Polymers

16 pages, 1541 KB

Open AccessArticle

Effects of Food-Simulating Liquids and Thermocycling on Surface Roughness and Color Stability of Highly Filled Flowable Resin Composites

by Nihat Can Yılmaz and Alper Kaptan

Polymers 2026, 18(18), 2196; https://doi.org/10.3390/polym18182196 (registering DOI) - 9 Sep 2026

Abstract

Highly filled flowable resin composites have been developed to improve the mechanical and esthetic performance of conventional flowable materials, but their long-term behavior under different aging conditions remains insufficiently characterized. This study evaluated the effects of thermocycling and food-simulating liquids on the surface [...] Read more.

Highly filled flowable resin composites have been developed to improve the mechanical and esthetic performance of conventional flowable materials, but their long-term behavior under different aging conditions remains insufficiently characterized. This study evaluated the effects of thermocycling and food-simulating liquids on the surface roughness and color stability of five highly filled flowable resin composites with a nanohybrid flowable composite included as a reference material. A total of 240 cylindrical specimens were randomly assigned to thermocycling, 10% citric acid, n-heptane, or 75% ethanol groups (n = 10 per material and protocol). Surface roughness was measured before and after aging, and color change (ΔE*ab) was determined after subsequent immersion in coffee solution. Data were analyzed using two-way analysis of variance (ANOVA) to evaluate the main effects of material and aging protocol and their interaction, followed by Tukey’s post hoc test for multiple comparisons (α = 0.05). Aging-related changes in surface roughness and color stability varied according to both the material and aging protocol. Significant material × aging-protocol interactions were observed for both ΔRa and ΔE*ab (p < 0.001). GrandioSO Heavy Flow showed the greatest increase in surface roughness after ethanol and n-heptane aging and the highest mean ΔE*ab values under each aging condition, whereas Neo-Spectra ST Flow showed the highest mean ΔRa after thermocycling, and G-ænial Universal Injectable showed the highest mean ΔRa after citric acid exposure. These findings indicate that the aging response of highly filled flowable resin composites is material-dependent and provide insight into their relative behavior under different laboratory aging conditions. Full article

(This article belongs to the Special Issue Recent Development of Polymeric Materials for Dental Applications)

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31 pages, 10891 KB

Open AccessArticle

Plasticizer-Dependent Vulcanization, Crosslinking, and Magneto-Viscoelasticity of Natural Rubber-Based Magnetorheological Elastomers

by Lili Fan, Haimin Zhu, Jianhua Du, Zhichao Li, Haisong Wu, Yicheng Su, Wangwei Li and Junhui Yao

Polymers 2026, 18(18), 2195; https://doi.org/10.3390/polym18182195 (registering DOI) - 9 Sep 2026

Abstract

Adaptive vibration control under variable dynamic loading requires damping materials that combine structural stability, efficient energy dissipation, and field-tunable mechanical response. Here, natural-rubber-based magnetorheological elastomers containing coumarone resin (MRE-C), naphthenic oil (MRE-N), or paraffin (MRE-P) were systematically compared through microstructural characterization, dynamic viscoelastic [...] Read more.

Adaptive vibration control under variable dynamic loading requires damping materials that combine structural stability, efficient energy dissipation, and field-tunable mechanical response. Here, natural-rubber-based magnetorheological elastomers containing coumarone resin (MRE-C), naphthenic oil (MRE-N), or paraffin (MRE-P) were systematically compared through microstructural characterization, dynamic viscoelastic testing, vulcanization kinetics, and equilibrium swelling. MRE-C exhibited pronounced strain-induced softening, whereas MRE-P showed a high relative dynamic sensitivity but limited absolute stiffness. MRE-N achieved the most favorable overall balance, with more continuous anisotropic particle-chain structures and the lowest Payne-effect amplitude (37.90%). At 5 A, its storage modulus increased by 25.8%, close to the 30.9% increase in MRE-P, while maintaining substantially higher absolute G′ and G″ and a nearly unchanged tan δ. MRE-N’s macroscopic advantage was associated with more favorable network formation, with 17.9% and 7.4% lower apparent activation energies and 7.2% and 18.1% higher apparent crosslink densities than MRE-C and MRE-P, respectively. Molecular simulations of representative sulfur bridges further indicated that monosulfidic bridges favored geometric constraint and structural recovery, whereas disulfidic bridges exhibited greater conformational adaptability. These results link plasticizer-dependent vulcanization and crosslinking state with macroscopic magneto-viscoelastic performance and identify naphthenic oil as the most effective of the investigated plasticizers for balancing stiffness, energy dissipation, and magnetic responsiveness. Full article

(This article belongs to the Special Issue Advances in Smart Polymers)

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25 pages, 1442 KB

Open AccessArticle

Chemical Variability of Recycled PET Bottles Driven by Packaging Inputs and Processing History: A Marker-Based Multivariate Approach

by Helena Raclavská, Marek Kucbel, Jana Růžičková, Barbora Švédová, Pavel Kantor, Karolina Slamová and Fabrizio Scala

Polymers 2026, 18(18), 2194; https://doi.org/10.3390/polym18182194 - 8 Sep 2026

Abstract

Recycled polyethylene terephthalate (rPET) intended for food-contact applications contains complex mixtures of non-intentionally added substances (NIAS) originating from polymer degradation, recycling, packaging-related inputs, and external contamination. Although non-targeted analytical techniques can characterise these complex chemical fingerprints, a standardised framework for their systematic interpretation [...] Read more.

