Polymers

20 pages, 1283 KiB

Open AccessArticle

Antioxidant Biocomposite Films Based on Grape Stalk Lignocellulosic Fractions and Biodegradable Polyesters

by Irene Maté, Lorena Atarés, Maria Vargas and Amparo Chiralt

Polymers 2025, 17(11), 1525; https://doi.org/10.3390/polym17111525 (registering DOI) - 29 May 2025

Grape stalk (GS) from winemaking is a waste rich in antioxidant compounds that can be valorized to obtain active food packaging materials. Biocomposite films of poly (butylene succinate) (PBS) and poly(3-hydroxybutyrate)-co-hydroxyvalerate (PHBV) with 10% of GS particles, previously submitted or not to subcritical [...] Read more.

Grape stalk (GS) from winemaking is a waste rich in antioxidant compounds that can be valorized to obtain active food packaging materials. Biocomposite films of poly (butylene succinate) (PBS) and poly(3-hydroxybutyrate)-co-hydroxyvalerate (PHBV) with 10% of GS particles, previously submitted or not to subcritical water extraction at 170 °C and 180 °C, were obtained by melt blending and characterized. The fibres were better integrated in the PHBV matrix than in PBS, while other molecular compounds from the fillers were released to the polymer matrix, allowing for their antioxidant action. Fillers promoted the stiffness of PBS films (11–44%), reducing their resistance to break and extensibility by 25%, without significant changes in polymer crystallinity or thermal stability. However, this reduced the crystallinity (13%) and thermal stability of PHBV films, decreasing their rigidity (55%). All fibres promoted the oxygen barrier capacity in composites (by about 20–35% for PBS and PHBV, respectively) while also providing them with UV light blocking effects. This barrier effect enhanced the ability of the films to preserve sunflower oil against oxidation, while in PHBV composites, the migration of antioxidant compounds was also detected. No remarkable differences in the effects of the different GS fillers on the properties of composites were detected. Full article

(This article belongs to the Section Biobased and Biodegradable Polymers)

13 pages, 754 KiB

Open AccessArticle

Multi-Objective Optimization of Injection Molding Process Parameters of Car Lamp Shell Based on Grey Correlation Analysis

by Ruixia Shan, Anqin Liu, Sen Jia, Changyou Liu and Wenguang Yang

Polymers 2025, 17(11), 1524; https://doi.org/10.3390/polym17111524 - 29 May 2025

Abstract

In order to improve the injection molding quality of the car lamp shell, orthogonal test, signal-to-noise ratio, gray correlation analysis, and CRITIC weight method were used to analyze the influence of mold temperature, melt temperature, injection time, velocity to pressure control, pressure holding [...] Read more.

In order to improve the injection molding quality of the car lamp shell, orthogonal test, signal-to-noise ratio, gray correlation analysis, and CRITIC weight method were used to analyze the influence of mold temperature, melt temperature, injection time, velocity to pressure control, pressure holding pressure and pressure holding time on the shrinkage index and the total deformation of warpage, and fully consider the difference and correlation between the evaluation parameters. The multi-objective optimization is transformed into single-objective optimization, and the optimal parameter set is obtained. The experimental results show that, compared with the initial analysis results, the indentation index of the headlight shell is reduced by 33.95%, the total warpage deformation is reduced by 13.99%, and the forming quality of the headlight shell is improved. The research results provide a theoretical reference value for multi-objective optimization of plastic injection molding process parameters. Full article

(This article belongs to the Section Polymer Processing and Engineering)

33 pages, 1843 KiB

Open AccessReview

Sawdust as a Byproduct of Wood Processing: Properties, Applications and a Reinforcing Filler in Hybrid Polymer Composites

by Tlholohelo Sylvia Sikhosana, Ntsoaki Joyce Malebo, Tladi Gideon Mofokeng, Mpho Phillip Motloung and Mokgaotsa Jonas Mochane

Polymers 2025, 17(11), 1523; https://doi.org/10.3390/polym17111523 - 29 May 2025

Abstract

There is a sizeable amount of sawdust produced from wood industries such as timber and furniture. In the past, sawdust has been utilized as a fuel source and in the manufacturing of furniture. Based on the limited use of sawdust, there is plenty [...] Read more.

