Polymers

13 pages, 970 KiB

Open AccessArticle

Influence of Molecular Weight and Temperature on the Pyrolysis Behavior of Polyethylene

by Eunji Chae and Sung-Seen Choi

Polymers 2025, 17(5), 576; https://doi.org/10.3390/polym17050576 - 21 Feb 2025

The pyrolysis technique is a useful recycling method for waste polyethylene (PE). Various PEs with different molecular weights have been produced and are widely used. The major pyrolysis products of PE include alkadienes (C_nH_2n−2), alkenes (C_nH_2n [...] Read more.

The pyrolysis technique is a useful recycling method for waste polyethylene (PE). Various PEs with different molecular weights have been produced and are widely used. The major pyrolysis products of PE include alkadienes (C_nH_2n−2), alkenes (C_nH_2n), and alkanes (C_nH_2n+2). In this study, the differences in pyrolysis behavior of PE based on its molecular weight and the pyrolysis temperature (423–764 °C) were investigated using four types of PEs, with M_w = 2.0 ´ 10³, 16.0 ´ 10³, 28.3 ´ 10³, and 56.8 ´ 10³ g/mol. More specifically, the pyrolysis products were compared in terms of their type (alkanes, alkenes, and alkadienes) and size (the number of carbon atoms). The order of production was alkenes > alkanes > alkadienes. The alkadiene/alkene ratios tended to increase with the PE molecular weight and size of the pyrolysis products. The alkadiene/alkene ratio increased until the pyrolysis temperature reached 670 °C. The alkane/alkene ratios tended to decrease as the PE molecular weight increased; however, they increased with the increasing size of the pyrolysis products. The alkane/alkene ratio decreased as the pyrolysis temperature increased, until it reached 670 °C. The formation of alkenes was more favorable than that of alkadienes and alkanes. Full article

(This article belongs to the Special Issue Advances in the Thermal Characterization of Polymers and Plastic Waste)

20 pages, 2279 KiB

Open AccessArticle

In Situ Crystalline Growth ZnS Nanoparticles on Conjugated Polymer for Enhancement of the Photocatalytic Performance

by Baotong Liu, Xuelian Li, Long Zhang, Chenghai Ma, Ying Chen, Xinyu Wang, Hongli Wei and Pengfei Wang

Polymers 2025, 17(5), 575; https://doi.org/10.3390/polym17050575 - 21 Feb 2025

Abstract

Photocatalysis is an important means of realizing the efficient use of solar energy and alleviating energy consumption and environmental pollution. This work used a simple solvothermal synthesis method to prepare a series of zinc sulfide/sulfur-doped polyimide (ZnS/SPI) direct Z-type heterostructured photocatalysts. ZnS/SPI heterostructured [...] Read more.

Photocatalysis is an important means of realizing the efficient use of solar energy and alleviating energy consumption and environmental pollution. This work used a simple solvothermal synthesis method to prepare a series of zinc sulfide/sulfur-doped polyimide (ZnS/SPI) direct Z-type heterostructured photocatalysts. ZnS/SPI heterostructured photocatalysts have better photogenerated electron–hole pairs separation and wider visible light absorption region. The effect of ZnS on the properties of ZnS/SPI composites, such as morphology, structure, and optoelectronic properties, was systematically investigated by a series of characterization tests. These results showed that the photocatalytic activity of the ZnS/SPI composite was significantly improved compared with SPI. The 10ZnS/SPI composite exhibited the highest photocatalytic hydrogen production rate under full irradiation (216.9 µmol/g/h), which was about 2.8 times higher than that of SPI (76.6 µmol/g/h). Moreover, it has a high stability over a long period in the photocatalytic process. The enhanced photocatalytic performance of the ZnS/SPI heterojunction is mainly due to the close contact between the ZnS nanoparticles and the SPI interface, which improves the charge separation and reduces the complexation rate of electron–hole. This work shows that the formation of ZnS/SPI composites Z-type heterojunction can effectively enhance the activity of polymer photocatalysts. Full article

(This article belongs to the Special Issue Advances in Polyimide: Synthesis, Modification, Characterization, Application and Beyond)

17 pages, 3548 KiB

Open AccessArticle

Formation of PEG-PLGA Microspheres for Controlled Release of Simvastatin and Carvacrol: Enhanced Lipid-Lowering Efficacy and Improved Patient Compliance in Hyperlipidemia Therapy

by Lin Fu, Hengxin Ren, Chaoxing Wang, Yaxin Zhao, Bohang Zou and Xiangyu Zhang

Polymers 2025, 17(5), 574; https://doi.org/10.3390/polym17050574 - 21 Feb 2025

Abstract

Polymer-based drug-controlled release systems offer greater efficacy and potency than conventional therapies. However, prominent drug side effects, lower circulation, and low drug loading capabilities limit their application range. In this work, the combination of Simvastatin (SIV) and Carvacrol (CAV) into PEG-PLGA microspheres (SIV-CAV-PP-MS) [...] Read more.

Polymer-based drug-controlled release systems offer greater efficacy and potency than conventional therapies. However, prominent drug side effects, lower circulation, and low drug loading capabilities limit their application range. In this work, the combination of Simvastatin (SIV) and Carvacrol (CAV) into PEG-PLGA microspheres (SIV-CAV-PP-MS) was achieved via an emulsification-solvent evaporation technique, resulting in microspheres characterized by high encapsulation efficiency and reduced particle size. In vitro studies demonstrated that the cumulative drug release increased with higher SIV and CAV levels in the release medium, reaching 88.91% and 89.35% at 25 days. Pharmacokinetic analysis revealed that the concentrations of SIV and CAV reached their maximum levels at approximately seven days in the SIV-CAV-PP-MS group, which indicates that using PEG-PLGA as a carrier significantly delays drug release. In vivo, evaluation demonstrated that the SIV-CAV-PP-MS high-dose group and positive drug control group showed reductions in low-density lipoprotein cholesterol levels by 0.39-fold and 0.36-fold compared to the Hyperlipidemia model group, and the addition of CAV significantly enhanced the lipid-lowering effects of SIV. Histological examinations indicated that the SIV-CAV-PP-MS medium-dose group displayed histological features more closely resembling those of normal mice compared to the Simvastatin control group, with a well-organized hepatocyte structure, a significant reduction in lipids, and improved liver health. The prepared polymeric microsphere utilizing SIV and SAV will be a promising dosage form for hyperlipidemia disease patients, with superior lipid-lowering efficacy and improved patient compliance. Full article