Recycled polyethylene terephthalate (rPET) intended for food-contact applications contains complex mixtures of non-intentionally added substances (NIAS) originating from polymer degradation, recycling, packaging-related inputs, and external contamination. Although non-targeted analytical techniques can characterise these complex chemical fingerprints, a standardised framework for their systematic interpretation is lacking. This study introduces a literature-informed, pattern-based framework for interpreting Py-GC/MS fingerprints of commercial PET bottles. Twenty-two commercial PET beverage bottles were analysed by pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS), and detected compounds were organised into four diagnostic profile groups: PET transformation products (C-PET), packaging-associated compounds (E-PS/PVC/FCM), mixed-origin compounds (M-MIX), and condensed aromatic structures (A-AROM). Principal component analysis and a composite Quality Index (QI) were used to evaluate chemical variability. PET transformation products formed a consistent chemical baseline across all samples, whereas chemical variability was primarily associated with packaging-associated compounds and condensed aromatic structures. Bottles containing 100% rPET spanned the full range of chemical profiles, suggesting that the observed variability may be influenced more strongly by feedstock quality, packaging-related inputs, and processing history than by declared recycled content alone. The proposed framework enables a systematic interpretation of Py-GC/MS fingerprints through diagnostic chemical patterns rather than unique source attribution of individual compounds. The proposed framework provides a scalable methodology for comparative evaluation of recycled PET. It highlights that improving chemical quality requires controlling feedstock purity, packaging-related contamination, and processing conditions rather than relying solely on recycled content. Full article

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

20 pages, 5163 KB

Open AccessArticle

Bio-Based Phenolic Aldehyde Functionalization of Cellulose Acetate–Polyethyleneimine Membranes for Enhanced Ni²⁺ and Cu²⁺ Retention

by Eduard Ionut Piscanu, Celina Maria Damian, Andreea Madalina Pandele, Madalina Oprea, Adrian Ionut Nicoara and Stefan Ioan Voicu

Polymers 2026, 18(18), 2193; https://doi.org/10.3390/polym18182193 - 8 Sep 2026

Abstract

The increasing occurrence of heavy metal ions in water and wastewater streams represents a serious concern for both the environment and human health. The efficient removal of such contaminants requires the development of stable and functional membrane materials capable of combining separation performance [...] Read more.

The increasing occurrence of heavy metal ions in water and wastewater streams represents a serious concern for both the environment and human health. The efficient removal of such contaminants requires the development of stable and functional membrane materials capable of combining separation performance with specific metal-binding interactions. This work proposes the use of bio-sourced phenols alongside branched polyethyleneimine and cellulose acetate to develop advanced membranes for the retention of Ni²⁺ and Cu²⁺ ions from aqueous solutions. The chemical modification of the cellulose acetate membrane was confirmed by structural and thermal analysis. Improved thermal resistance between 50–200 °C suggests that chemical interactions as well as hydrogen bonds were developed within the functionalized membranes. The effect of aldehyde modification on membrane chemistry, morphology, thermal behavior, mechanical properties, and filtration performance was systematically investigated. The vanillin-modified membrane showed the best mechanical response, likely due to improved matrix cohesion promoted by its methoxy-substituted aromatic structure. In contrast, the salicylaldehyde-modified membrane exhibited the highest metal-ion retention, reaching approximately 73% for Ni²⁺ and 67% for Cu²⁺ after five filtration cycles. These findings highlight the potential of bio-based phenolic aldehydes as active compounds for designing membranes with tailored morphology, stability, thermal, mechanical, and metallic ion-removal performances. Full article

(This article belongs to the Special Issue Advances in Cellulose and Lignocellulosic Composites)

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33 pages, 5673 KB

Open AccessArticle

Obsidian, Waste Ceramic Powder, and Recycled Concrete Powder as Alternative Aggregates in Hydroxypropyl Methylcellulose-Stabilized Foamed Concrete: Mechanical, Thermal, and Durability Performance

by Kenan Mert Oksuz, Talip Çakmak, İlker Ustabaş and Zafer Kurt

Polymers 2026, 18(18), 2192; https://doi.org/10.3390/polym18182192 - 8 Sep 2026

Abstract

The substitution of conventional materials with alternative resources is a significant approach for enhancing the engineering performance and sustainability of foamed concrete (FC). While supplementary cementitious materials, volcanic materials, and waste-derived materials have been extensively investigated, the use of obsidian as an alternative [...] Read more.