There is a sizeable amount of sawdust produced from wood industries such as timber and furniture. In the past, sawdust has been utilized as a fuel source and in the manufacturing of furniture. Based on the limited use of sawdust, there is plenty of sawdust accessible from the industries. Sawdust is the material of choice due to its cost effectiveness, environmental friendliness, and biodegradability. However, if sawdust is not appropriately disposed or utilized better, it may have negative impact on the aquatic life and organic products. Hence, this review paper discusses the best possible methods or proper routes for the utilization of sawdust to benefit the environment, society, and the economy at large. Sawdust possesses superior capabilities as a reinforcing filler in various polymer matrices for advanced applications. This paper provides an in-depth discussion on sawdust hybrid composites in comparison to other natural fibres hybrid composites. The applications of various sawdust hybrid polymer composites for specific systems are also mentioned. Furthermore, the morphology and preparation of the sawdust/polymer composites and/or sawdust hybrid polymers composites are also discussed since it is well known that the properties of the natural fibre composites are affected by the preparation method and the resultant morphology. Based on the above, the current paper also plays a critical role in providing more information about waste to value added products. Full article

(This article belongs to the Special Issue Agricultural Waste-Reinforced Polymer Composites: Preparation and Characterization)

24 pages, 1986 KiB

Open AccessArticle

Cheminformatics Approaches to the Analysis of Additives for Sustainable Polymeric Materials

by Alina Bărbulescu and Lucica Barbeș

Polymers 2025, 17(11), 1522; https://doi.org/10.3390/polym17111522 - 29 May 2025

Abstract

Additives are compounds used for material to increase specific properties. When used for polymers, they extend their life and contribute to environmental sustainability. This article presents the study findings related to 24 additives—antioxidants, UV stabilizers, and quenchers—using cheminformatics methods. The compounds’ characteristics (e.g., [...] Read more.

Additives are compounds used for material to increase specific properties. When used for polymers, they extend their life and contribute to environmental sustainability. This article presents the study findings related to 24 additives—antioxidants, UV stabilizers, and quenchers—using cheminformatics methods. The compounds’ characteristics (e.g., number of atoms, functional groups) were emphasized, followed by some descriptors. The Tanimoto coefficient, computed based on the maximum common structure algorithm, and the overlap coefficient indicated the degree of similarity between the molecules. The molecules were grouped by binning and hierarchical clustering (HC) based on the extracted results. In the last case, two scenarios were considered—with four (CL1–CL4) and six clusters (CL1.1, CL1.2, CL2, CL3, CL4.1, CL4.2) being built. Considering the mechanical properties of the compounds and the standard deviation and amplitude of their values, the most homogenous class was CL2 (respectively CL4.2). Considering the toxicity of additives, the highest possible negative impact on the environment is that of the compounds in CL1 and CL3. The clustering results guide the selection of additives with reduced environmental impact, thereby supporting the development of sustainable polymer formulations aligned with circular economy principles. Full article

(This article belongs to the Special Issue Sustainable Polymers for a Circular Economy)

► Show Figures

Figure 1

39 pages, 7808 KiB

Open AccessReview

Sustainable Solutions for Plastic Waste Mitigation in Sub-Saharan Africa: Challenges and Future Perspectives Review

by Comfort Yeboaa, Emmanuel Kweinor Tetteh, Martha Noro Chollom and Sudesh Rathilal

Polymers 2025, 17(11), 1521; https://doi.org/10.3390/polym17111521 - 29 May 2025

Abstract

The anthropogenic deployment of plastic waste, especially petroleum-based plastics with toxic hydrocarbons, presents a significant environmental and health threat in sub-Saharan Africa (SSA). Herein, the high demand and rapid plastic production, coupled with improper disposal and inadequate waste management, have led to widespread [...] Read more.

The anthropogenic deployment of plastic waste, especially petroleum-based plastics with toxic hydrocarbons, presents a significant environmental and health threat in sub-Saharan Africa (SSA). Herein, the high demand and rapid plastic production, coupled with improper disposal and inadequate waste management, have led to widespread contamination of air, water, and soil. Conventionally, plastic waste management, such as incineration and recycling, provides limited long-term solutions to this growing crisis. This necessitates urgent, sustainable, and eco-friendly remediation techniques to mitigate its far-reaching environmental implications. This comprehensive review focused on sustainable and eco-friendly techniques by exploring strengths, weaknesses, opportunities, and threats (SWOT) analysis of plastic waste management. Bioremediation techniques were found as potential solutions for addressing plastic waste in SSA. This paper examines advancements in physiochemical methods, the challenges in managing various plastic types, and the role of enzymatic and microbial consortia in enhancing biodegradation. It also explores the potential of genomic technologies and engineered microbial systems to convert plastic waste into valuable products, including bioenergy via bio-upcycling. These bioremediation strategies align with the United Nations Sustainable Development Goals (UN SDGs), offering a promising path to reduce the environmental and health impacts of plastic pollution in the region. This paper also considers future directions of integrating AI-powered recycling systems to facilitate the development of a circular economy in SSA. Additionally, this paper provides progress and future perspectives on bioremediation as a sustainable solution for plastic waste management in SSA. Full article

(This article belongs to the Special Issue Challenge and Prospect of Plastics and Bioplastics for Sustainable Circular Economy)

► Show Figures

Graphical abstract

26 pages, 4898 KiB

Open AccessArticle

Antibacterial Crosslinker for Ternary PCL-Reinforced Hydrogels Based on Chitosan, Polyvinyl Alcohol, and Gelatin for Tissue Engineering

by Karina Del Angel-Sánchez, Ana Victoria Treviño-Pacheco, Imperio Anel Perales-Martínez, Oscar Martínez-Romero, Daniel Olvera-Trejo and Alex Elías-Zúñiga

Polymers 2025, 17(11), 1520; https://doi.org/10.3390/polym17111520 - 29 May 2025

Abstract

Current hydrogels used for cartilage tissue engineering often lack the mechanical strength and structural integrity required to mimic native human cartilage. This study addresses this limitation by developing reinforced hydrogels based on a ternary polymer blend of poly(vinyl) alcohol (PVA), gelatin (GL), and [...] Read more.