(This article belongs to the Special Issue Fabrication and Application of Biopolymer-Based Advanced Functional Materials, 2nd Edition)

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17 pages, 7097 KiB

Open AccessArticle

Numerical Prediction and Experimental Validation of Deposited Filaments in Direct Ink Writing: Deposition Status and Profile Dimension

by Yongqiang Tu, Haoran Zhang, Xue Shi, Jianyu Fan, Baohua Bao, Gang Lu, Fuwei Han, Hao Wu and Alaa Hassan

Polymers 2025, 17(5), 573; https://doi.org/10.3390/polym17050573 - 21 Feb 2025

Abstract

The deposition status and profile dimension of deposited filaments have an impact on the quality of the printed parts fabricated by direct ink writing (DIW). Previous works often failed to realize the full quantitative characterizations of the detailed influence of the process parameters [...] Read more.

The deposition status and profile dimension of deposited filaments have an impact on the quality of the printed parts fabricated by direct ink writing (DIW). Previous works often failed to realize the full quantitative characterizations of the detailed influence of the process parameters on the deposition status and profile dimension. Herein, we predict and analyze the deposition status and profile dimension by proposing an improved three-dimensional (3D) numerical model. The prediction accuracy of the proposed numerical model is verified through filament deposition experiments. The maximum relative errors of width and height between the experimental and simulation results of cross-sections are 10.13% and 7.37%, respectively. The effect of process parameters on the deposition status and profile dimension has been quantified. Critical process parameters are identified as the dimensionless nozzle velocity (V*) and the dimensionless height (H*). Three deposition statuses named over-deposition, pressed deposition and freeform deposition are characterized depending on the combination of V* and H*. The current work demonstrates an effective approach for the prediction of the deposition status and profile dimension of the deposited filaments along with the investigation of the effects of process parameters in DIW based on numerical simulations. Full article

(This article belongs to the Section Polymer Physics and Theory)

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16 pages, 4873 KiB

Open AccessArticle

Evaluation of NADES for Pectin Films Reinforced with Oxalic Acid-Modified Chitin Nanowhiskers

by Andrea Mathilde Mebert, Cynthia Melisa Melian-Queirolo, Maria Fernanda Hamet, Guillermo Javier Copello and Andrea Gomez-Zavaglia

Polymers 2025, 17(5), 572; https://doi.org/10.3390/polym17050572 - 21 Feb 2025

Abstract

The effect of three NADESs as pectin film plasticizers was evaluated at 10%, 30%, and 50% w/w by using the casting method. Two hydrophilic (choline chloride with glycerol or citric acid) and one hydrophobic (thymol–camphor) NADESs were used as replacement for [...] Read more.

The effect of three NADESs as pectin film plasticizers was evaluated at 10%, 30%, and 50% w/w by using the casting method. Two hydrophilic (choline chloride with glycerol or citric acid) and one hydrophobic (thymol–camphor) NADESs were used as replacement for glycerol. Oxalic acid-modified chitin nanowhiskers (oCNWs) at 1% w/w were used to evaluate the effect of the NADESs on the nanofiller. The resulting films using the hydrophobic NADES were difficult to handle and prone to cracking and performed similarly to or worse than pure pectin films. As a result, they were not further evaluated. In contrast, the hydrophilic ones showed characteristics comparable to glycerol. It was found that films containing glycerol and choline chloride–glycerol NADESs showed a decrease in opacity and tensile strength and an increase in WVP, Young’s modulus, and maximum elongation. In contrast, those that contained citric acid exhibited a different behavior: opacity was less affected, and a decrease in WVP and an increase in tensile strength and Young’s modulus (at 10% and 30% plasticizer) were found. oCNWs tended to decrease WVP and increase Young’s modulus but not in a very significant way. Our findings demonstrate that NADESs can be used as plasticizers in pectin films without the need to include glycerol and that the nature of NADESs is relevant to tuning the final properties. Full article

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

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17 pages, 3763 KiB

Open AccessArticle

Bio-Based and Solvent-Free Epoxy Vitrimers Based on Dynamic Imine Bonds with High Mechanical Performance

by Lei Chen, Na Ning, Gang Zhou, Yan Li, Shicheng Feng, Zhengyan Guo and Yi Wei

Polymers 2025, 17(5), 571; https://doi.org/10.3390/polym17050571 - 21 Feb 2025

Abstract

Conventional epoxy thermosets, with irreversible crosslinking networks, cannot be reprocessed and recycled. Furthermore, the utilization of petroleum-based materials accelerates the depletion of non-renewable resources. The introduction of dynamic covalent bonds and the use of bio-based materials for thermosets can effectively address the above [...] Read more.

