10(9), 1016; https://doi.org/10.3390/polym10091016 - 13 Sep 2018

Cited by 29 | Viewed by 5760

Abstract

The purpose of this study was to improve the performance of soy protein isolate (SPI) adhesives using a polyurethane elastomer. Triglycidylamine (TGA), SPI, thermoplastic polyurethane elastomer (TPU), and γ-(2,3-epoxypropoxy) propyltrimethoxysilane (KH-560) were used to develop a novel SPI-based adhesive. The residual rate, functional [...] Read more.

The purpose of this study was to improve the performance of soy protein isolate (SPI) adhesives using a polyurethane elastomer. Triglycidylamine (TGA), SPI, thermoplastic polyurethane elastomer (TPU), and γ-(2,3-epoxypropoxy) propyltrimethoxysilane (KH-560) were used to develop a novel SPI-based adhesive. The residual rate, functional groups, thermal stability, and fracture surface micrographs of the cured adhesives were characterized. Three-ply plywood was fabricated, and the dry/wet shear strength was determined. The experimental results suggested that introducing 2% TGA improved the residual rate of the SPI/TGA adhesive by 4.1% because of the chemical cross-linking reaction between epoxy groups and protein molecules. Incorporating 7% TPU into the SPI/TGA adhesive, the residual rate of the adhesive increased by 5.2% and the dry/wet shear strength of plywood bonded by SPI/TGA/TPU adhesive increased by 10.7%/67.7%, respectively, compared with that of SPI/TGA adhesive. When using KH-560 and TPU together, the residual rate of the adhesive improved by 0.9% compared with that of SPI/TGA/TPU adhesive. The dry and wet shear strength of the plywood bonded by the SPI/TGA/TPU/KG-560 adhesive further increased by 23.2% and 23.6% respectively when compared with that of SPI/TGA/TPU adhesive. TPU physically combined with the SPI/TGA adhesive to form a interpenetration network and KH-560 acted as a bridge to connect TPU and SPI/TGA to form a joined crosslinking network, which improved the thermo stability/toughness of the adhesive and created a uniform ductile fracture section of the adhesive. Full article

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5 pages, 173 KiB

Open AccessEditorial

Thinking Green: Sustainable Polymers from Renewable Resources

by George Z. Papageorgiou

Polymers 2018, 10(9), 952; https://doi.org/10.3390/polym10090952 - 27 Aug 2018

Cited by 80 | Viewed by 8354

Abstract

n/a Full article

12 pages, 2796 KiB

Open AccessArticle

Dual Drug Delivery of Sorafenib and Doxorubicin from PLGA and PEG-PLGA Polymeric Nanoparticles

by György Babos, Emese Biró, Mónika Meiczinger and Tivadar Feczkó

Polymers 2018, 10(8), 895; https://doi.org/10.3390/polym10080895 - 9 Aug 2018

Cited by 66 | Viewed by 8146

Abstract

Combinatorial drug delivery is a way of advanced cancer treatment that at present represents a challenge for researchers. Here, we report the efficient entrapment of two clinically used single-agent drugs, doxorubicin and sorafenib, against hepatocellular carcinoma. Biocompatible and biodegradable polymeric nanoparticles provide a [...] Read more.

Combinatorial drug delivery is a way of advanced cancer treatment that at present represents a challenge for researchers. Here, we report the efficient entrapment of two clinically used single-agent drugs, doxorubicin and sorafenib, against hepatocellular carcinoma. Biocompatible and biodegradable polymeric nanoparticles provide a promising approach for controlled drug release. In this study, doxorubicin and sorafenib with completely different chemical characteristics were simultaneously entrapped by the same polymeric carrier, namely poly(d,l-lactide-co-glycolide) (PLGA) and polyethylene glycol-poly(d,l-lactide-co-glycolide) (PEG-PLGA), respectively, using the double emulsion solvent evaporation method. The typical mean diameters of the nanopharmaceuticals were 142 and 177 nm, respectively. The PLGA and PEG-PLGA polymers encapsulated doxorubicin with efficiencies of 52% and 69%, respectively, while these values for sorafenib were 55% and 88%, respectively. Sustained drug delivery under biorelevant conditions was found for doxorubicin, while sorafenib was released quickly from the PLGA-doxorubicin-sorafenib and PEG-PLGA-doxorubicin-sorafenib nanotherapeutics. Full article

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16 pages, 2914 KiB

Open AccessArticle

Furanoate-Based Nanocomposites: A Case Study Using Poly(Butylene 2,5-Furanoate) and Poly(Butylene 2,5-Furanoate)-co-(Butylene Diglycolate) and Bacterial Cellulose

by Marina Matos, Andreia F. Sousa, Nuno H. C. S. Silva, Carmen S. R. Freire, Márcia Andrade, Adélio Mendes and Armando J. D. Silvestre

Polymers 2018, 10(8), 810; https://doi.org/10.3390/polym10080810 - 24 Jul 2018

Cited by 36 | Viewed by 5443

Abstract

Polyesters made from 2,5-furandicarboxylic acid (FDCA) have been in the spotlight due to their renewable origins, together with the promising thermal, mechanical, and/or barrier properties. Following the same trend, (nano)composite materials based on FDCA could also generate similar interest, especially because novel materials [...] Read more.

Polyesters made from 2,5-furandicarboxylic acid (FDCA) have been in the spotlight due to their renewable origins, together with the promising thermal, mechanical, and/or barrier properties. Following the same trend, (nano)composite materials based on FDCA could also generate similar interest, especially because novel materials with enhanced or refined properties could be obtained. This paper presents a case study on the use of furanoate-based polyesters and bacterial cellulose to prepare nanocomposites, namely acetylated bacterial cellulose/poly(butylene 2,5-furandicarboxylate) and acetylated bacterial cellulose/poly(butylene 2,5-furandicarboxylate)-co-(butylene diglycolate)s. The balance between flexibility, prompted by the furanoate-diglycolate polymeric matrix; and the high strength prompted by the bacterial cellulose fibres, enabled the preparation of a wide range of new nanocomposite materials. The new nanocomposites had a glass transition between −25–46 °C and a melting temperature of 61–174 °C; and they were thermally stable up to 239–324 °C. Furthermore, these materials were highly reinforced materials with an enhanced Young’s modulus (up to 1239 MPa) compared to their neat copolyester counterparts. This was associated with both the reinforcing action of the cellulose fibres and the degree of crystallinity of the nanocomposites. In terms of elongation at break, the nanocomposites prepared from copolyesters with higher amounts of diglycolate moieties displayed higher elongations due to the soft nature of these segments. Full article

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15 pages, 2380 KiB

Open AccessArticle

Preparation and Characterization of Thermoplastic Potato Starch/Halloysite Nano-Biocomposites: Effect of Plasticizer Nature and Nanoclay Content

by Jiawei Ren, Khanh Minh Dang, Eric Pollet and Luc Avérous

Polymers 2018, 10(8), 808; https://doi.org/10.3390/polym10080808 - 24 Jul 2018

Cited by 62 | Viewed by 6017

Abstract

Nano-biocomposites based on halloysite nanoclay and potato starch were elaborated by melt blending with different polyol plasticizers such as glycerol, sorbitol or a mixture of both. The effects of the type of plasticizer and clay content on potato starch/halloysite nano-biocomposites were studied. SEM [...] Read more.

Nano-biocomposites based on halloysite nanoclay and potato starch were elaborated by melt blending with different polyol plasticizers such as glycerol, sorbitol or a mixture of both. The effects of the type of plasticizer and clay content on potato starch/halloysite nano-biocomposites were studied. SEM analyses combined with ATR-FTIR results showed that a high content of sorbitol had a negative effect on the dispersion of the halloysite nanoclay in the starchy matrix. XRD results demonstrated that incorporation of halloysite nanoclay into glycerol-plasticized starch systems clearly led to the formation of a new crystalline structure. The addition of halloysite nanoclay improved the thermal stability and decreased the moisture absorption of the nano-biocomposites, whatever the type of plasticizer used. Halloysite addition led to more pronounced improvement in mechanical properties for glycerol plasticized system compared to nanocomposites based on sorbitol and glycerol/sorbitol systems with a 47% increase in tensile strength for glycerol-plasticized starch compared to 10.5% and 11% for sorbitol and glycerol/sorbitol systems, respectively. The use of a mixture of polyols was found to be a promising way to optimize the mechanical properties of these starch-based nanocomposites. Full article

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15 pages, 3826 KiB

Open AccessArticle

Effects of Surface Functionalization of Lignin on Synthesis and Properties of Rigid Bio-Based Polyurethanes Foams

by Xuefeng Zhang, Dragica Jeremic, Yunsang Kim, Jason Street and Rubin Shmulsky

Polymers 2018, 10(7), 706; https://doi.org/10.3390/polym10070706 - 26 Jun 2018

Cited by 60 | Viewed by 9231

Abstract

We report the preparation of lignin-based rigid polyurethane (RPU) foams from surface functionalized kraft lignin via a simple and environmentally benign process. Lignin was functionalized with polyisocyanate at 80 °C for 1 h, the resulting lignin-polyisocyanate prepolymer was confirmed by increased viscosity and [...] Read more.