Current hydrogels used for cartilage tissue engineering often lack the mechanical strength and structural integrity required to mimic native human cartilage. This study addresses this limitation by developing reinforced hydrogels based on a ternary polymer blend of poly(vinyl) alcohol (PVA), gelatin (GL), and chitosan (CH), with gentamicin sulfate (GS) as an antimicrobial agent and a crosslinker. The hydrogels were produced using two crosslinking methods, the freeze/thaw and heated cycles, and reinforced with forcespun polycaprolactone (PCL) nanofiber to improve mechanical performance. Chemical characterization revealed that GS forms weak hydrogen bonds with the ternary polymers, leading to esterification with PVA, and covalent bonds are formed as the result of the free amino group (-NH₂) of chitosan that reacts with the carboxylic acid group (-COOH) of gelatin. SEM images help us to see how the hydrogels are reinforced with polycaprolactone (PCL) fibers produced via force spinning technology, while mechanical properties were evaluated via uniaxial tensile and compressive tests. Water retention measurements were performed to examine the crosslinking process’s influence on the hydrogel’s water retention, while the hydrogel surface roughness was obtained via confocal microscopy images. A constitutive model based on non-Gaussian strain energy density was introduced to predict experimental mechanical behavior data of the hydrogel, considering a non-monotonous softening function. Loading and unloading tests demonstrated that GS enhanced crosslinking without compromising water retention or biocompatibility because of the reaction between the free amino group of CH and the carboxylic group of gelatin. The PCL-reinforced PVA/GL/CH hydrogel shows strong potential for cartilage repair and tissue engineering applications. Full article

(This article belongs to the Special Issue (Bio)Polymer-Based Composite Materials: Advancements and New Trends in Biomedical Engineering and Research)

► Show Figures

Figure 1

16 pages, 4117 KiB

Open AccessArticle

Surface Modification of Poly(ethylene-alt-tetrafluoroethylene) by Atmospheric Pressure Dielectric Barrier Discharge Plasma

by Xiaoshan Yan, Zuohui Ji, Xiaopeng Li, Yue Zhao, Zhen Li, Zhai Chen and Heguo Li

Polymers 2025, 17(11), 1519; https://doi.org/10.3390/polym17111519 - 29 May 2025

Abstract

The fluororesin membrane emerges as an ideal chemical-protective clothing material due to its excellent permeation resistance. However, using a fluororesin membrane with a low surface energy for compounding fabrics is very challenging. Herein, we demonstrate a strategy to modify the surface of a [...] Read more.

The fluororesin membrane emerges as an ideal chemical-protective clothing material due to its excellent permeation resistance. However, using a fluororesin membrane with a low surface energy for compounding fabrics is very challenging. Herein, we demonstrate a strategy to modify the surface of a poly(ethylene-alt-tetrafluoroethylene) (ETFE) membrane by the atmospheric pressure dielectric barrier discharge (DBD) of plasma under different working voltages, processing times, and concentrations of acrylic acid (AA) in a helium (He) atmosphere. The increase in the hydrophilicity of the ETFE membrane is confirmed by the wettability test, which shows a significant decrease in the water contact angle, from 96° to 50°, after plasma modification. The interfacial T-peel strength of an ETFE membrane composited with polyester fabric increased from 0.53 N/cm to 13.64 N/cm after plasma modification. Significantly, the T-peel strength of the composite using a modified ETFE membrane with ultrasonic washing could still reach 11.75 N/cm. Various characterization methods clearly disclosed the physical and chemical changes on the ETFE membrane surface, such as introducing the polar -COOH group at a nano-level, improving the roughness, decreasing the ratios of the F/C element, and increasing the ratios of the O/C element, suggesting using nano-level grafted polyacrylic acid (g-PAA) on the surface of the membrane by DBD. Full article

(This article belongs to the Section Polymer Applications)

► Show Figures

Figure 1

25 pages, 4838 KiB

Open AccessArticle

Eugenol@Montmorillonite vs. Citral@Montmorillonite Nanohybrids for Gelatin-Based Extruded, Edible, High Oxygen Barrier, Active Packaging Films

by Achilleas Kechagias, Areti A. Leontiou, Yelyzaveta K. Oliinychenko, Alexandros Ch. Stratakos, Konstatninos Zaharioudakis, Charalampos Proestos, Emmanuel P. Giannelis, Nikolaos Chalmpes, Constantinos E. Salmas and Aris E. Giannakas

Polymers 2025, 17(11), 1518; https://doi.org/10.3390/polym17111518 - 29 May 2025

Abstract

In the context of the circular economy, the valorization of bio-derived waste has become a priority across various production sectors, including food processing and packaging. Gelatin (Gel), a protein which can be recovered from meat industry byproducts, offers a sustainable solution in this [...] Read more.