Conventional epoxy thermosets, with irreversible crosslinking networks, cannot be reprocessed and recycled. Furthermore, the utilization of petroleum-based materials accelerates the depletion of non-renewable resources. The introduction of dynamic covalent bonds and the use of bio-based materials for thermosets can effectively address the above issues. Herein, a series of bio-based epoxy vitrimers with dynamic covalent imine bonds were synthesized via a simple solvent-free, one-pot method using vanillin-derived aldehyde monomers, 4,4-diaminodiphenylsulfone (DDS) and bisphenol F diglycidyl ether (BFDGE) as raw materials. The effect of crosslinking density, crosslinking structure and imine bond content on the resulting bio-based vitrimers was studied, demonstrating their excellent thermal properties, UV shielding and solvent resistance, as well as outstanding mechanical properties compared to those of the previously reported vitrimers. In particular, the cured neat resin of vitrimer had a maximum tensile strength of 109 MPa and Young’s modulus of 6257 MPa, which are higher than those of previously reported imine-based vitrimers. The dynamic imine bonds endow these vitrimers with good reprocessability upon heating (over 70% recovery) and degradation under acidic conditions, enabling recycling by physical routes and gentle degradation by chemical routes. This study demonstrates a simple and effective process to prepare high-performance bio-based and recycled epoxy thermosets. Full article

(This article belongs to the Special Issue Bio-Based and Biodegradable Polymers: Synthesis, Characterization and Applications)

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13 pages, 3252 KiB

Open AccessArticle

CDW-Based Geopolymers: Pro and Cons of Using Unselected Waste

by Ilaria Capasso, Gigliola D’Angelo, Mercedes del Río Merino, Assunta Campanile, Domenico Caputo and Barbara Liguori

Polymers 2025, 17(5), 570; https://doi.org/10.3390/polym17050570 - 21 Feb 2025

Abstract

Geopolymer technology is considered a strategic alternative for recycling construction and demolition waste (CDW) and to produce new construction products which meet the requirements of environmental and energy sustainability. The separation and management of CDW fractions is still a technological complex process and, [...] Read more.

Geopolymer technology is considered a strategic alternative for recycling construction and demolition waste (CDW) and to produce new construction products which meet the requirements of environmental and energy sustainability. The separation and management of CDW fractions is still a technological complex process and, even if large-scale separation technology is quite common, the necessity to perform this treatment may reduce the environmental and economic benefits of CDW reuse. So, a very promising option is represented by the manufacturing of geopolymers using unseparated CDW. In this aim, waste deriving from cement-based mortars, bricks and natural stones have been selected and widely characterized from a mineralogical, chemical and morphological point of view. Then, geopolymer mortars were produced using several amounts of either a single fraction or a mixture of the selected waste. The chemical, physical, mechanical, and microstructural characterization of the geopolymer-produced mortars was carried out to assess how the combination and different quantities of the mixed CDW affected the final properties. In particular, geopolymeric mortars produced from the unselected CDW showed higher mechanical properties, despite the lower apparent density, when compared to geopolymeric mortars produced from single fractions of CDW. The improvement of mechanical features seems to be not affected by the waste amount used, providing encouraging findings to promote the actual use of unseparated CDW with the resulting enhancement of environmental and economic benefits. Full article

(This article belongs to the Section Circular and Green Polymer Science)

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16 pages, 4593 KiB

Open AccessArticle

Self-Healing Properties of Crosslinked PMMA-DVB Copolymer Microcapsules Based on Interfacial Polymerization

by Xiaowei Jiang, Chengwu Tang, Jiachuan Yu, Yuankai Zhou and Xue Zuo

Polymers 2025, 17(5), 569; https://doi.org/10.3390/polym17050569 - 21 Feb 2025

Abstract

To address the issue of metal corrosion caused by microcracks in the coating on the steel structures of offshore drilling platforms, this study employs interfacial polymerization to prepare microcapsules with self-healing functionality for coatings. The microcapsules are fabricated through free radical polymerization between [...] Read more.

To address the issue of metal corrosion caused by microcracks in the coating on the steel structures of offshore drilling platforms, this study employs interfacial polymerization to prepare microcapsules with self-healing functionality for coatings. The microcapsules are fabricated through free radical polymerization between methyl methacrylate (MMA) and ammonium persulfate (APS), along with crosslinking reactions involving divinylbenzene (DVB). The particle size distribution and surface morphology of the microcapsules were optimized by adjusting process parameters using optical microscopy and scanning electron microscopy. Fourier-transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) were used to characterize the chemical structure and thermal stability of the microcapsules. The results show that when polyvinyl alcohol is used as the emulsifier, the oil–water ratio was 7.5:200, the amount of emulsifier was 1 wt%, the emulsification speed was 2500 r/min, the amount of initiator was 2 g, the core-to-wall ratio was 4:1, and the ambient temperature was 60 °C showed good sphericity, the microcapsules prepared under the optimized parameters exhibit good sphericity, a smooth surface, and an average particle size of 35.17 μm. They have a good core material encapsulation effect and thermal stability, which impart excellent self-healing properties to the epoxy coating. Such microcapsules have promising applications in mitigating the problem of metal corrosion of coatings due to microcracks and improving the service life and reliability of equipment. Full article

(This article belongs to the Section Polymer Networks)

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14 pages, 5656 KiB

Open AccessArticle

Adhesive Hemostatic Flake Particulates Composed of Calcium Alginate–Starch–Polyacrylamide/Poly(Acrylic Acid) Ionic Networks

by Yunjeh Ko, Eun Jin Kim and Oh Hyeong Kwon

Polymers 2025, 17(5), 568; https://doi.org/10.3390/polym17050568 - 20 Feb 2025

Abstract

Hemostatic particles have specific advantages when applied to narrow and complicated bleeding sites with convenient usage compared to other types of hemostatic agents such as fabrics, foams, and pastes. However, powdery hemostatic agents are easy to desorb from the bleeding surface due to [...] Read more.

