Polymers

25 pages, 4922 KiB

Open AccessEditor’s ChoiceArticle

Ecological Design of New Efficient Energy-Performance Construction Materials with Rigid Polyurethane Foam Waste

by Raúl Briones-Llorente, Ricardo Barbosa, Manuela Almeida, Eduardo Atanasio Montero García and Ángel Rodríguez Saiz

Polymers 2020, 12(5), 1048; https://doi.org/10.3390/polym12051048 - 3 May 2020

Cited by 18 | Viewed by 3605

Abstract

An ecological mortar is designed from industrial sub-products, with the objective of utilizing both the slag residues, generated during steel manufacturing processes, and the waste from Polyurethane Foam (PF) panels, generated during refrigerator chamber manufacturing processes. The ecological mortar design involves the dosing [...] Read more.

An ecological mortar is designed from industrial sub-products, with the objective of utilizing both the slag residues, generated during steel manufacturing processes, and the waste from Polyurethane Foam (PF) panels, generated during refrigerator chamber manufacturing processes. The ecological mortar design involves the dosing of Electric Arc Furnace (EAF) slag, together with finely ground Polyurethane Foam, cement, and additives. An energy efficient prefabricated block is designed with the mortar, for use in construction, and its energy performance is assessed as a material inserted within the envelope of a service sector (hospital) building, either as an exterior skin, or as an enclosing component within the façade interior. The main contribution of this research is the characterization of the thermo-physical and mechanical properties of a new prefabricated panel made with recycled materials. The full characterization of the properties of these new materials is presented and discussed. The new prefabricated panel demonstrates adequate thermo-mechanical characteristics as a substitute for traditional materials, while improving the sustainability of the building. As a secondary objective, the energy behaviour of the new panels when integrated in a real building is presented by means of a case study simulation. The use of computational thermal simulation confirmed that the properties of the prefabricated block influenced the annual thermal demand of the building for heating and cooling. Improvements to the thermal inertia of the building envelope were also confirmed with the inclusion of PF waste, giving the mortar an energy performance that was similar to conventional materials, in such a way that its use in façade construction may be validated, in addition to its environmental benefits, due to it having been manufactured with critical recycled industrial waste such as EAF slag and PF, thereby contributing to both the circular economy and sustainable development. Full article

(This article belongs to the Special Issue Polymers and the Circular Economy Model)

► Show Figures

Figure 1

14 pages, 4399 KiB

Open AccessEditor’s ChoiceArticle

Preparation of Nanocomposite-Based High Performance Organic Field Effect Transistor via Solution Floating Method and Mechanical Property Evaluation

by Youn Kim, Yeon Ju Kwon, Seungwan Ryu, Cheol Jin Lee and Jea Uk Lee

Polymers 2020, 12(5), 1046; https://doi.org/10.3390/polym12051046 - 2 May 2020

Cited by 5 | Viewed by 3299

Abstract

We demonstrate that using nanocomposite thin films consisting of semiconducting polymer, poly(3-hexylthiophene) (P3HT), and electrochemically exfoliated graphene (EEG) for the active channel layer of organic field-effect transistors (OFETs) improves both device performances and mechanical properties. The nanocomposite film was developed by directly blending [...] Read more.

We demonstrate that using nanocomposite thin films consisting of semiconducting polymer, poly(3-hexylthiophene) (P3HT), and electrochemically exfoliated graphene (EEG) for the active channel layer of organic field-effect transistors (OFETs) improves both device performances and mechanical properties. The nanocomposite film was developed by directly blending P3HT solution with a dispersion of EEG at various weight proportions and simply transferring to an Si/SiO2 substrate by the solution floating method. The OFET based on P3HT/EEG nanocomposite film showed approximately twice higher field-effect mobility of 0.0391 cm²·V⁻¹·s⁻¹ and one order of magnitude greater on/off ratio of ~10⁴ compared with the OFET based on pristine P3HT. We also measured the mechanical properties of P3HT/EEG nanocomposite film via film-on-elastomer methods, which confirms that the P3HT/EEG nanocomposite film exhibited approximately 2.4 times higher modulus (3.29 GPa) than that of the P3HT film (1.38 GPa), while maintaining the good bending flexibility and durability over 10.0% of bending strain and bending cycles (1000 cycles). It was proved that the polymer hybridization technique, which involves adding EEG to a conjugated polymer, is a powerful route for enhancing both device performances and mechanical properties while maintaining the flexible characteristics of OFET devices. Full article

(This article belongs to the Special Issue Polymer and Carbon Materials Engineering)

► Show Figures

Graphical abstract

26 pages, 6064 KiB

Open AccessEditor’s ChoiceArticle

One-Step Preparation of Antifouling Polysulfone Ultrafiltration Membranes via Modification by a Cationic Polyelectrolyte Based on Polyacrylamide

by Tatiana V. Plisko, Alexandr V. Bildyukevich, Katsiaryna S. Burts, Sergey S. Ermakov, Anastasia V. Penkova, Anna I. Kuzminova, Maria E. Dmitrenko, Tatiana A. Hliavitskaya and Mathias Ulbricht

Polymers 2020, 12(5), 1017; https://doi.org/10.3390/polym12051017 - 30 Apr 2020

Cited by 20 | Viewed by 3627

Abstract

A novel method for one-step preparation of antifouling ultrafiltration membranes via a non-solvent induced phase separation (NIPS) technique is proposed. It involves using aqueous 0.05–0.3 wt.% solutions of cationic polyelectrolyte based on a copolymer of acrylamide and 2-acryloxyethyltrimethylammonium chloride (Praestol 859) as a [...] Read more.

A novel method for one-step preparation of antifouling ultrafiltration membranes via a non-solvent induced phase separation (NIPS) technique is proposed. It involves using aqueous 0.05–0.3 wt.% solutions of cationic polyelectrolyte based on a copolymer of acrylamide and 2-acryloxyethyltrimethylammonium chloride (Praestol 859) as a coagulant in NIPS. A systematic study of the effect of the cationic polyelectrolyte addition to the coagulant on the structure, performance and antifouling stability of polysulfone membranes was carried out. The methods for membrane characterization involved scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), contact angle and zeta-potential measurements and evaluation of the permeability, rejection and antifouling performance in human serum albumin solution and surface water ultrafiltration. It was revealed that in the presence of cationic polyelectrolyte in the coagulation bath, its concentration has a major influence on the rate of “solvent–non-solvent” exchange and thus also on the rate of phase separation which significantly affects membrane structure. The immobilization of cationic polyelectrolyte macromolecules into the selective layer was confirmed by FTIR spectroscopy. It was revealed that polyelectrolyte macromolecules predominately immobilize on the surface of the selective layer and not on the bottom layer. Membrane modification was found to improve the hydrophilicity of the selective layer, to increase surface roughness and to change zeta-potential which yields the substantial improvement of membrane antifouling stability toward natural organic matter and human serum albumin. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

► Show Figures

Graphical abstract

27 pages, 6394 KiB

Open AccessEditor’s ChoiceArticle

Enhancement of Oil Palm Waste Nanoparticles on the Properties and Characterization of Hybrid Plywood Biocomposites

by Arif Nuryawan, C. K. Abdullah, Che Mohamad Hazwan, N. G. Olaiya, Esam Bashir Yahya, Iwan Risnasari, Nanang Masruchin, M. S. Baharudin, Hasmawi Khalid and H. P. S. Abdul Khalil

Polymers 2020, 12(5), 1007; https://doi.org/10.3390/polym12051007 - 27 Apr 2020

Cited by 25 | Viewed by 4812

Abstract

Using oil palm trunk (OPT) layered with empty fruit bunch (EFB), so-called hybrid plywood enhanced with palm oil ash nanoparticles, with phenol-formaldehyde (PF) resin as a binder, was produced in this study. The phenol-formaldehyde (PF) resins filled with different loading of oil palm [...] Read more.

Using oil palm trunk (OPT) layered with empty fruit bunch (EFB), so-called hybrid plywood enhanced with palm oil ash nanoparticles, with phenol-formaldehyde (PF) resin as a binder, was produced in this study. The phenol-formaldehyde (PF) resins filled with different loading of oil palm ash (OPA) nanoparticles were prepared and used as glue for layers of the oil palm trunk (OPT) veneer and empty fruit bunch fibre mat. The resulting hybrid plywood produced was characterised. The physical, mechanical, thermal, and morphological properties of the hybrid plywood panels were investigated. The results obtained showed that the presence of OPA nanoparticles significantly affected the physical, mechanical, and thermal properties of the plywood panels. Significant improvements in dimension from water absorption and thickness swelling experiments were obtained for the plywood panels with the highest OPA nanoparticles loading in PF resin. The mechanical properties indicated that plywood composites showed improvement in flexural, shear, and impact properties until a certain loading of OPA nanoparticles in PF resin. Fracture surface morphology also showed the effectiveness of OPA nanoparticles in the reduction of layer breakage due to force and stress distribution. The thermal stability performance showed that PF filled OPA nanoparticles contributed to the thermal stability of the plywood panels. Therefore, the results obtained in this study showed that OPA nanoparticles certainly improved the characteristic of the hybrid plywood. Full article

(This article belongs to the Special Issue Multifunctional Ecocomposites)

► Show Figures

Figure 1

11 pages, 2759 KiB

Open AccessEditor’s ChoiceArticle

Preparation and Characteristics of Wet-Spun Filament Made of Cellulose Nanofibrils with Different Chemical Compositions

by Chan-Woo Park, Ji-Soo Park, Song-Yi Han, Eun-Ah Lee, Gu-Joong Kwon, Young-Ho Seo, Jae-Gyoung Gwon, Sun-Young Lee and Seung-Hwan Lee

Polymers 2020, 12(4), 949; https://doi.org/10.3390/polym12040949 - 19 Apr 2020

Cited by 11 | Viewed by 3614

Abstract

In this study, wet-spun filaments were prepared using lignocellulose nanofibril (LCNF), with 6.0% and 13.0% of hemicellulose and lignin, respectively, holocellulose nanofibril (HCNF), with 37% hemicellulose, and nearly purified-cellulose nanofibril (NP-CNF) through wet-disk milling followed by high-pressure homogenization. The diameter was observed to [...] Read more.

In this study, wet-spun filaments were prepared using lignocellulose nanofibril (LCNF), with 6.0% and 13.0% of hemicellulose and lignin, respectively, holocellulose nanofibril (HCNF), with 37% hemicellulose, and nearly purified-cellulose nanofibril (NP-CNF) through wet-disk milling followed by high-pressure homogenization. The diameter was observed to increase in the order of NP-CNF ≤ HCNF < LCNF. The removal of lignin improved the defibrillation efficiency, thus increasing the specific surface area and filtration time. All samples showed the typical X-ray diffraction pattern of cellulose I. The orientation of CNFs in the wet-spun filaments was observed to increase at a low concentration of CNF suspensions and high spinning rate. The increase in the CNF orientation improved the tensile strength and elastic modulus of the wet-spun filaments. The tensile strength of the wet-spun filaments decreased in the order of HCNF > NP-CNF > LCNF. Full article

(This article belongs to the Special Issue Nanocellulose Based Functional Materials)

► Show Figures

Graphical abstract

22 pages, 2274 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Tissue Adhesives for Clinical Medicine

by Liangpeng Ge and Shixuan Chen

Polymers 2020, 12(4), 939; https://doi.org/10.3390/polym12040939 - 18 Apr 2020

Cited by 92 | Viewed by 12339

Abstract

Tissue adhesives have attracted more attention to the applications of non-invasive wound closure. The purpose of this review article is to summarize the recent progress of developing tissue adhesives, which may inspire researchers to develop more outstanding tissue adhesives. It begins with a [...] Read more.

