Polymers

23 pages, 1381 KiB

Open AccessArticle

Size and Shape of Primary (Bio)Polyelectrolyte Complexes Chitosan/Gelatin: Study Using Small-Angle X-Ray Scattering from Synchrotron Radiation

by Podshivalov Aleksandr, Litvinov Mikhail, Kashurin Aleksandr and Danilova Ksenia

Polymers 2025, 17(9), 1236; https://doi.org/10.3390/polym17091236 (registering DOI) - 30 Apr 2025

Abstract

In this work, using small-angle X-ray scattering from synchrotron radiation, the macromolecular structure of chitosan and gelatin polyelectrolytes and their mixtures at various pH values and ratios was studied to determine the size and shape of primary supramolecular (bio)PEC. Analysis of the scattering [...] Read more.

In this work, using small-angle X-ray scattering from synchrotron radiation, the macromolecular structure of chitosan and gelatin polyelectrolytes and their mixtures at various pH values and ratios was studied to determine the size and shape of primary supramolecular (bio)PEC. Analysis of the scattering profiles of the initial solutions of chitosan and gelatin with the building of the pair distance function showed the formation of single-modal distributions with a maximum molecular size of 46 and 32.2 nm, respectively. Ab initio reconstruction of the macromolecule’s shape showed the formation of objects shaped like an oblate spheroid. In mixtures of chitosan and gelatin at a pH below the isoelectric point, it was found that the scattering structures correspond to the initial biopolymers. However, it is observed that values of the aspect ratio at a ratio above 1:10 gradually increase, which indicates a slight elongation of the average particle and indirectly indicates the formation of dissipative structures of (bio)PEC. In mixtures at a pH above the isoelectric point, it was shown that at ratios above 1:5, the formation of primary supramolecular complexes is observed, which is accompanied by an increase in zero-scattering intensity by about three times, maximum molecular size by two to two-and-a-half times relative to the initial polymers, and the formation of elongated structures corresponding to the cylinder (swollen spiral). It may be a consequence of the increased efficiency of the polyelectrolyte associative interaction between chitosan and gelatin. Full article

(This article belongs to the Special Issue Advances in Polyelectrolytes and Polyelectrolyte Complexes)

16 pages, 7475 KiB

Open AccessArticle

Environmental and Economic Impacts of Substituting Single-Use Plastic Straws: A Life-Cycle Assessment for Greece

by Panagiota Eleni and Christos Boukouvalas

Polymers 2025, 17(9), 1235; https://doi.org/10.3390/polym17091235 (registering DOI) - 30 Apr 2025

Abstract

The usage of more than 30 billion straws a year has been reported in the European Union (EU), in 2020, one year before the official ban of single-use plastics in Europe. The impacts of this plastic waste on the environment and on our [...] Read more.

The usage of more than 30 billion straws a year has been reported in the European Union (EU), in 2020, one year before the official ban of single-use plastics in Europe. The impacts of this plastic waste on the environment and on our health are global and can be drastic. Since then, various alternative straws have emerged. This study assesses their effectiveness, primarily from an environmental perspective, to determine the best option among those available. Life-cycle assessment (LCA) was conducted using ReCiPe 2016 methodology and ISO 14040/44 standards, alongside a preliminary cost analysis and a consumer preference survey. The findings reveal that wheat straws demonstrated the lowest overall environmental impact, with a climate change contribution of only 0.0568 kg CO₂ eq. per year, while plastic straws showed the lowest cost at EUR 0.30 per year but contributed 0.084 kg CO₂ eq. Metallic straws, despite being reusable, had the highest washing-related emissions, with 85% of their annual impact (~0.169 kg CO₂ eq.) attributed to dishwashing. Paper and bioplastic alternatives showed up to 2.5 times higher climate impacts than plastic. Cost-wise, bamboo straws reached EUR 7.97/year, while silicone and metal straws were more economically favorable at EUR 1.17 and EUR 2.81, respectively. The consumer survey highlighted that 85% of users preferred traditional plastic straws, but 76% were open to reusable alternatives. From a socio-economic point of view, cost seems to play a minor role. However, consumers’ preferences towards the new products and their awareness of health and environmental risks are very significant factors affecting their approval of new alternatives and their displeasure towards traditional straw elimination. Full article

(This article belongs to the Special Issue From Biomass Fractionation to Final Biobased Polymer Nanocomposites in European Sustainable Biobased Nanomaterials Community (BIOMAC))

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17 pages, 1820 KiB

Open AccessArticle

Biomimetic Grooved Ribbon Aerogel Inspired by the Structure of Pinus sylvestris var. mongolica Needles for Efficient Air Purification

by Bo Zhao, Zikun Huang, Mingze Han, Bernardo Predicala, Qiushi Wang, Yunhong Liang, Mo Li, Xin Liu, Jiangtao Qi and Li Guo

Polymers 2025, 17(9), 1234; https://doi.org/10.3390/polym17091234 (registering DOI) - 30 Apr 2025

Abstract

Air pollutants, such as particulate matter (PM) and ammonia (NH₃), generated by intensive animal farming pose considerable threats to human health, animal welfare, and ecological balance. Conventional materials are often ineffective at simultaneously removing multiple pollutants, maintaining a low pressure drop, [...] Read more.