Hemostatic particles have specific advantages when applied to narrow and complicated bleeding sites with convenient usage compared to other types of hemostatic agents such as fabrics, foams, and pastes. However, powdery hemostatic agents are easy to desorb from the bleeding surface due to blood flow, which causes a serious decrease in hemostasis function. Here, we introduce bioresorbable flake particulates composed of calcium alginate, starch and polyacrylamide/poly(acrylic acid) ionic networks as a wound adhesive hemostatic agent. The microstructure, chemical characteristics and blood infiltration of the flake hemostatic agent were analyzed. In vitro blood absorption, coagulation ability, adhesion force, cytotoxicity and in vivo bioresorption with biological safety were investigated. The tissue adhesive force of the hemostatic flakes showed a consistently higher value (−0.67 ± 0.06 N axial force) than Arista^TM AH powder. The in vivo rat hepatic hemorrhage model analysis demonstrated a significantly improved hemostasis rate in the flake group (36 ± 5 s) by wound adhesion and quick blood absorption. This adhesive flake particulate hemostatic is expected to provide an advanced option for medical treatments. Full article

(This article belongs to the Special Issue Polymer-Based Biomaterials for Tissue Engineering Applications)

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16 pages, 2961 KiB

Open AccessArticle

Adsorption of Aqueous Nickel Ion by Biomass Carboxymethyl Cellulose-Doped Boron Nitride Composites and Its Subsequent Energy Storage

by Xinran Li, Boyun Wang, Wanqi Zhang, Xiaotao Zhang and Ximing Wang

Polymers 2025, 17(5), 567; https://doi.org/10.3390/polym17050567 - 20 Feb 2025

Abstract

As a typical heavy metal pollutant discharged from industrial activities, nickel ions are highly bioaccumulative and carcinogenic, and low concentrations (>0.5 mg/L) can disrupt the balance of aquatic ecosystems and pose a threat to human health. In this study, a bifunctional adsorbent based [...] Read more.

As a typical heavy metal pollutant discharged from industrial activities, nickel ions are highly bioaccumulative and carcinogenic, and low concentrations (>0.5 mg/L) can disrupt the balance of aquatic ecosystems and pose a threat to human health. In this study, a bifunctional adsorbent based on a carboxymethyl cellulose/boron nitride hydrogel was prepared for the treatment of nickel-containing wastewater with a high adsorption capacity of Ni²⁺ (800 mg/L, 344 mg/g), and after adsorption, the waste gel was converted into nickel-doped porous carbon material through carbonization and used as a bilayer capacitor electrode to achieve a specific capacitance of 40.6 F/g at a current density of 1 A/g. The capacity retention rate was >98% after 150 cycles. This strategy simultaneously solves the problems of nickel-containing wastewater purification (the adsorption method is applicable to medium- and high-concentration heavy-metal wastewater) and environmental pollution caused by waste adsorbents, and provides a new paradigm of the “adsorption-resourcing” closed-loop treatment of heavy-metal pollutants. Full article

(This article belongs to the Special Issue Polysaccharides: From Synthesis to Applications)

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22 pages, 4227 KiB

Open AccessReview

Current Trends for Cementation in Prosthodontics: Part 1—The Substrate

by Tatjana Maravic, Claudia Mazzitelli, Eric Mayer-Santos, Edoardo Mancuso, Stefano Gracis, Lorenzo Breschi and Massimo Fuzzi

Polymers 2025, 17(5), 566; https://doi.org/10.3390/polym17050566 - 20 Feb 2025

Abstract

With the vast possibilities of restorative dentistry nowadays and the constant development and release of restorative materials with improved mechanical and esthetical properties, there is a growing body of research on adhesive systems and cementation materials, as well as the adequate choices thereof [...] Read more.

With the vast possibilities of restorative dentistry nowadays and the constant development and release of restorative materials with improved mechanical and esthetical properties, there is a growing body of research on adhesive systems and cementation materials, as well as the adequate choices thereof in everyday clinical practice. There are high demands from the dental cements with regard to their adhesion to various substrates and restorative materials, their mechanical properties, resistance to dissolution in the oral environment, esthetic considerations, etc. A material that meets all these requirements is not yet available, and each available material presents certain shortcomings. However, thanks to the advancements in dental material research, polymers-based cements have gained admirable mechanical and esthetic properties, as well as versatility. With the plethora of products available on the market, clinicians are often faced with difficulties in the choice of a material adequate for certain clinical situations. Indeed, important factors to consider are the substrate for cementation and the restoration material. The aim of this review was to provide clear and literature-based clinical recommendations for the adequate cementation of prosthodontic restorations with regard to the cementation substrate. Considering that there is no gold standard protocol applicable in all clinical cases, since the properties of the cementation abutment could substantially differ, important individual considerations must be made for each situation. Full article

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

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19 pages, 3225 KiB

Open AccessArticle

Tailoring Thermomechanical, Shape Memory and Self-Healing Properties of Furan-Based Polyketone via Diels-Alder Chemistry with Different Bismaleimide Crosslinkers

by Esteban Araya-Hermosilla, Marco Carlotti, Felipe Orozco, Guilherme Macedo R. Lima, Rodrigo Araya-Hermosilla, Daniela E. Ortega, Diego Cortés-Arriagada, Francesco Picchioni, Ranjita K. Bose, Virgilio Mattoli and Andrea Pucci

Polymers 2025, 17(5), 565; https://doi.org/10.3390/polym17050565 - 20 Feb 2025

Abstract

Furan/maleimide dynamic covalent chemistry has been extensively used to fabricate re-workable and self-healing thermosets. Understanding the relationship between crosslinker structure, network dynamics, and material final properties, however, remains a challenge. This study introduces self-healing and shape-memory thermosets derived from furan-functionalized polyketones (PKFU) crosslinked [...] Read more.