We report the preparation of lignin-based rigid polyurethane (RPU) foams from surface functionalized kraft lignin via a simple and environmentally benign process. Lignin was functionalized with polyisocyanate at 80 °C for 1 h, the resulting lignin-polyisocyanate prepolymer was confirmed by increased viscosity and Fourier-transform infrared spectroscopy (FTIR). The RPU foams containing up to 30% surface functionalized lignin as a substitute for petroleum-based polyols exhibited comparable thermal and mechanical properties to conventional RPU foams. The lignin-based RPU foams prepared from surface functionalization outperformed RPU foams without the surface functionalization, showing up to 47% and 45% higher specific compressive strength and modulus, respectively, with a 40% lignin substitution ratio. Thermal insulation and temperature-stability of the two types of the foams were comparable. The results indicate that the surface functionalization of lignin increases reactivity and homogeneity of the lignin as a building block in RPU foams. The life cycle assessment for the lignin-based RPU foams shows that the surface functionalization process would have overall lesser environmental impacts when compared with the traditional manufacturing of RPU foams with synthetic polyols. These findings suggest the potential use of surface functionalized lignin as a sustainable core material replacement for synthetic polyols in building materials. Full article

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15 pages, 1674 KiB

Open AccessArticle

Bleached Kraft Eucalyptus Fibers as Reinforcement of Poly(Lactic Acid) for the Development of High-Performance Biocomposites

by Marc Delgado-Aguilar, Rafel Reixach, Quim Tarrés, Francesc X. Espinach, Pere Mutjé and José A. Méndez

Polymers 2018, 10(7), 699; https://doi.org/10.3390/polym10070699 - 24 Jun 2018

Cited by 15 | Viewed by 4089

Abstract

Poly(lactic acid) (PLA) is one of the most well-known biopolymers. PLA is bio-based, biocompatible, biodegradable, and easy to produce. This polymer has been used to create natural fiber reinforced composites. However, to produce high-performance and presumably biodegradable composites, the interphase between PLA and [...] Read more.

Poly(lactic acid) (PLA) is one of the most well-known biopolymers. PLA is bio-based, biocompatible, biodegradable, and easy to produce. This polymer has been used to create natural fiber reinforced composites. However, to produce high-performance and presumably biodegradable composites, the interphase between PLA and natural fibers still requires further study. As such, we aimed to produce PLA-based composites reinforced with a commercial bleached kraft eucalyptus pulp. To become a real alternative, fully biodegradable composites must have similar properties to commercial materials. The results found in this research support the competence of wood fiber reinforced PLA composites to replace other glass fiber reinforced polypropylene composites from a tensile property point of view. Furthermore, the micromechanics analysis showed that obtaining strong interphases between the PLA and the reinforcement is possible without using any coupling agent. This work shows the ability of totally bio-based composites that fulfill the principles of green chemistry to replace composites based on polyolefin and high contents of glass fiber. To the best knowledge of the authors, previous studies obtaining such properties or lower ones involved the use of reagents or the modification of the fiber surfaces. Full article

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16 pages, 10706 KiB

Open AccessArticle

Green Binder Based on Enzymatically Polymerized Eucalypt Kraft Lignin for Fiberboard Manufacturing: A Preliminary Study

by Susana Gouveia, Luis Alberto Otero, Carmen Fernández-Costas, Daniel Filgueira, Ángeles Sanromán and Diego Moldes

Polymers 2018, 10(6), 642; https://doi.org/10.3390/polym10060642 - 9 Jun 2018

Cited by 30 | Viewed by 5504

Abstract

The capability of laccase from Myceliophthora thermophila to drive oxidative polymerization of Eucalyptus globulus Kraft lignin (KL) was studied as a previous step before applying this biotechnological approach for the manufacturing of medium-density fiberboards (MDF) at a pilot scale. This method, which improves [...] Read more.

The capability of laccase from Myceliophthora thermophila to drive oxidative polymerization of Eucalyptus globulus Kraft lignin (KL) was studied as a previous step before applying this biotechnological approach for the manufacturing of medium-density fiberboards (MDF) at a pilot scale. This method, which improves the self-bonding capacity of wood fibers by lignin enzymatic cross-linking, mimics the natural process of lignification in living plants and trees. An interesting pathway to promote these interactions could be the addition of lignin to the system. The characterization of E. globulus KL after enzymatic treatment showed a decrease of phenolic groups as well as the aromatic protons without loss of aromaticity. There was also an extensive oxidative polymerization of the biomolecule. In the manufacture of self-bonded MDF, the synergy generated by the added lignin and laccase provided promising results. Thus, whenever laccase was present in the treatment, MDF showed an increase in mechanical and dimensional stability for increasing amounts of lignin. In a pilot scale, this method produced MDF that meets the requirements of the European standards for both thickness swell (TS) and internal bonding (IB) for indoor applications. Full article

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19 pages, 2150 KiB

Open AccessArticle

Inhalable Fucoidan Microparticles Combining Two Antitubercular Drugs with Potential Application in Pulmonary Tuberculosis Therapy

by Ludmylla Cunha, Susana Rodrigues, Ana M. Rosa da Costa, M Leonor Faleiro, Francesca Buttini and Ana Grenha

Polymers 2018, 10(6), 636; https://doi.org/10.3390/polym10060636 - 8 Jun 2018

Cited by 37 | Viewed by 5497

Abstract

The pulmonary delivery of antitubercular drugs is a promising approach to treat lung tuberculosis. This strategy not only allows targeting the infected organ instantly, it can also reduce the systemic adverse effects of the antibiotics. In light of that, this work aimed at [...] Read more.

The pulmonary delivery of antitubercular drugs is a promising approach to treat lung tuberculosis. This strategy not only allows targeting the infected organ instantly, it can also reduce the systemic adverse effects of the antibiotics. In light of that, this work aimed at producing fucoidan-based inhalable microparticles that are able to associate a combination of two first-line antitubercular drugs in a single formulation. Fucoidan is a polysaccharide composed of chemical units that have been reported to be specifically recognised by alveolar macrophages (the hosts of Mycobacterium). Inhalable fucoidan microparticles were successfully produced, effectively associating isoniazid (97%) and rifabutin (95%) simultaneously. Furthermore, the produced microparticles presented adequate aerodynamic properties for pulmonary delivery with potential to reach the respiratory zone, with a mass median aerodynamic diameter (MMAD) between 3.6–3.9 µm. The formulation evidenced no cytotoxic effects on lung epithelial cells (A549), although mild toxicity was observed on macrophage-differentiated THP-1 cells at the highest tested concentration (1 mg/mL). Fucoidan microparticles also exhibited a propensity to be captured by macrophages in a dose-dependent manner, as well as an ability to activate the target cells. Furthermore, drug-loaded microparticles effectively inhibited mycobacterial growth in vitro. Thus, the produced fucoidan microparticles are considered to hold potential as pulmonary delivery systems for the treatment of tuberculosis. Full article

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19 pages, 3233 KiB

Open AccessArticle

Synthesis and Characterization of Renewable Polyester Coil Coatings from Biomass-Derived Isosorbide, FDCA, 1,5-Pentanediol, Succinic Acid, and 1,3-Propanediol

by Mónica Lomelí-Rodríguez, José Raúl Corpas-Martínez, Susan Willis, Robert Mulholland and Jose Antonio Lopez-Sanchez

Polymers 2018, 10(6), 600; https://doi.org/10.3390/polym10060600 - 29 May 2018

Cited by 56 | Viewed by 9460

Abstract

Biomass-derived polyester coatings for coil applications have been successfully developed and characterized. The coatings were constituted by carbohydrate-derived monomers, namely 2,5-furan dicarboxylic acid, isosorbide, succinic acid, 1,3-propanediol, and 1,5-pentanediol, the latter having previously been used as a plasticizer rather than a structural building [...] Read more.

Biomass-derived polyester coatings for coil applications have been successfully developed and characterized. The coatings were constituted by carbohydrate-derived monomers, namely 2,5-furan dicarboxylic acid, isosorbide, succinic acid, 1,3-propanediol, and 1,5-pentanediol, the latter having previously been used as a plasticizer rather than a structural building unit. The effect of isosorbide on the coatings is widely studied. The inclusion of these monomers diversified the mechanical properties of the coatings, and showed an improved performance against common petrochemical derived coatings. This research study provides a range of fully bio-derived polyester coil coatings with tunable properties of industrial interest, highlighting the importance of renewable polymers towards a successful bioeconomy. Full article

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16 pages, 7312 KiB

Open AccessArticle

Isothermal and Nonisothermal Crystallization Kinetics of Poly(ε-caprolactone) Blended with a Novel Ionic Liquid, 1-Ethyl-3-propylimidazolium Bis(trifluoromethanesulfonyl)imide

by Chun-Ting Yang, Li-Ting Lee and Tzi-Yi Wu

Polymers 2018, 10(5), 543; https://doi.org/10.3390/polym10050543 - 18 May 2018

Cited by 7 | Viewed by 4204

Abstract

Recently, ionic liquids (ILs) and biodegradable polymers have become crucial functional materials in green sustainable science and technology. In this study, we investigated the influence of a novel IL, 1-ethyl-3-propylimidazolium bis(trifluoromethanesulfonyl)imide ([EPrI][TFSI]), on the crystallization kinetics of a widely studied biodegradable polymer, poly(ε-caprolactone) [...] Read more.

Recently, ionic liquids (ILs) and biodegradable polymers have become crucial functional materials in green sustainable science and technology. In this study, we investigated the influence of a novel IL, 1-ethyl-3-propylimidazolium bis(trifluoromethanesulfonyl)imide ([EPrI][TFSI]), on the crystallization kinetics of a widely studied biodegradable polymer, poly(ε-caprolactone) (PCL). To obtain a comprehensive understanding, both the isothermal and nonisothermal crystallization kinetics of the PCL blends were studied. Incorporating [EPrI][TFSI] reduced the isothermal and nonisothermal crystallization rates of PCL. Regarding isothermal crystallization, the small k and 1/t_0.5 values of the blend, estimated using the Avrami equation, indicated that [EPrI][TFSI] decreased the rate of isothermal crystallization of PCL. The Mo model adequately described the nonisothermal crystallization kinetics of the blends. Increasing the [EPrI][TFSI] content caused the rate-related parameter F(T) to increase. This indicated that the crystallization rate of PCL decreased when [EPrI][TFSI] was incorporated. The spherulite appearance temperature of the blending sample was found to be lower than that of neat PCL under a constant cooling rate. The analysis of the effective activation energy proposed that the nonisothermal crystallization of PCL would not be favorited when the [EPrI][TFSI] was incorporated into the blends. The addition of [EPrI][TFSI] would not change the crystal structures of PCL according to the results of wide angle X-ray diffraction. Fourier transform infrared spectroscopy suggested that interactions occurred between [EPrI][TFSI] and PCL. The crystallization kinetics of PCL were inhibited when [EPrI][TFSI] was incorporated. Full article

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15 pages, 3873 KiB

Open AccessArticle

Renewable Resources and a Recycled Polymer as Raw Materials: Mats from Electrospinning of Lignocellulosic Biomass and PET Solutions

by Rachel Passos de Oliveira Santos, Patrícia Fernanda Rossi, Luiz Antônio Ramos and Elisabete Frollini

Polymers 2018, 10(5), 538; https://doi.org/10.3390/polym10050538 - 17 May 2018

Cited by 24 | Viewed by 6781

Abstract

Interest in the use of renewable raw materials in the preparation of materials has been growing uninterruptedly in recent decades. The aim of this strategy is to offer alternatives to the use of fossil fuel-based raw materials and to meet the demand for [...] Read more.