Air pollutants, such as particulate matter (PM) and ammonia (NH₃), generated by intensive animal farming pose considerable threats to human health, animal welfare, and ecological balance. Conventional materials are often ineffective at simultaneously removing multiple pollutants, maintaining a low pressure drop, and ensuring durability in heavily polluted environments. Inspired by the dust-retention properties of Pinus sylvestris var. mongolica (PS) needles, this study developed a biomimetic grooved ribbon fiber using electrospinning technology. These fibers were further assembled into a three-dimensional bioinspired aerogel structure through freeze-forming technology to achieve efficient dust capture. Additionally, the introduction of UiO-66-NH₂ nanoparticles significantly enhanced the properties of the aerogels for NH₃ adsorption. Among the various prepared aerogels (PG, UPG-5, UPG-10, UPG-15, and UPG-20), UPG-10 demonstrated the best performance, achieving a filtration efficiency of 99.24% with a pressure drop of 95 Pa. Notably, it exhibited a remarkable dust-holding capacity of 147 g/m², and its NH₃ adsorption capacity reached 99.89 cm³/g, surpassing PG aerogel by 31.46 cm³/g. Additionally, UPG-10 exhibited outstanding elasticity, maintaining over 80% of its original shape after 30 compression cycles. This biomimetic aerogel presents a promising solution for air purification, contributing to improved agricultural efficiency and environmental sustainability. Full article

(This article belongs to the Special Issue Electrospun Polymer Nanofibers: Preparation, Design, and Characterization)

27 pages, 6454 KiB

Open AccessArticle

Low-Temperature Sealing Material Database and Optimization Prediction Based on AI and Machine Learning

by Honghao Jia, Zhongxu Tai, Rui Lyu, Kousuke Ishikawa, Yixiao Sun, Jianting Cao and Dongying Ju

Polymers 2025, 17(9), 1233; https://doi.org/10.3390/polym17091233 (registering DOI) - 30 Apr 2025

Abstract

Optimization of low-temperature sealing materials is of great significance to improving low-temperature performance and durability. This study leverages DeepSeek-v3 (DS) and GPT-generated data and applies machine learning methods, including XGBoost and neural networks, to perform 3D prediction and analysis of key properties of [...] Read more.

Optimization of low-temperature sealing materials is of great significance to improving low-temperature performance and durability. This study leverages DeepSeek-v3 (DS) and GPT-generated data and applies machine learning methods, including XGBoost and neural networks, to perform 3D prediction and analysis of key properties of low temperature sealing materials. Data expansion techniques were employed to enhance data quality and improve model prediction accuracy. Additionally, the study evaluates the applicability of AI-generated data in material performance prediction. The results demonstrate the effectiveness of machine learning in material optimization and provide valuable insights for future optimization strategies. Full article

(This article belongs to the Section Artificial Intelligence in Polymer Science)

24 pages, 16372 KiB

Open AccessArticle

Impact of Macro-Polypropylene Fiber on the Mechanical Properties of Ultra-High-Performance Concrete

by Tamer Birol and Alper Avcıalp

Polymers 2025, 17(9), 1232; https://doi.org/10.3390/polym17091232 (registering DOI) - 30 Apr 2025

Abstract

Steel fibers are frequently used in ultra high-performance concrete (UHPC) due to their superior properties, but they also have disadvantages, such as corrosion exposure, high specific gravity and high cost. Although synthetic fibers have emerged as an alternative, the focus has generally been [...] Read more.

Steel fibers are frequently used in ultra high-performance concrete (UHPC) due to their superior properties, but they also have disadvantages, such as corrosion exposure, high specific gravity and high cost. Although synthetic fibers have emerged as an alternative, the focus has generally been on hybrid use with steel fibers in UHPC. This study investigates the applicability of macro-polypropylene (PP) fibers for UHPC in terms of mechanical properties. An experimental campaign was conducted for UHPC mixtures containing macro-PP fibers with varying volumetric ratios. The effects of macro-PP fiber on the mechanical properties of UHPC were investigated in terms of compressive strength, splitting tensile strength and flexural behavior. The two-dimensional digital image correlation (2D-DIC) method was adopted to examine the cracking behavior. In addition, tensile constitutive law for UHPC mixtures was obtained with inverse analysis based on Model Code 2020 (MC2020). The results showed that the use of macro-PP fibers had no significant impact on compressive and splitting tensile strength. However, residual flexural tensile strength and fracture energy increased by up to 2.8 and 2.5 times, respectively, compared to UHPC without fiber. It was determined that macro-PP fibers could exhibit effective crack control in UHPC. Full article