Tissue adhesives have attracted more attention to the applications of non-invasive wound closure. The purpose of this review article is to summarize the recent progress of developing tissue adhesives, which may inspire researchers to develop more outstanding tissue adhesives. It begins with a brief introduction to the emerging potential use of tissue adhesives in the clinic. Next, several critical mechanisms for adhesion are discussed, including van der Waals forces, capillary forces, hydrogen bonding, static electric forces, and chemical bonds. This article further details the measurement methods of adhesion and highlights the different types of adhesive, including natural or biological, synthetic and semisynthetic, and biomimetic adhesives. Finally, this review article concludes with remarks on the challenges and future directions for design, fabrication, and application of tissue adhesives in the clinic. This review article has promising potential to provide novel creative design principles for the generation of future tissue adhesives. Full article

(This article belongs to the Special Issue Advanced Polymeric Biomaterials for Tissue Engineering)

► Show Figures

Figure 1

15 pages, 4790 KiB

Open AccessEditor’s ChoiceArticle

Bio-Based Coatings for Food Metal Packaging Inspired in Biopolyester Plant Cutin

by José J. Benítez, Sonja Osbild, Susana Guzman-Puyol, Antonio Heredia and José A. Heredia-Guerrero

Polymers 2020, 12(4), 942; https://doi.org/10.3390/polym12040942 - 18 Apr 2020

Cited by 14 | Viewed by 5506

Abstract

Metals used for food canning such as aluminum (Al), chromium-coated tin-free steel (TFS) and electrochemically tin-plated steel (ETP) were coated with a 2–3-µm-thick layer of polyaleuritate, the polyester resulting from the self-esterification of naturally-occurring 9,10,16-trihydroxyhexadecanoic (aleuritic) acid. The kinetic of the esterification was [...] Read more.

Metals used for food canning such as aluminum (Al), chromium-coated tin-free steel (TFS) and electrochemically tin-plated steel (ETP) were coated with a 2–3-µm-thick layer of polyaleuritate, the polyester resulting from the self-esterification of naturally-occurring 9,10,16-trihydroxyhexadecanoic (aleuritic) acid. The kinetic of the esterification was studied by FTIR spectroscopy; additionally, the catalytic activity of the surface layer of chromium oxide on TFS and, in particular, of tin oxide on ETP, was established. The texture, gloss and wettability of coatings were characterized by AFM, UV-Vis total reflectance and static water contact angle (WCA) measurements. The resistance of the coatings to solvents was also determined and related to the fraction of unreacted polyhydroxyacid. The occurrence of an oxidative diol cleavage reaction upon preparation in air induced a structural modification of the polyaleuritate layer and conferred upon it thermal stability and resistance to solvents. The promoting effect of the tin oxide layer in such an oxidative cleavage process fosters the potential of this methodology for the design of effective long-chain polyhydroxyester coatings on ETP. Full article

(This article belongs to the Special Issue Sustainable Bio-Based Polymers: Towards a Circular Bioeconomy)

► Show Figures

Figure 1

38 pages, 2947 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Bioplastics: Application and Biodegradation

by Tanja Narancic, Federico Cerrone, Niall Beagan and Kevin E. O’Connor

Polymers 2020, 12(4), 920; https://doi.org/10.3390/polym12040920 - 15 Apr 2020

Cited by 197 | Viewed by 26882

Abstract

The success of oil-based plastics and the continued growth of production and utilisation can be attributed to their cost, durability, strength to weight ratio, and eight contributions to the ease of everyday life. However, their mainly single use, durability and recalcitrant nature have [...] Read more.

The success of oil-based plastics and the continued growth of production and utilisation can be attributed to their cost, durability, strength to weight ratio, and eight contributions to the ease of everyday life. However, their mainly single use, durability and recalcitrant nature have led to a substantial increase of plastics as a fraction of municipal solid waste. The need to substitute single use products that are not easy to collect has inspired a lot of research towards finding sustainable replacements for oil-based plastics. In addition, specific physicochemical, biological, and degradation properties of biodegradable polymers have made them attractive materials for biomedical applications. This review summarises the advances in drug delivery systems, specifically design of nanoparticles based on the biodegradable polymers. We also discuss the research performed in the area of biophotonics and challenges and opportunities brought by the design and application of biodegradable polymers in tissue engineering. We then discuss state-of-the-art research in the design and application of biodegradable polymers in packaging and emphasise the advances in smart packaging development. Finally, we provide an overview of the biodegradation of these polymers and composites in managed and unmanaged environments. Full article

(This article belongs to the Special Issue Recent Advances in Bioplastics II)

► Show Figures

Figure 1

13 pages, 3053 KiB

Open AccessEditor’s ChoiceArticle

Preparation of PVA Fluorescent Gel and Luminescence of Europium Sensitized by Terbium (III)

by Yifan Wei, Zhengquan Fu, Hao Zhao, Ruiqi Liang, Chengyu Wang, Di Wang and Jian Li

Polymers 2020, 12(4), 893; https://doi.org/10.3390/polym12040893 - 12 Apr 2020

Cited by 13 | Viewed by 3568

Abstract

Polyvinyl alcohol (PVA) gel has a very wide range of applications in agriculture, military, industry, and other fields. As a widely used water-soluble polymer, PVA has good mechanical properties, excellent spinnability, good hydrophilicity, remarkable physical and chemical stability, good film formation, is non-polluting, [...] Read more.

Polyvinyl alcohol (PVA) gel has a very wide range of applications in agriculture, military, industry, and other fields. As a widely used water-soluble polymer, PVA has good mechanical properties, excellent spinnability, good hydrophilicity, remarkable physical and chemical stability, good film formation, is non-polluting, and exhibits good natural degradation and biocompatibility. It is an ideal gel preparation material. Incorporation of rare-earth elements into PVA polymers can be used to prepare rare-earth luminescent gel materials. Results show that the luminescent efficiency of complexes is mainly related to their structure, ligand substituents, synergists, and the electronic configuration of doped rare-earth ions. Fluorescent gel films were prepared by adding europium, terbium, and europium/terbium co-doped into PVA, and their fluorescence properties were compared and analyzed. It was found that, in addition to the above factors, the sensitization of terbium to europium, and the fluorescence-quenching effect of hydroxyl groups, will influence the fluorescence properties. This has opened a new route for the application of rare-earth materials and may have value in the field of new materials. Full article

► Show Figures

Graphical abstract

15 pages, 1648 KiB

Open AccessEditor’s ChoiceArticle

Supramolecular Dimerization in a Polymer Melt from Small-Angle X-ray Scattering and Rheology: A Miscible Model System

by Mariapaola Staropoli, Margarita Kruteva, Jürgen Allgaier, Andreas Wischnewski and Wim Pyckhout-Hintzen

Polymers 2020, 12(4), 880; https://doi.org/10.3390/polym12040880 - 10 Apr 2020

Cited by 2 | Viewed by 2737

Abstract

We present a structural and dynamic study on the simplest supramolecular hetero-association, recently investigated by the authors to prepare architectural homogeneous structures in the melt state, based on the bio-inspired hydrogen-bonding of thymine/diaminotriazine (thy–DAT) base-pairs. In the combination with an amorphous low T [...] Read more.

We present a structural and dynamic study on the simplest supramolecular hetero-association, recently investigated by the authors to prepare architectural homogeneous structures in the melt state, based on the bio-inspired hydrogen-bonding of thymine/diaminotriazine (thy–DAT) base-pairs. In the combination with an amorphous low T_g poly(butylene oxide) (PBO), no micellar structures are formed, which is expected for nonpolar polymers because of noncompatibility with the highly polar supramolecular groups. Instead, a clear polymer-like transient architecture is retrieved. This makes the heterocomplementary thy–DAT association an ideal candidate for further exploitation of the hydrogen-bonding ability in the bulk for self-healing purposes, damage management in rubbers or even the development of easily processable branched polymers with built-in plasticizer. In the present work, we investigate the temperature range from T_g + 20 °C to T_g + 150 °C of an oligomeric PBO using small-angle X-ray scattering (SAXS) and linear rheology on the pure thy and pure DAT monofunctionals and on an equimolar mixture of thy/DAT oligomers. The linear rheology performed at low temperature is found to correspond to fully closed-state dimeric configurations. At intermediate temperatures, SAXS probes the equilibrium between open and closed states of the thy–DAT mixtures. The temperature-dependent association constant in the full range between open and closed H-bonds and an enhancement of the monomeric friction coefficient due to the groups is obtained. The thy–DAT association in the melt is more stable than the DAT–DAT, whereas the thy–thy association seems to involve additional long-lived interactions. Full article

(This article belongs to the Special Issue Multifunctional Supramolecular Polymers)

► Show Figures

Figure 1

14 pages, 3380 KiB

Open AccessEditor’s ChoiceArticle

Injectable Click Polypeptide Hydrogels via Tetrazine-Norbornene Chemistry for Localized Cisplatin Release

by Zhen Zhang, Chaoliang He and Xuesi Chen

Polymers 2020, 12(4), 884; https://doi.org/10.3390/polym12040884 - 10 Apr 2020

Cited by 11 | Viewed by 4866

Abstract

Injectable, covalently cross-linked hydrogels have been widely investigated in drug delivery systems due to their superior mechanical properties and long-term stability. Conventional covalently cross-linked hydrogels are formed by chemical reactions that may interfere with natural biochemical processes. In this work, we developed an [...] Read more.

Injectable, covalently cross-linked hydrogels have been widely investigated in drug delivery systems due to their superior mechanical properties and long-term stability. Conventional covalently cross-linked hydrogels are formed by chemical reactions that may interfere with natural biochemical processes. In this work, we developed an injectable polypeptide hydrogel via an inverse electron demand Diels-Alder reaction between norbornene modified poly(L-glutamic acid) (PLG-Norb) and tetrazine functionalized four-arm poly(ethylene glycol) (4aPEG-T) for localized release of cisplatin (CDDP). The rapid and bioorthogonal click reaction allowed for hydrogel formation within a few minutes after mixing the two polymer solutions in phosphate buffer saline (PBS). Dynamic mechanical analysis suggested that the storage modulus of the hydrogel could be readily tuned by changing the polymer concentration and the molar ratio of the two functional groups. The carboxyl groups of PLG-Norb were used to form polymer–metal complexation with CDDP, and the controlled release of the antitumor drug was achieved in PBS. The CDDP-loaded hydrogel displayed an antitumor effect against MCF-7 cells in vitro, through S phase cell cycle arrest. After subcutaneous injection in rats, the hydrogel was rapidly formed in situ and showed good stability in vivo. In an MCF-7-bearing nude mice model, the CDDP-loaded hydrogel exhibited an improved antitumor effect with reduced systemic toxicity. Overall, the injectable click polypeptide hydrogel shows considerable potential as a platform for localized and sustained delivery of antitumor drugs. Full article

(This article belongs to the Special Issue Polypeptide Polymers)

► Show Figures

Figure 1

11 pages, 6348 KiB

Open AccessEditor’s ChoiceArticle

A Simplified 2D Numerical Simulation of Photopolymerization Kinetics and Oxygen Diffusion–Reaction for the Continuous Liquid Interface Production (CLIP) System

by Kentaro Taki

Polymers 2020, 12(4), 875; https://doi.org/10.3390/polym12040875 - 10 Apr 2020

Cited by 14 | Viewed by 3378

Abstract

Additive manufacturing is a versatile technology for producing customized 3D products. In 2015, the Continuous Liquid Interface Production (CLIP) system was developed as a part of projection-type, UV-curable resin 3D printers. The CLIP system utilized the dead zone where oxygen inhibition occurs and [...] Read more.

Additive manufacturing is a versatile technology for producing customized 3D products. In 2015, the Continuous Liquid Interface Production (CLIP) system was developed as a part of projection-type, UV-curable resin 3D printers. The CLIP system utilized the dead zone where oxygen inhibition occurs and prevents the UV-cured product from adhering to the UV illumination window. The CLIP system successfully produced complex shapes in a short time. This study investigated how the relationship between the photopolymerization rate, oxygen inhibition rate, and oxygen diffusion rate affects the shape of the product by means of a numerical simulation of the photopolymerization kinetics with oxygen diffusion and reaction. The results indicate that the vertical production speed and transmittance of UV light are crucial to controlling the conversion and shape precision of products. Full article

(This article belongs to the Special Issue 3D/4D Printing with Polymers, Polymer Hydrogels and Adaptive Soft Materials)

► Show Figures

Graphical abstract

17 pages, 2607 KiB

Open AccessEditor’s ChoiceArticle

Impact of Current and Temperature on Extremely Low Loading Epoxy-CNT Conductive Composites

by Brian Earp, Jonathan Phillips, Dragoslav Grbovic, Stephen Vidmar, Matthew Porter and Claudia C. Luhrs

Polymers 2020, 12(4), 867; https://doi.org/10.3390/polym12040867 - 10 Apr 2020

Cited by 8 | Viewed by 2561

Abstract

Carbon nanotube (CNT) conductive composites have attracted significant attention for their potential use in applications such as electrostatic dissipation and/or electromagnetic interference shielding. The focus of this work is to evaluate resistivity trends of extremely low loading (<0.1 wt%) epoxy-CNT composites that lack [...] Read more.

