Polymers

21 pages, 3611 KiB

Open AccessArticle

Polymer Bionanocomposites Based on a P3BH/Polyurethane Matrix with Organomodified Montmorillonite—Mechanical and Thermal Properties, Biodegradability, and Cytotoxicity

by Beata Krzykowska, Łukasz Uram, Wiesław Frącz, Miroslava Kovářová, Vladimir Sedlařík, Dominika Hanusova, Maciej Kisiel, Joanna Paciorek-Sadowska, Marcin Borowicz and Iwona Zarzyka

Polymers 2024, 16(18), 2681; https://doi.org/10.3390/polym16182681 - 23 Sep 2024

Viewed by 789

Abstract

In the present work, hybrid nanobiocomposites based on poly(3-hydroxybutyrate), P3HB, with the use of aromatic linear polyurethane as modifier and organic nanoclay, Cloisite 30B, as a nanofiller were produced. The aromatic linear polyurethane (PU) was synthesized in a reaction of diphenylmethane 4,4′-diisocyanate and [...] Read more.

In the present work, hybrid nanobiocomposites based on poly(3-hydroxybutyrate), P3HB, with the use of aromatic linear polyurethane as modifier and organic nanoclay, Cloisite 30B, as a nanofiller were produced. The aromatic linear polyurethane (PU) was synthesized in a reaction of diphenylmethane 4,4′-diisocyanate and polyethylene glycol with a molecular mass of 1000 g/mole. The obtained nanobiocomposites were characterized by the small-angle X-ray scattering technique, scanning electron microscopy, Fourier infrared spectroscopy, thermogravimetry, and differential scanning calorimetry, and moreover, their selected mechanical properties, biodegradability, and cytotoxicity were tested. The effect of the organomodified montmorillonite presence in the biocomposites on their properties was investigated and compared to those of the native P3HB and the P3HB-PU composition. The obtained hybrid nanobiocomposites have an exfoliated structure. The presence and content of Cloisite 30B influence the P3HB-PU composition’s properties, and 2 wt.% Cloisite 30B leads to the best improvement in the aforementioned properties. The obtained results indicate that the thermal stability and mechanical properties of P3HB were improved, particularly in terms of increasing the degradation temperature, reducing hardness, and increasing impact strength, which were also confirmed by the morphological analysis of these bionanocomposites. However, the presence of organomodified montmorillonite in the obtained polymer biocomposites decreased their biodegradability slightly. The produced hybrid polymer nanobiocomposites have tailored mechanical and thermal properties and processing conditions for their expected application in the production of biodegradable, short-lived products for agriculture. Moreover, in vitro studies on human skin fibroblasts and keratinocytes showed their satisfactory biocompatibility and low cytotoxicity, which make them safe when in contact with the human body, for instance, in biomedical applications. Full article

(This article belongs to the Special Issue Polymer Nanocomposites with Improved Mechanical, Thermal, Electrical and Barrier Properties)

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17 pages, 2243 KiB

Open AccessArticle

Interpretable Machine Learning-Based Influence Factor Identification for 3D Printing Process–Structure Linkages

by Fuguo Liu, Ziru Chen, Jun Xu, Yanyan Zheng, Wenyi Su, Maozai Tian and Guodong Li

Polymers 2024, 16(18), 2680; https://doi.org/10.3390/polym16182680 - 23 Sep 2024

Viewed by 964

Abstract

Three-dimensional printing technology is a rapid prototyping technology that has been widely used in manufacturing. However, the printing parameters in the 3D printing process have an important impact on the printing effect, so these parameters need to be optimized to obtain the best [...] Read more.

Three-dimensional printing technology is a rapid prototyping technology that has been widely used in manufacturing. However, the printing parameters in the 3D printing process have an important impact on the printing effect, so these parameters need to be optimized to obtain the best printing effect. In order to further understand the impact of 3D printing parameters on the printing effect, make theoretical explanations from the dimensions of mathematical models, and clarify the rationality of certain important parameters in previous experience, the purpose of this study is to predict the impact of 3D printing parameters on the printing effect by using machine learning methods. Specifically, we used four machine learning algorithms: SVR (support vector regression): A regression method that uses the principle of structural risk minimization to find a hyperplane in a high-dimensional space that best fits the data, with the goal of minimizing the generalization error bound. Random forest: An ensemble learning method that constructs a multitude of decision trees and outputs the class that is the mode of the classes (classification) or mean prediction (regression) of the individual trees. GBDT (gradient boosting decision tree): An iterative ensemble technique that combines multiple weak prediction models (decision trees) into a strong one by sequentially minimizing the loss function. Each subsequent tree is built to correct the errors of the previous tree. XGB (extreme gradient boosting): An optimized and efficient implementation of gradient boosting that incorporates various techniques to improve the performance of gradient boosting frameworks, such as regularization and sparsity-aware splitting algorithms. The influence of the print parameters on the results under the feature importance and SHAP (Shapley additive explanation) values is compared to determine which parameters have the greatest impact on the print effect. We also used feature importance and SHAP values to compare the importance impact of print parameters on results. In the experiment, we used a dataset with multiple parameters and divided it into a training set and a test set. Through Bayesian optimization and grid search, we determined the best hyperparameters for each algorithm and used the best model to make predictions for the test set. We compare the predictive performance of each model and confirm that the extrusion expansion ratio, elastic modulus, and elongation at break have the greatest influence on the printing effect, which is consistent with the experience. In future, we will continue to delve into methods for optimizing 3D printing parameters and explore how interpretive machine learning can be applied to the 3D printing process to achieve more efficient and reliable printing results. Full article