(This article belongs to the Section Polymer Fibers)

54 pages, 29469 KiB

Open AccessReview

Recent Advances in the Hydrogen Gas Barrier Performance of Polymer Liners and Composites for Type IV Hydrogen Storage Tanks: Fabrication, Properties, and Molecular Modeling

by Omar Dagdag and Hansang Kim

Polymers 2025, 17(9), 1231; https://doi.org/10.3390/polym17091231 (registering DOI) - 30 Apr 2025

Abstract

Developing high-performance polymer liners and their composites is essential for ensuring the safety and efficiency of type IV high-pressure hydrogen storage tanks. This review provides a thorough analysis of recent innovations in hydrogen gas barrier materials, fabrication techniques, and molecular modeling approaches to [...] Read more.

Developing high-performance polymer liners and their composites is essential for ensuring the safety and efficiency of type IV high-pressure hydrogen storage tanks. This review provides a thorough analysis of recent innovations in hydrogen gas barrier materials, fabrication techniques, and molecular modeling approaches to minimize hydrogen gas permeation. It examines key polymeric materials, such as polyamide 6 (PA6) and high-density polyethylene (HDPE), and emerging nanofiller reinforcements, such as graphene and montmorillonite clay. Additionally, it discusses manufacturing methods in relation to their effects on liner integrity and permeability. Molecular modeling techniques, especially molecular dynamics simulations, are emphasized as powerful tools for understanding hydrogen transport mechanisms and optimizing the interactions between polymers and fillers. Despite these notable advancements, challenges remain in achieving ultra-low hydrogen gas permeability, long-term stability, and scalable production methods. Future research should focus on developing multifunctional hybrid fillers, enhancing computational modeling frameworks, and designing novel polymer architectures specifically tailored for hydrogen storage applications. Full article

(This article belongs to the Special Issue Advancements in Polymeric Material Characterization for Industrial Applications: From Properties to Performance)

12 pages, 3783 KiB

Open AccessArticle

Banana Peel Based Cellulose Material for Agriculture and Aquiculture: Toward Circular Economy

by Iris N. Serratos, Juan Antonio García Torres, Jorge Luis Mendoza Téllez, David Silva Roy, Ana María Soto Estrada, Norma Elena Leyva López, Hervey Rodríguez González, Sylvie Le Borgne, Karla Lorena Sánchez-Sánchez and Rebeca Sosa Fonseca

Polymers 2025, 17(9), 1230; https://doi.org/10.3390/polym17091230 (registering DOI) - 30 Apr 2025

Abstract

This study explores the creation and characterization of a compostable biopolymer derived from banana peels, addressing the issue of organic waste. Rich in protein, fiber, water, and cellulose, banana peels can be transformed into biodegradable polymers through acid hydrolysis, which breaks down cellulose [...] Read more.

This study explores the creation and characterization of a compostable biopolymer derived from banana peels, addressing the issue of organic waste. Rich in protein, fiber, water, and cellulose, banana peels can be transformed into biodegradable polymers through acid hydrolysis, which breaks down cellulose chains, making them suitable for use in aquiculture and agriculture. Methionine, an essential amino acid for aquiculture, was added to enhance the biopolymer’s value in fish feed. The biopolymer was synthesized by heating, crushing, and subjecting the peels to acid hydrolysis. The methionine was integrated by causing it to form ester bonds with the cellulose. The products were characterized using UV-VIS and IR spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). UV-VIS and IR spectra confirmed the incorporation of the methionine, while TGA showed reduced mass loss in the methionine-enriched biopolymer, likely due to the retention of water molecules. SEM images revealed roughness, indicating the crosslinking of the small cellulose chains. The incorporation of methionine led to a more uniform and compact structure. The obtained biopolymer has potential applications in agriculture, especially for potato cultivation, and shows promise for sustainable aquiculture, particularly in tilapia feed. This research contributes to both waste valorization and the development of eco-friendly materials. Full article

(This article belongs to the Special Issue Embracing the Circular Economy for a Promising Future in Sustainable Polymer Production)

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17 pages, 2749 KiB

Open AccessArticle

Low MXene Loading of Epoxy Composite with Enhanced Hydrothermal Resistance

by Mengke Jing, Shujie Zhang, Sichang Zhang, Mingzhou Li, Fan Chen, Yuchen Ma and Bo Sun

Polymers 2025, 17(9), 1229; https://doi.org/10.3390/polym17091229 (registering DOI) - 30 Apr 2025

Abstract

This work focuses on the hydrothermal aging of two-dimensional layered Ti₃C₂T_x (MXene)/epoxy (EP) nanocomposites. MXene/EP composites were successfully prepared by homogeneously dispersing multilayer MXene (m-MXene) and few-layer MXene (f-MXene) into the curing agent, methyl nadic anhydride (MNA). Considering [...] Read more.