Furan/maleimide dynamic covalent chemistry has been extensively used to fabricate re-workable and self-healing thermosets. Understanding the relationship between crosslinker structure, network dynamics, and material final properties, however, remains a challenge. This study introduces self-healing and shape-memory thermosets derived from furan-functionalized polyketones (PKFU) crosslinked with aromatic bis-maleimides, i.e., 1,1′-(methylenedi-4,1-phenylene)bis-maleimide (BISM1) and bis(3-ethyl-5-methyl-4-maleimidophenyl)methane (BISM2), via a thermally reversible Diels-Alder reaction. Polyketones were chemically modified with furfurylamine through the Paal-Knorr reaction, achieving varying furan grafting ratios. The resulting networks, characterized by ATR-FTIR, ¹H-NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and rheology, demonstrated tunable thermomechanical properties. BISM2-based thermosets exhibited enhanced thermal stability and reversibility over a broad temperature range (20–120 °C), with a shape recovery ratio of up to 89% and complete self-healing at 120 °C within 5 min. These findings highlight the potential of polyketone-based thermosets for applications requiring adaptive thermomechanical properties, efficient self-repair, and sustainability. Full article

(This article belongs to the Section Polymer Chemistry)

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24 pages, 4923 KiB

Open AccessReview

Proposal of a Modular Classification System for Direct Dental Resin Composites Based on Clinical Applications

by Philippe Francois, Mathieu Izart, Timothy Fasham, Yasmine Smail, Marie Jannot, Stéphane Le Goff, Fleur Beres, Max Troizier-Cheyne, Sara Bergman, Christian Moussally, Sarah Abdel-Gawad, Elisabeth Dursun, Romain Ceinos, Elisa Caussin and Jean-Pierre Attal

Polymers 2025, 17(5), 564; https://doi.org/10.3390/polym17050564 - 20 Feb 2025

Abstract

The adhesive–resin composite pair has been the cornerstone of direct restorations in dentistry for many years. Resin composites are traditionally classified in three ways based on their inorganic structure, their organic composition and their viscosity. While these classifications have long been associated with [...] Read more.

The adhesive–resin composite pair has been the cornerstone of direct restorations in dentistry for many years. Resin composites are traditionally classified in three ways based on their inorganic structure, their organic composition and their viscosity. While these classifications have long been associated with the optical, mechanical, and clinical properties of resin composites, recent studies indicate that this classification is not always valid. In recent years, a significant expansion of the range of clinical resin composite families has occurred, each with varying degrees of validation through in vitro and clinical studies. As a result, new resin composites with distinct structures, viscosities, and clinical indications have emerged. Despite this progress, a formal classification of the clinical features of all resin composites is still lacking, leading to terminological inconsistencies in research and potential confusion among clinicians. This brief review, supported by an exhaustive search of the dental literature, proposes a new clinical classification system for resin composites based on their key clinical features to help clinicians and researchers easily identify the key clinical characteristics of formulations. This modular classification, encompassing eight main families and 14 characteristics, is particularly suited to future developments, as current trends aim to simplify procedures by integrating multiple formulations into single products. Full article

(This article belongs to the Special Issue Multifunctional Polymers and Their Composites and Structures: Design, Preparation and Properties—Second Edition)

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13 pages, 1679 KiB

Open AccessArticle

Effect of Surface Treatments and Thermal Aging on Bond Strength Between Veneering Resin and CAD/CAM Provisional Materials

by Ali Robaian, Abdullah Mohammed Alshehri, Nasser Raqe Alqhtani, Abdulellah Almudahi, Khalid K. Alanazi, Mohammed A. S. Abuelqomsan, Eman Mohamed Raffat, Ali Elkaffas, Qamar Hashem and Tarek Ahmed Soliman

Polymers 2025, 17(5), 563; https://doi.org/10.3390/polym17050563 - 20 Feb 2025

Abstract

The oral environment significantly influences the esthetic appearance of CAD/CAM provisional restorative materials. Therefore, a veneering layer is required. Bonding veneering resin composites to these materials presents challenges, particularly under conditions of thermal aging. This study evaluated the impact of various surface treatments [...] Read more.

The oral environment significantly influences the esthetic appearance of CAD/CAM provisional restorative materials. Therefore, a veneering layer is required. Bonding veneering resin composites to these materials presents challenges, particularly under conditions of thermal aging. This study evaluated the impact of various surface treatments and thermal aging on the bond strength between veneering resin and CAD/CAM provisional materials. Fifty disk-shaped specimens of each CAD/CAM material (CAD-Temp, Everest C-Temp, and PEEK), measuring 10 mm in diameter and 3 mm in height, were fabricated. After being ultrasonically cleaned, specimens were embedded in acrylic resin blocks, leaving one surface exposed for surface treatments. Specimens were assigned to five groups at random. Group C: no surface treatments applied; DB: mechanically roughened with a diamond bur; DB + TC: DB group subjected to 5000 cycles of thermocycling; SB: treated with aluminum oxide airborne abrasion; SB + TC: SB group subjected to 5000 cycles of thermocycling. After the surface treatments, the primer and resin veneering composite were applied to the specimens. The shear bond strength (SBS) was calculated using a universal testing machine and the mode of failure was evaluated with an optical stereomicroscope with 40× magnification. Scanning electron microscopy evaluation was conducted to examine the surface topography of the materials’ surfaces after surface treatments. C-Temp in the SB group exhibited the highest SBS values (20.38 ± 1.04 MPa), while CAD-Temp in the C group showed the lowest values (4.60 ± 0.54 MPa). PEEK recorded significantly higher SBS values in DB + TC and SB + TC groups (9.26 ± 1.07 and 12.92 ± 0.97 MPa, respectively) compared to CAD-Temp in DB + TC and SB + TC groups (6.04 ± 0.76 and 8.82 ± 0.86 MPa, respectively). C-Temp exhibited higher SBS without surface treatment (13.11± 0.55 MPa), whereas PEEK showed higher SBS after diamond bur roughening and air particle abrasion (10.87 ± 1.02 MPa, and 14.37 ± 0.98 MPa, respectively). The thermocycling significantly reduced SBS values for C-Temp in the DB + TC and SB + TC groups (11.18 ± 0.92, 15.56 ± 0.87 MPa, respectively) and CAD-Temp in the DB + TC and SB + TC (6.04 ± 0.76 MPa and 8.82 ± 0.86 MPa, respectively). Conversely, the thermocycling had no significant effect on SBS values for PEEK material in the air particle abrasion group (12.92 ± 0.97 MPa). Full article

(This article belongs to the Special Issue Polymers in Restorative Dentistry: 2nd Edition)