Interest in the use of renewable raw materials in the preparation of materials has been growing uninterruptedly in recent decades. The aim of this strategy is to offer alternatives to the use of fossil fuel-based raw materials and to meet the demand for materials that are less detrimental to the environment after disposal. In this context, several studies have been carried out on the use of lignocellulosic biomass and its main components (cellulose, hemicelluloses, and lignin) as raw materials for polymeric materials. Lignocellulosic fibers have a high content of cellulose, but there has been a notable lack of investigations on application of the electrospinning technique for solutions prepared from raw lignocellulosic biomass, even though the presence of cellulose favors the alignment of the fiber chains during electrospinning. In this investigation, ultrathin (submicrometric) and nanoscale aligned fibers were successfully prepared via electrospinning (room temperature) of solutions prepared with different contents of lignocellulosic sisal fibers combined with recycled poly(ethylene terephthalate) (PET) using trifluoroacetic acid (TFA) as solvent. The “macro” fibers were deconstructed by the action of TFA, resulting in solutions containing their constituents, i.e., cellulose, hemicelluloses, and lignin, in addition to PET. The “macro” sisal fibers were reconstructed at the nanometer and submicrometric scale from these solutions. The SEM micrographs of the mats containing the components of sisal showed distinct fiber networks, likely due to differences in the solubility of these components in TFA and in their dielectric constants. The mechanical properties of the mats (dynamic mechanical analysis, DMA, and tensile properties) were evaluated with the samples positioned both in the direction (dir) of and in opposition (op) to the alignment of the nano and ultrathin fibers, which can be considered a novelty in the analysis of this type of material. DMA showed superior values of storage modulus (E’ at 30 °C) for the mats characterized in the preferential direction of fiber alignment. For example, for mats obtained from solutions prepared from a 0.4 ratio of sisal fibers/PET, Sisal/PET_0.40dir presented a high E’ value of 765 MPa compared to Sisal/PET_0.40op that presented an E’ value of 88.4 MPa. The fiber alignment did not influence the T_g values (from tan δ peak) of electrospun mats with the same compositions, as they presented similar values for this property. The tensile properties of the electrospun mats were significantly impacted by the alignment of the fibers: e.g., Sisal/PET_0.40dir presented a high tensile strength value of 15.72 MPa, and Sisal/PET_0.40op presented a value of approximately 2.5 MPa. An opposite trend was observed regarding the values of elongation at break for these materials. Other properties of the mats are also discussed; such as the index of fiber alignment, average porosity, and surface contact angle. To our knowledge, this is the first time that the influence of fiber alignment on the properties of electrospun mats based on untreated lignocellulosic biomass combined with a recycled polymer, such as PET, has been evaluated. The mats obtained in this study have potential for diversified applications, such as reinforcement for polymeric matrices in nanocomposites, membranes for filtration, and support for enzymes, wherein the fiber alignment, together with other evaluated properties, can impact their effectiveness in these applications. Full article

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14 pages, 2284 KiB

Open AccessArticle

FA Polymerization Disruption by Protic Polar Solvents

by Guillaume Falco, Nathanaël Guigo, Luc Vincent and Nicolas Sbirrazzuoli

Polymers 2018, 10(5), 529; https://doi.org/10.3390/polym10050529 - 15 May 2018

Cited by 32 | Viewed by 5342

Abstract

Furfuryl alcohol (FA) is a biobased monomer derived from lignocellulosic biomass. The present work describes its polymerization in the presence of protic polar solvents, i.e., water or isopropyl alcohol (IPA), using maleic anhydride (MA) as an acidic initiator. The polymerization was followed from [...] Read more.

Furfuryl alcohol (FA) is a biobased monomer derived from lignocellulosic biomass. The present work describes its polymerization in the presence of protic polar solvents, i.e., water or isopropyl alcohol (IPA), using maleic anhydride (MA) as an acidic initiator. The polymerization was followed from the liquid to the rubbery state by combining DSC and DMA data. In the liquid state, IPA disrupts the expected reactions during the FA polymerization due to a stabilization of the furfuryl carbenium center. This causes the initiation of the polymerization at a higher temperature, which is also reflected by a higher activation energy. In the water system, the MA opening allows the reaction to start at a lower temperature. A higher pre-exponential factor value is obtained in that case. The DMA study of the final branching reaction occurring in the rubbery state has highlighted a continuous increase of elastic modulus until 290 °C. This increasing tendency of modulus was exploited to obtain activation energy dependences (E_α) of FA polymerization in the rubbery state. Full article

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24 pages, 1185 KiB

Open AccessReview

Plant Secondary Metabolite-Derived Polymers: A Potential Approach to Develop Antimicrobial Films

by Ahmed Al-Jumaili, Avishek Kumar, Kateryna Bazaka and Mohan V. Jacob

Polymers 2018, 10(5), 515; https://doi.org/10.3390/polym10050515 - 10 May 2018

Cited by 27 | Viewed by 13918

Abstract

The persistent issue of bacterial and fungal colonization of artificial implantable materials and the decreasing efficacy of conventional systemic antibiotics used to treat implant-associated infections has led to the development of a wide range of antifouling and antibacterial strategies. This article reviews one [...] Read more.

The persistent issue of bacterial and fungal colonization of artificial implantable materials and the decreasing efficacy of conventional systemic antibiotics used to treat implant-associated infections has led to the development of a wide range of antifouling and antibacterial strategies. This article reviews one such strategy where inherently biologically active renewable resources, i.e., plant secondary metabolites (PSMs) and their naturally occurring combinations (i.e., essential oils) are used for surface functionalization and synthesis of polymer thin films. With a distinct mode of antibacterial activity, broad spectrum of action, and diversity of available chemistries, plant secondary metabolites present an attractive alternative to conventional antibiotics. However, their conversion from liquid to solid phase without a significant loss of activity is not trivial. Using selected examples, this article shows how plasma techniques provide a sufficiently flexible and chemically reactive environment to enable the synthesis of biologically-active polymer coatings from volatile renewable resources. Full article

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22 pages, 2379 KiB

Open AccessReview

Nanofiller Reinforced Biodegradable PLA/PHA Composites: Current Status and Future Trends

by Jingyao Sun, Jingjing Shen, Shoukai Chen, Merideth A. Cooper, Hongbo Fu, Daming Wu and Zhaogang Yang

Polymers 2018, 10(5), 505; https://doi.org/10.3390/polym10050505 - 7 May 2018

Cited by 166 | Viewed by 16589

Abstract

The increasing demand for environmental protection has led to the rapid development of greener and biodegradable polymers, whose creation provided new challenges and opportunities for the advancement of nanomaterial science. Biodegradable polymer materials and even nanofillers (e.g., natural fibers) are important because of [...] Read more.

The increasing demand for environmental protection has led to the rapid development of greener and biodegradable polymers, whose creation provided new challenges and opportunities for the advancement of nanomaterial science. Biodegradable polymer materials and even nanofillers (e.g., natural fibers) are important because of their application in greener industries. Polymers that can be degraded naturally play an important role in solving public hazards of polymer materials and maintaining ecological balance. The inherent shortcomings of some biodegradable polymers such as weak mechanical properties, narrow processing windows, and low electrical and thermal properties can be overcome by composites reinforced with various nanofillers. These biodegradable polymer composites have wide-ranging applications in different areas based on their large surface area and greater aspect ratio. Moreover, the polymer composites that exploit the synergistic effect between the nanofiller and the biodegradable polymer matrix can lead to enhanced properties while still meeting the environmental requirement. In this paper, a broad review on recent advances in the research and development of nanofiller reinforced biodegradable polymer composites that are used in various applications, including electronics, packing materials, and biomedical uses, is presented. We further present information about different kinds of nanofillers, biodegradable polymer matrixes, and their composites with specific concern to our daily applications. Full article

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17 pages, 2658 KiB

Open AccessArticle

Barrier Properties of Poly(Propylene Cyclohexanedicarboxylate) Random Eco-Friendly Copolyesters

by Valentina Siracusa, Laura Genovese, Carlo Ingrao, Andrea Munari and Nadia Lotti

Polymers 2018, 10(5), 502; https://doi.org/10.3390/polym10050502 - 5 May 2018

Cited by 23 | Viewed by 6809

Abstract

Random copolymers of poly(propylene 1,4-cyclohexanedicarboxylate) containing different amounts of neopentyl glycol sub-unit were investigated from the gas barrier point of view at the standard temperature of analysis (23 °C) with respect to the three main gases used in food packaging field: N₂ [...] Read more.