This work focuses on the hydrothermal aging of two-dimensional layered Ti₃C₂T_x (MXene)/epoxy (EP) nanocomposites. MXene/EP composites were successfully prepared by homogeneously dispersing multilayer MXene (m-MXene) and few-layer MXene (f-MXene) into the curing agent, methyl nadic anhydride (MNA). Considering the application, the MXene loading was designed to be 0.1 wt.%. Characterization included the characteristics of MXene, the water absorption behavior of the resin and composite samples, the glass transition temperatures (T_g) in various states, and the tensile strength evolution during aging. The curing behavior of the MXene composites was also discussed to facilitate an understanding of the processability. The results showed that MNA can chemically bond with MXene to obtain a stable suspension. The addition of MXene increased the curing characteristic temperature of the system, but the change in the activation energy of the curing reaction was minimal. The addition of MXene decreased the crosslink density of the epoxy resin, leading to a decrease in the T_g value of the initial samples. After hydrothermal aging, the T_g of pure EP decreased by 46.9 °C, and re-drying the samples did not fully restore the T_g. However, the T_g of the MXene/EP system decreased by only 8.9 °C (m-MXene) and 9.5 °C (f-MXene), respectively, and the T_g values of the samples were fully restored to their pre-aging levels via re-drying. Experiments with immersion at 25 °C and 100 °C showed that the difference in water absorption behavior between the MXene/EP and pure EP systems was minimal. Tensile tests showed that the addition of MXene increased the initial strength of the resin system by 14.7% (m-MXene) and 20.9% (f-MXene). After 400 h of hydrothermal aging, the tensile strength retention of the pure EP samples was 69.1%, while the strength retention of the MXene/EP samples was 85.3% (m-MXene) and 83.0% (f-MXene). The combined results demonstrate that the addition of MXene with a low loading of only 0.1% can effectively improve the hydrothermal resistance of epoxy resins. Full article

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

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14 pages, 4827 KiB

Open AccessArticle

Physicochemical Characteristics of Chitosan Extracted from Pleurotus ostreatus and Its Anticancer Activity Against the MDA-MB-231 Breast Cancer Cell Line

by Adil Aldhahrani

Polymers 2025, 17(9), 1228; https://doi.org/10.3390/polym17091228 - 30 Apr 2025

Abstract

One of the main causes of death worldwide is cancer, a disorder in which a solid or liquid mass of cells known as a tumor develops when one or more cells lose the capacity to regulate their development. This study aims to assess [...] Read more.

One of the main causes of death worldwide is cancer, a disorder in which a solid or liquid mass of cells known as a tumor develops when one or more cells lose the capacity to regulate their development. This study aims to assess the potential of chitosan as an anticancer agent in place of standard therapy regimens that have some degree of unselective cytotoxicity. PCR was performed for the RNA extraction of Caspase-3 and β-actin genes, and Cq values and quantification curves for each gene were recorded. Additionally, SRB and FITC apoptosis investigations were used to assess the effectiveness of chitosan powder’s anticancer activity against breast cancer cells. Full article

(This article belongs to the Special Issue Advances in Natural Polymers and Active Compounds: Extraction Methods and Applications)

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27 pages, 6230 KiB

Open AccessReview

Critical Perspectives on the Design of Polymeric Materials for Mitigating Thermal Runaway in Lithium-Ion Batteries

by Hangyu Zhou, Jianhong He, Shang Gao, Xuan Cao, Chenghui Li, Qing Zhang, Jialiang Gao, Yongzheng Yao, Chuanwei Zhai, Zhongchun Hu, Hongqing Zhu and Rongxue Kang

Polymers 2025, 17(9), 1227; https://doi.org/10.3390/polym17091227 - 30 Apr 2025

Abstract

During the global energy transition, electric vehicles and electrochemical energy storage systems are rapidly gaining popularity, leading to a strong demand for lithium battery technology with high energy density and long lifespan. This technological advancement, however, hinges critically on resolving safety challenges posed [...] Read more.