Carbon nanotube (CNT) conductive composites have attracted significant attention for their potential use in applications such as electrostatic dissipation and/or electromagnetic interference shielding. The focus of this work is to evaluate resistivity trends of extremely low loading (<0.1 wt%) epoxy-CNT composites that lack a connected CNT network, but still present electrical conductivity values appropriate for those uses. The impact of current, temperature, and cycle life on electrical properties are here identified and tied to possible performance limits. At extremely low loadings, the CNT content is not sufficient to form a completely interconnected grid, thus, electrons must travel through insulating media. While still in the semi-conductor range, resistivity values are observed to decrease with increasing direct current and demonstrate a non-ohmic behavior. CNT epoxy composites were subjected to elevated currents and/or temperatures over diverse periods of time to examine impacts on resistivity. Microstructural analyses of composite samples were conducted to observe signs of damage for specimens taken to extreme temperatures/currents. An understanding of the electrical conductivity characteristics of extremely low loading epoxy-CNT composites and their failure mechanisms will aid in understanding risks associated with their use in challenging environments that may include high temperatures, high currents, and/or high frequencies. Full article

(This article belongs to the Special Issue Carbonaceous Fillers-Reinforced Polymer Matrix Composite for Multi-Functional Applications)

► Show Figures

Graphical abstract

14 pages, 4016 KiB

Open AccessEditor’s ChoiceArticle

Highly Deformable Porous Electromagnetic Wave Absorber Based on Ethylene–Propylene–Diene Monomer/Multiwall Carbon Nanotube Nanocomposites

by Hasti Bizhani, Ali Asghar Katbab, Emil Lopez-Hernandez, Jose Miguel Miranda and Raquel Verdejo

Polymers 2020, 12(4), 858; https://doi.org/10.3390/polym12040858 - 8 Apr 2020

Cited by 17 | Viewed by 3405

Abstract

The need for electromagnetic interference (EMI) shields has risen over the years as the result of our digitally and highly connected lifestyle. This work reports on the development of one such shield based on vulcanized rubber foams. Nanocomposites of ethylene–propylene–diene monomer (EPDM) rubber [...] Read more.

The need for electromagnetic interference (EMI) shields has risen over the years as the result of our digitally and highly connected lifestyle. This work reports on the development of one such shield based on vulcanized rubber foams. Nanocomposites of ethylene–propylene–diene monomer (EPDM) rubber and multiwall carbon nanotubes (MWCNTs) were prepared via hot compression molding using a chemical blowing agent as foaming agent. MWCNTs accelerated the cure and led to high shear-thinning behavior, indicative of the formation of a 3D interconnected physical network. Foamed nanocomposites exhibited lower electrical percolation threshold than their solid counterparts. Above percolation, foamed nanocomposites displayed EMI absorption values of 28–45 dB in the frequency range of the X-band. The total EMI shielding efficiency of the foams was insignificantly affected by repeated bending with high recovery behavior. Our results highlight the potential of cross-linked EPDM/MWCNT foams as a lightweight EM wave absorber with high flexibility and deformability. Full article

(This article belongs to the Special Issue Functionalization Procedures and Emerging Applications of Polymer Foams and Composites)

► Show Figures

Graphical abstract

38 pages, 2616 KiB

Open AccessEditor’s ChoiceReview

Proteins and Peptides as Important Modifiers of the Polymer Scaffolds for Tissue Engineering Applications—A Review

by Katarzyna Klimek and Grazyna Ginalska

Polymers 2020, 12(4), 844; https://doi.org/10.3390/polym12040844 - 6 Apr 2020

Cited by 123 | Viewed by 9433

Abstract

Polymer scaffolds constitute a very interesting strategy for tissue engineering. Even though they are generally non-toxic, in some cases, they may not provide suitable support for cell adhesion, proliferation, and differentiation, which decelerates tissue regeneration. To improve biological properties, scaffolds are frequently enriched [...] Read more.

Polymer scaffolds constitute a very interesting strategy for tissue engineering. Even though they are generally non-toxic, in some cases, they may not provide suitable support for cell adhesion, proliferation, and differentiation, which decelerates tissue regeneration. To improve biological properties, scaffolds are frequently enriched with bioactive molecules, inter alia extracellular matrix proteins, adhesive peptides, growth factors, hormones, and cytokines. Although there are many papers describing synthesis and properties of polymer scaffolds enriched with proteins or peptides, few reviews comprehensively summarize these bioactive molecules. Thus, this review presents the current knowledge about the most important proteins and peptides used for modification of polymer scaffolds for tissue engineering. This paper also describes the influence of addition of proteins and peptides on physicochemical, mechanical, and biological properties of polymer scaffolds. Moreover, this article sums up the major applications of some biodegradable natural and synthetic polymer scaffolds modified with proteins and peptides, which have been developed within the past five years. Full article

(This article belongs to the Special Issue Biodegradable Polymer Scaffolds for Tissue Engineering)

► Show Figures

Graphical abstract

59 pages, 21028 KiB

Open AccessEditor’s ChoiceReview

Application of the Finite Element Method in the Analysis of Composite Materials: A Review

by Sarah David Müzel, Eduardo Pires Bonhin, Nara Miranda Guimarães and Erick Siqueira Guidi

Polymers 2020, 12(4), 818; https://doi.org/10.3390/polym12040818 - 4 Apr 2020

Cited by 104 | Viewed by 19605

Abstract

The use of composite materials in several sectors, such as aeronautics and automotive, has been gaining distinction in recent years. However, due to their high costs, as well as unique characteristics, consequences of their heterogeneity, they present challenging gaps to be studied. As [...] Read more.

The use of composite materials in several sectors, such as aeronautics and automotive, has been gaining distinction in recent years. However, due to their high costs, as well as unique characteristics, consequences of their heterogeneity, they present challenging gaps to be studied. As a result, the finite element method has been used as a way to analyze composite materials subjected to the most distinctive situations. Therefore, this work aims to approach the modeling of composite materials, focusing on material properties, failure criteria, types of elements and main application sectors. From the modeling point of view, different levels of modeling—micro, meso and macro, are presented. Regarding properties, different mechanical characteristics, theories and constitutive relationships involved to model these materials are presented. The text also discusses the types of elements most commonly used to simulate composites, which are solids, peel, plate and cohesive, as well as the various failure criteria developed and used for the simulation of these materials. In addition, the present article lists the main industrial sectors in which composite material simulation is used, and their gains from it, including aeronautics, aerospace, automotive, naval, energy, civil, sports, manufacturing and even electronics. Full article

► Show Figures

Graphical abstract

10 pages, 2881 KiB

Open AccessEditor’s ChoiceArticle

Morphological Transitions of Photoresponsive Vesicles from Amphiphilic Polypeptoid Copolymers for Controlled Release

by Xu Yang, Zhiwei Wang and Jing Sun

Polymers 2020, 12(4), 798; https://doi.org/10.3390/polym12040798 - 3 Apr 2020

Cited by 6 | Viewed by 2609

Abstract

Photoresponsive polymers have attracted increasing interest for a variety of applications. Here, we report a family of photoresponsive polypeptoid-based copolymer poly(ethylene glycol)-b-poly(N-(S-(o-nitrobenzyl)-thioethyl) glycine)-co-poly(N-(2-phenylethyl) glycine) (PEG-b-PNSN-co-PNPE) synthesized by the controlled ring-opening polymerization (ROP) technique. [...] Read more.

Photoresponsive polymers have attracted increasing interest for a variety of applications. Here, we report a family of photoresponsive polypeptoid-based copolymer poly(ethylene glycol)-b-poly(N-(S-(o-nitrobenzyl)-thioethyl) glycine)-co-poly(N-(2-phenylethyl) glycine) (PEG-b-PNSN-co-PNPE) synthesized by the controlled ring-opening polymerization (ROP) technique. The key feature of the design is to incorporate both o-nitrobenzyl group moiety to offer the photoresponsive property and phenethyl residues to tune the structural and amphiphilic property of the system. We demonstrate that the cleavage degree of the o-nitrobenzyl group can reach to 100% upon UV-irradiation. With delicate design, a photoresponsive vesicle-to-sphere transition has been observed that facilitates the release of the encapsulants. This work provides a facile approach to prepare a type of photoresponsive polymers with tunable properties for drug delivery. Full article

(This article belongs to the Special Issue Polypeptide Polymers)

► Show Figures

Graphical abstract

16 pages, 4731 KiB

Open AccessEditor’s ChoiceArticle

Synthesis and Conformational Characteristics of Thermosensitive Star-Shaped Six-Arm Polypeptoids

by Tatyana Kirila, Anna Smirnova, Alla Razina, Andrey Tenkovtsev and Alexander Filippov

Polymers 2020, 12(4), 800; https://doi.org/10.3390/polym12040800 - 3 Apr 2020

Cited by 11 | Viewed by 2529

Abstract

Star-shaped six-arm poly-2-alkyl-2-oxazine and poly-2-alkyl-2-oxazoline with hexaaza [2₆]orthoparacyclophane derivative core were synthesized successfully using cationic ring-opening polymerization. Conformational behavior of prepared polymer stars were investigated by the methods of molecular hydrodynamics and optics in molecular dispersed solutions. It was shown that [...] Read more.

Star-shaped six-arm poly-2-alkyl-2-oxazine and poly-2-alkyl-2-oxazoline with hexaaza [2₆]orthoparacyclophane derivative core were synthesized successfully using cationic ring-opening polymerization. Conformational behavior of prepared polymer stars were investigated by the methods of molecular hydrodynamics and optics in molecular dispersed solutions. It was shown that conformation characteristics of star-shaped polypeptoids depends on arm length, while the chemical structure weakly affects the behavior of the studied polymers in solutions. This behavior is caused by the close equilibrium rigidity of arms. The star-shaped polypeptoids have relatively high intramolecular density. All synthesized stars exhibit LCST behavior. Phase separation temperature depends on arm structure. It is lower for poly-2-alkyl-2-oxazines, monomer units of which contains one methylene group more than monomers of poly-2-alkyl-2-oxazoline. Full article

(This article belongs to the Section Polymer Analysis and Characterization)

► Show Figures

Graphical abstract

20 pages, 4647 KiB

Open AccessEditor’s ChoiceReview

A Mini-Review on Anion Exchange and Chelating Polymers for Applications in Hydrometallurgy, Environmental Protection, and Biomedicine

by Piotr Cyganowski and Anna Dzimitrowicz

Polymers 2020, 12(4), 784; https://doi.org/10.3390/polym12040784 - 2 Apr 2020

Cited by 14 | Viewed by 3867

Abstract

The rapidly increasing demand for technologies aiming to resolve challenges of separations and environmental protection causes a sharp increase in the demand for ion exchange (IX) and chelating polymers. These unique materials can offer target-selective adsorption properties vital for the removal or recovery [...] Read more.

The rapidly increasing demand for technologies aiming to resolve challenges of separations and environmental protection causes a sharp increase in the demand for ion exchange (IX) and chelating polymers. These unique materials can offer target-selective adsorption properties vital for the removal or recovery of harmful and precious materials, where trace concentrations thereof make other techniques insufficient. Hence, recent achievements in syntheses of IX and chelating resins designed and developed in our research group are discussed within this mini-review. The aim of the present work is to reveal that, due to the diversified and unique physiochemical characteristics of the proposed materials, they are not limited to traditional separation techniques and could be used in multifunctional areas of applications, including catalysis, heat management, and biomedicine. Full article

(This article belongs to the Special Issue Colloid and Interface)

► Show Figures

Graphical abstract

15 pages, 1362 KiB

Open AccessEditor’s ChoiceArticle

Exploring Needle-Like Zinc Oxide Nanostructures for Improving Dental Resin Sealers: Design and Evaluation of Antibacterial, Physical and Chemical Properties

by Fabrício M Collares, Isadora M Garcia, Mariana Klein, Clarissa F Parolo, Felipe Antonio L Sánchez, Antônio Takimi, Carlos P Bergmann, Susana Maria W Samuel, Mary Anne Melo and Vicente CB Leitune

Polymers 2020, 12(4), 789; https://doi.org/10.3390/polym12040789 - 2 Apr 2020

Cited by 11 | Viewed by 3221

Abstract

This study aimed to evaluate the effect of needle-like zinc oxide nanostructures (ZnO-NN) on the physical, chemical, and antibacterial properties of experimental methacrylate-based dental sealers. ZnO-NN was synthesized and characterized. ZnO-NN was added to a co-monomer blend at 20, 30, and 40 wt.%. [...] Read more.