In the context of the circular economy, the valorization of bio-derived waste has become a priority across various production sectors, including food processing and packaging. Gelatin (Gel), a protein which can be recovered from meat industry byproducts, offers a sustainable solution in this regard. In this study, pork-derived gelatin was used to develop novel edible active packaging films, designed for meat products. Glycerol (Gl) was used as a plasticizer. Two types of montmorillonite-based nanohybrids were employed as both reinforcing agents and carriers of antioxidant/antibacterial compounds: eugenol-functionalized montmorillonite (EG@Mt) and citral-functionalized montmorillonite (CT@Mt). The active films were formulated as Gel/Gl/xEG@Mt and Gel/Gl/xCT@Mt, where x = 5, 10, or 15 wt.%. Controlled-release kinetics showed that EG@Mt released up to 95% of its adsorbed eugenol, whereas CT@Mt released up to 55% of its adsorbed citral. The films were evaluated using the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay and tested for antibacterial activity against Escherichia coli and Listeria monocytogenes. Results demonstrated that the Gel/Gl/xEG@Mt films exhibited superior antioxidant and antibacterial performance compared to the Gel/Gl/xCT@Mt films. All formulations were impermeable to oxygen. Although the incorporation of EG and CT slightly reduced cell viability, values remained above 80%, indicating non-toxicity. In conclusion, the film containing 15 wt.% EG@Mt achieved an oxygen transmission rate of zero, an effective concentration (EC₆₀) of 9.9 mg/L to reach 60% antioxidant activity, and reduced E. coli and L. monocytogenes populations by at least 5.8 log CFU/mL (p < 0.05), bringing them below the detection limit. Moreover, it successfully extended the shelf life of fresh minced pork by two days. Full article

(This article belongs to the Special Issue Nano-Enhanced Biodegradable Polymers for Sustainable Food Packaging)

► Show Figures

Figure 1

12 pages, 638 KiB

Open AccessCommunication

Selected Properties of a TPS/PA12 Composite Material Produced in a Two-Stage Method

by Ewa Tomaszewska-Ciosk, Ewa Zdybel, Małgorzata Kapelko-Żeberska and Beata Anwajler

Polymers 2025, 17(11), 1517; https://doi.org/10.3390/polym17111517 - 29 May 2025

Abstract

The world economy is struggling with the increasing pollution of the natural environment with non-biodegradable synthetic polymers produced from petroleum products. This fact has prompted research on the use of natural renewable polymers. Starch is one of the polymers that has already been [...] Read more.

The world economy is struggling with the increasing pollution of the natural environment with non-biodegradable synthetic polymers produced from petroleum products. This fact has prompted research on the use of natural renewable polymers. Starch is one of the polymers that has already been used as an additive to synthetic polymers; however, its use is associated with a problem arising from the incompatibility of hydrophilic starch with hydrophobic synthetic polymers. For these reasons, other authors have not used more than 20% of the starch component in synthetic materials. In this work, a research hypothesis was put forward that the starch content can be increased in the polymer material. Pre-extrusion was used before the final material molding process. Pre-extrusion improved the phase dispersion of the synthetic polymer blended with starch. To produce the molds, the polyamide and starch blends were subjected to the processes of extrusion, milling, and pressing. The molded samples containing polyamide and starch were obtained with a starch component content of 50, 70, and 90%. The obtained homogeneous material was determined in terms of its water resistance and mechanical properties. The test results showed that increasing the starch content in the produced material, increased its susceptibility to water, and worsened its strength properties. However, these negative effects were not as large as expected, and in some cases were even statistically insignificant. The addition of 70% of the starch component allowed for the production of a composite material with satisfactory mechanical properties. Full article

(This article belongs to the Special Issue Additive Manufactuging of Polymer-Based Nanocomposites and Composites: Progress and Prospects)

► Show Figures

Graphical abstract

15 pages, 1056 KiB

Open AccessArticle

Optimizing Anticorrosion Coating Performance: Synthesis of Polyurethane/Epoxy Hybrids

by Lyazzat Bekbayeva, El-Sayed Negim, Khaldun M. Al Azzam, Rinat Zhanibekov, Gulzhakhan Yeligbayeva, Gulnaz Zhaksylykovna Moldabayeva and Ewies F. Ewies

Polymers 2025, 17(11), 1516; https://doi.org/10.3390/polym17111516 - 29 May 2025

Abstract

Corrosion-resistant coatings are essential for prolonging the lifespan of metal structures, yet conventional formulations often lack sufficient mechanical strength and chemical durability. This study focuses on the development of polyurethane/epoxy hybrid coatings (PUAE) with varying epoxy resin content (5%, 10%, and 15% by [...] Read more.