Random copolymers of poly(propylene 1,4-cyclohexanedicarboxylate) containing different amounts of neopentyl glycol sub-unit were investigated from the gas barrier point of view at the standard temperature of analysis (23 °C) with respect to the three main gases used in food packaging field: N₂, O₂, and CO₂. The effect of temperature was also evaluated, considering two temperatures close to the T_g sample (8 and 15 °C) and two above T_g (30 and 38 °C). Barrier performances were checked after food contact simulants and in different relative humidity (RH) environments obtained with two saturated saline solutions (Standard Atmosphere, 23 °C, 85% of RH, with saturated KCl solution; Tropical Climate, 38 °C, 90% RH, with saturated KNO₃ solution). The results obtained were compared to those of untreated film, which was used as a reference. The relationships between the gas transmission rate, the diffusion coefficients, the solubility, and the copolymer composition were established. The results highlighted a correlation between barrier performance and copolymer composition and the applied treatment. In particular, copolymerization did not cause a worsening of the barrier properties, whereas the different treatments differently influenced the gas barrier behavior, depending on the chemical polymer structure. After treatment, Fourier transform infrared analysis confirmed the chemical stability of these copolymers. Films were transparent, with a light yellowish color, slightly more intense after all treatments. Full article

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12 pages, 9400 KiB

Open AccessArticle

Partially Renewable Poly(butylene 2,5-furandicarboxylate-co-isophthalate) Copolyesters Obtained by ROP

by Juan Carlos Morales-Huerta, Antxon Martínez de Ilarduya and Sebastián Muñoz-Guerra

Polymers 2018, 10(5), 483; https://doi.org/10.3390/polym10050483 - 28 Apr 2018

Cited by 12 | Viewed by 4656

Abstract

Cyclic butylene furandicarboxylate (c(BF)_n) and butylene isophthalate (c(BI)_n) oligomers obtained by high dilution condensation reaction were polymerized in bulk at 200 °C with Sn(Oct)₂ catalyst via ring opening polymerization to give homopolyesters and copolyesters [...] Read more.

Cyclic butylene furandicarboxylate (c(BF)_n) and butylene isophthalate (c(BI)_n) oligomers obtained by high dilution condensation reaction were polymerized in bulk at 200 °C with Sn(Oct)₂ catalyst via ring opening polymerization to give homopolyesters and copolyesters (coPBF_xI_y) with weight average molar masses in the 60,000–70,000 g·mol⁻¹ range and dispersities between 1.3 and 1.9. The composition of the copolyesters as determined by NMR was practically the same as that of the feed, and they all showed an almost random microstructure. The copolyesters were thermally stable up to 300 °C and crystalline for all compositions, and have T_g in the 40–20 °C range with values decreasing almost linearly with their content in isophthalate units in the copolyester. Both melting temperature and enthalpy of the copolyesters decreased as the content in butylene isophthalate units increased up to a composition 30/70 (BF/BI), at which the triclinic crystal phase made exclusively of butylene furanoate units changed to the crystal structure of PBI. The partial replacement of furanoate by isophthalate units decreased substantially the crystallizability of PBF. Full article

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21 pages, 25113 KiB

Open AccessArticle

Solid-State Polymerization of Poly(Ethylene Furanoate) Biobased Polyester, II: An Efficient and Facile Method to Synthesize High Molecular Weight Polyester Appropriate for Food Packaging Applications

by Nejib Kasmi, George Z. Papageorgiou, Dimitris S. Achilias and Dimitrios N. Bikiaris

Polymers 2018, 10(5), 471; https://doi.org/10.3390/polym10050471 - 25 Apr 2018

Cited by 45 | Viewed by 9165

Abstract

The goal of this study was to synthesize, through a facile strategy, high molecular weight poly(ethylene furanoate) (PEF), which could be applicable in food packaging applications. The efficient method to generate PEF with high molecular weight consists of carrying out a first solid-state [...] Read more.

The goal of this study was to synthesize, through a facile strategy, high molecular weight poly(ethylene furanoate) (PEF), which could be applicable in food packaging applications. The efficient method to generate PEF with high molecular weight consists of carrying out a first solid-state polycondensation under vacuum for 6 h reaction time at 205 °C for the resulting polymer from two-step melt polycondensation process, which is catalyzed by tetrabutyl titanate (TBT). A remelting step was thereafter applied for 15 min at 250 °C for the obtained polyester. Thus, the PEF sample was ground into powder, and was then crystallized for 6 h at 170 °C. This polyester is then submitted to a second solid-state polycondensation (SSP) carried out at different reaction times (1, 2, 3.5, and 5 h) and temperatures 190, 200, and 205 °C, under vacuum. Ultimately, a significant increase in intrinsic viscosity is observed with only 5 h reaction time at 205 °C during the second SSP being needed to obtain very high molecular weight PEF polymer greater than 1 dL/g, which sufficient for manufacturing purposes. Intrinsic viscosity (IV), carboxyl end-group content (–COOH), and thermal properties, via differential scanning calorimetry (DSC), were measured for all resultant polyesters. Thanks to the post-polymerization process, DSC results showed that the melting temperatures of the prepared PEF samples were steadily enhanced in an obvious way as a function of reaction time and temperature increase. It was revealed, as was expected for all SSP samples, that the intrinsic viscosity and the average molecular weight of PEF polyester increased with increasing SSP time and temperature, whereas the number of carboxyl end-group concentration was decreased. A simple kinetic model was also developed and used to predict the time evolution of polyesters IV, as well as the carboxyl and hydroxyl end-groups of PEF during the SSP. Full article

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13 pages, 4822 KiB

Open AccessArticle

Effect of Selected Thiols on Cross-Linking of Acrylated Epoxidized Soybean Oil and Properties of Resulting Polymers

by Sigita Kasetaite, Silvia De la Flor, Angels Serra and Jolita Ostrauskaite

Polymers 2018, 10(4), 439; https://doi.org/10.3390/polym10040439 - 14 Apr 2018

Cited by 27 | Viewed by 10428

Abstract

The effect of the chemical structure and functionality of three structurally different thiols on the cross-linking of acrylated epoxidized soybean oil and on the properties of the resulting polymers was investigated in this study. 1,3-Benzenedithiol, pentaerythritol tetra(3-mercaptopropionate), and an hexathiol synthesized from squalene [...] Read more.

The effect of the chemical structure and functionality of three structurally different thiols on the cross-linking of acrylated epoxidized soybean oil and on the properties of the resulting polymers was investigated in this study. 1,3-Benzenedithiol, pentaerythritol tetra(3-mercaptopropionate), and an hexathiol synthesized from squalene were used in the cross-linking of acrylated epoxidized soybean oil by thiol–Michael addition reaction. The reactivity of thiols determined from calorimetric curves followed the order: 1,3-benzenedithiol > pentaerythritol tetra(3-mercaptopropionate) > hexathiolated squalene. Thermal and mechanical properties and the swelling in different solvents of the cross-linked polymers were studied. The cross-linked polymer obtained from 1,3-benzenedithiol showed the highest swelling values in chloroform and toluene. The cross-linked polymer with pentaerythritol tetra(3-mercaptopropionate) fragments showed the best mechanical performance (highest mechanical strength and Young’s modulus) and thermal stability. The cross-linked polymers from hexathiolated squalene showed the highest glass transition temperature. Full article

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12 pages, 23020 KiB

Open AccessArticle

Synthesis and Characterization of Wooden Magnetic Activated Carbon Fibers with Hierarchical Pore Structures

by Dongna Li, Jianing Li, Biyun Ren, Tongtong Li and Xiaojun Ma

Polymers 2018, 10(4), 435; https://doi.org/10.3390/polym10040435 - 13 Apr 2018

Cited by 5 | Viewed by 4901

Abstract

Wooden magnetic activated carbon fibers (WMACFs) with hierarchical pore structures were obtained by adding magnetic iron oxide (Fe₃O₄) nanoparticles into the liquefied wood. The structures and properties of WMACFs were analyzed by scanning electronmicroscopy (SEM), X-ray diffraction (XRD), Fourier [...] Read more.

Wooden magnetic activated carbon fibers (WMACFs) with hierarchical pore structures were obtained by adding magnetic iron oxide (Fe₃O₄) nanoparticles into the liquefied wood. The structures and properties of WMACFs were analyzed by scanning electronmicroscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N₂ adsorption, and vibrating sample magnetometer (VSM). The results showed that WMACFs had high Brunauer-Emmett-Teller (BET) surface area (1578 m²/g) and total pore volume (0.929 cm³/g), of which 45% was the contribution of small mesopores of 2–3 nm. It is believed that Fe₃O₄ nanoparticles play an important role in the formation of hierarchical pores. With the Fe₃O₄ content increasing, the yield rate of WMACFs decreased, and the Fe₃O₄ crystal plane diffraction peaks and characteristic adsorption peaks were obviously observed. At the same time, it was also found that WMACFs had favorable magnetic properties when the Fe₃O₄ content was above 1.5%. As a result, WMACFs could be a promising candidate for high efficiency, low cost, and convenient separation for the magnetic field. Full article

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15 pages, 22599 KiB

Open AccessArticle

3D Printable Filaments Made of Biobased Polyethylene Biocomposites

by Daniel Filgueira, Solveig Holmen, Johnny K. Melbø, Diego Moldes, Andreas T. Echtermeyer and Gary Chinga-Carrasco

Polymers 2018, 10(3), 314; https://doi.org/10.3390/polym10030314 - 13 Mar 2018

Cited by 64 | Viewed by 8105

Abstract

Two different series of biobased polyethylene (BioPE) were used for the manufacturing of biocomposites, complemented with thermomechanical pulp (TMP) fibers. The intrinsic hydrophilic character of the TMP fibers was previously modified by grafting hydrophobic compounds (octyl gallate and lauryl gallate) by means of [...] Read more.