This study aimed to evaluate the effect of needle-like zinc oxide nanostructures (ZnO-NN) on the physical, chemical, and antibacterial properties of experimental methacrylate-based dental sealers. ZnO-NN was synthesized and characterized. ZnO-NN was added to a co-monomer blend at 20, 30, and 40 wt.%. One group without ZnO-NN was used as a control. The dental resin sealers were evaluated for their flow, film thickness, water sorption, solubility, radiopacity, degree of conversion (DC), dental-sealer interface characterization via micro-Raman, and antibacterial activity. ZnO-NN presented a mean needle diameter of 40 nm and 16 m²/g of surface area. There was no difference among groups containing ZnO-NN regarding their flow. The ZnO-NN addition significantly increased the film thickness. Water sorption and solubility tests showed no difference among groups. The radiopacity increased, and DC decreased with higher concentrations of ZnO-NN. Micro-Raman suggested that ZnO-NN was in close contact with root canal dentin. Overall, the incorporation of ZnO-NN provided an antibacterial effect against Enterococcus faecalis without a significant detrimental impact on the physical and chemical functionality of the material. The use of ZnO-NN as an inorganic filler is a potential application within dental materials intended for root canal treatment. Full article

(This article belongs to the Special Issue Polymer-Based Materials in Dentistry)

► Show Figures

Graphical abstract

23 pages, 4869 KiB

Open AccessEditor’s ChoiceArticle

A Statistical Study on the Development of Metronidazole-Chitosan-Alginate Nanocomposite Formulation Using the Full Factorial Design

by Hazem Abdul Kader Sabbagh, Samer Hasan Hussein-Al-Ali, Mohd Zobir Hussein, Zead Abudayeh, Rami Ayoub and Suha Mujahed Abudoleh

Polymers 2020, 12(4), 772; https://doi.org/10.3390/polym12040772 - 1 Apr 2020

Cited by 24 | Viewed by 3572

Abstract

The goal of this study was to develop and statistically optimize the metronidazole (MET), chitosan (CS) and alginate (Alg) nanoparticles (NP) nanocomposites (MET-CS-AlgNPs) using a (2¹ × 3¹ × 2¹) × 3 = 36 full factorial design (FFD) to [...] Read more.

The goal of this study was to develop and statistically optimize the metronidazole (MET), chitosan (CS) and alginate (Alg) nanoparticles (NP) nanocomposites (MET-CS-AlgNPs) using a (2¹ × 3¹ × 2¹) × 3 = 36 full factorial design (FFD) to investigate the effect of chitosan and alginate polymer concentrations and calcium chloride (CaCl₂) concentration ondrug loading efficiency(LE), particle size and zeta potential. The concentration of CS, Alg and CaCl₂ were taken as independent variables, while drug loading, particle size and zeta potential were taken as dependent variables. The study showed that the loading efficiency and particle size depend on the CS, Alg and CaCl₂ concentrations, whereas zeta potential depends only on the Alg and CaCl₂ concentrations. The MET-CS-AlgNPs nanocomposites were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and in vitro drug release studies. XRD datashowed that the crystalline properties of MET changed to an amorphous-like pattern when the nanocomposites were formed.The XRD pattern of MET-CS-AlgNPs showed reflections at 2θ = 14.2° and 22.1°, indicating that the formation of the nanocompositesprepared at the optimum conditions havea mean diameter of (165±20) nm, with a MET loading of (46.0 ± 2.1)% and a zeta potential of (−9.2 ± 0.5) mV.The FTIR data of MET-CS-AlgNPs showed some bands of MET, such as 3283, 1585 and 1413 cm⁻¹, confirming the presence of the drug in the MET-CS-AlgNPs nanocomposites. The TGA for the optimized sample of MET-CS-AlgNPs showed a 70.2% weight loss compared to 55.3% for CS-AlgNPs, and the difference is due to the incorporation of MET in the CS-AlgNPs for the formation of MET-CS-AlgNPs nanocomposites. The release of MET from the nanocomposite showed sustained-release properties, indicating the presence of an interaction between MET and the polymer. The nanocomposite shows a smooth surface and spherical shape. The release profile of MET from its MET-CS-AlgNPs nanocomposites was found to be governed by the second kinetic model (R² between 0.956–0.990) with more than 90% release during the first 50 h, which suggests that the release of the MET drug can be extended or prolonged via the nanocomposite formulation. Full article

(This article belongs to the Special Issue Polymeric Carriers for Biomedical and Nanomedicine Application)

► Show Figures

Graphical abstract

26 pages, 7328 KiB

Open AccessEditor’s ChoiceReview

Thermal Welding by the Third Phase Between Polymers: A Review for Ultrasonic Weld Technology Developments

by Jianhui Qiu, Guohong Zhang, Eiichi Sakai, Wendi Liu and Limin Zang

Polymers 2020, 12(4), 759; https://doi.org/10.3390/polym12040759 - 31 Mar 2020

Cited by 26 | Viewed by 6232

Abstract

Ultrasonic welding (USW) is a promising method for the welds between dissimilar materials. Ultrasonic thermal welding by the third phase (TWTP) method was proposed in combination with the formation of a third phase, which was confirmed as an effective technology for polymer welding [...] Read more.

Ultrasonic welding (USW) is a promising method for the welds between dissimilar materials. Ultrasonic thermal welding by the third phase (TWTP) method was proposed in combination with the formation of a third phase, which was confirmed as an effective technology for polymer welding between the two dissimilar materials compared with the traditional USW. This review focused on the advances of applying the ultrasonic TWTP for thermoplastic materials. The research development on the ultrasonic TWTP of polycarbonate (PC) and polymethyl methacrylate (PMMA), polylactic acid (PLA) and polyformaldehyde (POM), and PLA and PMMA are summarized according to the preparation of the third phase, welded strength, morphologies of rupture surfaces, thermal stability, and others. The review aimed at providing guidance for using ultrasonic TWTP in polymers and a basic understanding of the welding mechanism, i.e., interdiffusion and molecular motion mechanisms between the phases. Full article

(This article belongs to the Special Issue Processing and Molding of Polymers)

► Show Figures

Figure 1

13 pages, 3561 KiB

Open AccessEditor’s ChoiceArticle

Comparative Investigation on the Soil Burial Degradation Behaviour of Polymer Films for Agriculture before and after Photo-Oxidation

by Francesco Paolo La Mantia, Laura Ascione, Maria Chiara Mistretta, Marco Rapisarda and Paola Rizzarelli

Polymers 2020, 12(4), 753; https://doi.org/10.3390/polym12040753 - 30 Mar 2020

Cited by 50 | Viewed by 5578

Abstract

Polymer films based on biodegradable polymers, polyethylene (PE) and modified PE with oxo-degradable additive were prepared by film blowing. Carbon black (1%) was added to all the films. Commercial biodegradable Ecovio^® and Mater-Bi^® samples were used. Mechanical properties, soil burial degradation [...] Read more.

Polymer films based on biodegradable polymers, polyethylene (PE) and modified PE with oxo-degradable additive were prepared by film blowing. Carbon black (1%) was added to all the films. Commercial biodegradable Ecovio^® and Mater-Bi^® samples were used. Mechanical properties, soil burial degradation and surface wettability were investigated, before and after UV irradiation. Chemical modifications induced by UV and soil degradation, or a synergic effect, were highlighted by Attenuated Total Reflection-Fourier Transform Infra-Red (ATR-FTIR). Photo-oxidized film samples with an elongation at break equal to 50% and 0.5 the initial value were selected for the soil burial degradation test at 30 °C. Weight loss measurements were used to follow biodegradation in soil. Predictably, the degradation in soil was higher for biodegradable polymer-based films than for the PE-based ones. UV irradiation increased surface wettability and encouraged the disintegration in soil of all the samples. In fact, photo-oxidation produced a molar mass reduction and hydrophilic end groups, thus increasing surface erosion and weight loss. This paper not only supplies new criteria to evaluate the performance of biodegradable films in agriculture, before and after lifetime, but also provides a comparative analysis on the soil burial degradation behaviour with traditional ones. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Italy (2019,2020))

► Show Figures

Graphical abstract

25 pages, 3195 KiB

Open AccessEditor’s ChoiceReview

Influence of Nanoparticles on Thermal and Electrical Conductivity of Composites

by Divan Coetzee, Mohanapriya Venkataraman, Jiri Militky and Michal Petru

Polymers 2020, 12(4), 742; https://doi.org/10.3390/polym12040742 - 27 Mar 2020

Cited by 90 | Viewed by 7577

Abstract

This review analyzes thermal and electrically conductive properties of composites and how they can be influenced by the addition of special nanoparticles. Composite functional characteristics—such as thermal and electrical conductivity, phase changes, dimensional stability, magnetization, and modulus increase—are tuned by selecting suitable nanoparticle [...] Read more.

This review analyzes thermal and electrically conductive properties of composites and how they can be influenced by the addition of special nanoparticles. Composite functional characteristics—such as thermal and electrical conductivity, phase changes, dimensional stability, magnetization, and modulus increase—are tuned by selecting suitable nanoparticle filler material. The conductivity of composites can be related to the formation of conductive pathways as nanofiller materials form connections in the bulk of a composite matrix. With increasing use of nanomaterial containing composites and relatively little understanding of the toxicological effects thereof, adequate disposal and recyclability have become an increasing environmental concern. Full article

(This article belongs to the Special Issue Damage Mechanics of Polymer Composites)

► Show Figures

Figure 1

18 pages, 15255 KiB

Open AccessEditor’s ChoiceArticle

Synthesis, Physical, Mechanical and Antibacterial Properties of Nanocomposites Based on Poly(vinyl alcohol)/Graphene Oxide–Silver Nanoparticles

by Mónica Cobos, Iker De-La-Pinta, Guillermo Quindós, María Jesús Fernández and María Dolores Fernández

Polymers 2020, 12(3), 723; https://doi.org/10.3390/polym12030723 - 24 Mar 2020

Cited by 75 | Viewed by 5316

Abstract

The design of new materials with antimicrobial properties has emerged in response to the need for preventing and controlling the growth of pathogenic microorganisms without the use of antibiotics. In this study, partially reduced graphene oxide decorated with silver nanoparticles (GO–AgNPs) was incorporated [...] Read more.

The design of new materials with antimicrobial properties has emerged in response to the need for preventing and controlling the growth of pathogenic microorganisms without the use of antibiotics. In this study, partially reduced graphene oxide decorated with silver nanoparticles (GO–AgNPs) was incorporated as a reinforcing filler with antibacterial properties to poly(vinyl alcohol) (PVA) for preparation of poly(vinyl alcohol)/graphene oxide-silver nanoparticles nanocomposites (PVA/GO–AgNPs). AgNPs, spherical in shape and with an average size of 3.1 nm, were uniformly anchored on the partially reduced GO surface. PVA/GO–AgNPs nanocomposites showed exfoliated structures with improved thermal stability, tensile properties and water resistance compared to neat PVA. The glass transition and crystallization temperatures of the polymer matrix increased with the incorporation of the hybrid. The nanocomposites displayed antibacterial activity against Staphylococcus aureus and Escherichia coli in a filler content- and time-dependent manner. S. aureus showed higher susceptibility to PVA/GO–AgNPs films than E. coli. Inhibitory activity was higher when bacterial cells were in contact with nanocomposite films than when in contact with leachates coming out of the films. GO–AgNPs based PVA nanocomposites could find application as wound dressings for wound healing and infection prevention. Full article

(This article belongs to the Special Issue Metal- and Metal Hybrid-Filled Polymer Nanocomposites)

► Show Figures

Graphical abstract

11 pages, 3113 KiB

Open AccessEditor’s ChoiceArticle

Ferrocene-Based Conjugated Microporous Polymers Derived from Yamamoto Coupling for Gas Storage and Dye Removal

by Zhiqiang Tan, Huimin Su, Yiwen Guo, Huan Liu, Bo Liao, Abid Muhammad Amin and Qingquan Liu

Polymers 2020, 12(3), 719; https://doi.org/10.3390/polym12030719 - 24 Mar 2020

Cited by 36 | Viewed by 4769

Abstract

Conjugated microporous polymers (CMPs) have conjugated skeleton and permanent porosity, and exhibit huge potential in developing novel functional materials for resolving the challenging energy and environment issues. Metal-containing CMPs often exhibited unique properties. In the present manuscript, ferrocene-based conjugated microporous polymers (FcCMPs) were [...] Read more.