Corrosion-resistant coatings are essential for prolonging the lifespan of metal structures, yet conventional formulations often lack sufficient mechanical strength and chemical durability. This study focuses on the development of polyurethane/epoxy hybrid coatings (PUAE) with varying epoxy resin content (5%, 10%, and 15% by weight) to enhance performance. The hybrid films demonstrated improved mechanical properties with increasing epoxy content, including a rise in tensile strength from 39.1 MPa (PUA) to 86.3 MPa (PUAE15) and adhesion from 2.5 MPa to 8.3 MPa. Hardness also increased from 69 Shore A to 98 Shore A, while elongation at break decreased from 158% to 95%, indicating a shift toward a stiffer material. The thermal stability, assessed by TGA, showed higher degradation temperatures, with PUAE15 reaching a maximum decomposition temperature of 390 °C, compared to 320 °C for pure polyurethane. Viscosity at 5 rpm increased from 12.300 mPa·s to 18.563 mPa·s, and the contact angle improved from 105° to 149°, highlighting enhanced hydrophobicity. PUAE15 also displayed superior resistance to solvents and acidic environments. These results affirm that epoxy content significantly influences the structural, mechanical, and corrosion-resistant properties of polyurethane-based coatings, making PUAE15 a promising candidate for advanced anticorrosive applications. Full article

(This article belongs to the Section Polymer Chemistry)

► Show Figures

Figure 1

13 pages, 1650 KiB

Open AccessArticle

Impact of BMI and PRP Platelet and Red Blood Cell Content on the Coagulation Kinetics of Ortho-R/PRP Mixtures

by Anik Chevrier and Marc Lavertu

Polymers 2025, 17(11), 1515; https://doi.org/10.3390/polym17111515 - 29 May 2025

Abstract

Ortho-R (ChitogenX Inc., Kirkland, QC, Canada) is a lyophilized chitosan formulation that also contains calcium chloride and trehalose. Ortho-R was designed to be solubilized in autologous platelet-rich plasma (PRP), a blood-derived component, in order to become an injectable implant that augments the surgical [...] Read more.

Ortho-R (ChitogenX Inc., Kirkland, QC, Canada) is a lyophilized chitosan formulation that also contains calcium chloride and trehalose. Ortho-R was designed to be solubilized in autologous platelet-rich plasma (PRP), a blood-derived component, in order to become an injectable implant that augments the surgical repair of soft tissues. The Ortho-R/PRP formulation coagulates post-application, similarly to blood. Having the ability to predict the speed of coagulation of an Ortho-R/PRP mixture prepared with PRP isolated from a specific patient would be an advantage in the operating room. The purpose of this study was to investigate whether human donor characteristics (age, sex, body mass index, habits) and autologous PRP properties would have an impact on Ortho-R/PRP mixture coagulation. Clot maximal amplitude and shear elastic modulus were significantly positively correlated with body mass index and platelet concentration in the isolated PRPs. Clot formation time, maximal amplitude and shear elastic modulus were all negatively correlated with PRP red blood cell concentration (and associated hemoglobin and hematocrit content). Donor characteristics were not good predictors of coagulation kinetics in Ortho-R/PRP mixtures. Some of the isolated PRP properties were better predictors of Ortho-R/PRP coagulation kinetics. However, predicting how an Ortho-R/PRP mixture from a particular patient will coagulate is very difficult since all PRP isolation devices yield heterogeneous PRPs and analysis of the isolated PRPs occurs post-administration. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

► Show Figures

Figure 1

22 pages, 3126 KiB

Open AccessArticle

Anti-Inflammatory and Osteogenic Effect of Phloroglucinol-Enriched Whey Protein Isolate Fibrillar Coating on Ti-6Al-4V Alloy

by Anna Mieszkowska, Laurine Martocq, Andrey Koptyug, Maria A. Surmeneva, Roman A. Surmenev, Javad Naderi, Maria Muchova, Katarzyna A. Gurzawska-Comis and Timothy E. L. Douglas

Polymers 2025, 17(11), 1514; https://doi.org/10.3390/polym17111514 - 29 May 2025

Abstract

Biomaterials play a crucial role in the long-term success of bone implant treatment. The accumulation of bacterial biofilm on the implants induces inflammation, leading to implant failure. Modification of the implant surface with bioactive molecules is one of the strategies to improve biomaterial [...] Read more.