During the global energy transition, electric vehicles and electrochemical energy storage systems are rapidly gaining popularity, leading to a strong demand for lithium battery technology with high energy density and long lifespan. This technological advancement, however, hinges critically on resolving safety challenges posed by intrinsically reactive components particularly flammable polymeric separators, organic electrolyte systems, and high-capacity electrodes, which collectively elevate risks of thermal runaway (TR) under operational conditions. The strategic integration of smart polymeric materials that enable early detection of TR precursors (e.g., gas evolution, thermal spikes, voltage anomalies) and autonomously interrupt TR propagation chains has emerged as a vital paradigm for next-generation battery safety engineering. This paper begins with the development characteristics of thermal runaway in lithium batteries and analyzes recent breakthroughs in polymer-centric component design, multi-parameter sensing polymers, and TR propagation barriers. The discussion extends to intelligent material systems for emerging battery chemistries (e.g., solid-state, lithium-metal) and extreme operational environments, proposing design frameworks that leverage polymer multifunctionality for hierarchical safety mechanisms. These insights establish foundational principles for developing polymer-integrated lithium batteries that harmonize high energy density with intrinsic safety, addressing critical needs in sustainable energy infrastructure. Full article

(This article belongs to the Special Issue Advanced Polymer Materials for Safe Ion Batteries)

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25 pages, 5938 KiB

Open AccessArticle

The Bactericide Effects of Chitosan When Used as an Indicator of Chlorine Demand

by Josefine Molina-Pinna and Félix R. Román-Velázquez

Polymers 2025, 17(9), 1226; https://doi.org/10.3390/polym17091226 - 30 Apr 2025

Abstract

The Miradero Water Treatment Plant (MWTP) in Mayagüez, Puerto Rico, uses sodium hypochlorite (SH) as a disinfectant. However, SH reacts with humic substances present in surface water, forming disinfection by-products (DBPs) regulated by the U.S. EPA. This study evaluated whether chitosan, a biopolymer [...] Read more.

The Miradero Water Treatment Plant (MWTP) in Mayagüez, Puerto Rico, uses sodium hypochlorite (SH) as a disinfectant. However, SH reacts with humic substances present in surface water, forming disinfection by-products (DBPs) regulated by the U.S. EPA. This study evaluated whether chitosan, a biopolymer with known bactericidal properties, could reduce chlorine demand and improve disinfection. Chitosan, with a 75% degree of deacetylation and a molecular weight of 460 kDa, was solubilized in four acids (acetic, citric, hydrochloric, and L-ascorbic) and tested under two turbidity ranges (236.0 and 2556 NTU). Chlorine demand curves were generated, and coliform presence–absence (P–A) tests were performed to assess bactericidal effects. Results showed that chitosan-treated samples achieved disinfection at the breakpoint with lower SH doses. For water with a turbidity of 236.0 NTU, all chitosan-acid solutions reached the breakpoint at 3.60 mg/L of SH. At 2556 NTU, three solutions required 4.20 mg/L SH, while hydrochloric acid–chitosan required only 3.60 mg/L. All chitosan-treated samples tested negative for coliforms, while controls treated with SH alone tested positive. These findings demonstrate that chitosan enhances bacterial removal and reduces chlorine demand, potentially lowering DBP formation in water treatment. Full article

(This article belongs to the Special Issue Biocompatible and Biodegradable Polymer Materials)

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24 pages, 10960 KiB

Open AccessArticle

Bacterial Cellulose-Based Nanocomposites for Wound Healing Applications

by Alexandra-Ionela Dogaru, Ovidiu-Cristian Oprea, Gabriela-Olimpia Isopencu, Adela Banciu, Sorin-Ion Jinga and Cristina Busuioc

Polymers 2025, 17(9), 1225; https://doi.org/10.3390/polym17091225 (registering DOI) - 29 Apr 2025

Abstract

Bacterial cellulose (BC) is a polysaccharide produced by Gram-positive and Gram-negative bacteria with a strictly aerobic metabolism, having a huge number of significant applications in the biomedical field. This study investigates the development of bacterial cellulose (BC)-based composite systems that incorporate cerium dioxide [...] Read more.

Bacterial cellulose (BC) is a polysaccharide produced by Gram-positive and Gram-negative bacteria with a strictly aerobic metabolism, having a huge number of significant applications in the biomedical field. This study investigates the development of bacterial cellulose (BC)-based composite systems that incorporate cerium dioxide nanoparticles (CeO₂ NPs) used as antibacterial agents to enhance wound healing, particularly for burn treatments. The innovation of this study resides in the integration of CeO₂ NPs synthesized by using a precipitation method using both chemical and green reducing agents, ammonium hydroxide (NH₄OH) and turmeric extract (TE), in BC membranes composed of ultrathin nanofibers interwoven into a three-dimensional network appearing as a hydrogel mass. Characterization by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy (FTIR) confirmed the effective deposition of this agent onto the BC matrix. Antibacterial activity tests against E. coli and B. subtilis indicated strong inhibition for the composites synthesized following these routes, particularly for the BC-CeO₂-TE-OH sample, processed by employing both precipitating agents. Cytotoxicity evaluations showed no inhibition of cell activity. Additionally, loading the composites with dexamethasone endowed them with analgesic release over 4 h, as observed through ultraviolet–visible spectroscopy (UV-Vis), while the FTIR spectra revealed a sustained drug presence post-release. These findings highlight BC-based films as promising candidates for advanced wound care and tissue engineering applications. Full article