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

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20 pages, 4142 KiB

Open AccessReview

Cross-Linking Agents in Three-Component Materials Dedicated to Biomedical Applications: A Review

by Sylwia Grabska-Zielińska

Polymers 2024, 16(18), 2679; https://doi.org/10.3390/polym16182679 - 23 Sep 2024

Viewed by 1308

Abstract

In biomaterials research, using one or two components to prepare materials is common. However, there is a growing interest in developing materials composed of three components, as these can offer enhanced physicochemical properties compared to those consisting of one or two components. The [...] Read more.

In biomaterials research, using one or two components to prepare materials is common. However, there is a growing interest in developing materials composed of three components, as these can offer enhanced physicochemical properties compared to those consisting of one or two components. The introduction of a third component can significantly improve the mechanical strength, biocompatibility, and functionality of the resulting materials. Cross-linking is often employed to further enhance these properties, with chemical cross-linking agents being the most widely used method. This article provides an overview of the chemical agents utilized in the cross-linking of three-component biomaterials. The literature review focused on cases where the material was composed of three components and a chemical substance was employed as the cross-linking agent. The most commonly used cross-linking agents identified in the literature include glyoxal, glutaraldehyde, dialdehyde starch, dialdehyde chitosan, and the EDC/NHS mixture. Additionally, the review briefly discusses materials cross-linked with the MES/EDC mixture, caffeic acid, tannic acid, and genipin. Through a critical analysis of current research, this work aims to guide the development of more effective and safer biopolymeric materials tailored for biomedical applications, highlighting potential areas for further investigation and optimization. Full article

(This article belongs to the Special Issue Medical Application of Polymer-Based Composites IV)

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16 pages, 5565 KiB

Open AccessArticle

Analysis and Evaluation of Load-Carrying Capacity of CFRP-Reinforced Steel Structures

by Jian Zhao, Yongxing Huang, Kun Gong, Zhiguo Wen, Sinan Liu, Yanyan Hou, Xuewu Hong, Xuecheng Tong, Kai Shi and Ziyi Qu

Polymers 2024, 16(18), 2678; https://doi.org/10.3390/polym16182678 - 23 Sep 2024

Viewed by 602

Abstract

Carbon Fiber Reinforced Polymer (CFRP) can be used to reinforce steel structures depending on its high strength and lightweight resistance. To analyze and evaluate the load-carrying capacity of CFRP-reinforced steel structures. This study uses the Finite Element Analysis (FEA) and the experimental tests [...] Read more.

Carbon Fiber Reinforced Polymer (CFRP) can be used to reinforce steel structures depending on its high strength and lightweight resistance. To analyze and evaluate the load-carrying capacity of CFRP-reinforced steel structures. This study uses the Finite Element Analysis (FEA) and the experimental tests combined to investigate the influence that the reinforcement patterns and the relevant parameters have on the load-carrying capacity. We made specimens with different reinforcement patterns. Take the steel beam specimen with full reinforcement as an example. Compared with the load-carrying capacity of the steel beam reinforced by two-layer CFRP cloth, that respectively increases by 5.16% and 11.1% when the number of the CFRP cloth increases to four and six, respectively. Based on a specimen set consisting of CFRP-reinforced steel structures under different reinforcement patterns, the random forest algorithm is used to develop an evaluation model for the load carrying. The performance test results show that the MAE (Mean Absolute Error) of the evaluation model can reach 0.12 and the RMSE (Root Mean Square Error) is 0.25, presenting a good prediction accuracy, which lays a solid foundation for the research on the CFRP-based reinforcement technology and process. Full article

(This article belongs to the Special Issue High-Performance Short-Fiber-Reinforced Polymer Composites)

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13 pages, 5236 KiB

Open AccessArticle

Three-Dimensionally Printed K-Band Radar Stealth Lightweight Material with Lotus Leaf Structure

by Chuangji Liu, Yingjie Xu, Beiqing Huang, Wan Zhang and Yuxin Wang

Polymers 2024, 16(18), 2677; https://doi.org/10.3390/polym16182677 - 23 Sep 2024

Viewed by 697

Abstract

K-band radar waves have high penetration and low attenuation coefficients. However, the wavelength of this radar wave is relatively short; thus, designing and preparing both broadband and wide-angle radar wave absorbers in this band presents considerable challenges. In this study, a resin-based K-band [...] Read more.

