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Polymers
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Recent Advances in Bioplastics
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Recent Advances in Bioplastics

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Biomacromolecules, Biobased and Biodegradable Polymers".

Deadline for manuscript submissions: closed (20 October 2018) | Viewed by 101798

Special Issue Editors

Prof. Dr. Beom Soo Kim

E-Mail Website
Guest Editor
Department of Chemical Engineering, Chungbuk National University, Cheongju, Chungbuk, Republic of Korea
Interests: bioplastics; biodegradable polymers; molecularly imprinted polymers; polyhydroxyalkanoates; green synthesis of nanoparticles; bioprocess engineering
Special Issues, Collections and Topics in MDPI journals
Dr. Prasun Kumar

E-Mail Website
Guest Editor
Department of Chemical Engineering, Chungbuk National University, Cheongju 28644, Republic of Korea
Interests: bioconversion; biopolymers; biofuels; biodiesel; infectious disease; Electro-fermentation; applied microbiology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Current civilization is facing multiple global problems that include depletion of fossil fuel reserves, pollution based on synthetic plastics, and increasing piles of waste streams of different industrial origins. Research in renewable polymers as substitutes for fossil fuel-based synthetic plastics presents a topical R&D field worldwide to develop a circular bio-economy. In this context, bio-based plastics have emerged as a promising candidate that possess the potential to replace established petroleum-based plastics. It is more preferable that these polymers are biodegradable irrespective of their origins. Most bioplastics with biological origins are biocompatible in nature and possess competitive thermoplastic properties. The possibility to customize monomeric units/blocks makes bioplastics more beneficial for bulk and niche applications in the area of packaging, biomedicine, electronics, etc. Polylactic acid, polyhydroxyalkanoates, and other aliphatic polyesters are considered to have the necessary potential as bioplastics. Integrated bioprocessing has always been an attractive alternative to significantly reduce the cost of producing bioplastics. If such strategies are combined proficiently, it will pave the way for bioplastics and their blends to achieve the anticipated market breakthrough by the improvement of both economics and product quality. The recent research based on the concept of the economic potential of biorefinery may also lead to the production of a wide range of valuable bioproducts.

Therefore, this Special Issue will encompass the current and applied research showcasing high quality works in this discipline. Submissions are welcome on the topics related to bioplastic production strategies, bioconversion of agro-industrial wastes into polymers, customized production of copolymers, bioplastics based composites, their applications in the area of nanotechnology and biotechnological processes, cost-based analysis for the best possible industrial output.

Prof. Beom Soo Kim
Dr. Prasun Kumar
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Bioplastics from natural polymers
  • Bioplastics from synthetic polymers
  • Biodegradable plastics
  • Polyhydroxyalkanoates and their copolymers
  • Bioplastics from renewable substrates
  • Bioplastics based composites
  • Bioplastics based functional materials
  • Applications of bioplastics
  • Nanotechnology for bioplastics
  • Biotechnology for bioplastics

Published Papers (15 papers)

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Research

Jump to: Review

20 pages, 4260 KiB  
Article
Synergistic Mechanisms Underlie the Peroxide and Coagent Improvement of Natural-Rubber-Toughened Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Mechanical Performance
by Xiaoying Zhao, Katrina Cornish and Yael Vodovotz
Polymers 2019, 11(3), 565; https://doi.org/10.3390/polym11030565 - 26 Mar 2019
Cited by 25 | Viewed by 10952
Abstract
Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a promising bio-based and biodegradable thermoplastic with restricted industrial applications due to its brittleness and poor processability. Natural rubber (NR) has been used as a toughening agent, but further physical improvements are desired. In this study, rubber toughening efficiency was [...] Read more.
Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a promising bio-based and biodegradable thermoplastic with restricted industrial applications due to its brittleness and poor processability. Natural rubber (NR) has been used as a toughening agent, but further physical improvements are desired. In this study, rubber toughening efficiency was significantly improved through the synergistic use of a trifunctional acrylic coagent and an organic peroxide during reactive extrusion of PHBV and NR. The rheological, crystallization, thermal, morphological, and mechanical properties of PHBV/NR blends with 15% rubber loading were characterized. The peroxide and coagent synergistically crosslinked the rubber phase and grafted PHBV onto rubber backbones, leading to enhanced rubber modulus and cohesive strength as well as improved PHBV–rubber compatibility and blend homogeneity. Simultaneously, the peroxide–coagent treatment decreased PHBV crystallinity and crystal size and depressed peroxy-radical-caused PHBV degradation. The new PHBV/NR blends had a broader processing window, 75% better toughness (based on the notched impact strength data), and 100% better ductility (based on the tensile elongation data) than pristine PHBV. This new rubber-toughened PHBV material has balanced mechanical performance comparable to that of conventional thermoplastics and is suitable for a wide range of plastic applications. Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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14 pages, 2596 KiB  
Article
Towards High-performance Materials Based on Carbohydrate-Derived Polyamide Blends
by Aleksandra A. Wróblewska, Nils Leoné, Stefaan M. A. De Wildeman and Katrien V. Bernaerts
Polymers 2019, 11(3), 413; https://doi.org/10.3390/polym11030413 - 04 Mar 2019
Cited by 3 | Viewed by 3880
Abstract
A bio-derived monomer called 2,3:4,5-di-O-isopropylidene-galactarate acid/ester (GalXMe) has great potential in polymer production. The unique properties of this molecule, such as its rigidity and bulkiness, contribute to the good thermal properties and appealing transparency of the material. The main problem, however, [...] Read more.
A bio-derived monomer called 2,3:4,5-di-O-isopropylidene-galactarate acid/ester (GalXMe) has great potential in polymer production. The unique properties of this molecule, such as its rigidity and bulkiness, contribute to the good thermal properties and appealing transparency of the material. The main problem, however, is that like other biobased materials, the polymers derived thereof are very brittle. In this study, we report on the melt blending of GalXMe polyamides (PAs) with different commercial PA grades using extrusion as well as blend characterization. Biobased PA blends showed limited to no miscibility with other polyamides. However, their incorporation resulted in strong materials with high Young moduli. The increase in modulus of the prepared GalXMe blends with commercial PAs ranged from up to 75% for blends with aliphatic polyamide composed of 1,6-diaminohexane and 1,12-dodecanedioic acid PA(6,12) to up to 82% for blends with cycloaliphatic polyamide composed of 4,4′-methylenebis(cyclohexylamine) and 1,12-dodecanedioic acid PA(PACM,12). Investigation into the mechanism of blending revealed that for some polyamides a transamidation reaction improved the blend compatibility. The thermal stability of the biobased PAs depended on which diamine was used. Polymers with aliphatic/aromatic or alicyclic diamines showed no degradation, whereas with fully aromatic diamines such as p-phenylenediamine, some degradation processes were observed under extrusion conditions (260/270 °C). Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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22 pages, 9475 KiB  
Article
Incorporation of Carbon Nanofillers Tunes Mechanical and Electrical Percolation in PHBV:PLA Blends
by Jesse Arroyo and Cecily Ryan
Polymers 2018, 10(12), 1371; https://doi.org/10.3390/polym10121371 - 11 Dec 2018
Cited by 16 | Viewed by 4356
Abstract
Biobased fillers, such as bio-derived cellulose, lignin byproducts, and biochar, can be used to modify the thermal, mechanical, and electrical properties of polymer composites. Biochar (BioC), in particular, is of interest for enhancing thermal and electrical conductivities in composites, and can potentially serve [...] Read more.