Conjugated microporous polymers (CMPs) have conjugated skeleton and permanent porosity, and exhibit huge potential in developing novel functional materials for resolving the challenging energy and environment issues. Metal-containing CMPs often exhibited unique properties. In the present manuscript, ferrocene-based conjugated microporous polymers (FcCMPs) were designed and synthesized with 1,1′-dibromoferrocene and 5,10,15,20-Tetrakis(4- bromophenyl) porphyrin (FcCMP-1) or Tetra (p-bromophenyl) methane (FcCMP-2) as building units via Yamamoto coupling. FcCMPs were amorphous, and exhibited excellent thermal and physicochemical stability. The BET surface area of FcCMP-1 and FcCMP-2 was 638 m²/g and 422 m²/g, respectively. In comparison with FcCMP-2, FcCMP-1 displayed better gas storage capacity due to higher porosity. FcCMPs were also used as an adsorbent for removal of methyl violet from aqueous solution, and exhibited excellent adsorption properties due to the interaction between electron-rich conjugated structure of the polymers and methyl violet with cationic groups. Moreover, FcCMPs could be extracted and regenerated by an eluent and then re-used for high efficient removal of methyl violet. Full article

(This article belongs to the Special Issue Porous Polymer Micro- and Nano-Structures)

► Show Figures

Graphical abstract

14 pages, 2845 KiB

Open AccessEditor’s ChoiceArticle

Material Properties Influencing the Charge Decay of Electret Filters and their Impact on Filtration Performance

by Jinwook Lee and Jooyoun Kim

Polymers 2020, 12(3), 721; https://doi.org/10.3390/polym12030721 - 24 Mar 2020

Cited by 59 | Viewed by 9088

Abstract

Electret filters as opposed to mechanical filters display the enhanced ability to capture airborne particles with the electrostatic attraction. However, the environmental aging during shelf-life or use may cancel its benefit by dissipating the charges. This work investigates the polymeric attributes influencing the [...] Read more.

Electret filters as opposed to mechanical filters display the enhanced ability to capture airborne particles with the electrostatic attraction. However, the environmental aging during shelf-life or use may cancel its benefit by dissipating the charges. This work investigates the polymeric attributes influencing the charge decay and the electrostatic filtration of electret filters, employing polymers with different dielectric constants (ε_r) and wettability. As accelerated aging, high temperature (120 °C) or high humidity (25 °C, 90% RH) was applied to the electret filters for 48 h. For the humidity aging, wetting property of material was a critical factor affecting the charge decay and the filtration performance, as the absorbed water increases the electrical conductivity. For the thermal aging, the material with the highest ε_r deteriorated the electric potential and the filtration performance by the largest extent, due to the lower band gap energy for charge transfer. The results of this study implicate that ε_r and wettability are important material parameters influencing the electric conductivity and chain mobility, and they can be used as convenient predictors for charge retention capacity affecting the robust electrostatic filtration performance. Full article

(This article belongs to the Special Issue Polymeric Materials for Filtration and Purification)

► Show Figures

Graphical abstract

14 pages, 2772 KiB

Open AccessEditor’s ChoiceArticle

Catalytic Fast Pyrolysis of Poly (Ethylene Terephthalate) (PET) with Zeolite and Nickel Chloride

by Hang Jia, Haoxi Ben, Ying Luo and Rui Wang

Polymers 2020, 12(3), 705; https://doi.org/10.3390/polym12030705 - 23 Mar 2020

Cited by 55 | Viewed by 5645

Abstract

The pyrolysis of poly (ethylene terephthalate) (PET) in the presence of ZSM-5 zeolite and NiCl₂ as a catalyst was studied at different temperatures under N₂ atmosphere. Quantitative ¹³C nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FT-IR) were applied [...] Read more.

The pyrolysis of poly (ethylene terephthalate) (PET) in the presence of ZSM-5 zeolite and NiCl₂ as a catalyst was studied at different temperatures under N₂ atmosphere. Quantitative ¹³C nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FT-IR) were applied to characterize the waxy and solid residue. The carboxyl and aliphatic hydroxyl groups in the waxy residue have been greatly depleted after the use of zeolite during pyrolysis on the basis of the results of ¹³C NMR and FT-IR analysis. The proportion of aromatic hydroxyl groups increased by 21.82% when the mass ratio of zeolite to PET was set to 2.0/1.0. The results indicate that ZSM-5 is able to facilitate the decomposition of carboxyl, aliphatic groups, and ether bonds in the primary products produced from the pyrolysis of PET. In addition, the deoxygenation effects on the waxy products have been significantly enhanced with the addition of zeolite based on the results of NMR. Full article

(This article belongs to the Special Issue Thermal Analysis of Polymer Materials)

► Show Figures

Figure 1

11 pages, 3218 KiB

Open AccessEditor’s ChoiceArticle

The Piezoresistive Highly Elastic Sensor Based on Carbon Nanotubes for the Detection of Breath

by Romana Daňová, Robert Olejnik, Petr Slobodian and Jiri Matyas

Polymers 2020, 12(3), 713; https://doi.org/10.3390/polym12030713 - 23 Mar 2020

Cited by 23 | Viewed by 3543

Abstract

Wearable electronic sensor was prepared on a light and flexible substrate. The breathing sensor has a broad assumption and great potential for portable devices in wearable technology. In the present work, the application of a flexible thermoplastic polyurethane/multiwalled carbon nanotubes (TPU/MWCNTs) strain sensor [...] Read more.

Wearable electronic sensor was prepared on a light and flexible substrate. The breathing sensor has a broad assumption and great potential for portable devices in wearable technology. In the present work, the application of a flexible thermoplastic polyurethane/multiwalled carbon nanotubes (TPU/MWCNTs) strain sensor was demonstrated. This composite was prepared by a novel technique using a thermoplastic filtering membrane based on electrospinning technology. Aqueous dispersion of MWCNTs was filtered through membrane, dried and then welded directly on a T-shirt and encapsulated by a thin silicone layer. The sensing layer was also equipped by electrodes. A polymer composite sensor is capable of detecting a deformation by changing its electrical resistance. A T-shirt was capable of analyzing a type, frequency and intensity of human breathing. The sensitivity to the applied strain of the sensor was improved by the oxidation of MWCNTs by potassium permanganate (KMnO₄) and also by subsequent application of the prestrain. Full article

(This article belongs to the Special Issue Polymer Processing and Surfaces)

► Show Figures

Graphical abstract

13 pages, 4840 KiB

Open AccessEditor’s ChoiceArticle

The Inhibition Property and Mechanism of a Novel Low Molecular Weight Zwitterionic Copolymer for Improving Wellbore Stability

by Weichao Du, Michal Slaný, Xiangyun Wang, Gang Chen and Jie Zhang

Polymers 2020, 12(3), 708; https://doi.org/10.3390/polym12030708 - 23 Mar 2020

Cited by 78 | Viewed by 5019

Abstract

In this work, a novel low molecular weight zwitterionic copolymer for improving wellbore stability, which is expected to be an alternative to the current shale inhibitors, was obtained by copolymerization of tris hydroxyethyl allyl ammonium bromide (THAAB), 2-acrylamido-2- methyl propane sulfonic acid (AMPS) [...] Read more.

In this work, a novel low molecular weight zwitterionic copolymer for improving wellbore stability, which is expected to be an alternative to the current shale inhibitors, was obtained by copolymerization of tris hydroxyethyl allyl ammonium bromide (THAAB), 2-acrylamido-2- methyl propane sulfonic acid (AMPS) and acrylamide (AM), initiated by a redox initiation system in an aqueous solution. The copolymer, denoted as SX-1, was characterized by FT-IR, TGA-DSC, and GPC. Results demonstrated that the molecular weight of SX-1 was approximately 13,683 g/mol and it displayed temperature resistance up to 225 °C. Regarding the inhibition performance, evaluation experiments showed the hot rolling recovery of a Longmaxi shale sample in 2.0 wt % SX-1 solutions was up to 90.31% after hot rolling for 16 h at 120 °C. The Linear swelling height of Na-MMT artificial core in 2.0 wt % SX-1 solution was just 4.74 mm after 16 h. Methods including particle size analysis, FTIR, XRD, and SEM were utilized to study the inhibition mechanism of SX-1; results demonstrated that SX-1 had entered into the inner layer of sodium montmorillonite (Na-MMT) and adsorbed on the inner surface, and the micro-structure of Na-MMT was successfully changed by SX-1. The particle size of Na-MMT in distilled water was 8.05 μm, and it was observed that its size had increased to 603 μm after the addition of 2.0 wt % of SX-1. Its superior properties make this novel low molecular weight copolymer promising for ensuring wellbore stability, particularly for high temperature wells. Full article

(This article belongs to the Special Issue Colloid and Interface)

► Show Figures

Graphical abstract

13 pages, 4651 KiB

Open AccessEditor’s ChoiceArticle

Dielectric Relaxation in the Hybrid Epoxy/MWCNT/MnFe₂O₄ Composites

by Darya Meisak, Jan Macutkevic, Artyom Plyushch, Polina Kuzhir, Algirdas Selskis and Juras Banys

Polymers 2020, 12(3), 697; https://doi.org/10.3390/polym12030697 - 21 Mar 2020

Cited by 17 | Viewed by 2594

Abstract

The electrical properties of epoxy/MWCNT (multi-walled carbon nanotubes)/MnFe₂O₄ hybrid composites loaded with MWCNTs (below, 0.09 vol.%, and above, 0.58 vol.%, percolation threshold) and varying concentrations of MnFe₂O₄ up to 10 vol.% were studied in a wide frequency [...] Read more.

The electrical properties of epoxy/MWCNT (multi-walled carbon nanotubes)/MnFe₂O₄ hybrid composites loaded with MWCNTs (below, 0.09 vol.%, and above, 0.58 vol.%, percolation threshold) and varying concentrations of MnFe₂O₄ up to 10 vol.% were studied in a wide frequency range (20 Hz–40 GHz) at different temperatures (20 K–500 K). At low frequencies, the dielectric permittivity and the electrical conductivity of composites with fixed amounts of MWCNT are strongly dependent on MnFe₂O₄ content. For MWCNT concentrations above the percolation threshold (i.e., 0.58 vol.%), the electrical conductivity highly decreases with the increase of the MnFe₂O₄ fraction. In contrast, for the epoxy/MWCNT just below the onset of electrical conductivity (0.09 vol.% of MWCNTs), there exists an optimal concentration of MnFe₂O₄ inclusions (i.e., 0.025 vol.%), leading to a dramatic increase of the electrical conductivity by three orders of magnitude. The electrical transport in composites is mainly governed by electron tunneling at lower temperatures (below 200 K), and it is highly impacted by the matrix conductivity at higher temperatures (above 400 K). The electrical properties were discussed in terms of the Maxwell–Wagner relaxation and distributions of relaxation times. A non-invasive platform based on dielectric relaxation spectroscopy was proposed for enhancing the synergetic effect coursed by using multiple nanoinclusions in polymer composites just below the percolation threshold. Full article

(This article belongs to the Special Issue Epoxy Resins and Composites)

► Show Figures

Graphical abstract

13 pages, 3390 KiB

Open AccessEditor’s ChoiceArticle

Synthesis and Investigation of Thermo-Induced Gelation of Partially Cross-Linked Poly-2-isopropyl-2-oxazoline in Aqueous Media

by Alina Amirova, Serafim Rodchenko, Mikhail Kurlykin, Andrey Tenkovtsev, Illia Krasnou, Andres Krumme and Alexander Filippov

Polymers 2020, 12(3), 698; https://doi.org/10.3390/polym12030698 - 21 Mar 2020

Cited by 7 | Viewed by 3189

Abstract

Water-soluble, partially cross-linked poly-2-isopropyl-2-oxazoline combining the properties of chemical and physical gels was synthesized by a two-step procedure. Thermally induced sol-gel transition in its aqueous solution was studied by rheology, light scattering, and turbidimetry. It was demonstrated that the synthesized product is bimodal; [...] Read more.