Two different series of biobased polyethylene (BioPE) were used for the manufacturing of biocomposites, complemented with thermomechanical pulp (TMP) fibers. The intrinsic hydrophilic character of the TMP fibers was previously modified by grafting hydrophobic compounds (octyl gallate and lauryl gallate) by means of an enzymatic-assisted treatment. BioPE with low melt flow index (MFI) yielded filaments with low void fraction and relatively low thickness variation. The water absorption of the biocomposites was remarkably improved when the enzymatically-hydrophobized TMP fibers were used. Importantly, the 3D printing of BioPE was improved by adding 10% and 20% TMP fibers to the composition. Thus, 3D printable biocomposites with low water uptake can be manufactured by using fully biobased materials and environmentally-friendly processes. Full article

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9 pages, 2491 KiB

Open AccessArticle

Structural Investigation of Poly(ethylene furanoate) Polymorphs

by Lucia Maini, Matteo Gigli, Massimo Gazzano, Nadia Lotti, Dimitrios N. Bikiaris and George Z. Papageorgiou

Polymers 2018, 10(3), 296; https://doi.org/10.3390/polym10030296 - 9 Mar 2018

Cited by 61 | Viewed by 6618

Abstract

α and β crystalline phases of poly(ethylene furanoate) (PEF) were determined using X-ray powder diffraction by structure resolution in direct space and Rietveld refinement. Moreover, the α’ structure of a PEF sample was refined from data previously reported for PEF fiber. Triclinic α-PEF [...] Read more.

α and β crystalline phases of poly(ethylene furanoate) (PEF) were determined using X-ray powder diffraction by structure resolution in direct space and Rietveld refinement. Moreover, the α’ structure of a PEF sample was refined from data previously reported for PEF fiber. Triclinic α-PEF a = 5.729 Å, b = 7.89 Å, c = 9.62 Å, α = 98.1°, β = 65.1°, γ = 101.3°; monoclinic α’-PEF a = 5.912 Å, b = 6.91 Å, c = 19.73 Å, α = 90°, β = 90°, γ = 104.41°; and monoclinic β-PEF a = 5.953 Å, b = 6.60 Å, c = 10.52 Å, α = 90°, β = 107.0°, γ = 90° were determined as the best fitting of X-ray diffraction (XRD) powder patterns. Final atomic coordinates are reported for all polymorphs. In all cases PEF chains adopted an almost planar configuration. Full article

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13 pages, 2050 KiB

Open AccessArticle

Lipase-Catalyzed Synthesis, Properties Characterization, and Application of Bio-Based Dimer Acid Cyclocarbonate

by Xin He, Guiying Wu, Li Xu, Jinyong Yan and Yunjun Yan

Polymers 2018, 10(3), 262; https://doi.org/10.3390/polym10030262 - 3 Mar 2018

Cited by 11 | Viewed by 5245

Abstract

Dimer acid cyclocarbonate (DACC) is synthesized from glycerol carbonate (GC) and Sapium sebiferum oil-derived dimer acid (DA, 9-[(Z)-non-3-enyl]-10-octylnonadecanedioic acid). Meanwhile, DACC can be used for synthetic materials of bio-based non-isocyanate polyurethane (bio-NIPU). In this study, DACC was synthesized by the esterification [...] Read more.

Dimer acid cyclocarbonate (DACC) is synthesized from glycerol carbonate (GC) and Sapium sebiferum oil-derived dimer acid (DA, 9-[(Z)-non-3-enyl]-10-octylnonadecanedioic acid). Meanwhile, DACC can be used for synthetic materials of bio-based non-isocyanate polyurethane (bio-NIPU). In this study, DACC was synthesized by the esterification of dimer acid and glycerol carbonate using Novozym 435 (Candida antarctica lipase B) as the biocatalyst. Via the optimizing reaction conditions, the highest yield of 76.00% and the lowest acid value of 43.82 mg KOH/g were obtained. The product was confirmed and characterized by Fourier transform-infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). Then, the synthetic DACC was further used to synthesize bio-NIPU, which was examined by FTIR, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), indicating that it possesses very good physio-chemical properties and unique material quality with a potential prospect in applications. Full article

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21 pages, 8271 KiB

Open AccessArticle

Starch-Chitosan Polyplexes: A Versatile Carrier System for Anti-Infectives and Gene Delivery

by Hanzey Yasar, Duy-Khiet Ho, Chiara De Rossi, Jennifer Herrmann, Sarah Gordon, Brigitta Loretz and Claus-Michael Lehr

Polymers 2018, 10(3), 252; https://doi.org/10.3390/polym10030252 - 1 Mar 2018

Cited by 33 | Viewed by 8614

Abstract

Despite the enormous potential of nanomedicine, the search for materials from renewable resources that balance bio-medical requirements and engineering aspects is still challenging. This study proposes an easy method to make nanoparticles composed of oxidized starch and chitosan, both isolated from natural biopolymers. [...] Read more.

Despite the enormous potential of nanomedicine, the search for materials from renewable resources that balance bio-medical requirements and engineering aspects is still challenging. This study proposes an easy method to make nanoparticles composed of oxidized starch and chitosan, both isolated from natural biopolymers. The careful adjustment of C/N ratio, polymer concentration and molecular weight allowed for tuning of particle characteristics. The system’s carrier capability was assessed both for anti-infectives and for nucleic acid. Higher starch content polyplexes were found to be suitable for high encapsulation efficiency of cationic anti-infectives and preserving their bactericidal function. A cationic carrier was obtained by coating the anionic polyplex with chitosan. Coating allowed for a minimal amount of cationic polymer to be employed and facilitated plasmid DNA loading both within the particle core and on the surface. Transfection studies showed encouraging result, approximately 5% of A549 cells with reporter gene expression. In summary, starch-chitosan complexes are suitable carriers with promising perspectives for pharmaceutical use. Full article

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14 pages, 7448 KiB

Open AccessArticle

Gas Dissolution Foaming as a Novel Approach for the Production of Lightweight Biocomposites of PHB/Natural Fibre Fabrics

by Heura Ventura, Luigi Sorrentino, Ester Laguna-Gutierrez, Miguel Angel Rodriguez-Perez and Monica Ardanuy

Polymers 2018, 10(3), 249; https://doi.org/10.3390/polym10030249 - 28 Feb 2018

Cited by 16 | Viewed by 5037

Abstract

The aim of this study is to propose and explore a novel approach for the production of cellular lightweight natural fibre, nonwoven, fabric-reinforced biocomposites by means of gas dissolution foaming from composite precursors of polyhydroxybutyrate-based matrix and flax fabric reinforcement. The main challenge [...] Read more.

The aim of this study is to propose and explore a novel approach for the production of cellular lightweight natural fibre, nonwoven, fabric-reinforced biocomposites by means of gas dissolution foaming from composite precursors of polyhydroxybutyrate-based matrix and flax fabric reinforcement. The main challenge is the development of a regular cellular structure in the polymeric matrix to reach a weight reduction while keeping a good fibre-matrix stress transfer and adhesion. The viability of the process is evaluated through the analysis of the cellular structure and morphology of the composites. The effect of matrix modification, nonwoven treatment, expansion temperature, and expansion pressure on the density and cellular structure of the cellular composites is evaluated. It was found that the nonwoven fabric plays a key role in the formation of a uniform cellular morphology, although limiting the maximum expansion ratio of the composites. Cellular composites with a significant reduction of weight (relative densities in the range 0.4–0.5) were successfully obtained. Full article

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21 pages, 7211 KiB

Open AccessArticle

Impact of Nanoclays on the Biodegradation of Poly(Lactic Acid) Nanocomposites

by Edgar Castro-Aguirre, Rafael Auras, Susan Selke, Maria Rubino and Terence Marsh

Polymers 2018, 10(2), 202; https://doi.org/10.3390/polym10020202 - 17 Feb 2018

Cited by 75 | Viewed by 8395

Abstract

Poly(lactic acid) (PLA), a well-known biodegradable and compostable polymer, was used in this study as a model system to determine if the addition of nanoclays affects its biodegradation in simulated composting conditions and whether the nanoclays impact the microbial population in a compost [...] Read more.

Poly(lactic acid) (PLA), a well-known biodegradable and compostable polymer, was used in this study as a model system to determine if the addition of nanoclays affects its biodegradation in simulated composting conditions and whether the nanoclays impact the microbial population in a compost environment. Three different nanoclays were studied due to their different surface characteristics but similar chemistry: organo-modified montmorillonite (OMMT), Halloysite nanotubes (HNT), and Laponite® RD (LRD). Additionally, the organo-modifier of MMT, methyl, tallow, bis-2-hydroxyethyl, quaternary ammonium (QAC), was studied. PLA and PLA bio-nanocomposite (BNC) films were produced, characterized, and used for biodegradation evaluation with an in-house built direct measurement respirometer (DMR) following the analysis of evolved CO2 approach. A biofilm formation essay and scanning electron microscopy were used to evaluate microbial attachment on the surface of PLA and BNCs. The results obtained from four different biodegradation tests with PLA and its BNCs showed a significantly higher mineralization of the films containing nanoclay in comparison to the pristine PLA during the first three to four weeks of testing, mainly attributed to the reduction in the PLA lag time. The effect of the nanoclays on the initial molecular weight during processing played a crucial role in the evolution of CO2. PLA-LRD5 had the greatest microbial attachment on the surface as confirmed by the biofilm test and the SEM micrographs, while PLA-QAC0.4 had the lowest biofilm formation that may be attributed to the inhibitory effect also found during the biodegradation test when the QAC was tested by itself. Full article

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11 pages, 3119 KiB

Open AccessArticle

Renewable, Eugenol—Modified Polystyrene Layer for Liquid Crystal Orientation

by Changha Ju, Taehyung Kim and Hyo Kang

Polymers 2018, 10(2), 201; https://doi.org/10.3390/polym10020201 - 17 Feb 2018

Cited by 11 | Viewed by 6988

Abstract

We synthesized a series of plant-based and renewable, eugenol-modified polystyrene (PEUG#) (# = 20, 40, 60, 80, and 100, in which # is the molar content of the eugenol moiety in the side group). Eugenol is extracted from clove oil. We used polymer [...] Read more.