Biobased fillers, such as bio-derived cellulose, lignin byproducts, and biochar, can be used to modify the thermal, mechanical, and electrical properties of polymer composites. Biochar (BioC), in particular, is of interest for enhancing thermal and electrical conductivities in composites, and can potentially serve as a bio-derived graphitic carbon alternative for certain composite applications. In this work, we investigate a blended biopolymer system: poly(lactic acid) (PLA)/poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), and addition of carbon black (CB), a commonly used functional filler as a comparison for Kraft lignin-derived BioC. We present calculations and experimental results for phase-separation and nanofiller phase affinity in this system, indicating that the CB localizes in the PHBV phase of the immiscible PHBV:PLA blends. The addition of BioC led to a deleterious reaction with the biopolymers, as indicated by blend morphology, differential scanning calorimetry showing significant melting peak reduction for the PLA phase, and a reduction in melt viscosity. For the CB nanofilled composites, electrical conductivity and dynamic mechanical analysis supported the ability to use phase separation in these blends to tune the percolation of mechanical and electrical properties, with a minimum percolation threshold found for the 80:20 blends of 1.6 wt.% CB. At 2% BioC (approximately the percolation threshold for CB), the 80:20 BioC nanocomposites had a resistance of 3.43 × 10 8 Ω as compared to 2.99 × 10 8 Ω for the CB, indicating that BioC could potentially perform comparably to CB as a conductive nanofiller if the processing challenges can be overcome for higher BioC loadings. Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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11 pages, 8992 KiB  
Article
Reinforcement of Castor Oil-Based Polyurethane with Surface Modification of Attapulgite
by Chengshuang Wang, Lili Dai, Zhengrui Yang, Chengcheng Ge, Shuiping Li, Meng He, Liang Ding and Hongfeng Xie
Polymers 2018, 10(11), 1236; https://doi.org/10.3390/polym10111236 - 07 Nov 2018
Cited by 12 | Viewed by 3937
Abstract
Polyurethane/attapulgite (PU/ATT) nanocomposites derived from castor oil were prepared by incorporation of 8 wt % ATT, acid-treated ATT, and KH560-treated ATT. The effects of three ATTs (ATT, acid-ATT, and KH560-ATT) on the comprehensive properties of PU/ATT nanocomposites were systematically investigated. The results showed [...] Read more.
Polyurethane/attapulgite (PU/ATT) nanocomposites derived from castor oil were prepared by incorporation of 8 wt % ATT, acid-treated ATT, and KH560-treated ATT. The effects of three ATTs (ATT, acid-ATT, and KH560-ATT) on the comprehensive properties of PU/ATT nanocomposites were systematically investigated. The results showed that the incorporation of 8 wt % of three ATTs could produce an obvious reinforcement on the castor oil-based PU and that the silane modification treatment, rather than the acid treatment, has the more effective reinforcement effect. SEM images revealed the uniform dispersion of ATT in the PU matrix. DMA confirmed that the storage modulus and glass transition temperature (Tg) of PU/ATT nanocomposites were significantly increased after blending with different ATTs. For PU/KH560-ATT8 nanocomposites, the thermal stability of the PU was obviously enhanced by the addition of KH560-ATT. In particular, 8 wt % KH560-ATT loaded castor oil-based PU nanocomposites exhibit an obvious improvement in tensile strength (255%), Young’s modulus (200%), Tg (5.1 °C), the storage modulus at 25 °C (104%), and the initial decomposition temperature (7.7 °C). The prepared bio-based PU materials could be a potential candidate to replace petroleum-based PU products in practical applications. Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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10 pages, 1388 KiB  
Article
Influence of Chain-Extension Reaction on Stereocomplexation, Mechanical Properties and Heat Resistance of Compressed Stereocomplex-Polylactide Bioplastic Films
by Yodthong Baimark and Sumet Kittipoom
Polymers 2018, 10(11), 1218; https://doi.org/10.3390/polym10111218 - 02 Nov 2018
Cited by 13 | Viewed by 3009
Abstract
Stereocomplex polylactide (scPLA) films were prepared by melt blending of poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) with and without an epoxy-based chain extender before compression molding. The obtained scPLA films were characterized through differential scanning calorimetry, X-ray diffractometry (XRD), tensile [...] Read more.
Stereocomplex polylactide (scPLA) films were prepared by melt blending of poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) with and without an epoxy-based chain extender before compression molding. The obtained scPLA films were characterized through differential scanning calorimetry, X-ray diffractometry (XRD), tensile testing and dimensional stability to heat. XRD patterns revealed that all the scPLA films had only stereocomplex crystallites. The obtained results showed that the chain-extension reaction improved mechanical properties of the scPLA films, however, it suppressed stereocomplexation and heat resistance. Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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12 pages, 1343 KiB  
Article
Application of Adzuki Bean Starch in Antioxidant Films Containing Cocoa Nibs Extract
by Sujin Kim, Su-Kyoung Baek, Eunjeong Go and Kyung Bin Song
Polymers 2018, 10(11), 1210; https://doi.org/10.3390/polym10111210 - 31 Oct 2018
Cited by 24 | Viewed by 3864
Abstract
In this study, starch extracted from adzuki bean (ABS) was used as a biodegradable film source. In addition, to develop a new antioxidant film, various amounts of cocoa nibs extract (CNE, 0.3%, 0.7%, and 1%) were incorporated. With the addition of CNE, the [...] Read more.
In this study, starch extracted from adzuki bean (ABS) was used as a biodegradable film source. In addition, to develop a new antioxidant film, various amounts of cocoa nibs extract (CNE, 0.3%, 0.7%, and 1%) were incorporated. With the addition of CNE, the elongation at break of the ABS films increased and the tensile strength decreased. The ABS films with CNE showed increased 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activities with increasing amounts of CNE. In particular, the ABTS and DPPH radical scavenging activities of the ABS films containing 1% CNE were 100% and 94.9%, respectively. Furthermore, decomposition of the films was observed after 28 days of biodegradation. Thus, ABS films containing CNE can be applied as a new active packaging material. Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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18 pages, 2785 KiB  
Article
Polyhydroxyalkanoate (PHA) Polymer Accumulation and pha Gene Expression in Phenazine (phz-) and Pyrrolnitrin (prn-) Defective Mutants of Pseudomonas chlororaphis PA23
by Parveen K. Sharma, Riffat I. Munir, Jocelyn Plouffe, Nidhi Shah, Teresa De Kievit and David B. Levin
Polymers 2018, 10(11), 1203; https://doi.org/10.3390/polym10111203 - 27 Oct 2018
Cited by 14 | Viewed by 5830
Abstract
Pseudomonas chlororaphis PA23 was isolated from the rhizosphere of soybeans and identified as a biocontrol bacterium against Sclerotinia sclerotiorum, a fungal plant pathogen. This bacterium produces a number of secondary metabolites, including phenazine-1-carboxylic acid, 2-hydroxyphenazine, pyrrolnitrin (PRN), hydrogen cyanide, proteases, lipases [...] Read more.
Pseudomonas chlororaphis PA23 was isolated from the rhizosphere of soybeans and identified as a biocontrol bacterium against Sclerotinia sclerotiorum, a fungal plant pathogen. This bacterium produces a number of secondary metabolites, including phenazine-1-carboxylic acid, 2-hydroxyphenazine, pyrrolnitrin (PRN), hydrogen cyanide, proteases, lipases and siderophores. It also synthesizes and accumulates polyhydroxyalkanoate (PHA) polymers as carbon and energy storage compounds under nutrient-limited conditions. Pseudomonads like P. chlororaphis metabolize glucose via the Entner-Doudoroff and Pentose Phosphate pathways, which provide precursors for phenazine production. Mutants defective in phenazine (PHZ; PA23-63), PRN (PA23-8), or both (PA23-63-1) accumulated higher concentrations of PHAs than the wild-type strain (PA23) when cultured in Ramsay’s Minimal Medium with glucose or octanoic acid as the carbon source. Expression levels of six pha genes, phaC1, phaZ, phaC2, phaD, phaF, and phaI, were compared with wild type PA23 by quantitative real time polymerase chain reaction (qPCR). The qPCR studies indicated that there was no change in levels of transcription of the PHA synthase genes phaC1 and phaC2 in the phz- (PA23-63) and phz- prn- (PA23-63-1) mutants in glucose medium. There was a significant increase in expression of phaC2 in octanoate medium. Transcription of phaD, phaF and phaI increased significantly in the phz- prn- (PA23-63-1) mutant. Mutations in regulatory genes like gacS, rpoS, and relA/spoT, which affect PHZ and PRN production, also resulted in altered gene expression. The expression of phaC1, phaC2, phaF, and phaI genes was down-regulated significantly in gacS and rpoS mutants. Thus, it appears that PHZ, PRN, and PHA production is regulated by common mechanisms. Higher PHA production in the phz- (PA23-63), prn- (PA23-8), and phz- prn- (PA23-63-1) mutants in octanoic medium could be correlated with higher expression of phaC2. Further, the greater PHA production observed in the phz- and prn- mutants was not due to increased transcription of PHA synthase genes in glucose medium, but due to more accessibility of carbon substrates and reducing power, which were otherwise used for the synthesis of PHZ and PRN. Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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12 pages, 2631 KiB  
Article
Highly Selective Enzymatic Recovery of Building Blocks from Wool-Cotton-Polyester Textile Waste Blends
by Felice Quartinello, Sara Vecchiato, Simone Weinberger, Klemens Kremenser, Lukas Skopek, Alessandro Pellis and Georg M. Guebitz
Polymers 2018, 10(10), 1107; https://doi.org/10.3390/polym10101107 - 07 Oct 2018
Cited by 44 | Viewed by 8290
Abstract
In Europe, most of the discarded and un-wearable textiles are incinerated or landfilled. In this study, we present an enzyme-based strategy for the recovery of valuable building blocks from mixed textile waste and blends as a circular economy concept. Therefore, model and real [...] Read more.
In Europe, most of the discarded and un-wearable textiles are incinerated or landfilled. In this study, we present an enzyme-based strategy for the recovery of valuable building blocks from mixed textile waste and blends as a circular economy concept. Therefore, model and real textile waste were sequentially incubated with (1) protease for the extraction of amino acids from wool components (95% efficiency) and (2) cellulases for the recovery of glucose from cotton and rayon constituents (85% efficiency). The purity of the remaining poly(ethylene terephthalate) (PET) unaltered by the enzymatic treatments was assessed via Fourier-transformed infrared spectroscopy. Amino acids recovered from wool were characterized via elementary and molecular size analysis, while the glucose resulting from the cotton hydrolysis was successfully converted into ethanol by fermentation with Saccharomyces cerevisiae. This work demonstrated that the step-wise application of enzymes can be used for the recovery of pure building blocks (glucose) and their further reuse in fermentative processes. Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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12 pages, 1502 KiB  
Article
Modification of Pea Starch and Dextrin Polymers with Isocyanate Functional Groups
by Reza Hosseinpourpia, Arantzazu Santamaria Echart, Stergios Adamopoulos, Nagore Gabilondo and Arantxa Eceiza
Polymers 2018, 10(9), 939; https://doi.org/10.3390/polym10090939 - 23 Aug 2018
Cited by 35 | Viewed by 5046
Abstract
Pea starch and dextrin polymers were modified through the unequal reactivity of isocyanate groups in isophorone diisocyanate (IPDI) monomer. The presence of both urethane and isocyanate functionalities in starch and dextrin after modification were confirmed by Fourier transform infrared spectroscopy (FTIR) and 13 [...] Read more.
Pea starch and dextrin polymers were modified through the unequal reactivity of isocyanate groups in isophorone diisocyanate (IPDI) monomer. The presence of both urethane and isocyanate functionalities in starch and dextrin after modification were confirmed by Fourier transform infrared spectroscopy (FTIR) and 13C nuclear magnetic resonance (13C NMR). The degree of substitution (DS) was calculated using elemental analysis data and showed higher DS values in modified dextrin than modified starch. The onsets of thermal degradation and temperatures at maximum mass losses were improved after modification of both starch and dextrin polymers compared to unmodified ones. Glass transition temperatures (Tg) of modified starch and dextrin were lower than unmodified control ones, and this was more pronounced in modified dextrin at a high molar ratio. Dynamic water vapor sorption of starch and dextrin polymers indicated a slight reduction in moisture sorption of modified starch, but considerably lower moisture sorption in modified dextrin as compared to that of unmodified ones. Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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16 pages, 4412 KiB  
Article
Microbial Conversion of Vegetable Oil to Hydroxy Fatty Acid and Its Application to Bio-Based Polyurethane Synthesis
by Tuan Kiet Tran, Prasun Kumar, Hak-Ryul Kim, Ching T. Hou and Beom Soo Kim
Polymers 2018, 10(8), 927; https://doi.org/10.3390/polym10080927 - 19 Aug 2018
Cited by 16 | Viewed by 6611
Abstract
New polyurethanes were synthesized based on dihydroxy fatty acid obtained by the microbial conversion of olive oil. Monounsaturated 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) was produced from olive oil by Pseudomonas aeruginosa PR3 and reacted with hexamethylene diisocyanate (HMDI) at different ratios to form polyurethanes. Fourier [...] Read more.
New polyurethanes were synthesized based on dihydroxy fatty acid obtained by the microbial conversion of olive oil. Monounsaturated 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) was produced from olive oil by Pseudomonas aeruginosa PR3 and reacted with hexamethylene diisocyanate (HMDI) at different ratios to form polyurethanes. Fourier transform infrared spectroscopy and gas chromatography/mass spectrometry confirmed the synthesis of DOD. The thermal and tensile properties of the polyurethanes were investigated by differential scanning calorimetry, thermogravimetric analysis, and a universal testing machine. At an isocyanate/hydroxyl ratio of 1.4, the polyurethane exhibited an elongation at break of 59.2% and a high tensile strength of 37.9 MPa. DOD was also mixed with polycaprolactone diol or polyethylene glycol at different weight ratios and then reacted with HMDI to produce new polyurethanes of various properties. These polyurethanes displayed higher elongation at break and good thermal stability. This is the first report on the synthesis of polyurethanes based on DOD produced by the microbial conversion of vegetable oil. Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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15 pages, 2404 KiB  
Article
Wood-PHA Composites: Mapping Opportunities
by Luigi-Jules Vandi, Clement Matthew Chan, Alan Werker, Des Richardson, Bronwyn Laycock and Steven Pratt
Polymers 2018, 10(7), 751; https://doi.org/10.3390/polym10070751 - 07 Jul 2018
Cited by 62 | Viewed by 9160
Abstract
Polyhydroxyalkanoate (PHA) biopolymers are emerging as attractive new sustainable polymers due to their true biodegradability and highly tuneable mechanical properties. However, despite significant investments, commercialisation barriers are hindering the capacity growth of PHA. In this work, we investigated the market potential for wood [...] Read more.
Polyhydroxyalkanoate (PHA) biopolymers are emerging as attractive new sustainable polymers due to their true biodegradability and highly tuneable mechanical properties. However, despite significant investments, commercialisation barriers are hindering the capacity growth of PHA. In this work, we investigated the market potential for wood plastic composites (WPCs) based on PHAs. We considered the latest global production capacity of PHAs, estimated at 66,000 tonnes/year, and examined the implications of using PHAs for WPC production on the WPC market. Results indicate that a hypothetical usage of the current global PHA production for WPC manufacture would only represent the equivalent of 4.4% of the global WPC market, which is currently experiencing a 10.5% compounded annual growth rate. An economic assessment revealed that a wood-PHA composite as a drop-in alternative WPC product could cost as little as 37% of the cost of its neat PHA counterpart. Thus, WPCs with PHA offer a means to access benefits of PHA in engineering applications at reduced costs; however, further developments are required to improve strain at failure. The successful adoption of wood-PHA composites into the market is furthermore reliant on support from public sector to encourage biodegradable products where recycling is not a ready solution. Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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11 pages, 3270 KiB  
Article
Sustainable Boron Nitride Nanosheet-Reinforced Cellulose Nanofiber Composite Film with Oxygen Barrier without the Cost of Color and Cytotoxicity
by Hoang-Linh Nguyen, Zahid Hanif, Seul-A Park, Bong Gill Choi, Thang Hong Tran, Dong Soo Hwang, Jeyoung Park, Sung Yeon Hwang and Dongyeop X. Oh
Polymers 2018, 10(5), 501; https://doi.org/10.3390/polym10050501 - 05 May 2018
Cited by 32 | Viewed by 5904
Abstract
This paper introduces a boron nitride nanosheet (BNNS)-reinforced cellulose nanofiber (CNF) film as a sustainable oxygen barrier film that can potentially be applied in food packaging. Most commodity plastics are oxygen-permeable. CNF exhibits an ideal oxygen transmission rate (OTR) of <1 cc/m2 [...] Read more.
This paper introduces a boron nitride nanosheet (BNNS)-reinforced cellulose nanofiber (CNF) film as a sustainable oxygen barrier film that can potentially be applied in food packaging. Most commodity plastics are oxygen-permeable. CNF exhibits an ideal oxygen transmission rate (OTR) of <1 cc/m2/day in highly controlled conditions. A CNF film typically fabricated by the air drying of a CNF aqueous solution reveals an OTR of 19.08 cc/m2/day. The addition of 0–5 wt % BNNS to the CNF dispersion before drying results in a composite film with highly improved OTR of 4.7 cc/m2/day, which is sufficient for meat and cheese packaging. BNNS as a 2D nanomaterial increases the pathway of oxygen gas and reduces the chances of pinhole formation during film fabrication involving water drying. In addition, BNNS improves the mechanical properties of the CNF films (Young’s modulus and tensile strength) without significant elongation reductions, probably due to the good miscibility of CNF and BNNS in the aqueous solution. Addition of BNNS also produces negligible color change, which is important for film aesthetics. An in vitro cell experiment was performed to reveal the low cytotoxicity of the CNF/BNNS composite. This composite film has great potential as a sustainable high-performance food-packaging material. Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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Review

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29 pages, 4730 KiB  
Review
Thermoplastic Processing of PLA/Cellulose Nanomaterials Composites
by T. C. Mokhena, J. S. Sefadi, E. R. Sadiku, M. J. John, M. J. Mochane and A. Mtibe
Polymers 2018, 10(12), 1363; https://doi.org/10.3390/polym10121363 - 09 Dec 2018
Cited by 115 | Viewed by 9209
Abstract
Over the past decades, research has escalated on the use of polylactic acid (PLA) as a replacement for petroleum-based polymers. This is due to its valuable properties, such as renewability, biodegradability, biocompatibility and good thermomechanical properties. Despite possessing good mechanical properties comparable to [...] Read more.
Over the past decades, research has escalated on the use of polylactic acid (PLA) as a replacement for petroleum-based polymers. This is due to its valuable properties, such as renewability, biodegradability, biocompatibility and good thermomechanical properties. Despite possessing good mechanical properties comparable to conventional petroleum-based polymers, PLA suffers from some shortcomings such as low thermal resistance, heat distortion temperature and rate of crystallization, thus different fillers have been used to overcome these limitations. In the framework of environmentally friendly processes and products, there has been growing interest on the use of cellulose nanomaterials viz. cellulose nanocrystals (CNC) and nanofibers (CNF) as natural fillers for PLA towards advanced applications other than short-term packaging and biomedical. Cellulosic nanomaterials are renewable in nature, biodegradable, eco-friendly and they possess high strength and stiffness. In the case of eco-friendly processes, various conventional processing techniques, such as melt extrusion, melt-spinning, and compression molding, have been used to produce PLA composites. This review addresses the critical factors in the manufacturing of PLA-cellulosic nanomaterials by using conventional techniques and recent advances needed to promote and improve the dispersion of the cellulosic nanomaterials. Different aspects, including morphology, mechanical behavior and thermal properties, as well as comparisons of CNC- and CNF-reinforced PLA, are also discussed. Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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29 pages, 358 KiB  
Review
Bioreactor Operating Strategies for Improved Polyhydroxyalkanoate (PHA) Productivity
by Warren Blunt, David B. Levin and Nazim Cicek
Polymers 2018, 10(11), 1197; https://doi.org/10.3390/polym10111197 - 26 Oct 2018
Cited by 61 | Viewed by 12025
Abstract
Microbial polyhydroxyalkanoates (PHAs) are promising biodegradable polymers that may alleviate some of the environmental burden of petroleum-derived polymers. The requirements for carbon substrates and energy for bioreactor operations are major factors contributing to the high production costs and environmental impact of PHAs. Improving [...] Read more.