(This article belongs to the Special Issue Synthesis, Design, Preparation and Processing of Functional Polymer Composites)

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12 pages, 1813 KiB

Open AccessArticle

Bond Strength of Universal Adhesive/Resin Cement Combinations Relying on Touch-Cure Mechanisms

by Annamaria Forte, Eugenia Baena, Claudia Mazzitelli, Edoardo Mancuso, Diego D’Urso, Gerardo Pellegrino, Laura Ceballos, Lorenzo Breschi, Annalisa Mazzoni and Tatjana Maravic

Polymers 2025, 17(9), 1224; https://doi.org/10.3390/polym17091224 - 29 Apr 2025

Abstract

New dual-curing resin cements are constantly launched into the market to improve the bond strength between dentine and indirect restorations when light irradiation is limited by the restoration material. The present study evaluated the microshear bond strength (μSBS) of two dual-cured resin cements, [...] Read more.

New dual-curing resin cements are constantly launched into the market to improve the bond strength between dentine and indirect restorations when light irradiation is limited by the restoration material. The present study evaluated the microshear bond strength (μSBS) of two dual-cured resin cements, Estecem II Plus (EP) and Variolink Esthetic DC (VAR), when resin composite or dentine substrates were conditioned with their corresponding universal adhesives, Tokuyama Universal Bond II (TUB) and Adhese Universal DC (ADH). The experimental groups (n = 20) were (1) TUB/EP light-cured, (2) TUB/EP self-cured, (3) ADH/VAR light-cured, and (4) ADH/VAR self-cured. A μSBS test was performed after 24 h (T0) or after thermocycling (TC), and failure modes were assessed. Data analysis was performed using three-way ANOVA and Tukey tests (p < 0.05). In composite, TUB/EP self-cured demonstrated the highest μSBS at T0 and TC. After TC, TUB/EP self-cured and ADH/VAR light-cured remained stable (p > 0.05). In dentine, TUB/EP light-cured was statistically superior to TUB/EP self-cured and ADH/VAR self-cured at T0. Thermocycling decreased the μSBS of light-curing groups. TUB/EP achieved optimal μSBS when the manufacturer’s instructions were followed and the adhesive was self-cured, irrespective of the bonding substrate. However, ADH/VAR was more dependent on the type of bonding substrate than on the curing mode of the resin cement. Full article

(This article belongs to the Section Polymer Applications)

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19 pages, 3364 KiB

Open AccessArticle

Specificity of Thermal Destruction of Nonwoven Mixture Systems Based on Bast and Viscose Fibers

by Altynay S. Kalauova, Ekaterina E. Palchikova, Igor S. Makarov, Georgiy A. Shandryuk, Amangeldi I. Abilkhairov, Danagul Zh. Kalimanova, Meirbek Zh. Naukenov, Gulbarshin K. Shambilova, Egor M. Novikov, Junlong Song and Alexander G. Smyslov

Polymers 2025, 17(9), 1223; https://doi.org/10.3390/polym17091223 - 29 Apr 2025

Abstract

The research investigates the thermal behavior of mixed systems based on natural and artificial cellulose fibers used as precursors for carbon nonwoven materials. Flax and hemp fibers were employed as natural components; they were first chemically treated to remove impurities and enriched with [...] Read more.

The research investigates the thermal behavior of mixed systems based on natural and artificial cellulose fibers used as precursors for carbon nonwoven materials. Flax and hemp fibers were employed as natural components; they were first chemically treated to remove impurities and enriched with alpha-cellulose. The structure, chemical composition, and mechanical properties of both natural and viscose fibers were studied. It was shown that fiber properties depend on the fiber production process history; natural fibers are characterized by a high content of impurities and exhibit high strength characteristics, whereas viscose fibers have greater deformation properties. The thermal behavior of blended compositions was investigated using TGA and DSC methods across a wide range of component ratios. Carbon yield values at 1000 °C were found to be lower for blended systems containing 10–40% by weight of bast fibers, with carbon yield increasing as the quantity of natural fibers increased. Thus, the composition of the cellulose composite affects carbon yield and thermal processes in the system. Using the Kissinger method, data were obtained on the value of the activation energy of thermal decomposition for various cellulose and composite systems. It was found that natural fiber systems have three-times higher activation energy than viscose fiber systems, indicating their greater thermal stability. Blends of natural and artificial fibers combine the benefits of both precursors, enabling the deliberate regulation of thermal behavior and carbon material yield. This approach opens up prospects for the creation of functional carbon materials used in various high-tech areas, including thermal insulation. Full article

(This article belongs to the Special Issue Natural Fiber-Based Green Materials, Second Edition)

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15 pages, 6035 KiB

Open AccessArticle

Improving Tribological Performance of Poly(phenylene sulfide) by Incorporating PTFE Fillers: The Influence of Filler Type and Concentrations

by Junpeng Li, Jixiang Li, Jianbo Xiang, Xiaoxi Gong, Peng Xie, Yang Chen, Mei Liang, Huawei Zou and Shengtai Zhou

Polymers 2025, 17(9), 1222; https://doi.org/10.3390/polym17091222 - 29 Apr 2025

Abstract

Poly(phenylene sulfide) (PPS) is a high-performance thermoplastic engineering material with excellent comprehensive performance that finds application in many fields due to its good processability, excellent heat resistance, and mechanical properties. However, the poor friction and wear properties of PPS limit its wide application [...] Read more.