Water-soluble, partially cross-linked poly-2-isopropyl-2-oxazoline combining the properties of chemical and physical gels was synthesized by a two-step procedure. Thermally induced sol-gel transition in its aqueous solution was studied by rheology, light scattering, and turbidimetry. It was demonstrated that the synthesized product is bimodal; it consists of linear and cross-linked components. The cross-linked components are responsible for the gelation, while the linear ones abate the viscosity growth. Heating the solution above the phase transition temperature leads to the self-assembly of the particles into a physical gel. The combination of chemical and physical cross-linking was found to be a prospective route for thermosensitive gel development. Full article

(This article belongs to the Special Issue Polymer Rheology: Fundamentals and Applications)

► Show Figures

Graphical abstract

29 pages, 2039 KiB

Open AccessEditor’s ChoiceReview

Recent Progress on Luminescent Metal-Organic Framework-Involved Hybrid Materials for Rapid Determination of Contaminants in Environment and Food

by Chi-Xuan Yao, Ning Zhao, Ji-Chao Liu, Li-Jun Chen, Jing-Min Liu, Guo-Zhen Fang and Shuo Wang

Polymers 2020, 12(3), 691; https://doi.org/10.3390/polym12030691 - 20 Mar 2020

Cited by 49 | Viewed by 7060

Abstract

The high speed of contaminants growth needs the burgeoning of new analytical techniques to keep up with the continuous demand for monitoring and legislation on food safety and environmental pollution control. Metal-organic frameworks (MOFs) are a kind of advanced crystal porous materials with [...] Read more.

The high speed of contaminants growth needs the burgeoning of new analytical techniques to keep up with the continuous demand for monitoring and legislation on food safety and environmental pollution control. Metal-organic frameworks (MOFs) are a kind of advanced crystal porous materials with controllable apertures, which are self-assembled by organic ligands and inorganic metal nodes. They have the merits of large specific surface areas, high porosity and the diversity of structures and functions. Latterly, the utilization of metal-organic frameworks has attracted much attention in environmental protection and the food industry. MOFs have exhibited great value as sensing materials for many targets. Among many sensing methods, fluorometric sensing is one of the widely studied methods in the detection of harmful substances in food and environmental samples. Fluorometric detection based on MOFs and its functional materials is currently one of the most key research subjects in the food and environmental fields. It has gradually become a hot research direction to construct the highly sensitive rapid sensors to detect harmful substances in the food matrix based on metal-organic frameworks. In this paper, we introduced the synthesis and detection application characteristics (absorption, fluorescence, etc.) of metal-organic frameworks. We summarized their applications in the MOFs-based fluorometric detection of harmful substances in food and water over the past few years. The harmful substances mainly include heavy metals, organic pollutants and other small molecules, etc. On this basis, the future development and possible application of the MOFs have prospected in this review paper. Full article

(This article belongs to the Special Issue Polymers in Agriculture and Food Science)

► Show Figures

Graphical abstract

33 pages, 7363 KiB

Open AccessEditor’s ChoiceReview

Hybrid Sol–gel Coatings for Corrosion Mitigation: A Critical Review

by Rita B. Figueira

Polymers 2020, 12(3), 689; https://doi.org/10.3390/polym12030689 - 19 Mar 2020

Cited by 75 | Viewed by 8958

Abstract

The corrosion process is a major source of metallic material degradation, particularly in aggressive environments, such as marine ones. Corrosion progression affects the service life of a given metallic structure, which may end in structural failure, leakage, product loss and environmental pollution linked [...] Read more.

The corrosion process is a major source of metallic material degradation, particularly in aggressive environments, such as marine ones. Corrosion progression affects the service life of a given metallic structure, which may end in structural failure, leakage, product loss and environmental pollution linked to large financial costs. According to NACE, the annual cost of corrosion worldwide was estimated, in 2016, to be around 3%–4% of the world’s gross domestic product. Therefore, the use of methodologies for corrosion mitigation are extremely important. The approaches used can be passive or active. A passive approach is preventive and may be achieved by emplacing a barrier layer, such as a coating that hinders the contact of the metallic substrate with the aggressive environment. An active approach is generally employed when the corrosion is set in. That seeks to reduce the corrosion rate when the protective barrier is already damaged and the aggressive species (i.e., corrosive agents) are in contact with the metallic substrate. In this case, this is more a remediation methodology than a preventive action, such as the use of coatings. The sol-gel synthesis process, over the past few decades, gained remarkable importance in diverse areas of application. Sol–gel allows the combination of inorganic and organic materials in a single-phase and has led to the development of organic–inorganic hybrid (OIH) coatings for several applications, including for corrosion mitigation. This manuscript succinctly reviews the fundamentals of sol–gel concepts and the parameters that influence the processing techniques. The state-of-the-art of the OIH sol–gel coatings reported in the last few years for corrosion protection, are also assessed. Lastly, a brief perspective on the limitations, standing challenges and future perspectives of the field are critically discussed. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry in Polymers Research)

► Show Figures

Figure 1

17 pages, 4951 KiB

Open AccessEditor’s ChoiceArticle

Influence of Magnetic Nanoparticles on Modified Polypyrrole/m-Phenylediamine for Adsorption of Cr(VI) from Aqueous Solution

by Thabiso Carol Maponya, Kabelo Edmond Ramohlola, Nazia Hassan Kera, Kwena Desmond Modibane, Arjun Maity, Lebogang Maureen Katata-Seru and Mpitloane Joseph Hato

Polymers 2020, 12(3), 679; https://doi.org/10.3390/polym12030679 - 19 Mar 2020

Cited by 38 | Viewed by 3728

Abstract

A novel, modified polypyrrole/m-phenylediamine (PPy–mPD) composite, decorated with magnetite (Fe₃O₄) nanoparticles, and prepared via an in-situ oxidative polymerisation, was investigated. The PPy–mPD/Fe₃O₄ nanocomposite was employed for the removal of highly [...] Read more.

A novel, modified polypyrrole/m-phenylediamine (PPy–mPD) composite, decorated with magnetite (Fe₃O₄) nanoparticles, and prepared via an in-situ oxidative polymerisation, was investigated. The PPy–mPD/Fe₃O₄ nanocomposite was employed for the removal of highly toxic oxyanion hexavalent chromium Cr(VI) from an aqueous solution. The structure and successful formation of the PPy–mPD/Fe₃O₄ nanocomposite was confirmed and investigated using various techniques. The presence of Fe₃O₄ was confirmed by high resolution transmission electron microscopy, with an appearance of Fe lattice fringes. The estimation of the saturation magnetisation of the nanocomposite, using a vibrating sample magnetometer, was observed to be 6.6 emu/g. In batch adsorption experiments, PPy–mPD/Fe₃O₄ nanocomposite (25 mg) was able to remove 99.6% of 100 mg/L of Cr(VI) at pH 2 and 25 °C. Adsorption isotherms were investigated at different Cr(VI) concentration (100–600 mg/L) and temperature (15–45 °C). It was deduced that adsorption follows the Langmuir model, with a maximum adsorption capacity of 555.6 mg/g for Cr(VI) removal. Furthermore, isotherm data were used to calculate thermodynamic values for Gibbs free energy, enthalpy change and entropy change, which indicated that Cr(VI) adsorption was spontaneous and endothermic in nature. Adsorption–desorption experiments revealed that the nanocomposite was usable for two consecutive cycles with no significant loss of adsorption capacity. This research demonstrates the application potential for the fascinating properties of PPy–mPD/Fe₃O₄ nanocomposite as a highly efficient adsorbent for the removal of heavy metal ions from industrial wastewater. Full article

(This article belongs to the Section Polymer Applications)

► Show Figures

Figure 1

11 pages, 2436 KiB

Open AccessEditor’s ChoiceArticle

Nano- And Microfiber-Based Fully Fabric Triboelectric Nanogenerator For Wearable Devices

by Jong Hyuk Bae, Hyun Ju Oh, Jinkyu Song, Do Kun Kim, Byeong Jin Yeang, Jae Hoon Ko, Seong Hun Kim, Woosung Lee and Seung Ju Lim

Polymers 2020, 12(3), 658; https://doi.org/10.3390/polym12030658 - 13 Mar 2020

Cited by 27 | Viewed by 6749

Abstract

The combination of the triboelectric effect and static electricity as a triboelectric nanogenerator (TENG) has been extensively studied. TENGs using nanofibers have advantages such as high surface roughness, porous structure, and ease of production by electrospinning; however, their shortcomings include high-cost, limited yield, [...] Read more.

The combination of the triboelectric effect and static electricity as a triboelectric nanogenerator (TENG) has been extensively studied. TENGs using nanofibers have advantages such as high surface roughness, porous structure, and ease of production by electrospinning; however, their shortcomings include high-cost, limited yield, and poor mechanical properties. Microfibers are produced on mass scale at low cost; they are solvent-free, their thickness can be easily controlled, and they have relatively better mechanical properties than nanofiber webs. Herein, a nano- and micro-fiber-based TENG (NMF-TENG) was fabricated using a nylon 6 nanofiber mat and melt blown nonwoven polypropylene (PP) as triboelectric layers. Hence, the advantages of nanofibers and microfibers are maintained and mutually complemented. The NMF-TENG was manufactured by electrospinning nylon 6 on the nonwoven PP, and then attaching Ni coated fabric electrodes on the top and bottom of the triboelectric layers. The morphology, porosity, pore size distribution, and fiber diameters of the triboelectric layers were investigated. The triboelectric output performances were confirmed by controlling the pressure area and basis weight of the nonwoven PP. This study proposes a low-cost fabrication process of NMF-TENGs with high air-permeability, durability, and productivity, which makes them applicable to a variety of wearable electronics. Full article

(This article belongs to the Special Issue Advances in Polymer Nanofibers)

► Show Figures

Figure 1

19 pages, 3052 KiB

Open AccessEditor’s ChoiceArticle

Acoustic, Mechanical and Thermal Properties of Green Composites Reinforced with Natural Fibers Waste

by Tufail Hassan, Hafsa Jamshaid, Rajesh Mishra, Muhammad Qamar Khan, Michal Petru, Jan Novak, Rostislav Choteborsky and Monika Hromasova

Polymers 2020, 12(3), 654; https://doi.org/10.3390/polym12030654 - 13 Mar 2020

Cited by 96 | Viewed by 7452

Abstract

The use of acoustic panels is one of the most important methods for sound insulation in buildings. Moreover, it has become increasingly important to use green/natural origin materials in this area to reduce environmental impact. This study focuses on the investigation of acoustic, [...] Read more.

The use of acoustic panels is one of the most important methods for sound insulation in buildings. Moreover, it has become increasingly important to use green/natural origin materials in this area to reduce environmental impact. This study focuses on the investigation of acoustic, mechanical and thermal properties of natural fiber waste reinforced green epoxy composites. Three different types of fiber wastes were used, e.g., cotton, coconut and sugarcane with epoxy as the resin. Different fiber volume fractions, i.e., 10%, 15% and 20% for each fiber were used with a composite thickness of 3 mm. The sound absorption coefficient, impact strength, flexural strength, thermal conductivity, diffusivity, coefficient of thermal expansion and thermogravimetric properties of all samples were investigated. It has been found that by increasing the fiber content, the sound absorption coefficient also increases. The coconut fiber-based composites show a higher sound absorption coefficient than in the other fiber-reinforced composites. The impact and flexural strength of the cotton fiber-reinforced composite samples are higher than in other samples. The coefficient of thermal expansion of the cotton fiber-based composite is also higher than the other composites. Thermogravimetric analysis revealed that all the natural fiber-reinforced composites can sustain till 300 °C with a minor weight loss. The natural fiber-based composites can be used in building interiors, automotive body parts and household furniture. Such composite development is an ecofriendly approach to the acoustic world. Full article

(This article belongs to the Special Issue Polymer Materials in Environmental Chemistry)

► Show Figures

Figure 1

22 pages, 5490 KiB

Open AccessEditor’s ChoiceArticle

Curing Kinetics and Thermal Stability of Epoxy Composites Containing Newly Obtained Nano-Scale Aluminum Hypophosphite (AlPO₂)

by Farimah Tikhani, Shahab Moghari, Maryam Jouyandeh, Fouad Laoutid, Henri Vahabi, Mohammad Reza Saeb and Philippe Dubois

Polymers 2020, 12(3), 644; https://doi.org/10.3390/polym12030644 - 12 Mar 2020

Cited by 49 | Viewed by 5427

Abstract

For the first time, nano-scale aluminum hypophosphite (AlPO₂) was simply obtained in a two-step milling process and applied in preparation of epoxy nanocomposites varying concentration (0.1, 0.3, and 0.5 wt.% based on resin weight). Studying the cure kinetics and thermal stability [...] Read more.