Biomaterials play a crucial role in the long-term success of bone implant treatment. The accumulation of bacterial biofilm on the implants induces inflammation, leading to implant failure. Modification of the implant surface with bioactive molecules is one of the strategies to improve biomaterial compatibility and limit inflammation. In this study, whey protein isolate (WPI) fibrillar coatings were used as a matrix to incorporate biologically active phenolic compound phloroglucinol (PG) at different concentrations (0.1% and 0.5%) on titanium alloy (Ti6Al4V) scaffolds. Successful Ti6Al4V coatings were validated by X-ray photoelectron spectroscopy (XPS), showing a decrease in %Ti and increases in %C, %N, and %O, which demonstrate the presence of the protein layer. The biological activity of PG-enriched WPI (WPI/PG) coatings was assessed using bone-forming cells, human bone marrow-derived mesenchymal stem cells (BM-MSCs). WPI/PG coatings modulated the behavior of BM-MSCs but did not have a negative impact on cell viability. A WPI with higher concentrations of PG increased gene expression relative to osteogenesis and reduced the pro-inflammatory response of BM-MSCs after biofilm stimulation. Autoclaving reduced WPI/PG bioactivity compared to filtration. By using WPI/PG coatings, this study addresses the challenge of improving osteogenic potential while limiting biofilm-induced inflammation at the Ti6Al4V surface. These coatings represent a promising strategy to enhance implant bioactivity. Full article

(This article belongs to the Special Issue Smart and Bio-Medical Polymers: 2nd Edition)

► Show Figures

Figure 1

18 pages, 7622 KiB

Open AccessArticle

Recycling of Epoxy/Fiberglass Composite Using Pyridine

by Alexander E. Protsenko, Alexandra N. Protsenko, Olga G. Shakirova and Victor V. Petrov

Polymers 2025, 17(11), 1513; https://doi.org/10.3390/polym17111513 - 29 May 2025

Abstract

This study presents a new approach to chemical processing using pyridine-based solvolysis to produce high-quality glass fiber from epoxy composites. Pyridine was chosen due to its solubility parameter, which precisely matches the parameters calculated for the epoxy matrix segment. Experiments with exposure in [...] Read more.

This study presents a new approach to chemical processing using pyridine-based solvolysis to produce high-quality glass fiber from epoxy composites. Pyridine was chosen due to its solubility parameter, which precisely matches the parameters calculated for the epoxy matrix segment. Experiments with exposure in a pyridine medium demonstrated effective swelling and the potential for destruction. The solvolysis experiments were conducted in a round-bottomed flask with a reflux condenser and stirrer, under ambient conditions (20 °C) until the boiling point was reached (115.2 °C). Additionally, data from experimental studies conducted at subcritical temperatures before reaching 280 °C are presented. The dependences of changes in the mass of composites on time and temperature during the solvolysis process were determined. The tensile strength of the recovered fibers was examined, and thermogravimetric analysis was used to determine their properties. Fiberglass recovered at the boiling point is characterized by 91% tensile strength and 20% residual degradation products on the surface. The residual strength of fiberglass-reinforced plastic (FGRP) is 70.3%. The use of subcritical pyridine helps improve the quality of plastic products made from recycled fibers. This process retains 93% of the residual tensile strength for fibers that have been processed at 250 °C for two hours. Recycled fibers also contain 2.82% organic components on their surfaces. Using this material results in an increase in flexural strength of FGRP by 16.1%, compared to the reference samples. Full article

(This article belongs to the Special Issue Advances in Polymer Composites with Upcycling Waste)

► Show Figures

Figure 1

13 pages, 2356 KiB

Open AccessArticle

Tribological Performance of High-Density Polyethylene (HDPE) and Recycled Polyvinyl Butyral (PVB) Blends During Pin-on-Disk Tests

by Scarlette Alejo-Martínez, Ulises Figueroa-López and Andrea Guevara-Morales

Polymers 2025, 17(11), 1512; https://doi.org/10.3390/polym17111512 - 29 May 2025

Abstract

High-density polyethylene (HDPE) is a widely used thermoplastic known for its chemical resistance and ease of processing, but it has limited wear performance and moderate mechanical properties. In this study, recycled polyvinyl butyral (rPVB) was incorporated into HDPE at 5, 10, 15, and [...] Read more.

High-density polyethylene (HDPE) is a widely used thermoplastic known for its chemical resistance and ease of processing, but it has limited wear performance and moderate mechanical properties. In this study, recycled polyvinyl butyral (rPVB) was incorporated into HDPE at 5, 10, 15, and 20 wt.% to evaluate its effect on tribological performance. Pin-on-disk wear tests were conducted at 12, 15, and 18 N to assess the coefficient of friction (CoF) and wear resistance. Mean CoF values decreased by up to 40% with rPVB addition, with the best performance observed at 15 wt.% rPVB, although some variation was observed across replicates. SEM analysis revealed that rPVB promotes finer debris and transfer film formation, explaining the CoF reduction. However, wear resistance exhibited a complex trend: while rPVB improved adhesion and reduced material loss at lower loads, volume loss increased at higher loads, likely due to rPVB’s lower hardness. Mechanical testing showed an increase in elastic modulus at low rPVB contents due to higher crystallinity, confirmed by DSC; however, tensile strength and impact resistance decreased with rPVB. The results suggest that incorporating 10–15 wt.% of rPVB into HDPE can enhance frictional performance without severely compromising mechanical integrity, offering a sustainable way to valorize rPVB. Full article