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13 pages, 949 KiB

Open AccessArticle

Potential of Annatto Seeds (Bixa orellana L.) Extract Together with Pectin-Edible Coatings: Application on Mulberry Fruits (Morus nigra L.)

by Igor Gabriel Silva Oliveira, Karina Sayuri Ueda Flores, Vinícius Nelson Barboza de Souza, Nathaly Calister Moretto, Maria Helena Verdan, Caroline Pereira Moura Aranha, Vitor Augusto Dos Santos Garcia, Claudia Andrea Lima Cardoso and Silvia Maria Martelli

Polymers 2025, 17(5), 562; https://doi.org/10.3390/polym17050562 - 20 Feb 2025

Abstract

Morus nigra L., or mulberry, is a susceptible fleshy fruit due to its high respiratory rate and low storage stability, which shortens its shelf life and makes it difficult to commercialize in natura. Edible coatings, thin membranes produced directly on the desired surface, [...] Read more.

Morus nigra L., or mulberry, is a susceptible fleshy fruit due to its high respiratory rate and low storage stability, which shortens its shelf life and makes it difficult to commercialize in natura. Edible coatings, thin membranes produced directly on the desired surface, could improve food preservation, among other properties. Annatto (Bixa orellana L.) seeds are natural pigments with high antioxidant activity. This work aimed to develop a pectin-based edible coating with annatto extract to increase the shelf life of fruits, using mulberries as a study model. The mulberries were randomly separated into five groups: without coating, coated with different extract concentrations (0%, 5%, and 10%), and a layer-by-layer treatment consisting of a pectin layer under a 10% extract layer. The samples were evaluated for the following parameters: titratable acidity, maturity index, mass loss, pH, soluble solids, moisture contents, and bioactive compounds. The coated group with 10% annatto extract had the best result for the maturity index (25.52), while the group with 5% showed better mass loss and moisture (37.28% and 83.66%, respectively). Herein, it was demonstrated that pectin-based edible coatings with annatto extract delay the maturation and senescence of mulberries, preserving the bioactive compounds and increasing shelf life. Full article

(This article belongs to the Special Issue Biopolymer-Based Materials for Edible Food Packaging)

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20 pages, 8212 KiB

Open AccessArticle

Extracted Spent Coffee Grounds as a Performance-Enhancing Additive for Poly(Lactic Acid) Biodegradable Nursery Bags in Agriculture

by Amonrut Waisarikit, Nattawut Suadaung, Benjawan Khantho, Bawan Hadad, Gareth M. Ross, Paul D. Topham, Sukunya Ross and Sararat Mahasaranon

Polymers 2025, 17(5), 561; https://doi.org/10.3390/polym17050561 - 20 Feb 2025

Abstract

This study introduces biodegradable nursery bags using poly(lactic acid) (PLA), a widely used biodegradable polymer, and spent coffee grounds (SCGs), a byproduct of the brewing process in the coffee industry. SCGs were oil-extracted to produce extracted spent coffee grounds (exSCGs), which were characterized [...] Read more.

This study introduces biodegradable nursery bags using poly(lactic acid) (PLA), a widely used biodegradable polymer, and spent coffee grounds (SCGs), a byproduct of the brewing process in the coffee industry. SCGs were oil-extracted to produce extracted spent coffee grounds (exSCGs), which were characterized by their physical properties, chemical functionality, and thermal behavior. The exSCGs were blended with PLA at loadings of 5, 10, and 15 wt%. Analysis showed that exSCGs retained 3–5 wt% residual coffee oil, exhibiting a lower surface area (1.1163 m²/g) compared to SCGs (1.5010 m²/g), along with a higher pore volume (1.148 × 10⁻³ cm³/g) and pore size (~410 nm). All PLA/exSCG bio-composite films displayed a light brown color, well-dispersed exSCG particles, and excellent UV light barrier properties, with transmittance reduced to 1–2%. The residual coffee oil acted as a plasticizer, reducing the glass transition temperature, melting temperature, and crystallinity with increasing exSCG content. Mechanical testing revealed enhanced flexibility compared to neat PLA. Soil burial tests showed increased biodegradability with higher exSCG content, supported by SEM analysis revealing cracks around exSCG particles. The PLA/exSCG blend containing 10 wt% exSCGs exhibited optimal performance, with a significant increase in melt flow index (from 4.22 to 8.17 g/10 min) and approximately double the melt strength of neat PLA, balancing processability and mechanical properties. This innovation provides a sustainable alternative to plastic nursery bags, addressing waste valorization and promoting eco-friendly material development for agricultural applications. Full article

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

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1 pages, 128 KiB

Open AccessCorrection

Correction: Staszczak et al. Nucleation, Development and Healing of Micro-Cracks in Shape Memory Polyurethane Subjected to Subsequent Tension Cycles. Polymers 2024, 16, 1930

by Maria Staszczak, Leszek Urbański, Arkadiusz Gradys, Mariana Cristea and Elżbieta Alicja Pieczyska

Polymers 2025, 17(5), 560; https://doi.org/10.3390/polym17050560 - 20 Feb 2025

Abstract

In the original publication [...] Full article

38 pages, 11494 KiB

Open AccessReview

Research Advances in Natural Polymers for Environmental Remediation

by Muhammad Sheraz, Xiao-Feng Sun, Adeena Siddiqui, Sihai Hu and Zhengcang Song

Polymers 2025, 17(5), 559; https://doi.org/10.3390/polym17050559 - 20 Feb 2025

Abstract

The search for sustainable and efficient remediation techniques is required to control increasing environmental pollution caused by synthetic dyes, heavy metal ions, and other harmful pollutants. From this point of view, natural polymers like chitosan, cellulose, lignin, and pectin have been found highly [...] Read more.