Poly(phenylene sulfide) (PPS) is a high-performance thermoplastic engineering material with excellent comprehensive performance that finds application in many fields due to its good processability, excellent heat resistance, and mechanical properties. However, the poor friction and wear properties of PPS limit its wide application in industrial sectors. In this work, polytetrafluoroethylene (PTFE) was adopted as the solid tribo-modifier to improve the tribological performance of PPS. The efficacy of using three types of PTFE fillers, namely PTFE fiber, micropowder, and nanopowder, was comparatively investigated. The results revealed that the incorporation of PTFE was beneficial to improving the tribological properties of PPS and PTFE nanopowders, which were prepared by irradiation treatment technology that demonstrated the best modification effect in terms of both tribological and mechanical performance among the studied systems. In addition, the coefficient of friction and specific wear rate of PPS composites with 30 wt% nanopowders reached 0.165 and 3.59 × 10⁻⁵ mm³/Nm, respectively, which were 70.7% and 99.0% lower than their pure PPS counterparts. The above finding was attributed to the improved compatibility between the PTFE nanopowders and the PPS substrate as well as the easier formation of intact PTFE transfer film on the contact surface. This work shows some perspective for designing self-lubricating polymer composites that broaden their application in industrial sectors. Full article

(This article belongs to the Special Issue Mechanical and Structure–Property Relationships of Polymer Composites II)

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22 pages, 10121 KiB

Open AccessArticle

Exploring the Characteristics of Carbon Structures Obtained from LignoBoost Lignin

by Adina Coroabă, Irina Apostol, Ioan Andrei Dascălu, Adrian Bele, Narcisa Laura Marangoci, Florica Doroftei, Cristina Mariana Uritu and Iuliana Spiridon

Polymers 2025, 17(9), 1221; https://doi.org/10.3390/polym17091221 - 29 Apr 2025

Abstract

In the present study, carbon structures from LignoBoost lignin were synthetized using HNO₃/H₂SO₄ one-pot hydrothermal treatment, followed by a thermal treatment. The obtained compounds were characterized using different techniques, such as FTIR, DVS, DLS, XRD, fluorescence imaging and [...] Read more.

In the present study, carbon structures from LignoBoost lignin were synthetized using HNO₃/H₂SO₄ one-pot hydrothermal treatment, followed by a thermal treatment. The obtained compounds were characterized using different techniques, such as FTIR, DVS, DLS, XRD, fluorescence imaging and STEM. The formed LCMs presented graphitized structure with quasi-spherical shapes. All obtained materials presented negative values of zeta potential due to the charge from the hydroxyl and carboxyl groups, as confirmed by XPS analysis. All the data obtained sustained the heterogeneous composition of the lignin-based carbon materials, which arise from the complex structure of lignin. Fluorescence imaging demonstrated the potential of the materials as optical imaging agents. Full article

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

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20 pages, 7168 KiB

Open AccessArticle

Cellulose Extraction from Soybean Hulls and Hemp Waste by Alkaline and Acidic Treatments: An In-Depth Investigation on the Effects of the Chemical Treatments on Biomass

by Antonella Moramarco, Edoardo Ricca, Elisa Acciardo, Enzo Laurenti and Pierangiola Bracco

Polymers 2025, 17(9), 1220; https://doi.org/10.3390/polym17091220 - 29 Apr 2025

Abstract

The agri-food supply chain and other industries that convert agricultural raw materials into various consumer goods generate large quantities of by-products, most of which end up in landfills. This waste, rich in cellulose, provides a significant opportunity for the conversion of agricultural residues [...] Read more.