We synthesized a series of plant-based and renewable, eugenol-modified polystyrene (PEUG#) (# = 20, 40, 60, 80, and 100, in which # is the molar content of the eugenol moiety in the side group). Eugenol is extracted from clove oil. We used polymer modification reactions to determine the liquid crystal (LC) orientation properties of the polymer films. In general, the LC cells fabricated using the polymer films with a higher molar content of eugenol side groups exhibited vertical LC orientation behavior. The vertical orientation behavior was well correlated with the surface energy value of the polymer films. The vertical LC orientation could be formed due to the low polar surface energy value on the polymer film generated by the nonpolar carbon group. Electro-optical performances (e.g., voltage holding ratio (VHR), residual DC voltage (R-DC), and thermal orientation stabilities) were good enough to be observed for LC cells using PEUG100 polymer as an eco-friendly LC orientation material. Full article

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13 pages, 4974 KiB

Open AccessArticle

Preparation and Characterization of Graphene Oxide-Modified Sapium sebiferum Oil-Based Polyurethane Composites with Improved Thermal and Mechanical Properties

by Guiying Wu, Xiaoling Xu, Xin He and Yunjun Yan

Polymers 2018, 10(2), 133; https://doi.org/10.3390/polym10020133 - 30 Jan 2018

Cited by 35 | Viewed by 6192

Abstract

Bio-based polyurethane (PU) composites with superior thermal and mechanical properties have received wide attention. This is due to the recent rapid developments in the PU industry. In the work reported here, novel nano-composites with graphene oxide (GO)-modified Sapium sebiferum oil (SSO)-based PU has [...] Read more.

Bio-based polyurethane (PU) composites with superior thermal and mechanical properties have received wide attention. This is due to the recent rapid developments in the PU industry. In the work reported here, novel nano-composites with graphene oxide (GO)-modified Sapium sebiferum oil (SSO)-based PU has been synthesized via in situ polymerization. GO, prepared using the improved Hummers method from natural graphene (NG), and SSO-based polyol with a hydroxyl value of 211 mg KOH/g, prepared by lipase hydrolysis, were used as raw materials. The microstructures and properties of GO and the nano-composites were both characterized using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and tensile tests. The results showed that GO with its nano-sheet structure possessed a significant number of oxygen-containing functional groups at the surface. The nano-composites containing 1 wt % GO in the PU matrix (PU1) exhibited excellent comprehensive properties. Compared with those for pure PU, the glass transition temperature (T_g) and initial decomposition temperature (IDT) of the PU1 were enhanced by 14.1 and 31.8 °C, respectively. In addition, the tensile strength and Young’s modulus of the PU1 were also improved by 126% and 102%, respectively, compared to the pure PU. The significant improvement in both the thermal stability and mechanical properties for PU/GO composites was attributed to the homogeneous dispersion and good compatibility of GO with the PU matrix. The improvement in the properties upon the addition of GO may be attributable to the strong interfacial interaction between the reinforcing agent and the PU matrix. Full article

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2017

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5917 KiB

Open AccessArticle

Crystallization and Stereocomplexation of PLA-mb-PBS Multi-Block Copolymers

by Rosa M. D’Ambrosio, Rose Mary Michell, Rosica Mincheva, Rebeca Hernández, Carmen Mijangos, Philippe Dubois and Alejandro J. Müller

Polymers 2018, 10(1), 8; https://doi.org/10.3390/polym10010008 - 22 Dec 2017

Cited by 13 | Viewed by 7151

Abstract

The crystallization and morphology of PLA-mb-PBS copolymers and their corresponding stereocomplexes were studied. The effect of flexible blocks (i.e., polybutylene succinate, PBS) on the crystallization of the copolymers and stereocomplex formation were investigated using polarized light optical microscopy (PLOM), differential scanning [...] Read more.

The crystallization and morphology of PLA-mb-PBS copolymers and their corresponding stereocomplexes were studied. The effect of flexible blocks (i.e., polybutylene succinate, PBS) on the crystallization of the copolymers and stereocomplex formation were investigated using polarized light optical microscopy (PLOM), differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), and carbon-13 nuclear magnetic resonance spectroscopy (¹³C-NMR). The PLA and PBS multiple blocks were miscible in the melt and in the glassy state. When the PLA-mb-PBS copolymers are cooled from the melt, the PLA component crystallizes first creating superstructures, such as spherulites or axialites, which constitute a template within which the PBS component has to crystallize when the sample is further cooled down. The Avrami theory was able to fit the overall crystallization kinetics of both semi-crystalline components, and the n values for both blocks in all the samples had a correspondence with the superstructural morphology observed by PLOM. Solution mixtures of PLLA-mb-PBS and PLDA-mb-PBS copolymers were prepared, as well as copolymer/homopolymer blends with the aim to study the stereocomplexation of PLLA and PDLA chain segments. A lower amount of stereocomplex formation was observed in copolymer mixtures as compared to neat L₁₀₀/D₁₀₀ stereocomplexes. The results show that PBS chain segments perturb the formation of stereocomplexes and this perturbation increases with the amount of PBS in the samples. However, when relatively low amounts of PBS in the copolymer blends are present, the rate of stereocomplex formation is enhanced. This effect dissappears when higher amounts of PBS are present. The stereocomplexation was confirmed by FTIR and solid state ¹³C-NMR analyses. Full article

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6083 KiB

Open AccessArticle

Styrene-Assisted Maleic Anhydride Grafted Poly(lactic acid) as an Effective Compatibilizer for Wood Flour/Poly(lactic acid) Bio-Composites

by Jun Du, Youyong Wang, Xinfeng Xie, Min Xu and Yongming Song

Polymers 2017, 9(11), 623; https://doi.org/10.3390/polym9110623 - 15 Nov 2017

Cited by 26 | Viewed by 10847

Abstract

This study aimed to evaluate the effect of styrene-assisted maleic anhydride-grafted poly(lactic acid) (PLA-g-St/MAH) on the interfacial properties of wood flour/poly(lactic acid) (PLA) bio-composites. PLA-g-St/MAH was synthesized by free-radical melt grafting using styrene as a comonomer and dicumyl peroxide [...] Read more.

This study aimed to evaluate the effect of styrene-assisted maleic anhydride-grafted poly(lactic acid) (PLA-g-St/MAH) on the interfacial properties of wood flour/poly(lactic acid) (PLA) bio-composites. PLA-g-St/MAH was synthesized by free-radical melt grafting using styrene as a comonomer and dicumyl peroxide as an initiator. The structure of PLA-g-St/MAH was characterized by Fourier transform infrared spectroscopy. Wood flour/PLA composites were prepared by compression molding using PLA-g-St/MAH as a compatibilizer. The effects of PLA-g-St/MAH on the rheological and mechanical properties, as well as on the fractured surface morphology of the composites were investigated. Results indicated that storage modulus, complex viscosity, equilibrium torque, and shear heat were significantly increased. The mechanical properties of the wood flour/PLA composites were also significantly increased after the addition of PLA-g-St/MAH. The maximum values were achieved at the loading rate of 3 wt % because of the improved interfacial adhesion between the wood flour and the PLA matrix. Full article

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2708 KiB

Open AccessArticle

Cardanol Groups Grafted on Poly(vinyl chloride)—Synthesis, Performance and Plasticization Mechanism

by Puyou Jia, Meng Zhang, Lihong Hu, Rui Wang, Chao Sun and Yonghong Zhou

Polymers 2017, 9(11), 621; https://doi.org/10.3390/polym9110621 - 15 Nov 2017

Cited by 70 | Viewed by 9866

Abstract

Internally plasticized poly(vinyl chloride) (PVC) materials are investigated via grafting of propargyl ether cardanol (PEC). The chemical structure of the materials was studied by FT-IR and ¹H NMR. The performace of the obtained internally plasticized PVC materials was also investigated with TGA, [...] Read more.

Internally plasticized poly(vinyl chloride) (PVC) materials are investigated via grafting of propargyl ether cardanol (PEC). The chemical structure of the materials was studied by FT-IR and ¹H NMR. The performace of the obtained internally plasticized PVC materials was also investigated with TGA, DSC and leaching tests. The results showed that grafting of propargyl ether cardanol (PEC) on PVC increased the free volume and distance of PVC chains, which efficiently decreased the glass transition temperature (T_g). No migration was found in the leaching tests for internally plasticized PVC films compared with plasticized PVC materials with commercial plasticizer dioctyl phthalate (DOP). The internal plasticization mechanism was also disscussed according to lubrication theory and free volume theory. This work provides a meaningful strategy for designing no-migration PVC materials by introducing cardanol groups as branched chains. Full article

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5477 KiB

Open AccessArticle

Thiolated Chitosan Masked Polymeric Microspheres with Incorporated Mesocellular Silica Foam (MCF) for Intranasal Delivery of Paliperidone

by Stavroula Nanaki, Maria Tseklima, Evi Christodoulou, Konstantinos Triantafyllidis, Margaritis Kostoglou and Dimitrios N. Bikiaris

Polymers 2017, 9(11), 617; https://doi.org/10.3390/polym9110617 - 15 Nov 2017

Cited by 47 | Viewed by 7021

Abstract

In this study, mesocellular silica foam (MCF) was used to encapsulate paliperidone, an antipsychotic drug used in patients suffering from bipolar disorder. MCF with the drug adsorbed was further encapsulated into poly(lactic acid) (PLA) and poly(lactide-co-glycolide) (PLGA) 75/25 w/w [...] Read more.