For the first time, nano-scale aluminum hypophosphite (AlPO₂) was simply obtained in a two-step milling process and applied in preparation of epoxy nanocomposites varying concentration (0.1, 0.3, and 0.5 wt.% based on resin weight). Studying the cure kinetics and thermal stability of these nanocomposites would pave the way toward the design of high-performance nanocomposites for special applications. Scanning electron microscopy (SEM) and transmittance electron microscopy (TEM) revealed AlPO₂ particles having domains less than 60 nm with high potential for agglomeration. Excellent (at heating rate of 5 °C/min) and Good (at heating rates of 10, 15 and 20 °C/min) cure states were detected for nanocomposites under nonisothermal differential scanning calorimetry (DSC). While the dimensionless curing temperature interval (ΔT*) was almost equal for epoxy/AlPO₂ nanocomposites, dimensionless heat release (ΔH*) changed by densification of polymeric network. Quantitative cure analysis based on isoconversional Friedman and Kissinger methods gave rise to the kinetic parameters such as activation energy and the order of reaction as well as frequency factor. Variation of glass transition temperature (T_g) was monitored to explain the molecular interaction in the system, where T_g increased from 73.2 °C for neat epoxy to just 79.5 °C for the system containing 0.1 wt.% AlPO₂. Moreover, thermogravimetric analysis (TGA) showed that nanocomposites were thermally stable. Full article

(This article belongs to the Special Issue Epoxy Resins and Composites)

► Show Figures

Graphical abstract

13 pages, 3439 KiB

Open AccessEditor’s ChoiceArticle

Tensile Mechanical Behaviour of Multi-Polymer Sandwich Structures via Fused Deposition Modelling

by David Moises Baca Lopez and Rafiq Ahmad

Polymers 2020, 12(3), 651; https://doi.org/10.3390/polym12030651 - 12 Mar 2020

Cited by 59 | Viewed by 7360

Abstract

The application of single homogeneous materials produced through the fused deposition modelling (FDM) technology restricts the production of high-level multi-material components. The fabrication of a sandwich-structured specimen with different material combinations using conventional thermoplastics such as poly (lactic acid) (PLA), acrylonitrile butadiene styrene [...] Read more.

The application of single homogeneous materials produced through the fused deposition modelling (FDM) technology restricts the production of high-level multi-material components. The fabrication of a sandwich-structured specimen with different material combinations using conventional thermoplastics such as poly (lactic acid) (PLA), acrylonitrile butadiene styrene (ABS) and high impact polystyrene (HIPS) through the filament-based extrusion process can demonstrate an improvement on its properties. This paper aims to assess among these materials, the best material sandwich-structured arrangement design, to enhance the mechanical properties of a part and to compare the results with the homogeneous materials selected. The samples were subjected to tensile testing to identify the tensile strength, elongation at break and Young’s modulus of each material combination. The experimental results demonstrate that applying the PLA-ABS-PLA sandwich arrangement leads to the best mechanical properties between these materials. This study enables users to consider sandwich structure designs as an alternative to manufacturing multi-material components using conventional and low-cost materials. Future work will consider the flexural tests to identify the maximum stresses and bending forces under pressure. Full article

(This article belongs to the Special Issue Bio-Based Polymers: Synthesis and Properties)

► Show Figures

Figure 1

26 pages, 4263 KiB

Open AccessEditor’s ChoiceReview

Coumarins into Polyurethanes for Smart and Functional Materials

by José María Cuevas, Rubén Seoane-Rivero, Rodrigo Navarro and Ángel Marcos-Fernández

Polymers 2020, 12(3), 630; https://doi.org/10.3390/polym12030630 - 10 Mar 2020

Cited by 24 | Viewed by 6149

Abstract

Polyurethanes are of undoubted interest for the scientific community and the industry. Their outstanding versatility from tailor-made structures turns them into major polymers for use in a wide range of different applications. As with other polymers, new, emerging molecules and monomers with specific [...] Read more.

Polyurethanes are of undoubted interest for the scientific community and the industry. Their outstanding versatility from tailor-made structures turns them into major polymers for use in a wide range of different applications. As with other polymers, new, emerging molecules and monomers with specific attributes can provide new functions and capabilities to polyurethanes. Natural and synthetic coumarin and its derivatives are characterised by interesting biological, photophysical and photochemical properties. Then, the polyurethanes can exploit those features of many coumarins which are present in their composition to achieve new functions and performances. This article reviews the developments in the proper use of the special properties of coumarins in polyurethanes to produce functional and smart materials that can be suitable for new specific applications. Full article

► Show Figures

Graphical abstract

16 pages, 2970 KiB

Open AccessEditor’s ChoiceArticle

Self-Consistent Mean Field Calculations of Polyelectrolyte-Surfactant Mixtures in Solution and upon Adsorption onto Negatively Charged Surfaces

by Eduardo Guzmán, Laura Fernández-Peña, Gustavo S. Luengo, Ana María Rubio, Antonio Rey and Fabien Léonforte

Polymers 2020, 12(3), 624; https://doi.org/10.3390/polym12030624 - 9 Mar 2020

Cited by 25 | Viewed by 3329

Abstract

Self-Consistent Mean-Field Calculations (SCF) have provided a semi-quantitative description of the physico-chemical behavior of six different polyelectrolyte-surfactant mixtures. The SCF calculations performed showed that both the formation of polymer-surfactant in bulk and the adsorption of the formed complexes onto negatively-charged surfaces are strongly [...] Read more.

Self-Consistent Mean-Field Calculations (SCF) have provided a semi-quantitative description of the physico-chemical behavior of six different polyelectrolyte-surfactant mixtures. The SCF calculations performed showed that both the formation of polymer-surfactant in bulk and the adsorption of the formed complexes onto negatively-charged surfaces are strongly affected by the specific nature of the considered systems, with the polymer-surfactant interactions playing a central role in the self-assembly of the complexes that, in turn, affects their adsorption onto interfaces and surfaces. This work evidences that SCF calculations are a valuable tool for deepening on the understanding of the complex physico-chemical behavior of polyelectrolyte-surfactant mixtures. However, it is worth noting that the framework obtained on the basis of an SCF approach considered an equilibrium situation which may, in some cases, be far from the real situation appearing in polyelectrolyte-surfactant systems. Full article

(This article belongs to the Special Issue Polymers and Nanomaterials: Interactions and Applications)

► Show Figures

Figure 1

18 pages, 3193 KiB

Open AccessEditor’s ChoiceReview

Hydrogel-Based Colloidal Photonic Crystal Devices for Glucose Sensing

by Wenwei Tang and Cheng Chen

Polymers 2020, 12(3), 625; https://doi.org/10.3390/polym12030625 - 9 Mar 2020

Cited by 52 | Viewed by 8575

Abstract

Diabetes, a common epidemic disease, is increasingly hazardous to human health. Monitoring body glucose concentrations for the prevention and therapy of diabetes has become very important. Hydrogel-based responsive photonic crystal (PC) materials are noninvasive options for glucose detection. This article reviews glucose-sensing materials/devices [...] Read more.

Diabetes, a common epidemic disease, is increasingly hazardous to human health. Monitoring body glucose concentrations for the prevention and therapy of diabetes has become very important. Hydrogel-based responsive photonic crystal (PC) materials are noninvasive options for glucose detection. This article reviews glucose-sensing materials/devices composed of hydrogels and colloidal photonic crystals (CPCs), including the construction of 2D/3D CPCs and 2D/3D hydrogel-based CPCs (HCPCs). The development and mechanisms of glucose-responsive hydrogels and the achieved technologies of HCPC glucose sensors were also concluded. This review concludes by showing a perspective for the future design of CPC glucose biosensors with functional hydrogels. Full article

(This article belongs to the Special Issue Biodegradable Polymers for Biomedical Application)

► Show Figures

Graphical abstract

30 pages, 4737 KiB

Open AccessEditor’s ChoiceReview

Polymer- and Hybrid-Based Biomaterials for Interstitial, Connective, Vascular, Nerve, Visceral and Musculoskeletal Tissue Engineering

by Anatolii Abalymov, Bogdan Parakhonskiy and Andre G. Skirtach

Polymers 2020, 12(3), 620; https://doi.org/10.3390/polym12030620 - 9 Mar 2020

Cited by 63 | Viewed by 6952

Abstract

In this review, materials based on polymers and hybrids possessing both organic and inorganic contents for repairing or facilitating cell growth in tissue engineering are discussed. Pure polymer based biomaterials are predominantly used to target soft tissues. Stipulated by possibilities of tuning the [...] Read more.

In this review, materials based on polymers and hybrids possessing both organic and inorganic contents for repairing or facilitating cell growth in tissue engineering are discussed. Pure polymer based biomaterials are predominantly used to target soft tissues. Stipulated by possibilities of tuning the composition and concentration of their inorganic content, hybrid materials allow to mimic properties of various types of harder tissues. That leads to the concept of “one-matches-all” referring to materials possessing the same polymeric base, but different inorganic content to enable tissue growth and repair, proliferation of cells, and the formation of the ECM (extra cellular matrix). Furthermore, adding drug delivery carriers to coatings and scaffolds designed with such materials brings additional functionality by encapsulating active molecules, antibacterial agents, and growth factors. We discuss here materials and methods of their assembly from a general perspective together with their applications in various tissue engineering sub-areas: interstitial, connective, vascular, nervous, visceral and musculoskeletal tissues. The overall aims of this review are two-fold: (a) to describe the needs and opportunities in the field of bio-medicine, which should be useful for material scientists, and (b) to present capabilities and resources available in the area of materials, which should be of interest for biologists and medical doctors. Full article

(This article belongs to the Special Issue Bioactive Polymer Scaffolds and Thin Films for Biomedical Applications: State-of-the-Art and Challenges)

► Show Figures

Graphical abstract

23 pages, 10643 KiB

Open AccessEditor’s ChoiceArticle

Micrometer Copper-Zinc Alloy Particles-Reinforced Wood Plastic Composites with High Gloss and Antibacterial Properties for 3D Printing

by Feiwen Yang, Jianhui Zeng, Haibo Long, Jialin Xiao, Ying Luo, Jin Gu, Wuyi Zhou, Yen Wei and Xianming Dong

Polymers 2020, 12(3), 621; https://doi.org/10.3390/polym12030621 - 9 Mar 2020

Cited by 30 | Viewed by 4673

Abstract

In this work, micrometer copper-zinc alloy particles-reinforced particleboard wood flour/poly (lactic acid) (mCu-Zn/PWF/PLA) wood plastic composites with high gloss and antibacterial properties for 3D printing were prepared by a melt blending process. The structure and properties of the composites with different contents of [...] Read more.