(This article belongs to the Special Issue Recycling of Engineering Polymers: Process and Physico-Chemical Changes)

► Show Figures

Figure 1

3 pages, 121 KiB

Open AccessEditorial

Processing, Characterization and Engineering Applications of Fiber-Reinforced Thermoplastic Polymer Composites

by Ankit Gupta

Polymers 2025, 17(11), 1511; https://doi.org/10.3390/polym17111511 - 29 May 2025

Abstract

Fiber-reinforced thermoplastic polymer composites (FRTPCs) represent a transformative class of advanced engineering materials that combine the high specific strength and stiffness typical of fiber reinforcements with the inherent advantages of thermoplastic matrices, including rapid processing, recyclability, and thermal weldability [...] Full article

(This article belongs to the Special Issue Processing, Characterization and Engineering Application of Fiber-Reinforced Thermoplastic Polymer Composites)

23 pages, 9131 KiB

Open AccessArticle

Modulated Degradation of Polylactic Acid Electrospun Coating on WE43 Stents

by Mariana Macías-Naranjo, Marilena Antunes-Ricardo, Christopher Moreno González, Andrea Noelia De la Peña Aguirre, Ciro A. Rodríguez, Erika García-López and Elisa Vazquez-Lepe

Polymers 2025, 17(11), 1510; https://doi.org/10.3390/polym17111510 - 28 May 2025

Abstract

Magnesium-based coronary stents have gained significant interest due to their excellent biocompatibility, biodegradability, and mechanical properties. However, a key limitation of magnesium in biomedical applications is its low corrosion resistance, which compromises its structural integrity and mechanical strength over time. Polymeric coatings can [...] Read more.

Magnesium-based coronary stents have gained significant interest due to their excellent biocompatibility, biodegradability, and mechanical properties. However, a key limitation of magnesium in biomedical applications is its low corrosion resistance, which compromises its structural integrity and mechanical strength over time. Polymeric coatings can overcome this challenge, enhancing magnesium-based implants’ corrosion resistance and overall performance. This study applied a polylactic acid (PLA) nanofiber coating to WE43 magnesium (Mg) stents via electrospinning to reduce their corrosion rate. Both uncoated and coated stents underwent in vitro immersion tests in Hank’s solution for 1, 3, 7, and 14 days. The effectiveness of the PLA coating was evaluated through morphological analysis, chemical composition assessment, corrosion behavior (weight change), magnesium ion release, and in vitro biocompatibility. The corrosion observed in the uncoated WE43 stents indicates that protective coatings are necessary to regulate degradation rates over extended implantation periods. The results demonstrated that coated stents exhibited improved performance, maintaining the integrity of the PLA coating for up to 14 days. The coated stents demonstrated reduced surface damage and lower weight loss resulting from lower magnesium release. In our study, the coated stents demonstrated a reduced corrosion rate (0.216 ± 0.013 mm/year) compared with the uncoated stents (0.312 ± 0.010 mm/year), both after 14 days. Additionally, in vitro biocompatibility results confirmed the non-toxic nature of PLA-coated stents, which enhances cellular proliferation and contributes to a more favorable environment for vascular healing. These findings suggest that PLA coatings can effectively prolong the functional durability of WE43 Mg stents, offering a promising solution for enhancing the performance of biodegradable stents in cardiovascular applications. Full article

(This article belongs to the Section Polymer Applications)

► Show Figures

Figure 1

13 pages, 2042 KiB

Open AccessArticle

Degradation of Polypropylene and Polypropylene Compounds on Co-Rotating Twin-Screw Extruders

by Paul Albrecht, Matthias Altepeter and Florian Brüning

Polymers 2025, 17(11), 1509; https://doi.org/10.3390/polym17111509 - 28 May 2025

Abstract

The degradation of polypropylene (PP) through thermal and mechanical stress, as well as the influence of oxygen, are unavoidable when processing on a co-rotating twin-screw extruder. In previous studies, a mathematical model was developed to predict the degradation while compounding on different twin-screw [...] Read more.

The degradation of polypropylene (PP) through thermal and mechanical stress, as well as the influence of oxygen, are unavoidable when processing on a co-rotating twin-screw extruder. In previous studies, a mathematical model was developed to predict the degradation while compounding on different twin-screw extruder sizes. Additionally, the examination of filled PPs was conducted. To this end, a range of operating parameters and extruder sizes were used to process PP, and the molar mass was then determined by melt flow rate (MFR) and gel permeation chromatography (GPC) measurements to derive the degree of degradation. The model was then modified by adjusting the sensitivity parameters to allow the degradation behavior of the PPs to be described independently of extruder size. Consistent with prior research, comprehensive measurements of a PP/titanium dioxide (TiO₂) compound revealed that, with a few exceptions, increasing temperatures and screw speeds and decreasing throughputs generally resulted in higher degradation. However, the application of the model to the compounds did not achieve good agreement with the measured degradation, indicating different degradation conditions due to the different thermodynamic and rheological properties of the compounds. Full article

(This article belongs to the Section Polymer Processing and Engineering)

► Show Figures

Figure 1

16 pages, 4556 KiB

Open AccessArticle

In Situ Following Oriented Crystallization of Pre-Stretched Poly(ethylene 2,5-Furandicarboxylate) Under Post Heating

by Jianguo Zhao, Mengcheng Yang, Binhang Wu, Hang Li and Yiguo Li

Polymers 2025, 17(11), 1508; https://doi.org/10.3390/polym17111508 - 28 May 2025

Abstract

Post-processing plays a vital role in the determination of the final structures and properties of oriented materials. As a sustainable candidate of oil-based poly(ethylene terephthalate), biobased poly(ethylene 2,5-furandicarboxylate) (PEF) reflects great promise in green fiber, film, and packaging applications, but it undergoes poor [...] Read more.

Post-processing plays a vital role in the determination of the final structures and properties of oriented materials. As a sustainable candidate of oil-based poly(ethylene terephthalate), biobased poly(ethylene 2,5-furandicarboxylate) (PEF) reflects great promise in green fiber, film, and packaging applications, but it undergoes poor stress-induced crystallization (SIC) under tensile deformation, necessitating a post-processing technique to improve its crystallinity and stability. Here, the structural evolution of pre-stretched PEF under post heating after uniaxial deformation was monitored by online synchrotron X-ray diffraction/scattering, differential scanning calorimetry, and ex situ infrared spectroscopy. The results delineate the significantly enhanced crystallization of pre-deformed PEF that happened far below its cold crystallization temperature. Through the isochronous analyses of the temperature-dependent evolution of mechanical response, the mesophase, crystal structure, orientation factor, chain conformation, and interchain ═C−H···O═C hydrogen bonding, the molecular mechanisms of microstructural transition and oriented crystallization of pre-drawn PEF under post heating were clarified. This research can enhance the understanding of PEF crystallization in an oriented state and provide guidelines on the structural design and technical control for processing high-performance PEF-based materials. Full article

(This article belongs to the Special Issue Synthesis and Processing of Functional Polymer Materials–2nd Edition)

► Show Figures

Figure 1

17 pages, 4800 KiB

Open AccessArticle

Preparation of Phenolic Epoxy-Based Electronic Packaging Materials with High Thermal Conductivity by Creating an Interfacial Heat Conduction Network

by Minghao Ye, Jing Jiang, Lin Zhao, Hongyu Zhu, Junjie Wang, Zicai Sun, Dewei Zhang, Ming Li and Yagang Zhang

Polymers 2025, 17(11), 1507; https://doi.org/10.3390/polym17111507 - 28 May 2025

Abstract

As one of the most widely used packaging materials, epoxy composite (EP) offers excellent insulation properties; however, its intrinsic low thermal conductivity (TC) limits its application in high-frequency and high-power devices. To enhance the TC of EP, six highly thermally conductive inorganic fillers, [...] Read more.

As one of the most widely used packaging materials, epoxy composite (EP) offers excellent insulation properties; however, its intrinsic low thermal conductivity (TC) limits its application in high-frequency and high-power devices. To enhance the TC of EP, six highly thermally conductive inorganic fillers, namely, Al₂O₃, MgO, ZnO, Si₃N₄, h-BN, and AlN, were incorporated into the EP matrix at varying contents (60–90 wt.%). The resulting epoxy molding compounds (EMCs) demonstrated significant improvement in thermal conductivity coefficient (λ) at high filler contents (90 wt.%), ranging from 0.67 W m⁻¹ K⁻¹ to 1.19 W m⁻¹ K⁻¹, compared to the pristine epoxy composite preform (ECP, 0.36 W m⁻¹ K⁻¹). However, it was found that the interfacial thermal resistance (ITR) between EP and filler materials is a major hindrance restricting TC improvement. In order to address this challenge, graphene nanosheets (GNSs) and carbon nanotubes (CNTs) were introduced as additives to reduce the ITR. The experimental results indicated that CNTs were effective in enhancing the TC, with the optimized EMC achieving a λ value of 1.14 W m⁻¹ K⁻¹ using 60 wt.% Si₃N₄ + 2 wt.% CNTs. Through the introduction of a small amount of CNT (2 wt.%), the inorganic filler content was significantly reduced from 90 wt.% to 60 wt.% while still maintaining high thermal conductivity (1.14 W m⁻¹ K⁻¹). We propose that the addition of CNTs helps in the construction of a partial heat conduction network within the EP matrix, thereby facilitating interfacial heat transfer. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)

► Show Figures

Graphical abstract

Journal Description

Polymers

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Topical Collections

Further Information

Guidelines

MDPI Initiatives

Follow MDPI