In this study, mesocellular silica foam (MCF) was used to encapsulate paliperidone, an antipsychotic drug used in patients suffering from bipolar disorder. MCF with the drug adsorbed was further encapsulated into poly(lactic acid) (PLA) and poly(lactide-co-glycolide) (PLGA) 75/25 w/w microspheres and these have been coated with thiolated chitosan. As found by TEM analysis, thiolated chitosan formed a thin layer on the polymeric microspheres’ surface and was used in order to enhance their mucoadhesiveness. These microspheres aimed at the intranasal delivery of paliperidone. The DSC and XRD studies showed that paliperidone was encapsulated in amorphous form inside the MCF silica and for this reason its dissolution profile was enhanced compared to the neat drug. In coated microspheres, thiolated chitosan reduced the initial burst effect of the paliperidone dissolution profile and in all cases sustained release formulations have been prepared. The release mechanism was also theoretically studied and three kinetic models were proposed and successfully fitted for a dissolution profile of prepared formulations to be found. Full article

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2261 KiB

Open AccessArticle

Effect of Glycerol Pretreatment on Levoglucosan Production from Corncobs by Fast Pyrolysis

by Liqun Jiang, Nannan Wu, Anqing Zheng, Xiaobo Wang, Ming Liu, Zengli Zhao, Fang He, Haibin Li and Xinjun Feng

Polymers 2017, 9(11), 599; https://doi.org/10.3390/polym9110599 - 10 Nov 2017

Cited by 15 | Viewed by 6415

Abstract

In this manuscript, glycerol was used in corncobs’ pretreatment to promote levoglucosan production by fast pyrolysis first and then was further utilized as raw material for chemicals production by microbial fermentation. The effects of glycerol pretreatment temperatures (220–240 °C), time (0.5–3 h) and [...] Read more.

In this manuscript, glycerol was used in corncobs’ pretreatment to promote levoglucosan production by fast pyrolysis first and then was further utilized as raw material for chemicals production by microbial fermentation. The effects of glycerol pretreatment temperatures (220–240 °C), time (0.5–3 h) and solid-to-liquid ratios (5–20%) were investigated. Due to the accumulation of crystalline cellulose and the removal of minerals, the levoglucosan yield was as high as 35.8% from corncobs pretreated by glycerol at 240 for 3 h with a 5% solid-to-liquid ratio, which was obviously higher than that of the control (2.2%). After glycerol pretreatment, the fermentability of the recovered glycerol remaining in the liquid stream from glycerol pretreatment was evaluated by Klebsiella pneumoniae. The results showed that the recovered glycerol had no inhibitory effect on the growth and metabolism of the microbe, which was a promising substrate for fermentation. The value-added applications of glycerol could reduce the cost of biomass pretreatment. Correspondingly, this manuscript offers a green, sustainable, efficient and economic strategy for an integrated biorefinery process. Full article

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Open AccessArticle

Synthesis and Characterization of Cellulose Nanofibril-Reinforced Polyurethane Foam

by Weiqi Leng, Jinghao Li and Zhiyong Cai

Polymers 2017, 9(11), 597; https://doi.org/10.3390/polym9110597 - 10 Nov 2017

Cited by 47 | Viewed by 8227

Abstract

In this study, traditional polyol was partially replaced with green, environmentally friendly cellulose nanofibrils (CNF). The effects of CNF on the performance of CNF-reinforced polyurethane foam nanocomposites were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, thermogravimetric [...] Read more.

In this study, traditional polyol was partially replaced with green, environmentally friendly cellulose nanofibrils (CNF). The effects of CNF on the performance of CNF-reinforced polyurethane foam nanocomposites were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and a compression test. The results showed that the introduction of CNF into the polyurethane matrix not only created stronger urethane bonding between the hydroxyl groups in the cellulose chain and isocyanate groups in polymethylene polyphenylisocyanate, but also developed an additional filler–matrix interaction between CNF and polyurethane. With the increase of the CNF replacement ratio, a higher glass transition temperature was obtained, and a higher amount of char residue was generated. In addition, an increase of up to 18-fold in compressive strength was achieved for CNF-PUF (polyurethane foam) nanocomposites with a 40% CNF replacement ratio. CNF has proved to be a promising substitute for traditional polyols in the preparation of polyurethane foams. This study provides an interesting method to synthesize highly green bio-oriented polyurethane foams. Full article

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Open AccessArticle

Novel Isocyanate-Modified Carrageenan Polymer Materials: Preparation, Characterization and Application Adsorbent Materials of Pharmaceuticals

by Myrsini Papageorgiou, Stavroula G. Nanaki, George Z. Kyzas, Christina Koulouktsi, Dimitrios N. Bikiaris and Dimitra A. Lambropoulou

Polymers 2017, 9(11), 595; https://doi.org/10.3390/polym9110595 - 10 Nov 2017

Cited by 15 | Viewed by 6104

Abstract

The present study focused on the synthesis and application of novel isocyanate-modified carrageenan polymers as sorbent materials for pre-concentration and removal of diclofenac (DCF) and carbamazepine (CBZ) in different aqueous matrices (surface waters and wastewaters). The polymer materials were characterized using Fourier transform [...] Read more.

The present study focused on the synthesis and application of novel isocyanate-modified carrageenan polymers as sorbent materials for pre-concentration and removal of diclofenac (DCF) and carbamazepine (CBZ) in different aqueous matrices (surface waters and wastewaters). The polymer materials were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Thermal Gravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM). The effects on the adsorption behavior were studied, and the equilibrium data were fitted by the Langmuir and Freundlich models. The maximum adsorption capacity (Q_max) was determined by Langmuir–Freundlich model and was ranged for iota-carrageenan (iCAR) from 7.44 to 8.51 mg/g for CBZ and 23.41 to 35.78 mg/g for DCF and for kappa-carrageenan (kCAR) from 7.07 to 13.78 mg/g for CBZ and 22.66 to 49.29 mg/g for DCF. In the next step, dispersive solid phase extraction (D-SPE) methodology followed by liquid desorption and liquid chromatography mass spectrometry (LC/MS) has been developed and validated. The factors, which affect the performance of D-SPE, were investigated. Then, the optimization of extraction time, sorbent mass and eluent’s volume was carried out using a central composite design (CCD) and response surface methodology (RSM). Under the optimized conditions, good linear relationships have been achieved with the correlation coefficient (R²) varying from 0.9901 to 0.995. The limits of detections (LODs) and limits of quantifications (LOQs) ranged 0.042–0.090 μg/L and 0.137–0.298 μg/L, respectively. The results of the recoveries were 70–108% for both analytes, while the precisions were 2.8–17.5% were obtained, which indicated that the method was suitable for the analysis of both compounds in aqueous matrices. Full article

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5172 KiB

Open AccessArticle

Fully Biodegradable Biocomposites with High Chicken Feather Content

by Ibon Aranberri, Sarah Montes, Itxaso Azcune, Alaitz Rekondo and Hans-Jürgen Grande

Polymers 2017, 9(11), 593; https://doi.org/10.3390/polym9110593 - 9 Nov 2017

Cited by 67 | Viewed by 10896

Abstract

The aim of this work was to develop new biodegradable polymeric materials with high loadings of chicken feather (CF). In this study, the effect of CF concentration and the type of biodegradable matrix on the physical, mechanical and thermal properties of the biocomposites [...] Read more.

The aim of this work was to develop new biodegradable polymeric materials with high loadings of chicken feather (CF). In this study, the effect of CF concentration and the type of biodegradable matrix on the physical, mechanical and thermal properties of the biocomposites was investigated. The selected biopolymers were polylactic acid (PLA), polybutyrate adipate terephthalate (PBAT) and a PLA/thermoplastic copolyester blend. The studied biocomposites were manufactured with a torque rheometer having a CF content of 50 and 60 wt %. Due to the low tensile strength of CFs, the resulting materials were penalized in terms of mechanical properties. However, high-loading CF biocomposites resulted in lightweight and thermal-insulating materials when compared with neat bioplastics. Additionally, the adhesion between CFs and the PLA matrix was also investigated and a significant improvement of the wettability of the feathers was obtained with the alkali treatment of the CFs and the addition of a plasticizer like polyethylene glycol (PEG). Considering all the properties, these 100% fully biodegradable biocomposites could be adequate for panel components, flooring or building materials as an alternative to wood–plastic composites, contributing to the valorisation of chicken feather waste as a renewable material. Full article

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Open AccessArticle

Stereocomplexation, Thermal and Mechanical Properties of Conetworks Composed of Star-Shaped l-Lactide, d-Lactide and ε-Caprolactone Oligomers Utilizing Sugar Alcohols as Core Molecules

by Kaito Sugane, Hayato Takahashi, Toshiaki Shimasaki, Naozumi Teramoto and Mitsuhiro Shibata

Polymers 2017, 9(11), 582; https://doi.org/10.3390/polym9110582 - 6 Nov 2017

Cited by 9 | Viewed by 5635

Abstract

It is important to develop tailor-made biodegradable/biocompatible polymer networks usable for biomaterials whose thermal and mechanical properties are easily controlled by changing the composition. We synthesized sugar-alcohol-based polymer networks (SPN-mscLAO/3CLO, m = 4, 5 or 6) by the crosslinking reactions of [...] Read more.