In this work, micrometer copper-zinc alloy particles-reinforced particleboard wood flour/poly (lactic acid) (mCu-Zn/PWF/PLA) wood plastic composites with high gloss and antibacterial properties for 3D printing were prepared by a melt blending process. The structure and properties of the composites with different contents of mCu-Zn were analyzed by means of mechanical testing, dynamic mechanical analysis, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and antibacterial testing. The results showed that the mechanical properties, thermal stability, and antibacterial performance of the composites were significantly improved, as mCu-Zn was added into the wood plastic composites. When adding 2 wt.% mCu-Zn, the flexural strength of mCu-Zn/PWF/PLA composites (with 5 wt.% of particleboard wood flour) (PWF) increased by 47.1% compared with pure poly (lactic acid) (PLA), and 18.9% compared with PWF/PLA wood plastic composites. The surface gloss was increased by 1142.6% compared with PWF/PLA wood plastic composites. Furthermore, the inhibition rates of mCu-Zn/PWF/PLA composites against Escherichia coli reached 90.43%. Therefore, this novel high gloss and antibacterial wood plastic composites for fused deposition modeling (FDM) 3D printing have potential applications in personalized and classic furniture, art, toys, etc. Full article

(This article belongs to the Special Issue Advances in Composite Polymers for 3D Printing)

► Show Figures

Figure 1

13 pages, 4891 KiB

Open AccessEditor’s ChoiceArticle

Development of a Lidocaine-Loaded Alginate/CMC/PEO Electrospun Nanofiber Film and Application as an Anti-Adhesion Barrier

by Seungho Baek, Heekyung Park, Youngah Park, Hyun Kang and Donghyun Lee

Polymers 2020, 12(3), 618; https://doi.org/10.3390/polym12030618 - 8 Mar 2020

Cited by 28 | Viewed by 6437

Abstract

Surgery, particularly open surgery, is known to cause tissue/organ adhesion during healing. These adhesions occur through contact between the surgical treatment site and other organ, bone, or abdominal sites. Fibrous bands can form in unnecessary contact areas and cause various complications. Consequently, film- [...] Read more.

Surgery, particularly open surgery, is known to cause tissue/organ adhesion during healing. These adhesions occur through contact between the surgical treatment site and other organ, bone, or abdominal sites. Fibrous bands can form in unnecessary contact areas and cause various complications. Consequently, film- and gel-type anti-adhesion agents have been developed. The development of sustained drug delivery systems is very important for disease treatment and prevention. In this study, the drug release behavior was controlled by crosslinking lidocaine-loaded alginate/carboxymethyl cellulose (CMC)/polyethylene oxide (PEO) nanofiber films prepared by electrospinning. Lidocaine is mainly used as an anesthetic and is known to have anti-adhesion effects. Our results show that drug release is regulated by the crosslinking degree of the lidocaine-loaded alginate/CMC/PEO film. The drug release behavior was confirmed by HPLC, and, as a result, an excellent anti-adhesion barrier was developed that can be applied to treat patients in the medical field. Full article

(This article belongs to the Special Issue Biodegradable Polymers for Biomedical Application)

► Show Figures

Graphical abstract

23 pages, 3956 KiB

Open AccessEditor’s ChoiceArticle

Durability of an Epoxy Resin and Its Carbon Fiber- Reinforced Polymer Composite upon Immersion in Water, Acidic, and Alkaline Solutions

by Arya Uthaman, Guijun Xian, Sabu Thomas, Yunjia Wang, Qiang Zheng and Xiaoling Liu

Polymers 2020, 12(3), 614; https://doi.org/10.3390/polym12030614 - 7 Mar 2020

Cited by 96 | Viewed by 10197

Abstract

The usage of polymer composites in various engineering fields has increased. However, the long-term service performance of such materials under aggressive conditions is still poorly understood, which limits the development of safe and economically effective designs. In this study, the aging of an [...] Read more.

The usage of polymer composites in various engineering fields has increased. However, the long-term service performance of such materials under aggressive conditions is still poorly understood, which limits the development of safe and economically effective designs. In this study, the aging of an epoxy resin and its carbon fiber-reinforced polymer (CFRP) composites upon immersion in water, acidic, and alkaline solutions was evaluated at different temperatures. The service life of the CFRP composites under various conditions could be predicted by the Arrhenius theory. The thermal and mechanical analysis results indicated that the CFRP composites were more vulnerable to HCl owing to the higher moisture absorption and diffusion of HCl into their cracks. The scanning electron microscopy results showed that the polymer matrix was damaged and degraded. Therefore, to allow long-term application, CFRP composites must be protected from acidic environments. Full article

(This article belongs to the Special Issue Epoxy Resins and Composites)

► Show Figures

Graphical abstract

13 pages, 3066 KiB

Open AccessEditor’s ChoiceArticle

Biodegradable, Flexible, and Transparent Conducting Silver Nanowires/Polylactide Film with High Performance for Optoelectronic Devices

by Junjun Wang, Junsheng Yu, Dongyu Bai, Zhuobin Li, Huili Liu, Ying Li, Shanyong Chen, Jiang Cheng and Lu Li

Polymers 2020, 12(3), 604; https://doi.org/10.3390/polym12030604 - 6 Mar 2020

Cited by 20 | Viewed by 4300

Abstract

As a synthetic renewable and biodegradable material, the application of polylactide (PLA) in the green flexible electronics has attracted intensive attention due to the increasingly serious issue of electronic waste. Unfortunately, the development of PLA-based optoelectronic devices is greatly hindered by the poor [...] Read more.

As a synthetic renewable and biodegradable material, the application of polylactide (PLA) in the green flexible electronics has attracted intensive attention due to the increasingly serious issue of electronic waste. Unfortunately, the development of PLA-based optoelectronic devices is greatly hindered by the poor heat resistance and mechanical property of PLA. To overcome these limitations, herein, we report a facile and promising route to fabricate silver nanowires/PLA (AgNW/PLA) film with largely improved properties by utilizing the stereocomplex (SC) crystallization between poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA). Through embedding the AgNW networks into the PLLA:PDLA blend matrix via a transfer method, the AgNW/PLLA:PDLA film with both high transparency and excellent conductivity was obtained. Compared with the AgNW/PLLA film, the formation of SC crystallites in the composites matrix could significantly enhance not only heat resistance but also mechanical strength of the AgNW/PLLA:PDLA film. Exceptionally, the AgNW/PLLA:PDLA film exhibited superior flexibility and could maintain excellent electrical conductivity stability even under the condition of 10,000 repeated bending cycles and 100 tape test cycles. In addition, the organic light-emitting diodes (OLEDs) with the AgNW/PLLA:PDLA films as electrodes were successfully fabricated in this work for the first time and they exhibited highly flexible, luminous, as well as hydrolytic degradation properties. This work could provide a low-cost and environment-friendly avenue towards fabricating high-performanced PLA-based biodegradable electronics. Full article

(This article belongs to the Section Polymer Applications)

► Show Figures

Figure 1

32 pages, 1301 KiB

Open AccessEditor’s ChoiceReview

Progress in Polymeric Nano-Medicines for Theranostic Cancer Treatment

by Imran Ali, Mosa Alsehli, Luciana Scotti, Marcus Tullius Scotti, Shang-Ting Tsai, Ruei-Siang Yu, Ming Fa Hsieh and Jung-Chih Chen

Polymers 2020, 12(3), 598; https://doi.org/10.3390/polym12030598 - 6 Mar 2020

Cited by 72 | Viewed by 8019

Abstract

Cancer is a life-threatening disease killing millions of people globally. Among various medical treatments, nano-medicines are gaining importance continuously. Many nanocarriers have been developed for treatment, but polymerically-based ones are acquiring importance due to their targeting capabilities, biodegradability, biocompatibility, capacity for drug loading [...] Read more.

Cancer is a life-threatening disease killing millions of people globally. Among various medical treatments, nano-medicines are gaining importance continuously. Many nanocarriers have been developed for treatment, but polymerically-based ones are acquiring importance due to their targeting capabilities, biodegradability, biocompatibility, capacity for drug loading and long blood circulation time. The present article describes progress in polymeric nano-medicines for theranostic cancer treatment, which includes cancer diagnosis and treatment in a single dosage form. The article covers the applications of natural and synthetic polymers in cancer diagnosis and treatment. Efforts were also made to discuss the merits and demerits of such polymers; the status of approved nano-medicines; and future perspectives. Full article

(This article belongs to the Special Issue Polymeric Colloidal Materials for Biomedical Applications)

► Show Figures

Graphical abstract

22 pages, 2296 KiB

Open AccessEditor’s ChoiceReview

Poly(N-isopropylacrylamide)-Based Thermoresponsive Composite Hydrogels for Biomedical Applications

by Xiaomin Xu, Yang Liu, Wenbo Fu, Mingyu Yao, Zhen Ding, Jiaming Xuan, Dongxiang Li, Shengjie Wang, Yongqing Xia and Meiwen Cao

Polymers 2020, 12(3), 580; https://doi.org/10.3390/polym12030580 - 5 Mar 2020

Cited by 232 | Viewed by 18534

Abstract

Poly(N-isopropylacrylamide) (PNIPAM)-based thermosensitive hydrogels demonstrate great potential in biomedical applications. However, they have inherent drawbacks such as low mechanical strength, limited drug loading capacity and low biodegradability. Formulating PNIPAM with other functional components to form composited hydrogels is an effective strategy to make [...] Read more.

Poly(N-isopropylacrylamide) (PNIPAM)-based thermosensitive hydrogels demonstrate great potential in biomedical applications. However, they have inherent drawbacks such as low mechanical strength, limited drug loading capacity and low biodegradability. Formulating PNIPAM with other functional components to form composited hydrogels is an effective strategy to make up for these deficiencies, which can greatly benefit their practical applications. This review seeks to provide a comprehensive observation about the PNIPAM-based composite hydrogels for biomedical applications so as to guide related research. It covers the general principles from the materials choice to the hybridization strategies as well as the performance improvement by focusing on several application areas including drug delivery, tissue engineering and wound dressing. The most effective strategies include incorporation of functional inorganic nanoparticles or self-assembled structures to give composite hydrogels and linking PNIPAM with other polymer blocks of unique properties to produce copolymeric hydrogels, which can improve the properties of the hydrogels by enhancing the mechanical strength, giving higher biocompatibility and biodegradability, introducing multi-stimuli responsibility, enabling higher drug loading capacity as well as controlled release. These aspects will be of great help for promoting the development of PNIPAM-based composite materials for biomedical applications. Full article

(This article belongs to the Special Issue Stimuli-Sensitive Amphiphilic Polymers and Their Biomedical Applications)

► Show Figures

Figure 1

18 pages, 6016 KiB

Open AccessEditor’s ChoiceArticle

Microscopic Structure of Swollen Hydrogels by Scanning Electron and Light Microscopies: Artifacts and Reality

by Zhansaya Kaberova, Evgeny Karpushkin, Martina Nevoralová, Miroslav Vetrík, Miroslav Šlouf and Miroslava Dušková-Smrčková

Polymers 2020, 12(3), 578; https://doi.org/10.3390/polym12030578 - 5 Mar 2020

Cited by 63 | Viewed by 9556

Abstract

The exact knowledge of hydrogel microstructure, mainly its pore topology, is a key issue in hydrogel engineering. For visualization of the swollen hydrogels, the cryogenic or high vacuum scanning electron microscopies (cryo-SEM or HVSEM) are frequently used while the possibility of artifact-biased images [...] Read more.

The exact knowledge of hydrogel microstructure, mainly its pore topology, is a key issue in hydrogel engineering. For visualization of the swollen hydrogels, the cryogenic or high vacuum scanning electron microscopies (cryo-SEM or HVSEM) are frequently used while the possibility of artifact-biased images is frequently underestimated. The major cause of artifacts is the formation of ice crystals upon freezing of the hydrated gel. Some porous hydrogels can be visualized with SEM without the danger of artifacts because the growing crystals are accommodated within already existing primary pores of the gel. In some non-porous hydrogels the secondary pores will also not be formed due to rigid network structure of gels that counteracts the crystal nucleation and growth. We have tested the limits of true reproduction of the hydrogel morphology imposed by the swelling degree and mechanical strength of gels by investigating a series of methacrylate hydrogels made by crosslinking polymerization of glycerol monomethacrylate and 2-hydroxyethyl methacrylate including their interpenetrating networks. The hydrogel morphology was studied using cryo-SEM, HVSEM, environmental scanning electron microscopy (ESEM), laser scanning confocal microscopy (LSCM) and classical wide-field light microscopy (LM). The cryo-SEM and HVSEM yielded artifact-free micrographs for limited range of non-porous hydrogels and for macroporous gels. A true non-porous structure was observed free of artifacts only for hydrogels exhibiting relatively low swelling and high elastic modulus above 0.5 MPa, whereas for highly swollen and/or mechanically weak hydrogels the cryo-SEM/HVSEM experiments resulted in secondary porosity. In this contribution we present several cases of severe artifact formation in PHEMA and PGMA hydrogels during their visualization by cryo-SEM and HVSEM. We also put forward empirical correlation between hydrogel morphological and mechanical parameters and the occurrence and intensity of artifacts. Full article

(This article belongs to the Special Issue Hydrogels and Gels for Biomedical and Sustainable Applications)

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Editor’s Choice Articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI