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Environment-Friendly Polymers and Composites: Synthesis, Processing and Applications

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A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Applications".

Deadline for manuscript submissions: closed (25 June 2023) | Viewed by 20246

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Dr. Francesca Ferrari

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Department of Engineering for Innovation, University of Salento, 73100 Lecce, Italy
Interests: bio-based thermoplastics and thermosets; synthesis of bio-precursors; thermal analysis; rheology; plasticization; recycling
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In recent years, growing environmental awareness has motivated researchers from both industry and academia to replace petroleum-derived polymers and additives with bioplastics by developing environmentally friendly thermoplastic polymers from bio-based and biodegradable raw materials. The use of petroleum-based raw materials for the synthesis of starting monomers is also a strong limit for thermoset matrices, which are often used for the production of composites. The synthesis of bio-based monomers involves the use of natural sources such as vegetable oils, natural acids, lignin, and so forth. Recently, innovative feedstocks obtained from food scraps, algae biomass and industrial or municipal waste have been used for the production of bio-polymers, thus allowing the valorization of the waste. New procedures for the synthesis of precursors from natural renewable resources have also recently emerged which aim to decrease or remove the use of organic solvents, thus developing a truly green approach.

Hence, polymers obtained from renewable resources are becoming increasingly important as highly sustainable, eco-efficient, and biodegradable products. Due to the rapid rate of development, bio-based polymers are expected to be seen in commodity applications in the near future.

This Special Issue aims to investigate the synthesis, processing and applications of bio-based polymers. Both original contributions and comprehensive reviews are welcome. Potential topics include but are not limited to the following:

Synthesis of bio-polymers;
Classification of raw materials and waste valorization;
Analysis of bio-polymers;
Physics of bio-based polymers;
Processing and performances of bio-based polymers;
Additive manufacturing of bio-based materials;
Biodegradability of polymeric materials;
Bio-composites;
Recycling of bio-based thermoplastics and thermosets;
Bio-based additives for polymers.

Dr. Francesca Ferrari
Guest Editor

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

bio-based polymers
waste valorization
synthesis, physics, and analysis of bio-polymers
bio-based composites
additive manufacturing of bio-polymers
recycling strategies of bio-thermoplastics and bio-thermosets
application of bio-based polymeric materials
biodegradability
bio-based additives

Published Papers (10 papers)

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Research

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12 pages, 3944 KiB

Open AccessArticle

A Biodegradable, Polymer-Supported Oxygen Atom Transfer Reagent

by Erin E. Ramey, Elizabeth L. Whitman, Cole E. Buller, James R. Tucker, Charles S. Jolly, Kjersti G. Oberle, Austin J. Becksvoort, Mark Turlington and Christopher R. Turlington

Polymers 2023, 15(9), 2052; https://doi.org/10.3390/polym15092052 - 26 Apr 2023

Viewed by 1189

Abstract

Biodegradable polymers are desirable to mitigate the environmental impact of plastic waste in the environment. Over the past several decades, the development of organocatalytic ring-opening polymerization (OROP) has made the synthesis of many new types of biodegradable polymers possible. In this research article, the first example of an oxygen atom transfer reagent pendant on a biodegradable polymer backbone is reported. The monomers for the polycarbonate backbone are sourced from the biodegradable 2,2-bis(hydroxymethyl) propionic acid molecule, and an iodoaryl group is installed pendant to the cyclic monomer for post-polymerization modification into an iodosylaryl oxygen atom transfer reagent. The key I-O bond is characterized by XPS spectroscopy, and a test reaction to triphenylphosphine demonstrates the ability of the polymer to engage in an oxygen atom transfer reaction with a substrate. Full article

(This article belongs to the Special Issue Environment-Friendly Polymers and Composites: Synthesis, Processing and Applications)

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17 pages, 6635 KiB

Open AccessArticle

In Situ Synthesis of Environmentally Friendly Waterborne Polyurethane Extended with Regenerated Cellulose Nanoparticles for Enhanced Mechanical Performances

by Soon Mo Choi, Soo Young Lee, Sunhee Lee, Sung Soo Han and Eun Joo Shin

Polymers 2023, 15(6), 1541; https://doi.org/10.3390/polym15061541 - 20 Mar 2023

Cited by 2 | Viewed by 1235

Abstract

The development of waterborne polyurethane (WPU) has been stimulated as an alternative to solvent-based polyurethanes due to low-VOC alternatives and reduced exposure to solvents. However, their relatively low mechanical performance and degradation have presented challenges in their wide application. Here, we developed environmentally-friendly bio polyol-based WPU nanocomposite dispersions and films, and presented the optimal process conditions for their manufacture. Additionally, the condition was established without using harmful catalysts or ethyl methyl ketone (MEK) during the polymerization. Moreover, regenerated cellulose nanoparticles (RCNs) were employed as natural chain-extenders in order to improve the biodegradability and mechanical performances of the nanocomposite films. The RCNs have a lower crystallinity compared to cellulose nanocrystals (CNCs), allowing them to possess high toughness without interfering with the elastomeric properties of polyurethane. The prepared CWPU/RCNs nanocomposite films exhibited high toughness of 58.8 ± 3 kgf∙mm and elongation at break of 240 ± 20%. In addition, depending on the molar ratio of NCO/OH, the polyurethane particle size is variously controlled from 70 to 230 nm, enabling to fabricate their dispersions with various transmittances. We believe that our findings not only open a meaningful path toward green elastomers with biodegradability but provides the design concept for bio-elastomers in order to develop industrial elastomers with mechanical and thermal properties. Full article

(This article belongs to the Special Issue Environment-Friendly Polymers and Composites: Synthesis, Processing and Applications)

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21 pages, 7799 KiB

Open AccessArticle

Antibacterial Activity of Ulva/Nanocellulose and Ulva/Ag/Cellulose Nanocomposites and Both Blended with Fluoride against Bacteria Causing Dental Decay

by Ragaa A. Hamouda, Fauzia A. K. Qarabai, Fathi S. Shahabuddin, Turki M. Al-Shaikh and Rabab R. Makharita

Polymers 2023, 15(4), 1047; https://doi.org/10.3390/polym15041047 - 20 Feb 2023

Cited by 7 | Viewed by 1816

Abstract

One of the most prevalent chronic infectious disorders is tooth decay. Acids produced when plaque bacteria break down sugar in the mouth cause tooth decay. Streptococcus mutans and Lactobacillus acidophilus are the most prominent species related to dental caries. Innovative biocidal agents that integrate with a biomaterial to prevent bacterial colonization have shown remarkable promise as a result of the rapid advancement of nanoscience and nanotechnology. In this study, Ulva lactuca was used as a cellulose source and reducing agent to synthesize nanocellulose and Ulva/Ag/cellulose/nanocomposites. The characterizations of nanocellulose and Ulva/Ag/cellulose/nanocomposites were tested for FT-IR, TEM, SEM, EDS, XRD, and zeta potential. Ulva/Ag/cellulose/nanocomposites and Ulva/nanocellulose, both blended with fluoride, were tested as an antibacterial against S. mutans ATCC 25175 and L. acidophilus CH-2. The results of the SEM proved that nanocellulose is filament-shaped, and FT-IR proved that the functional groups of Ulva/nanocellulose and Ulva/Ag/cellulose/nanocomposites and cellulose are relatively similar but present some small diffusion in peaks. The TEM image demonstrated that the more piratical size distribution of Ulva/Ag/cellulose/nanocomposites ranged from 15 to 20 nm, and Ulva/nanocellulose ranged from 10 to 15 nm. Ulva/Ag/cellulose/nanocomposites have higher negativity than Ulva/nanocellulose. Ulva/Ag/cellulose/nanocomposites and Ulva/nanocellulose possess antibacterial activity against S. mutans ATCC 25175 and L. acidophilus CH-2, but Ulva/Ag/cellulose/nanocomposites are more effective, followed by that blended with fluoride. It is possible to use Ulva/Ag/cellulose/nanocomposites as an antimicrobial agent when added to toothpaste. It is promising to discover an economic and safe nanocomposite product from a natural source with an antimicrobial agent that might be used against tooth bacteria. Full article

(This article belongs to the Special Issue Environment-Friendly Polymers and Composites: Synthesis, Processing and Applications)

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17 pages, 4366 KiB

Open AccessArticle

Improved Denitrification Performance of Polybutylene Succinate/Corncob Composite Carbon Source by Proper Pretreatment: Performance, Functional Genes and Microbial Community Structure

by Zhongchen Yang, Yanhong Lou, Hong Pan, Hui Wang, Quangang Yang, Yuping Zhuge and Jingying Hu

Polymers 2023, 15(4), 801; https://doi.org/10.3390/polym15040801 - 05 Feb 2023

Cited by 4 | Viewed by 1244

Abstract

Blending biodegradable polymers with plant materials is an effective method to improve the biodegradability of solid carbon sources and save denitrification costs, but the recalcitrant lignin in plant materials hinders the microbial decomposition of available carbon sources. In the present study, corncob pretreated by different methods was used to prepare polybutylene succinate/corncob (PBS/corncob) composites for biological denitrification. The PBS/corncob composite with alkaline pretreatment achieved the optimal NO₃⁻-N removal rate (0.13 kg NO₃⁻-N m⁻³ day⁻¹) with less adverse effects. The pretreatment degree, temperature, and their interaction distinctly impacted the nitrogen removal performance and dissolved organic carbon (DOC) release, while the N₂O emission was mainly affected by the temperature and the interaction of temperature and pretreatment degree. Microbial community analysis showed that the bacterial community was responsible for both denitrification and lignocellulose degradation, while the fungal community was primarily in charge of lignocellulose degradation. The outcomes of this study provide an effective strategy for improving the denitrification performance of composite carbon sources. Full article

(This article belongs to the Special Issue Environment-Friendly Polymers and Composites: Synthesis, Processing and Applications)

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14 pages, 1407 KiB

Open AccessArticle

Biopolymer Non-Parametric Analysis: A Degradation Study under Accelerated Destructive Tests

by Elias H. Arias-Nava, Delia J. Valles-Rosales and B. Patrick Sullivan

Polymers 2023, 15(3), 620; https://doi.org/10.3390/polym15030620 - 25 Jan 2023

Cited by 4 | Viewed by 1318

Abstract

The degradation of biopolymers such as polylactic acid (PLA) has been studied for several years; however, the results regarding the mechanism of degradation are not completely understood yet. PLA is easily processed by traditional techniques including injection molding, blow molding, extrusion, and thermoforming; in this research, the extrusion and injection molding processes were used to produce PLA samples for accelerated destructive testing. The methodology employed consisted of carrying out material testing under the guidelines of several ASTM standards; this research hypothesized that the effects of UV light, humidity, and temperature exposure have a statistical difference in the PLA degradation rate. The multivariate analysis of non-parametric data is presented as an alternative to multivariate analysis, in which the data do not satisfy the essential assumptions of a regular MANOVA, such as multivariate normality. A package in the R software that allows the user to perform a non-parametric multivariate analysis when necessary was used. This paper presents a study to determine if there is a significant difference in the degradation rate after 2000 h of accelerated degradation of a biopolymer using the multivariate and non-parametric analyses of variance. The combination of the statistical techniques, multivariate analysis of variance and repeated measures, provided information for a better understanding of the degradation path of the biopolymer. Full article

(This article belongs to the Special Issue Environment-Friendly Polymers and Composites: Synthesis, Processing and Applications)

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21 pages, 5683 KiB

Open AccessArticle

Recycling of EPDM via Continuous Thermo-Mechanical Devulcanization with Co-Rotating Twin-Screw Extruder

by Valentina Brunella, Veronica Aresti, Umberto Romagnolli, Bruno Muscato, Marco Girotto, Paola Rizzi and Maria Paola Luda

Polymers 2022, 14(22), 4853; https://doi.org/10.3390/polym14224853 - 11 Nov 2022

Cited by 5 | Viewed by 2574

Abstract

Devulcanization represents the recycling of choice for a homogenous rubber waste stream because it allows revulcanization of samples previously devulcanized, making the life of the rubber virtually endless, according to the principles of circular economy. Among the many devulcanization processes, the thermo-mechanical one is the most appealing because it is a continuous process, easy to be industrialized. In this paper a comprehensive set of analyses (FTIR, TGA, DSC, elemental analyses, Py-GC/MS, swelling tests) were carried out on a post-industrial ethylene propylene diene monomer (EPDM), thermo-mechanical devulcanized in a co-rotating twin-screw extruder with different process parameters (thermal and screw profile, rpm). Results of the swelling test according to the Flory–Rehner theory and Horikx analyses show that the higher the thermal profile and the higher the rpm, the higher is the percentage of devulcanization. The quality of the devulcanized sample in terms of sol fraction and percentage of random scissions depends on the process conditions. The screw profile concurs to the efficiency of the devulcanization: the different number of kneading elements and more in general the screw profile composition affects the percentage of devulcanization, making the results in some tests more dependent on the screw speed. Full article

(This article belongs to the Special Issue Environment-Friendly Polymers and Composites: Synthesis, Processing and Applications)

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12 pages, 3435 KiB

Open AccessArticle

Innovative Closed-Loop Recyclable Bio-Based Composites from Epoxidized Waste Flour and Recycled Carbon Fibers

by Francesca Ferrari, Gloria Anna Carallo and Antonio Greco

Polymers 2022, 14(18), 3878; https://doi.org/10.3390/polym14183878 - 16 Sep 2022

Cited by 3 | Viewed by 1781

Abstract

Epoxy-based composites are designed for long-lasting applications, though their wide use is in contrast with their poor recyclability, which poses serious end-of-life issues. In order to reduce their environmental impact, precursors derived from fossil fuel based raw materials should be replaced with eco-friendly sources. This can be attained by using naturally derived epoxy matrices, or by finding a suitable solution for recycling at the end of life. In this paper, both strategies were analyzed, by replacing traditional monomers with epoxidized waste flour (EWF), an innovative bio-precursor derived from the organic waste stream, and a cleavable hardener, which allowed the recyclability of the matrix. The recyclable matrix was reinforced with recycled carbon fibers, derived from pyrolysis. DSC measurements were carried out in order to optimize the curing steps of the matrix, then flexural tests were performed in order to evaluate the mechanical response of the composite. A green recycling procedure was then investigated, which involved the use of non-toxic solvents and mild working conditions, and allowed recovery of the matrix while still preserving the properties of the carbon fibers. The components obtained after recycling were analyzed by FTIR analysis, which revealed the presence of the epoxy ring on the recycled waste flour. Hence, recycled waste flour was again used as a precursor and mixed with the cleavable hardener, thus, obtaining a closed-loop recycling. Full article

(This article belongs to the Special Issue Environment-Friendly Polymers and Composites: Synthesis, Processing and Applications)

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Review

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28 pages, 64856 KiB

Open AccessReview

Advances in the One-Step Approach of Polymeric Materials Using Enzymatic Techniques

by Richard Ansah Herman, Xuan Zhu, Ellen Ayepa, Shuai You and Jun Wang

Polymers 2023, 15(3), 703; https://doi.org/10.3390/polym15030703 - 30 Jan 2023

Cited by 1 | Viewed by 2028

Abstract

The formulation in which biochemical enzymes are administered in polymer science plays a key role in retaining their catalytic activity. The one-step synthesis of polymers with highly sequence-controlled enzymes is a strategy employed to provide enzymes with higher catalytic activity and thermostability in material sustainability. Enzyme-catalyzed chain growth polymerization reactions using activated monomers, protein–polymer complexation techniques, covalent and non-covalent interaction, and electrostatic interactions can provide means to develop formulations that maintain the stability of the enzyme during complex material processes. Multifarious applications of catalytic enzymes are usually attributed to their efficiency, pH, and temperature, thus, progressing with a critical structure-controlled synthesis of polymer materials. Due to the obvious economics of manufacturing and environmental sustainability, the green synthesis of enzyme-catalyzed materials has attracted significant interest. Several enzymes from microorganisms and plants via enzyme-mediated material synthesis have provided a viable alternative for the appropriate synthesis of polymers, effectively utilizing the one-step approach. This review analyzes more and deeper strategies and material technologies widely used in multi-enzyme cascade platforms for engineering polymer materials, as well as their potential industrial applications, to provide an update on current trends and gaps in the one-step synthesis of materials using catalytic enzymes. Full article

(This article belongs to the Special Issue Environment-Friendly Polymers and Composites: Synthesis, Processing and Applications)

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35 pages, 15696 KiB

Open AccessReview

Biodegradable Polymers in Triboelectric Nanogenerators

by Yajun Mi, Yin Lu, Yalin Shi, Zequan Zhao, Xueqing Wang, Jiajing Meng, Xia Cao and Ning Wang

Polymers 2023, 15(1), 222; https://doi.org/10.3390/polym15010222 - 31 Dec 2022

Cited by 31 | Viewed by 3961

Abstract

Triboelectric nanogenerators (TENGs) have attracted much attention because they not only efficiently harvest energy from the surrounding environment and living organisms but also serve as multifunctional sensors toward the detection of various chemical and physical stimuli. In particular, biodegradable TENG (BD-TENG) represents an emerging type of self-powered device that can be degraded, either in physiological environments as an implantable power source without the necessity of second surgery for device retrieval, or in the ambient environment to minimize associated environmental pollution. Such TENGs or TNEG-based self-powered devices can find important applications in many scenarios, such as tissue regeneration, drug release, pacemakers, etc. In this review, the recent progress of TENGs developed on the basis of biodegradable polymers is comprehensively summarized. Material strategies and fabrication schemes of biodegradable and self-powered devices are thoroughly introduced according to the classification of plant-degradable polymer, animal-degradable polymer, and synthetic degradable polymer. Finally, current problems, challenges, and potential opportunities for the future development of BD-TENGs are discussed. We hope this work may provide new insights for modulating the design of BD-TNEGs that can be beneficial for both environmental protection and healthcare. Full article

(This article belongs to the Special Issue Environment-Friendly Polymers and Composites: Synthesis, Processing and Applications)

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23 pages, 1389 KiB

Open AccessReview

Utilization of Polymeric Materials toward Sustainable Biodiesel Industry: A Recent Review

by Fozy Binhweel, Mardiana Idayu Ahmad and Sheikh Ahmad Zaki

Polymers 2022, 14(19), 3950; https://doi.org/10.3390/polym14193950 - 21 Sep 2022

Cited by 7 | Viewed by 1882

Abstract

The biodiesel industry is expanding rapidly in accordance with the high energy demand and environmental deterioration related to the combustion of fossil fuel. However, poor physicochemical properties and the malperformance of biodiesel fuel still concern the researchers. In this flow, polymers were introduced in biodiesel industry to overcome such drawbacks. This paper reviewed the current utilizations of polymers in biodiesel industry. Hence, four utilizing approaches were discussed, namely polymeric biodiesel, polymeric catalysts, cold-flow improvers (CFIs), and stabilized exposure materials. Hydroxyalkanoates methyl ester (HAME) and hydroxybutyrate methyl ester (HBME) are known as polymeric biodiesel sourced from carbon-enriched polymers with the help of microbial activity. Based on the literature, the highest HBME yield was 70.7% obtained at 10% H₂SO₄ ratio in methanol, 67 °C, and 50 h. With increasing time to 60 h, HAME highest yield was reported as 68%. In addition, polymers offer wide range of esterification/transesterification catalysts. Based on the source, this review classified polymeric catalysts as chemically, naturally, and waste derived polymeric catalysts. Those catalysts proved efficiency, non-toxicity, economic feasibility, and reusability till the 10th cycle for some polymeric composites. Besides catalysis, polymers proved efficiency to enhance the biodiesel flow-properties. The best effect reported in this review was an 11 °C reduction for the pour point (PP) of canola biodiesel at 1 wt% of ethylene/vinyl acetate copolymers and cold filter plugging point (CFPP) of B20 waste oil biodiesel at 0.08 wt% of EVA copolymer. Polymeric CFIs have the capability to modify biodiesel agglomeration and facilitate flowing. Lastly, polymers are utilized for storage tanks and auto parts products in direct contact with biodiesel. This approach is completely exclusive for polymers that showed stability toward biodiesel exposure, such as polyoxymethylene (POM) that showed insignificant change during static immersion test for 98 days at 55 °C. Indeed, the introduction of polymers has expanded in the biodiesel industry to promote green chemistry. Full article

(This article belongs to the Special Issue Environment-Friendly Polymers and Composites: Synthesis, Processing and Applications)

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