The agri-food supply chain and other industries that convert agricultural raw materials into various consumer goods generate large quantities of by-products, most of which end up in landfills. This waste, rich in cellulose, provides a significant opportunity for the conversion of agricultural residues into valuable products. In this paper, soybean hulls and hemp waste were subjected to chemical treatments with alkaline (NaOH 2% w/v) and acidic solutions (HCl 1 M) to remove non-cellulosic components and isolate cellulose. The biomass was characterized after each chemical process through FTIR, SEM, EDX, elemental analysis, TGA, and XRD. Lignin was determined following two different procedures, a conventional TAPPI protocol and a method recently proposed in the literature (CASA method). The results indicated that the chemical treatments favored the removal of organic compounds and minerals, increasing the cellulose content in biomass after each step. The purified product of soybean hulls consists of fibers 35–50 µm long and 5–11 µm thick, containing nearly pure cellulose arranged in crystalline domains. Fibers of variable sizes, rich in crystalline cellulose, were isolated from hemp waste. These fibers have diameters ranging between 2 and 60 µm and lengths from 40 to 800 µm and contain considerable amounts of lignin (~14%). Full article

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

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11 pages, 1403 KiB

Open AccessArticle

Novel High-Efficiency Single-Site Rare Earth (RE) Catalyst System for Isoprene Polymerization

by Di Kang, Rongqing Ma, Hongfan Hu, Yi Zhou, Guoliang Mao and Shixuan Xin

Polymers 2025, 17(9), 1219; https://doi.org/10.3390/polym17091219 - 29 Apr 2025

Abstract

Bis-(o-dipheylphosphinophenyl)amine, a tridentate (PNP) chelating ligand, and several of their Rare Earth (RE) metal complexes, [bis-(o-dipheylphosphinophenyl)amido]-RER₂, {[(C₆H₅)₂P-o-(C₆H₄)]₂NMR₂ (R = -CH₂- [...] Read more.

Bis-(o-dipheylphosphinophenyl)amine, a tridentate (PNP) chelating ligand, and several of their Rare Earth (RE) metal complexes, [bis-(o-dipheylphosphinophenyl)amido]-RER₂, {[(C₆H₅)₂P-o-(C₆H₄)]₂NMR₂ (R = -CH₂-o-(C₆H₄)NMe₂: M = Y, 1; Nd, 2; Gd, 3;), are prepared in high yields. When activated with the strong Lewis acid MMAO-7, all these complexes exhibit catalytic activity toward the polymerization of isoprene (IP) in non-protic hydrocarbons. While the Nd complex (2) showed moderate activity and stereoselectivity, the Y and Gd complexes (1 and 3) exhibited extremely high catalytic efficiency in IP homo-polymerization, and produced polyisoprene rubber (PI) with 95% to over 99% cis-1,4 stereoselectivity and narrow polydispersity indices (<2.0). Moreover, under industrially relevant conditions, complex 3 can catalyze IP to produce ultrahigh molecular weight PI (UHMW-PI, MW up to 1200–2600 kg/mol) rubber with a very narrow polydispersity index (PDI ca. 1.1–1.6), a high-performance elastomeric material mimic of natural rubber (NR). Full article

(This article belongs to the Section Polymer Chemistry)

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14 pages, 4910 KiB

Open AccessArticle

Enhanced Compression Properties of Open-Cell Foams Reinforced with Shear-Thickening Fluids and Shear-Stiffening Polymers

by Jian Li, Yaoguang Zhou, Mohammad Rauf Sheikhi and Selim Gürgen

Polymers 2025, 17(9), 1218; https://doi.org/10.3390/polym17091218 - 29 Apr 2025

Abstract

Open-cell PU foams have a wide range of industrial applications due to their excellent cushioning, impact protection, packaging, thermal insulation, and sound reduction benefits. The foams absorb impact energy while deforming under compressing and are ideal for applications with severe and repeated loading [...] Read more.

Open-cell PU foams have a wide range of industrial applications due to their excellent cushioning, impact protection, packaging, thermal insulation, and sound reduction benefits. The foams absorb impact energy while deforming under compressing and are ideal for applications with severe and repeated loading conditions. Enhancing and improving their compressive durability is a vital area of ongoing research. We investigated the effect of incorporating shear-stiffening polymers (SSPs) and shear-thickening fluids (STFs) on the compression properties of open-cell foams. Rheological properties of STFs and SSPs prepared for incorporation into the foams confirmed the shear-thickening and shear-stiffening characteristics. Quasi-static compression tests performed at different speeds (6, 60, 120, 180, and 240 mm/s), as well as load-unload compression tests (6 and 24 mm/s), showed that the SSP-filled foam exhibited the most pronounced improvement in the elastic, plateau, and densification regions compared to the neat foam. While the STF-filled foam also improved performance over the neat foam, its advantages over the SSP-filled foam were less pronounced. The performance of the SSP-filled foam improved with increasing compression speeds, while the performance of the STF-filled foam remained relatively stable between 60 and 240 mm/s of load-unload tests. Post-test compression evaluations showed that neat and STF-filled foams quickly regained their original shape, while SSP-filled foams required more time before recovery. This research shows that combining SSP and STF smart materials with open-cell foams substantially improves their compressive performance, especially at high compression rates and load-unloading scenarios, increasing their functional life. Full article

(This article belongs to the Special Issue Mechanical Behaviors and Properties of Polymer Materials, 2nd Edition)

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