The search for sustainable and efficient remediation techniques is required to control increasing environmental pollution caused by synthetic dyes, heavy metal ions, and other harmful pollutants. From this point of view, natural polymers like chitosan, cellulose, lignin, and pectin have been found highly promising due to their biodegradability, availability, and possibility of chemical functionalization. Natural polymers possess inherent adsorption properties that can be further enhanced by cross-linking and surface activation. This review discusses the main properties, adsorption mechanisms, and functional groups such as hydroxyl, carboxyl, and amino groups responsible for pollutant sequestration. The paper also emphasizes the effectiveness of natural polymers in removing heavy metals and dyes from wastewater and discusses recent advances in polymer modifications, including ionic crosslinking and grafting. This study underlines the ecological potential of natural polymer-based adsorbents in the treatment of wastewater and the protection of the environment as a sustainable solution to pollution challenges. Full article

(This article belongs to the Special Issue Functional Polymeric Materials for Water Treatment)

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19 pages, 1066 KiB

Open AccessReview

Chitosan as a Plurivalent Biopolymer in Nanodelivery Systems

by Marius Gabriel Dabija, Iulia Olaru, Tudor Ciuhodaru, Alina Stefanache, Cozmin Mihai, Ionut Iulian Lungu, Gabriela Calin, Carmen Stadoleanu and Daniela Liliana Damir

Polymers 2025, 17(5), 558; https://doi.org/10.3390/polym17050558 - 20 Feb 2025

Abstract

(1) Background: This review study will delve into the potential of chitosan nanoparticles (NPs) as adaptable carriers for targeted drug delivery in different therapeutic areas. Chitosan is a biopolymer derived from chitin that has attracted interest in drug delivery applications because of its [...] Read more.

(1) Background: This review study will delve into the potential of chitosan nanoparticles (NPs) as adaptable carriers for targeted drug delivery in different therapeutic areas. Chitosan is a biopolymer derived from chitin that has attracted interest in drug delivery applications because of its high biocompatibility and biodegradability. (2) Methods: A comprehensive literature review was conducted by following a careful systematized protocol for searching databases like PubMed, Google Scholar and ScienceDirect. (3) Results: Chitosan NPs are good drug delivery vehicles, notably for cancer. Studies reveal that doxorubicin-loaded chitosan NPs dramatically enhance toxicity to tumor cells compared to free medicines, yielding tumor suppression rates of up to 60%. Researchers found that chemotherapeutics had an 85% encapsulation efficiency (EE), lowering systemic toxicity. Magnetic and pH-responsive chitosan NPs boost drug accumulation by 63% and apoptosis by 54%. Chitosan also boosts medication retention in the lungs by 2.3×, per pulmonary delivery trials. Chitosan NPs also boost ocular medication bioavailability by 3× and improve nasal absorption by 30%, crossing the blood–brain barrier. For bone regeneration, chitosan scaffolds enhance bone mineral density by 46%, facilitating osteogenesis and healing. (4) Conclusions: NPs made of chitosan provide a solid foundation for improving drug delivery systems; yet there are still issues with material variability, scalability, and meeting regulatory requirements that need fixing. Research into combination treatments, ways to increase their specificity, and ways to optimize these NPs offers promising prospects for the creation of novel therapeutic approaches with the potential to improve patient outcomes. Full article

(This article belongs to the Special Issue Nanoparticles in Drug Delivery Systems)

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45 pages, 6287 KiB

Open AccessReview

Polymeric Heart Valves: Do They Represent a Reliable Alternative to Current Prosthetic Devices?

by Martina Todesco, Gianluca Lezziero, Gino Gerosa and Andrea Bagno

Polymers 2025, 17(5), 557; https://doi.org/10.3390/polym17050557 - 20 Feb 2025

Abstract

With the increasing number of people suffering from heart valve diseases (e.g., stenosis and/or insufficiency), the attention paid to prosthetic heart valves has grown significantly. Developing a prosthetic device that fully replaces the functionality of the native valve remains a huge challenge. Polymeric [...] Read more.

With the increasing number of people suffering from heart valve diseases (e.g., stenosis and/or insufficiency), the attention paid to prosthetic heart valves has grown significantly. Developing a prosthetic device that fully replaces the functionality of the native valve remains a huge challenge. Polymeric heart valves (PHVs) represent an appealing option, offering the potential to combine the robustness of mechanical valves with the enhanced biocompatibility of bioprosthetic ones. Over the years, novel biomaterials (such as promising new polymers and nanocomposites) and innovative designs have been explored for possible applications in manufacturing PHVs. This work provides a comprehensive overview of PHVs’ evolution in terms of materials, design, and fabrication techniques, including in vitro and in vivo studies. Moreover, it addresses the drawbacks associated with PHV implementation, such as their limited biocompatibility and propensity for sudden failure in vivo. Future directions for further development are presented. Notably, PHVs can be particularly relevant for transcatheter application, the most recent minimally invasive approach for heart valve replacement. Despite current challenges, PHVs represent a promising area of research with the potential to revolutionize the treatment of heart valve diseases, offering more durable and less invasive solutions for patients. Full article

(This article belongs to the Section Polymer Applications)

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17 pages, 18993 KiB

Open AccessArticle

Study on the Mechanical and Thermal Properties of Waterborne Polyurethane-Modified Aluminum Hydroxide and Its Application in LDPE Plastics

by Xianrong Yang, Gaoxiang Du, Huan Shuai, Xi Xu and Jiao Wang

Polymers 2025, 17(5), 556; https://doi.org/10.3390/polym17050556 - 20 Feb 2025

Abstract

This study investigates the modification of aluminum hydroxide (ATH) powder using waterborne polyurethane (WPU) as a novel modifier, along with its subsequent effects on the dispersion, mechanical properties, and thermal performance of ATH-filled low-density polyethylene (LDPE) composites. ATH was modified through an optimized [...] Read more.