The substitution of conventional materials with alternative resources is a significant approach for enhancing the engineering performance and sustainability of foamed concrete (FC). While supplementary cementitious materials, volcanic materials, and waste-derived materials have been extensively investigated, the use of obsidian as an alternative aggregate in FC systems remains largely unexplored, and the combined, systematic comparative use of obsidian, waste ceramic powder (WCP), and recycled concrete powder (RCP) within a unified experimental framework has not been previously investigated. This paper evaluates the use of obsidian, WCP, and RCP as alternative aggregates in hydroxypropyl methylcellulose (HPMC)-stabilized FC by replacing standard sand at 25%, 50%, and 100% levels. The thermal, durability and mechanical characteristics of the mixtures were assessed through density, compressive strength (CS), ultrasonic pulse velocity (UPV), water absorption (WA), elevated temperature resistance (200 °C, 400 °C, 600 °C and 800 °C), freeze–thaw performance, thermal conductivity (TC), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS) and X-ray diffraction (XRD) analyses. The results showed that the 28-day CS increased from 0.545 MPa in the control mixture to a maximum value of 2.590 MPa in the obsidian-based FC. Moreover, WA decreased markedly from 117.7% to 46.9% in the obsidian-based FC. The UPV varied from 1355 to 1795 m/s due to the incorporation of RCP, WCP and obsidian at different replacement ratios in the mixture designs. The lowest TC of 0.08185 W/(m·K) was recorded in the obsidian-based FC at 50% substitution level. Under elevated-temperature exposure, the mixture with 100% obsidian replacement retained a compressive strength of 0.5936 MPa at 800 °C. To conclude, the use of obsidian, WCP and RCP as alternative aggregates in FC shows promising potential for the development of durable, thermally efficient, and sustainable lightweight construction materials. Full article

(This article belongs to the Section Polymer Applications)

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27 pages, 5577 KB

Open AccessArticle

Enhanced Multifunctional Properties of Bipyridyl-Containing Polyurethane Nanocomposites Reinforced with Graphene/ZnO Hybrid Fillers

by Jing-Lun Chen, Yun-Shao Huang, Wen-Chin Tsen, Chi-Hui Tsou, Chin-Wen Chen and Maw-Cherng Suen

Polymers 2026, 18(18), 2191; https://doi.org/10.3390/polym18182191 - 8 Sep 2026

Abstract

A series of polyurethane (PU) nanocomposites incorporating 4,4′-bis(hydroxymethyl)-2,2′-bipyridine (BBD) as a chain extender and a commercially supplied graphene/zinc oxide (G/ZnO) hybrid filler were successfully synthesized. The effects of G/ZnO loading (0–2.0 wt.%) on the structural, thermal, mechanical, surface-wettability, and antibacterial properties of the [...] Read more.

A series of polyurethane (PU) nanocomposites incorporating 4,4′-bis(hydroxymethyl)-2,2′-bipyridine (BBD) as a chain extender and a commercially supplied graphene/zinc oxide (G/ZnO) hybrid filler were successfully synthesized. The effects of G/ZnO loading (0–2.0 wt.%) on the structural, thermal, mechanical, surface-wettability, and antibacterial properties of the nanocomposites were systematically investigated. Fourier-transform infrared spectroscopy confirmed the formation of the polyurethane structure and revealed changes in characteristic absorption bands following G/ZnO incorporation. Morphological observation of the pristine G/ZnO hybrid filler revealed an irregular and aggregated morphology, while X-ray diffraction confirmed the presence of crystalline ZnO. Energy-dispersive X-ray spectroscopy and elemental mapping showed Zn-containing regions within the examined areas of the G/ZnO-containing PU samples. X-ray photoelectron spectroscopy further confirmed the surface presence of Zn-containing species, with the Zn atomic concentration increasing from 0 at.% in PU-01 to 0.82 at.% in PU-04. Thermogravimetric analysis showed modest changes in thermal decomposition behavior with increasing G/ZnO loading, while differential scanning calorimetry and dynamic mechanical analysis revealed shifts in glass-transition and relaxation behavior, consistent with changes in polymer-chain mobility and the local interfacial environment. The tensile strength increased from 2.68 MPa for neat PU to 11.76 MPa for the nanocomposite containing 2.0 wt.% G/ZnO, accompanied by an increase in Young’s modulus. The water contact angle increased from approximately 68° to 89°, indicating reduced apparent surface wettability with increasing G/ZnO loading. The nanocomposites also exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus, with antibacterial efficiencies exceeding 95% at higher G/ZnO loadings. Overall, the incorporation of the commercial G/ZnO hybrid filler was associated with changes in the thermal, mechanical, surface, and antibacterial properties of the BBD-containing PU system. Because separate PU systems without BBD and individual graphene- and ZnO-containing controls were not included, the individual contributions of BBD, graphene, and ZnO, as well as any synergistic effect between graphene and ZnO, cannot be established from the present results. Further studies addressing filler leaching, long-term antibacterial stability, coating adhesion, environmental durability, and cytocompatibility are required to establish the practical applicability of these materials. Full article

(This article belongs to the Special Issue Recent Advances in Polyurethane-Based Composite Materials)

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24 pages, 2500 KB

Open AccessArticle

Bacterial Cellulose- and Laponite-Reinforced Corn Starch Bioplastics for Sustainable Packaging

by Rysgul Tuleyeva, Nargiz Gizatullina, Alexey Shakhvorostov, Zhanserik Shynykul and Gaukhar Toleutay

Polymers 2026, 18(18), 2190; https://doi.org/10.3390/polym18182190 - 8 Sep 2026

Abstract

Growing environmental concerns associated with petroleum-based plastics have stimulated the development of renewable and biodegradable alternatives. In this study, corn-starch-based composite films were prepared with bacterial cellulose (BC), α-cellulose (α-C), or carboxylated cellulose nanofibers (CNC) in the presence of laponite and glycerol. The [...] Read more.

Growing environmental concerns associated with petroleum-based plastics have stimulated the development of renewable and biodegradable alternatives. In this study, corn-starch-based composite films were prepared with bacterial cellulose (BC), α-cellulose (α-C), or carboxylated cellulose nanofibers (CNC) in the presence of laponite and glycerol. The films were characterized using Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis, optical measurements at 600 nm, tensile testing, qualitative solvent-exposure tests, and thermally induced repair experiments. Among the films containing different cellulose types, the bacterial-cellulose-containing bioplastic (BC-BP) exhibited the highest tensile strength and Young’s modulus, reaching 4.47 and 0.229 MPa, respectively. The carboxylated-cellulose-nanofiber-containing bioplastic (CNC-BP) showed the highest elongation at break (100%) and the lowest thickness-normalized optical attenuation (0.38 mm⁻¹), whereas the α-cellulose-containing bioplastic (α-C-BP) exhibited the highest maximum degradation-rate temperature (approximately 315 °C). Increasing the BC content from 0.25 to 1.0 g increased tensile strength from 3.17 ± 0.13 to 7.78 ± 0.31 MPa and Young’s modulus from 0.260 ± 0.002 to 0.996 ± 0.009 MPa. This increase was accompanied by a reduction in elongation at break from 41 ± 1.6% to 16 ± 0.6%. The BC-BP films retained their visible integrity after exposure to selected organic solvents but underwent substantial changes under strongly acidic and alkaline conditions. Following thermally induced repair, the BC-BP film recovered approximately 55% of its tensile strength and 45% of its Young’s modulus while retaining an elongation at break close to that of the original film. These results demonstrate that cellulose type and BC content can be used to adjust the measured thermal, optical, mechanical, and repair properties of starch–cellulose–Laponite films. Further structural, barrier, migration, and food-contact safety evaluations are required to establish their suitability for packaging applications. Full article

(This article belongs to the Topic Advances in Nanocellulose and Related Polysaccharide-Based Nanomaterials in a Green Context)

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14 pages, 1041 KB

Open AccessArticle

From Carbohydrate to Biocompatible Carriers: Impact of Pegylation on the Physicochemical Properties and Quercetin Delivery Performance of Fructose Hydrothermal Carbons

by Ivan Bracanović, Ana Kalijadis, Lela Korićanac, Miljana Mirković, Mario Zlatović, Svetlana Butulija and Aleksandar Krstić

Polymers 2026, 18(18), 2189; https://doi.org/10.3390/polym18182189 - 8 Sep 2026

Abstract

The aim of this study was to investigate the effect of PEG functionalization of hydrothermal carbon (HTC) on quercetin adsorption and desorption kinetics and, through that, evaluate the potential of functionalized HTC as a carrier for quercetin. Hydrothermal carbon (HTC) was synthesized using [...] Read more.

The aim of this study was to investigate the effect of PEG functionalization of hydrothermal carbon (HTC) on quercetin adsorption and desorption kinetics and, through that, evaluate the potential of functionalized HTC as a carrier for quercetin. Hydrothermal carbon (HTC) was synthesized using fructose as a precursor at a temperature of 160 °C. Structural and morphological analyses using X-ray diffraction and scanning electron microscopy (SEM) confirmed an amorphous carbon structure and microspherical particles with an average size of 5.6 µm. X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared (FT-IR) spectroscopy characterization revealed a surface enriched with hydroxyl and carboxyl groups, which facilitated successful PEG modification. Surface modification was further corroborated by a zeta potential shift from –26.4 mV to –16.4 mV. Cytotoxicity assays in MRC-5 and HeLa cell lines confirmed high biocompatibility, with cell viability remaining above 70%. Quercetin binding experiments showed that PEG functionalization increased binding capacity up to 14%, reaching 19.50 mg/g for PEG-functionalized fructose-derived carbon. Desorption kinetics followed a pseudo-second-order model, with the PEG-modified sample exhibiting significantly slower rates than the unmodified sample. These findings indicate that PEG functionalization can improve the adsorption/desorption properties of HTC compared with the pristine material, highlighting its potential as a promising, environmentally friendly, and efficient delivery system for quercetin. Full article

(This article belongs to the Special Issue Biodegradable Polymer Materials for Biocompatible Systems and Eco-Friendly Approaches)

19 pages, 4641 KB

Open AccessArticle

Multi-Objective Optimization of Curing Profiles for CFRP Patch Repair Under Thermochemical Coupling

by Ning Han, Yuan Wang, Yungang Sun, Erliang Liu and Longxin Fan

Polymers 2026, 18(18), 2188; https://doi.org/10.3390/polym18182188 - 8 Sep 2026

Abstract

This study addresses the challenge of temperature non-uniformity during carbon fibre-reinforced polymer (CFRP) composite patch repair, which compromises curing quality and process efficiency. A coupled heat transfer–curing kinetics finite element model was developed and experimentally validated to investigate the heat sink effect of [...] Read more.

This study addresses the challenge of temperature non-uniformity during carbon fibre-reinforced polymer (CFRP) composite patch repair, which compromises curing quality and process efficiency. A coupled heat transfer–curing kinetics finite element model was developed and experimentally validated to investigate the heat sink effect of support structures. Key findings reveal that temperature differences concentrate near aluminum components and increase with curing temperature. For the present scarf-repair configuration, global sensitivity analysis identified the second-stage holding temperature (T₂) and heating rate (r₂) as the dominant factors governing temperature uniformity, whereas the holding times (dt₁ and dt₂) primarily determine the total curing time (t_total). A novel multi-objective optimization framework combining optimal Latin hypercube sampling, radial basis functions, and NSGA-II was established. The optimized curing profile achieves a surrogate-predicted reduction of 22.5% in maximum temperature difference (22.0% when confirmed by high-fidelity finite element verification) and 36% in total curing time, while maintaining a minimum degree of cure above 0.98. These results provide a validated, surrogate-based framework for designing curing protocols that resolve metal-induced thermal non-uniformity in composite repairs without sacrificing cure quality. Full article

(This article belongs to the Special Issue Processing of Polymer Composites—Preparation, Structure, Properties and Applications)

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25 pages, 3050 KB

Open AccessArticle

Application of Sodium Polyacrylate Superabsorbent Polymer on Moisture Stability of Clay and Prediction of the Suction Potential of the Mixture

by Elahe Jafari, Jie Huang and Drew W. Johnson

Polymers 2026, 18(18), 2187; https://doi.org/10.3390/polym18182187 - 8 Sep 2026

Abstract

Superabsorbent polymers (SAPs), such as sodium polyacrylate (PAAS), are the neutralized form of poly (acrylic acid) and belong to a class of materials characterized by three-dimensional networks of flexible polymer chains with exceptional water absorption and retention capacities. Due to these properties, PAAS [...] Read more.

Superabsorbent polymers (SAPs), such as sodium polyacrylate (PAAS), are the neutralized form of poly (acrylic acid) and belong to a class of materials characterized by three-dimensional networks of flexible polymer chains with exceptional water absorption and retention capacities. Due to these properties, PAAS has been widely used in agriculture as a soil water conditioner. This study investigates the potential of PAAS as a soil stabilizer for infrastructure applications. Three suction measurement techniques, namely the axis translation method, osmotic technique, and vapor equilibrium method, were employed to determine the suction behavior of PAAS and soil–PAAS mixtures over a wide range of water contents and to develop their soil–water characteristic curves (SWCCs). The investigation covers the full suction spectrum, from near-complete dryness to full saturation. Experimental results show that the SWCC of PAAS exhibits the three characteristic zones commonly observed in soils: boundary, transition, and residual zones. However, when PAAS is mixed with soil, the boundary and transition zones disappear from the SWCCs of the soil–PAAS mixtures. This behavior is attributed to the suppression of PAAS suction capacity caused by soil confinement. Unlike agricultural applications, where SAP particles are relatively unconstrained, engineering applications typically involve highly compacted soils that restrict polymer expansion and water absorption. The study also evaluates the feasibility of predicting the suction behavior of soil–PAAS mixtures using numerical modeling techniques based on limited experimental datasets. Among the methods considered, Lagrange interpolation and K-nearest neighbors (KNN) produced prediction models with errors below 10%. In contrast, deep neural network models demonstrated lower predictive accuracy, primarily due to the limited size of the available dataset. Full article

(This article belongs to the Special Issue Applications of Polymers in Civil Engineering)

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31 pages, 33144 KB

Open AccessArticle

Behavior of Drinking Water Distribution Pipes Made of HDPE, AC, OLT 37, and OL37.1 in Contact with Water

by Daniela Simina Stefan, Georgeta Teodorescu, Adrian Ionut Nicoara, Lucretia Ghenghea and Ana Iulia Stefan

Polymers 2026, 18(18), 2186; https://doi.org/10.3390/polym18182186 - 8 Sep 2026

Abstract

Drinking water is essential for humans; its quality determines the health and proper functioning of the body. In order to obtain drinking water in accordance with the legislation in force, the performance of the technology applied for water treatment and the infrastructure for [...] Read more.

Drinking water is essential for humans; its quality determines the health and proper functioning of the body. In order to obtain drinking water in accordance with the legislation in force, the performance of the technology applied for water treatment and the infrastructure for transport and distribution to the consumer are equally important. Particular importance to this last aspect was given by the introduction of European Directive 2020/2184. Infrastructure can significantly influence water quality due to the fact that there are periods when water stagnates in the pipe and electro-corrosion processes, and salt deposits or degradation/corrosion of the pipes can occur, or periods when water circulates under pressure, when deposits but also particles from the pipes are mechanically detached and transported to the consumer. In this article, we aim to present the behavior of asbestos-cement pipes, AC, special steel for pipes OLT 37, galvanized steel, OLT 37.1, and high-density polyethylene, HDPE, in contact with drinking water. The study was conducted in Calarasi city, Calarasi county, Romania, where some of the old pipes were replaced. A comparative study of new pipes of the same type with pipes in use for more than 20 years, up to 46 years, was conducted, and at the same time the changes that the pipes (which have not yet been replaced) have on the quality of drinking water for street consumers were also analyzed. Following the analyses performed, it can be stated that the water quality is within the maximum permissible limits, but the micropollutants that appear can accumulate in the body (such as AC microfibers, microplastics, metallic zinc, zinc ions, iron ions, manganese, aluminum) with effects that can be evident after a long period of consumption through bioaccumulation. Full article

(This article belongs to the Section Polymer Analysis and Characterization)

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14 pages, 2951 KB

Open AccessArticle

Comparison of Recycled Polymers with Their Virgin Counterparts: Properties and Eco-Indicators

by Carmen Alonso Herr and Marina P. Arrieta

Polymers 2026, 18(18), 2185; https://doi.org/10.3390/polym18182185 - 8 Sep 2026

Abstract

Plastics represent one of the biggest challenges related to the circular economy (CE) and sustainable development goals (SDGs). In this study, both the virgin and mechanically recycled versions of three traditional petroleum-based polymers, polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET), are compared. [...] Read more.

Plastics represent one of the biggest challenges related to the circular economy (CE) and sustainable development goals (SDGs). In this study, both the virgin and mechanically recycled versions of three traditional petroleum-based polymers, polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET), are compared. For that, an investigation of the different mechanical, chemical and thermal properties was conducted. Additionally, the life cycle eco-indicators were studied for each case. Finally, correlations between all of the factors were studied in order to get a more comprehensive understanding of how the properties influence one another. Full article

(This article belongs to the Special Issue Advances in Recycling and Reuse of Polymers)

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24 pages, 22419 KB

Open AccessArticle

Developing Polymer Semi-Solid-State Gel Electrolyte with High-Performance Aqueous Zn-Mn Battery-Type Hybrid Capacitor Device for MnO₂–MWCNT Cathode

by Vediyappan Thirumal, Perumal Rajivgandhi and Jinho Kim

Polymers 2026, 18(18), 2184; https://doi.org/10.3390/polym18182184 - 8 Sep 2026

Abstract

In recent years, energy storage devices have had a lower energy density for supercapacitor devices. Fortunately, certain drawbacks limit the liquid-based battery-type aqueous zinc-ion hybrid capacitor electrodes. For this reason, zinc–manganese (Zn-Mn)-based zinc-ion hybrid supercapacitors (ZIHSCs) have been designed using a manganese-dioxide-functionalized carbon [...] Read more.

In recent years, energy storage devices have had a lower energy density for supercapacitor devices. Fortunately, certain drawbacks limit the liquid-based battery-type aqueous zinc-ion hybrid capacitor electrodes. For this reason, zinc–manganese (Zn-Mn)-based zinc-ion hybrid supercapacitors (ZIHSCs) have been designed using a manganese-dioxide-functionalized carbon nanotube (MnO₂–f-MWCNT) battery-type cathode in a semi-solid gel–free-standing film electrolyte. Herein, as-prepared MnO₂–MWCNTs are synthesized and assembled for nanostructured cathode composite materials by a facile hydrothermal technique. In this work, MnO₂ nanorods with f-MWCNTs are applied to the electrode, resulting in a semi-solid-state gel film electrolyte realized by assembling the Zn-Mn hybrid capacitor. The materials’ physical–chemical conformation and their unique characteristics, crystalline structures, and different morphologies are studied through XRD, FE-SEM, FE-TEM, and XPS analysis. In this work, the design of major-source MnO₂-based materials for positive and battery-type zinc metal anode approaches, along with the electrochemical properties of MnO₂–MWCNT//Zn hybrid charge storage mechanisms, are evaluated. The coin-cell-type ZIHSC investigation of cyclic voltammetric (CV) curves and lower constant current charge/discharge (GCD) and electrochemical impedance (EIS) methods is also carried out. In addition, the maximum specific capacitance values, 339.98 mAh/g and 203.52 mAh/g, were observed for MnO₂–MWCNT//Zn and MnO₂//Zn at 0.2 mA/g, respectively. Finally, the higher cycling stability of MnO₂−f-MWCNT of a 94.15% capacity retention after 15,000 cycles was evaluated and compared to MnO₂//Zn of 73.05% retention in ZIHSC device applications. The assessment of electrochemical MnO₂ cathode-based Zn-Mn ZIHSC performance is applicable for future aqueous electrical energy storage devices. Full article

(This article belongs to the Special Issue Application and Development of Polymeric Materials in Electrochemistry)

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19 pages, 25376 KB

Open AccessArticle

Synergistic Effects of GGBS and Recycled Aggregates on the Tribological, Mechanical, and Fracture Behavior of Polymer Concretes

by Batuhan Aykanat

Polymers 2026, 18(18), 2183; https://doi.org/10.3390/polym18182183 - 8 Sep 2026

Abstract

While the individual effects of sustainable fillers on cementitious systems are widely known, their combined tribological and fracture behaviors within a polymer concrete matrix remain largely unexplored. Addressing this gap, this study experimentally investigates the physical, mechanical, and tribological characteristics of polyester-based polymer [...] Read more.

While the individual effects of sustainable fillers on cementitious systems are widely known, their combined tribological and fracture behaviors within a polymer concrete matrix remain largely unexplored. Addressing this gap, this study experimentally investigates the physical, mechanical, and tribological characteristics of polyester-based polymer concrete (PC). In addition to reference specimens produced with polyester resin and silica sand, modified mixtures were developed by replacing the silica sand with ground granulated blast-furnace slag (GGBS) and recycled waste concrete aggregate (WC) at various substitution ratios (0%, 5%, 10%, 15%, 20%, and 25%). To evaluate the performance of the developed PCs, parameters including unit weight, water absorption capacity, flexural and compressive strengths, Shore D hardness, surface roughness, acid resistance, Bohme abrasion resistance, and fracture energy were analyzed. Furthermore, temperature variations on the friction surfaces were monitored in real time using a thermal camera during the Bohme abrasion tests. To elucidate the fracture mechanisms, the fractured surfaces were examined via digital microscopy. The quantitative findings indicate that a 25% GGBS replacement optimizes mechanical performance, increasing the compressive and flexural strengths by 21.2% (108.30 MPa) and 30.6% (35.29 MPa), respectively, alongside a 27% improvement in Bohme abrasion resistance. However, this modification significantly increases material brittleness, reducing the fracture energy by 53.3% compared to the reference. Conversely, although incorporating WC offers sustainability advantages, it limits mechanical performance, leading to decreases of up to 9.9% (80.46 MPa) in compressive strength and 15% (22.97 MPa) in flexural strength at a 20% substitution rate. Regarding fracture energy, while the W20 series absorbed more energy than the B25 series, it still remained 47.8% lower than the reference. Additionally, the GGBS-incorporated series demonstrated higher susceptibility to sulfuric acid attack compared to the WC-incorporated series. Full article

(This article belongs to the Special Issue Advanced Polymeric Materials for Buildings)

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21 pages, 1957 KB

Open AccessArticle

Interpretable Machine Learning Prediction of the Dielectric Constant and Bandgap of Polymers for Flexible Electronics

by Fatih Gül

Polymers 2026, 18(18), 2182; https://doi.org/10.3390/polym18182182 - 8 Sep 2026

Abstract

Polymer dielectrics are central to flexible and printed electronics, where a material must combine a sufficiently high dielectric constant with a wide electronic bandgap to suppress leakage. Experimental or first-principles screening is slow, motivating data-driven surrogates. Here we develop an interpretable machine learning [...] Read more.

Polymer dielectrics are central to flexible and printed electronics, where a material must combine a sufficiently high dielectric constant with a wide electronic bandgap to suppress leakage. Experimental or first-principles screening is slow, motivating data-driven surrogates. Here we develop an interpretable machine learning workflow that predicts both the total dielectric constant and the HSE bandgap of polymer repeat units directly from a monomer structure, using an open density-functional-theory dataset of 284 four-block polymers. Polymers are encoded with 217 RDKit descriptors and a 1024-bit Morgan fingerprint; four regressors are benchmarked under nested five-fold cross-validation with paired significance testing. The bandgap reaches

R^{2} = 0.83 \pm 0.04

(MAE

= 0.35

eV) and the total dielectric constant

R^{2} = 0.64 \pm 0.06

(MAE

= 0.44

), but paired tests find the models statistically indistinguishable for the bandgap. Decomposing the permittivity explains its lower ceiling: the ionic component is only

15 %

of the magnitude yet carries

28 %

of the squared error, and learning curves confirm a representational rather than a data-quantity limit. Read through the Penn relation, the SHAP descriptors yield an explicit design rule—raise permittivity with polar, non-conjugated motifs rather than extended conjugation. Screening 571 unseen candidates with bootstrap uncertainties, an applicability domain and a threshold sensitivity analysis nominates carbamate/urea-type wide-bandgap high-k repeat units. Full article

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

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50 pages, 44441 KB

Open AccessReview

Advances in Dissolvable Polymers and Composites for the Oil and Gas Industry

by Lei Zhao, Jiaxiang Ren, Peixiang Xing, Donggang Yao, Meng Lu and Peng Cheng

Polymers 2026, 18(17), 2181; https://doi.org/10.3390/polym18172181 - 7 Sep 2026

Abstract

The oil and gas industry has emerged as one of the largest consumers of polymer composites, with dissolvable polymers and composites representing one of the most significant technological advancements in this sector. These materials are essential for the manufacturing of high-performance tools such [...] Read more.

The oil and gas industry has emerged as one of the largest consumers of polymer composites, with dissolvable polymers and composites representing one of the most significant technological advancements in this sector. These materials are essential for the manufacturing of high-performance tools such as hydraulic fracturing plugs, which must withstand extreme downhole conditions—temperatures of up to 250 °C and a pressure differential of up to 150 MPa—before dissolving rapidly in wellbore fluids to facilitate continuous production. Unlike traditional dissolvable polymers from the medical or consumer industries, which lack the required thermal stability, mechanical strength, and cost-effectiveness, these advanced materials must be formulated from readily available raw materials and manufactured on an industrial scale. Over the past two decades, significant progress has been made in the design and application of polymers like poly(glycolic acid), polyurethane, polyamide, epoxy, and isocyanate ester, developed through collaborative efforts between academia and industry. This review provides a comprehensive overview of the evolution of dissolvable polymer composites, covering material design, degradation mechanisms, manufacturing processes, and field applications. It concludes with insights into future development opportunities in the field. Full article

(This article belongs to the Special Issue Advances in Mechanical and Thermal Characterization and Optimization of Polymer Composites)

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20 pages, 2203 KB

Open AccessArticle

Role of Acid Structure in Structure–Property Relationships of Reprocessable Epoxidized Soybean Oil Thermosetting Networks

by Madina Mussalimova, Ainash Baidullayeva, Alexey Shakhvorostov, Zhanserik Shynykul and Gaukhar Toleutay

Polymers 2026, 18(17), 2180; https://doi.org/10.3390/polym18172180 - 7 Sep 2026

Abstract

Thermosetting polymers offer excellent thermal stability, chemical resistance, and mechanical integrity, but their permanent covalent crosslinks limit recyclability and reprocessability. In this work, ESO-based vitrimer-like polyester networks were synthesized from epoxidized soybean oil (ESO) using tartaric, maleic, succinic, and tannic acids as catalyst-free [...] Read more.

Thermosetting polymers offer excellent thermal stability, chemical resistance, and mechanical integrity, but their permanent covalent crosslinks limit recyclability and reprocessability. In this work, ESO-based vitrimer-like polyester networks were synthesized from epoxidized soybean oil (ESO) using tartaric, maleic, succinic, and tannic acids as catalyst-free curing agents. The influence of curing-agent structure on epoxy conversion, network homogeneity, thermal behavior, mechanical properties, chemical resistance, and reprocessing performance was systematically investigated. FTIR analysis indicated extensive epoxide ring opening and polyester network formation in all formulations. Tartaric and maleic acid systems exhibited stronger ester absorptions, higher gel content, and improved film uniformity, indicating more efficient network formation. The resulting materials showed good thermal stability, with degradation onset temperatures of 265–280 °C and maximum decomposition temperatures up to 400 °C. Mechanical performance strongly depended on acid structure: tannic acid produced the stiffest and strongest films, tartaric acid provided the best balance between strength and ductility, and succinic acid yielded less-uniform networks with reduced structural integrity. Reprocessing experiments demonstrated thermo-mechanical reprocessability consistent with vitrimer-like behavior in the tartaric- and maleic-acid-cured systems. These findings highlight curing-agent architecture as a key parameter for designing catalyst-free, renewable, and reprocessable ESO-based thermosets with tunable structure–property relationships. Full article

(This article belongs to the Topic Green and Recycled Polymer Materials Towards Sustainability)

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16 pages, 1075 KB

Open AccessArticle

Seasonal Algae and Nutrient Removal by Polyaluminum Chloride and Chitosan in a Drinking Water Reservoir

by Kechang Dai, Lixue Cheng, Zhenxiu Zhang, Lei Zou, Jiayu Wang, Qingji Zhang, Wenqing Shi and Lin Zhu

Polymers 2026, 18(17), 2179; https://doi.org/10.3390/polym18172179 - 7 Sep 2026

Abstract

Emergency treatment of algal blooms in lake and reservoir source waters requires coagulants that remain effective under changing raw water conditions. This study compared polyaluminum chloride (PAC) and chitosan (CTS) in raw water collected from Yangku Reservoir during wet and dry seasons. Jar [...] Read more.

Emergency treatment of algal blooms in lake and reservoir source waters requires coagulants that remain effective under changing raw water conditions. This study compared polyaluminum chloride (PAC) and chitosan (CTS) in raw water collected from Yangku Reservoir during wet and dry seasons. Jar tests evaluated algal density, algal biomass, and nitrogen and phosphorus fractions across a 3~15 mg/L reagent-mass dosage range. Treatment performance differed between seasons. Mean algal density and soluble reactive phosphorus (SRP) removals in the wet season were 63.12% and 68.51%, respectively, and an apparent 70.05% decrease in measured NH₄⁺-N concentration was also observed. Because the fate of dissolved inorganic nitrogen was not resolved, the NH₄⁺-N decrease should not be interpreted as direct coagulative removal. Dry season water had higher algal density and a higher SRP/TP ratio. PAC maintained relatively stable algal biomass removal across seasons and showed stronger phosphorus removal, whereas CTS was more sensitive to seasonal changes in the raw water matrix. These findings support season-specific preliminary screening of coagulants while highlighting the need for residual-Al, pilot-scale, and process-mechanism validation before full-scale application. Full article

(This article belongs to the Section Polymer Applications)

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19 pages, 12006 KB

Open AccessArticle

LPE-Grown Lanthanide-MOF/Cellulose Paper for Visual Sensing and Selective Dye Removal

by Xiang Hou, Yipan Zeng, Yuhang Zhang, Yujie Li and Qutong Zheng

Polymers 2026, 18(17), 2178; https://doi.org/10.3390/polym18172178 - 7 Sep 2026

Abstract

Cellulose-based functional materials have attracted increasing attention for portable environmental monitoring and pollutant management; however, achieving a robust integration of functional components with cellulose substrates remains challenging due to weak interfacial adhesion and instability of conventional coating strategies. Herein, a binder-free liquid-phase epitaxy [...] Read more.

Cellulose-based functional materials have attracted increasing attention for portable environmental monitoring and pollutant management; however, achieving a robust integration of functional components with cellulose substrates remains challenging due to weak interfacial adhesion and instability of conventional coating strategies. Herein, a binder-free liquid-phase epitaxy (LPE) strategy was developed to construct lanthanide metal–organic framework (Ln-MOF) coatings directly on unmodified cellulose fibers, yielding a stable and multifunctional Ln-MOF/cellulose composite material. The LPE process enabled uniform growth of Ln-MOF layers on cellulose paper, resulting in homogeneous luminescence with relative standard deviations below 2% and stable fluorescence performance over a wide pH range of 3–11. By regulating the Eu³⁺/Tb³⁺ ratio, the obtained composite paper exhibited tunable dual-emission characteristics and enabled smartphone-assisted ratiometric visualization of dipicolinic acid (DPA), a representative biomarker of bacterial spores, with a linear response range of 0–2000 μM and a detection limit of 10 μM. Furthermore, the anionic Ln-MOF coating endowed the cellulose material with charge-selective adsorption capability, allowing efficient removal of cationic dyes while maintaining structural integrity after four regeneration cycles. The applicability of the LPE strategy was further demonstrated using different lanthanide–organic linker systems. This work provides a versatile approach for fabricating stable cellulose/MOF composite materials and highlights their potential applications in portable chemical sensing and selective water purification. Full article

(This article belongs to the Special Issue MOF-Polymer Composites: Design, Derivatives and Applications)

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