Microbial polyhydroxyalkanoates (PHAs) are promising biodegradable polymers that may alleviate some of the environmental burden of petroleum-derived polymers. The requirements for carbon substrates and energy for bioreactor operations are major factors contributing to the high production costs and environmental impact of PHAs. Improving the process productivity is an important aspect of cost reduction, which has been attempted using a variety of fed-batch, continuous, and semi-continuous bioreactor systems, with variable results. The purpose of this review is to summarize the bioreactor operations targeting high PHA productivity using pure cultures. The highest volumetric PHA productivity was reported more than 20 years ago for poly(3-hydroxybutryate) (PHB) production from sucrose (5.1 g L−1 h−1). In the time since, similar results have not been achieved on a scale of more than 100 L. More recently, a number fed-batch and semi-continuous (cyclic) bioreactor operation strategies have reported reasonably high productivities (1 g L−1 h−1 to 2 g L−1 h−1) under more realistic conditions for pilot or industrial-scale production, including the utilization of lower-cost waste carbon substrates and atmospheric air as the aeration medium, as well as cultivation under non-sterile conditions. Little development has occurred in the area of fully continuously fed bioreactor systems over the last eight years. Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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12 pages, 507 KiB  
Review
Role of PhaC Type I and Type II Enzymes during PHA Biosynthesis
by Valeria Mezzolla, Oscar Fernando D’Urso and Palmiro Poltronieri
Polymers 2018, 10(8), 910; https://doi.org/10.3390/polym10080910 - 13 Aug 2018
Cited by 43 | Viewed by 6954
Abstract
PHA synthases (PhaC) are grouped into four classes based on the kinetics and mechanisms of reaction. The grouping of PhaC enzymes into four classes is dependent on substrate specificity, according to the preference in forming short-chain-length (scl) or medium-chain-length (mcl) polymers: Class I, [...] Read more.
PHA synthases (PhaC) are grouped into four classes based on the kinetics and mechanisms of reaction. The grouping of PhaC enzymes into four classes is dependent on substrate specificity, according to the preference in forming short-chain-length (scl) or medium-chain-length (mcl) polymers: Class I, Class III and Class IV produce scl-PHAs depending on propionate, butyrate, valerate and hexanoate precursors, while Class II PhaC synthesize mcl-PHAs based on the alkane (C6 to C14) precursors. PHA synthases of Class I, in particular PhaCCs from Chromobacterium USM2 and PhaCCn/RePhaC1 from Cupriavidus necator/Ralstonia eutropha, have been analysed and the crystal structures of the C-domains have been determined. PhaCCn/RePhaC1 was also studied by X-ray absorption fine-structure (XAFS) analysis. Models have been proposed for dimerization, catalysis mechanism, substrate recognition and affinity, product formation, and product egress route. The assays based on amino acid substitution by mutagenesis have been useful to validate the hypothesis on the role of amino acids in catalysis and in accommodation of bulky substrates, and for the synthesis of PHB copolymers and medium-chain-length PHA polymers with optimized chemical properties. Full article
(This article belongs to the Special Issue Recent Advances in Bioplastics)
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