It is important to develop tailor-made biodegradable/biocompatible polymer networks usable for biomaterials whose thermal and mechanical properties are easily controlled by changing the composition. We synthesized sugar-alcohol-based polymer networks (SPN-mscLAO/3CLO, m = 4, 5 or 6) by the crosslinking reactions of erythritol, xylitol or sorbitol-based m-armed star-shaped l-lactide and d-lactide oligomers (HmSLLAO and HmSDLAO), a glycerol-based 3-armed star-shaped ε-caprolactone oligomer (H3SCLO) and hexamethylene diisocyanate (HDI) at the weight ratios of HmSLLAO/HmSDLAO = 1/1 and (HmSLLAO + HmSDLAO)/H3CLO = 100/0, 75/25, 50/50, 25/75 or 0/100). The influence of the arm number on the crystallization behavior, thermal and mechanical properties of SPN-mscLAO/3CLOs were systematically investigated by comparing with those of sugar-alcohol-based homochiral polymer network (SPN-mLLAO, m = 4, 5 or 6) prepared by the reaction of HmSLLAO and HDI. Stereocomplex (sc) crystallites are dominantly formed for SPN-mscLAO/3CLOs 100/0–25/75, whereas SPN-mLLAOs were amorphous. The higher order of melting temperature of sc-crystals for SPN-mscLAO/3CLOs 100/0–25/75 was m = 5 > m = 6 > m = 4. The sc-crystallinities of SPN-4scLAO/3CLOs 100/0–50/50 were significantly lower than those of SPN-mscLAO/3CLOs 100/0–50/50 (m = 5 and 6). The larger order of the sc-spherulite size at crystallization temperature of 110 °C was m = 5 > m = 6 > m = 4 for SPN-mscLAO/3CLO 100/0. The size and number of sc-spherulites decreased with increasing crystallization temperature over the range of 110–140 °C and with increasing CLO fraction. Among all the networks, SPN-5scLAO/3CLOs 75/25 and 50/50 exhibited the highest and second highest tensile toughnesses (21.4 and 20.3 MJ·m⁻³), respectively. Full article

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4683 KiB

Open AccessReview

The Recent Developments in Biobased Polymers toward General and Engineering Applications: Polymers that are Upgraded from Biodegradable Polymers, Analogous to Petroleum-Derived Polymers, and Newly Developed

by Hajime Nakajima, Peter Dijkstra and Katja Loos

Polymers 2017, 9(10), 523; https://doi.org/10.3390/polym9100523 - 18 Oct 2017

Cited by 317 | Viewed by 31123

Abstract

The main motivation for development of biobased polymers was their biodegradability, which is becoming important due to strong public concern about waste. Reflecting recent changes in the polymer industry, the sustainability of biobased polymers allows them to be used for general and engineering [...] Read more.

The main motivation for development of biobased polymers was their biodegradability, which is becoming important due to strong public concern about waste. Reflecting recent changes in the polymer industry, the sustainability of biobased polymers allows them to be used for general and engineering applications. This expansion is driven by the remarkable progress in the processes for refining biomass feedstocks to produce biobased building blocks that allow biobased polymers to have more versatile and adaptable polymer chemical structures and to achieve target properties and functionalities. In this review, biobased polymers are categorized as those that are: (1) upgrades from biodegradable polylactides (PLA), polyhydroxyalkanoates (PHAs), and others; (2) analogous to petroleum-derived polymers such as bio-poly(ethylene terephthalate) (bio-PET); and (3) new biobased polymers such as poly(ethylene 2,5-furandicarboxylate) (PEF). The recent developments and progresses concerning biobased polymers are described, and important technical aspects of those polymers are introduced. Additionally, the recent scientific achievements regarding high-spec engineering-grade biobased polymers are presented. Full article

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Open AccessArticle

Two-Sided Surface Oxidized Cellulose Membranes Modified with PEI: Preparation, Characterization and Application for Dyes Removal

by Wei Wang, Qian Bai, Tao Liang, Huiyu Bai and Xiaoya Liu

Polymers 2017, 9(9), 455; https://doi.org/10.3390/polym9090455 - 16 Sep 2017

Cited by 29 | Viewed by 7286

Abstract

Porous regenerated cellulose (RC) membranes were prepared with cotton linter pulp as a raw material. These membranes were first oxidized on both sides by a modified (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidation system using a controlled oxidation reaction technique. Then, the oxidized RC membranes were functionalized

[...] Read more.

Porous regenerated cellulose (RC) membranes were prepared with cotton linter pulp as a raw material. These membranes were first oxidized on both sides by a modified (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidation system using a controlled oxidation reaction technique. Then, the oxidized RC membranes were functionalized with polyethylenimine (PEI) via the glutaraldehyde crosslinking method to obtain bifunctional (carboxyl and amino) porous RC membranes, as revealed by Fourier transform infrared spectroscopy (FT-IR), elemental analysis and zeta potential measurement. The scanning electron microscopy (SEM) and the tests of the mechanical properties and permeability characteristics of modified RC membranes demonstrated that the porous structure and certain mechanical properties could be retained. The adsorption performance of the modified membranes towards dyes was subsequently investigated. The modified membranes displayed good adsorption capacities, rapid adsorption equilibrium and removal efficiencies towards both anionic (xylenol orange (XO)) and cationic (methylene blue (MB)) dyes, making them suitable bioadsorbents for wastewater treatment.

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Fast Curing Bio-Based Phenolic Resins via Lignin Demethylated under Mild Reaction Condition

by Jiongjiong Li, Jizhi Zhang, Shifeng Zhang, Qiang Gao, Jianzhang Li and Wei Zhang

Polymers 2017, 9(9), 428; https://doi.org/10.3390/polym9090428 - 7 Sep 2017

Cited by 79 | Viewed by 9483

Abstract

Demethylation technique has been used to enhance lignin reactivity for preparation of phenolic resins. However, the demethylation efficiency and the demethylated lignin (DL) reactivity were still unsatisfactory. To improve the demethylation efficiency, alkali lignin was demethylated under different mild conditions using sodium sulfite [...] Read more.

Demethylation technique has been used to enhance lignin reactivity for preparation of phenolic resins. However, the demethylation efficiency and the demethylated lignin (DL) reactivity were still unsatisfactory. To improve the demethylation efficiency, alkali lignin was demethylated under different mild conditions using sodium sulfite as a catalyst. Lignin and DL were characterized by ¹H-NMR (nuclear magnetic resonance) and Fourier transform infrared (FT-IR) spectroscopy to determine the demethylation mechanism. With the demethylation of lignin, the methoxyl group content decreased from 1.93 m mol/g to 1.09 m mol/g, and the phenolic hydroxyl group content increased from 0.56 m mol/g to 0.82 m mol/g. These results revealed that methoxyl groups were attacked by SO₃²⁻, and some methoxyl groups were converted to phenolic hydroxyl groups by a nucleophilic substitution reaction, generating DL with high reactivity. The chemical properties of lignin-based phenolic resins were studied by ¹³C-NMR and FT-IR spectroscopy, and their physical properties were also investigated. The results indicated that lignin-based phenolic resins exhibited faster curing rate and shorter gel time. In addition, the bonding strength increased from 0.92 MPa to 1.07 MPa, and the formaldehyde emission decreased from 0.58 mg/L to 0.22 mg/L after lignin demethylated at the optimum condition. Full article

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Open AccessArticle

Hyaluronic Acid Promotes the Osteogenesis of BMP-2 in an Absorbable Collagen Sponge

by Hairong Huang, Jianying Feng, Daniel Wismeijer, Gang Wu and Ernst B. Hunziker

Polymers 2017, 9(8), 339; https://doi.org/10.3390/polym9080339 - 4 Aug 2017

Cited by 29 | Viewed by 6115

Abstract

(1) Background: We tested the hypothesis that hyaluronic acid (HA) can significantly promote the osteogenic potential of BMP-2/ACS (absorbable collagen sponge), an efficacious product to heal large oral bone defects, thereby allowing its use at lower dosages and, thus, reducing its side-effects due [...] Read more.

(1) Background: We tested the hypothesis that hyaluronic acid (HA) can significantly promote the osteogenic potential of BMP-2/ACS (absorbable collagen sponge), an efficacious product to heal large oral bone defects, thereby allowing its use at lower dosages and, thus, reducing its side-effects due to the unphysiologically-high doses of BMP-2; (2) Methods: In a subcutaneous bone induction model in rats, we first sorted out the optimal HA-polymer size and concentration with micro CT. Thereafter, we histomorphometrically quantified the effect of HA on new bone formation, total construct volume, and densities of blood vessels and macrophages in ACS with 5, 10, and 20 μg of BMP-2; (3) Results: The screening experiments revealed that the 100 µg/mL HA polymer of 48 kDa molecular weight could yield the highest new bone formation. Eighteen days post-surgery, HA could significantly enhance the total volume of newly-formed bone by approximately 100%, and also the total construct volume in the 10 μg BMP-2 group. HA could also significantly enhance the numerical area density of blood vessels in 5 μg BMP-2 and 10 μg BMP-2 groups. HA did not influence the numerical density of macrophages; and (4) Conclusions: An optimal combined administration of HA could significantly promote osteogenic and angiogenic activity of BMP-2/ACS, thus potentially minimizing its potential side-effects. Full article

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Open AccessArticle

Tailoring Drug Release Properties by Gradual Changes in the Particle Engineering of Polysaccharide Chitosan Based Powders

by Ednaldo G. Do Nascimento, Lilia B. De Caland, Arthur S.A. De Medeiros, Matheus F. Fernandes-Pedrosa, José L. Soares-Sobrinho, Kátia S.C.R. Dos Santos and Arnóbio Antonio Da Silva-Júnior

Polymers 2017, 9(7), 253; https://doi.org/10.3390/polym9070253 - 29 Jun 2017

Cited by 17 | Viewed by 5730

Abstract

Chitosan is a natural copolymer generally available in pharmaceutical and food powders associated with drugs, vitamins, and nutraceuticals. This study focused on monitoring the effect of the morphology and structural features of the chitosan particles for controlling the release profile of the active [...] Read more.

Chitosan is a natural copolymer generally available in pharmaceutical and food powders associated with drugs, vitamins, and nutraceuticals. This study focused on monitoring the effect of the morphology and structural features of the chitosan particles for controlling the release profile of the active pharmaceutical ingredient (API) propranolol hydrochloride. Chitosan with distinct molecular mass (low and medium) were used in the formulations as crystalline and irregular particles from commercial raw material, or as spherical, uniform, and amorphous spray-dried particles. The API–copolymer interactions were assessed when adding the drug before (drug-loaded particles) or after the spray drying (only mixed with blank particles). The formulations were further compared with physical mixtures of the API with chitin and microcrystalline cellulose. The scanning electron microscopy (SEM) images, surface area, particle size measurements, X-ray diffraction (XRD) analysis and drug loading have supported the drug release behavior. The statistical analysis of experimental data demonstrated that it was possible to control the drug release behavior (immediate or slow drug release) from chitosan powders using different types of particles. Full article

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