This study investigates the modification of aluminum hydroxide (ATH) powder using waterborne polyurethane (WPU) as a novel modifier, along with its subsequent effects on the dispersion, mechanical properties, and thermal performance of ATH-filled low-density polyethylene (LDPE) composites. ATH was modified through an optimized wet process, and the modification efficiency was evaluated using various characterization techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The results show that WPU, as a modifier, effectively improved the dispersion of ATH in the organic phase, as demonstrated by the reduced settling time and enhanced interfacial compatibility between ATH and LDPE. The modified ATH demonstrated enhanced mechanical properties in LDPE-based composites, with a tensile strength of 30.02 MPa, flexural strength of 13.20 MPa, impact strength of 65.75 kJ/m², and elongation at break of 59.84%, all reaching their maximum at 3.0 wt.% WPU modification. Additionally, the flame retardancy of the composites was significantly improved due to the incorporation of ATH, with the ATH content in the composites reaching up to 60%, further enhancing their fire resistance. This study highlights the effectiveness of WPU-modified ATH as both a flame retardant and a reinforcing filler for LDPE composites, offering potential advantages in enhancing material properties while reducing manufacturing costs. Full article

(This article belongs to the Special Issue Modification and Functionalization of Polymer Materials for Sustainable Development)

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15 pages, 2926 KiB

Open AccessArticle

Effects of Modification on Properties of Wood Flour/PBAT Biocomposites

by Wangwang Yu, Rui Qiu, Wen Lei and Yong Chen

Polymers 2025, 17(5), 555; https://doi.org/10.3390/polym17050555 - 20 Feb 2025

Abstract

Wood flour (WF)-reinforced poly (butylene adipate-co-terephthalate) (PBAT) composites were successfully fabricated by injection-molding process after being mixed using an extruder. The effects of fiber modifications, including mercerization, acetylation, as well as coupling agent treatment on the properties of WF/PBAT composites, were studied. The [...] Read more.

Wood flour (WF)-reinforced poly (butylene adipate-co-terephthalate) (PBAT) composites were successfully fabricated by injection-molding process after being mixed using an extruder. The effects of fiber modifications, including mercerization, acetylation, as well as coupling agent treatment on the properties of WF/PBAT composites, were studied. The results indicated that all the modifications increased the mechanical properties (e.g., tensile strength, tensile modulus, flexural strength, flexural modulus, elongation at break, and Charpy impact strength) of the composites. After modification, all the composites showed better interfacial bonding, hydrophobicity, and thermal properties compared to the untreated fiber composites; meanwhile, the moisture absorption test showed that all the modified fiber composites exhibited a much lower saturated water absorption rate than untreated ones. WF modification by addition of a coupling agent could improve the properties most obviously, except for the tensile strength, elongation at break, and saturated water absorption rate. By this modification, the tensile modulus, flexural strength, flexural modulus, impact strength, onset temperature during thermal degradation, degree of crystallinity, and water contact angle of the composite were 313.47 MPa, 20.55 MPa, 830.79 MPa, 16.01 kJ/cm², 367.71 °C, 17.10%, and 101.8°, all increased from those of untreated composites by 17.95%, 30.73%, 87.52%, 35.79%, 61.49%, 25.67 °C, 89.16%, and 6.6°, respectively. Full article

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

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12 pages, 1497 KiB

Open AccessArticle

Evaluation of Shear Bond Strength and Failure Modes of Lithium Disilicate Ceramic Veneering Material to Different High-Performance Polymers

by Sarah M. Alnafaiy, Nawaf Labban, Refal Albaijan, Rawan N. AlKahtani, Khulud A. Al-Aali, Heba Wageh Abozaed, Nada Y. Alturki and Jomana E. Alenezi

Polymers 2025, 17(5), 554; https://doi.org/10.3390/polym17050554 - 20 Feb 2025

Abstract

This study assessed the shear bond strength (SBS) and failure modes of lithium disilicate ceramic veneering material to different high-performance polymers. Thirty-six square specimens measuring 7 × 7 × 2 ± 0.05 mm were prepared from pure polyetheretherketone (PEEK), Bio-high performance PEEK (BioHPP) [...] Read more.

This study assessed the shear bond strength (SBS) and failure modes of lithium disilicate ceramic veneering material to different high-performance polymers. Thirty-six square specimens measuring 7 × 7 × 2 ± 0.05 mm were prepared from pure polyetheretherketone (PEEK), Bio-high performance PEEK (BioHPP) and Trilor discs. Polymer specimens were air-borne abraded utilizing aluminum oxide particles, cleaned, and a bonding agent was applied (visio. link). The veneering LDC material (3 × 2 mm) was milled, hydrofluoric acid etched (9.5%) and primed (Clearfil ceramic). The LDC was bonded to the polymer specimens using dual-cured resin cement (Panavia V5) and light polymerized. The bonded specimens were subjected to 5000 cycles of physiological aging by thermocycling, and the SBS test was performed in a universal testing machine at 0.5 mm/min cross-head speed. The debonded specimens were analyzed to determine the primary bond failure sites (adhesive, mixed or cohesive). Data analysis was performed using one-way ANOVA and a post hoc Tukey test (α ≤ 0.05). The BioHPP material demonstrated the highest SBS values (23.94 ± 1.43 MPa), and the Trilor group recorded the lowest SBS values (17.09 ± 1.07 MPa). The PEEK group showed a mean SBS of 21.21 ± 1.51 MPa. The SBS comparison showed significant variations across all material groups (p < 0.001). Regarding failure modes, adhesive failure was observed in 40% of BioHPP and PEEK specimens and 90% of Trilor specimens. The cohesive failure occurred in 50% of PEEK and 30% of BioHPP specimens, while the Trilor specimens showed no cohesive failure. Mixed failures were reported in 30% of BioHPP and 10% of PEEK and Trilor specimens. The BioHPP material demonstrated high SBS followed by PEEK and Trilor. The SBS between the tested materials was statistically significant. However, the SBS of the tested implant framework materials was above the limit stipulated by the ISO 10477 standard (5 MPa) and the clinically acceptable range of 10–12 MPa. Full article

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

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Polymers, Volume 17, Issue 5 (March-1 2025) – 23 articles

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