K-band radar waves have high penetration and low attenuation coefficients. However, the wavelength of this radar wave is relatively short; thus, designing and preparing both broadband and wide-angle radar wave absorbers in this band presents considerable challenges. In this study, a resin-based K-band radar wave absorber with a biomimetic lotus leaf structure was designed and formed by UV curing. Here, microscale lotus leaf papillae and antireflection structures were prepared using a DLP 3D printer, and the contact angle between the material and water droplets was increased from 56° to 130°. In addition, the influence of the geometric parameters of the lotus leaf antireflection structure on the electromagnetic absorption performance and mechanical strength was investigated. After simulation optimization, the maximum electromagnetic loss of the lotus leaf structure 3D-printed sample was −32.3 dB, and the electromagnetic loss was below −10 dB in the 20.8–26.5 GHz frequency range. When the radar incidence angle was 60°, the maximum electromagnetic loss was still less than −10 dB. The designed lotus leaf structure has a higher mechanical energy absorption per unit volume (337.22 KJ/m³) and per unit mass (0.55 KJ/Kg) than commonly used honeycomb lightweight structures during the elastic deformation stage, and we expect that the designed structure can be used as an effective lightweight material for K-band radar stealth. Full article

(This article belongs to the Special Issue 3D Printing of Polymer Composite Materials)

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22 pages, 595 KiB

Open AccessArticle

Numerical Investigation of Fracture Behaviour of Polyurethane Adhesives under the Influence of Moisture

by Siva Pavan Josyula and Stefan Diebels

Polymers 2024, 16(18), 2676; https://doi.org/10.3390/polym16182676 - 23 Sep 2024

Viewed by 556

Abstract

The mechanical behaviour of polymer adhesives is influenced by the environmental conditions leading to ageing and affecting the integrity of the material. The polymer adhesives have hygroscopic behaviour and tend to absorb moisture from the environment, causing the material to swell without applying [...] Read more.

The mechanical behaviour of polymer adhesives is influenced by the environmental conditions leading to ageing and affecting the integrity of the material. The polymer adhesives have hygroscopic behaviour and tend to absorb moisture from the environment, causing the material to swell without applying external load. The focus of the work is to investigate the viscoelastic material behaviour under ageing conditions. The constitutive equations and the governing equations to numerically investigate the fracture in swollen viscoelastic material are discussed to describe the numerical implementation. Phase-field damage modelling has been used in numerical studies of ductile and brittle materials for a long time. The finite-strain phase-field damage model is used to investigate the fracture behaviour in aged viscoelastic polymer adhesives. The finite-strain viscoelastic model is formulated based on the continuum rheological model by combining spring and Maxwell elements in parallel. Commercially available post-cured crosslinked polyurethane adhesives are used in the current investigation. Post-cured samples of crosslinked polyurethane adhesives are prepared for different humidity conditions under isothermal conditions. These aged samples are used to perform tensile and tear tests and the test data are used to identify the material parameters from the curve fitting process. The experiment and simulation are compared to relate the findings and are the first step forward to improve the method to model crosslinked polymers. Full article

(This article belongs to the Special Issue Mechanical and Failure Behavior of Polymeric Composites)

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16 pages, 4616 KiB

Open AccessArticle

Analyzing Homogeneity of Highly Viscous Polymer Suspensions in Change Can Mixers

by Michael Roland Larsen, Erik Tomas Holmen Olofsson and Jon Spangenberg

Polymers 2024, 16(18), 2675; https://doi.org/10.3390/polym16182675 - 23 Sep 2024

Viewed by 538

Abstract

The mixing of highly viscous non-Newtonian suspensions is a critical process in various industrial applications. This computational fluid dynamics (CFD) study presents an in-depth analysis of non-isothermal mixing performance in change can mixers. The aim of the study was to identify parameters that [...] Read more.

The mixing of highly viscous non-Newtonian suspensions is a critical process in various industrial applications. This computational fluid dynamics (CFD) study presents an in-depth analysis of non-isothermal mixing performance in change can mixers. The aim of the study was to identify parameters that significantly influence both distributive and dispersive mixing in these mixers, which are essential for optimizing industrial mixing processes. The study employed a numerical design of experiments (DOE) approach to identify the parameters that most significantly influence both distributive and dispersive mixing, as measured by the Kramer mixing index (

M_{K r a m e r}

) and the Ica Manas-Zloczower mixing index

(\bar{λ_{M Z}})

. The investigated parameters included mixing time, number of arms, arm size ratio, revolutions per minute (RPM), z-axis rotation, z-axis movement, and initial and mixing temperatures. The methodology involved employing the bootstrap forest algorithm for predicting the mixing indices, achieving an

R^{2}

of 0.949 for

M_{K r a m e r}

and an

R^{2}

of 0.836 for

\bar{λ_{M Z}}

. The results indicate that the z-axis rotation has the greatest impact on both distributive and dispersive mixing. An increased number of arms negatively impacted

λ_{M Z}

, but had a small positive effect on

M_{K r a m e r}

. Surprisingly, in this study, neither the initial temperature of the material nor the mixing temperature significantly impacted the mixing performance. These findings highlight the relative importance of operational parameters over traditional temperature factors and provide a new perspective on mixing science. Full article

(This article belongs to the Special Issue Polymers Physics: From Theory to Experimental Applications)

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17 pages, 6749 KiB

Open AccessArticle

High-Quality Foaming and Weight Reduction in Microcellular-Injection-Molded Polycarbonate Using Supercritical Fluid Carbon Dioxide under Gas Counter Pressure

by Yogi Hendra Agustion, Shia-Chung Chen, Ching-Te Feng and Bermawi Priyatna Iskandar

Polymers 2024, 16(18), 2674; https://doi.org/10.3390/polym16182674 - 23 Sep 2024

Viewed by 936

Abstract

Microcellular injection molding (MuCell^®) using supercritical fluid (SCF) as a foaming agent to achieve weight reduction has become popular in carbon emission reduction. In the typical MuCell® process, SCF N₂ is commonly used. Although SCF CO₂ exhibits high solubility [...] Read more.

Microcellular injection molding (MuCell^®) using supercritical fluid (SCF) as a foaming agent to achieve weight reduction has become popular in carbon emission reduction. In the typical MuCell® process, SCF N₂ is commonly used. Although SCF CO₂ exhibits high solubility and can achieve a high weight reduction, controlling the foaming is not easy, and its foaming cells are usually larger and less uniform, which limits its industrial application. Our previous studies have shown that gas counter pressure (GCP) can improve the foaming quality effectively. Here, we investigated whether or not the CO₂ SCF foaming quality could be improved, and weight reduction was achieved for polycarbonate (PC) material. This is quite important for the electronics industry, in which most of the housing for devices is made of PC materials. MuCell^® was subjected to molding experiments using the parameters of the SCF dosage, melt temperature, mold temperature, and injection speed. The results revealed that using CO₂ gas for the PC material can reduce the size of microcellular cells to 40 µm and increase the cell densities to 3.97 × 10⁶ cells/cm³. Using GCP significantly improved the microcellular injection-molded parts by reducing the cell size to 20.9 µm (a 45.41% improvement) and increasing the cell density to 8.04 × 10⁶ cells/cm³ (a 102.48% improvement). However, implementing GCP may slightly decrease the target weight reduction. This study reveals that microcellular injection molding of PC parts using SCF CO₂ can achieve high-quality foaming and reduce the weight by about 30%. Full article

(This article belongs to the Special Issue Thermoplastic Foams: Processing, Manufacturing, and Characterization)

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1 pages, 383 KiB

Open AccessCorrection

Correction: Rehman et al. Nanocomposite Membranes for PEM-FCs: Effect of LDH Introduction on the Physic-Chemical Performance of Various Polymer Matrices. Polymers 2023, 15, 502

by Muhammad Habib Ur Rehman, Ernestino Lufrano and Cataldo Simari

Polymers 2024, 16(18), 2673; https://doi.org/10.3390/polym16182673 - 23 Sep 2024

Viewed by 885

Abstract

Error in Figure [...] Full article

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12 pages, 2939 KiB

Open AccessCommunication

In Situ Efficient End Functionalization of Polyisoprene by Epoxide Compounds via Neodymium-Mediated Coordinative Chain Transfer Polymerization

by Xiuhui Zhang, Jing Dong, Feng Wang, Xuequan Zhang and Heng Liu

Polymers 2024, 16(18), 2672; https://doi.org/10.3390/polym16182672 - 22 Sep 2024

Viewed by 869

Abstract

The Nd-mediated coordinative chain transfer polymerization (CCTP) of dienes represents one of the state-of-the-art techniques in the current synthetic rubber field. Besides having well-controlled polymerization behaviors as well as high atom economies, it also allows for the generation of highly reactive Al-capped polydienyl [...] Read more.

The Nd-mediated coordinative chain transfer polymerization (CCTP) of dienes represents one of the state-of-the-art techniques in the current synthetic rubber field. Besides having well-controlled polymerization behaviors as well as high atom economies, it also allows for the generation of highly reactive Al-capped polydienyl chain-ends, which hold great potential, yet much less explored up to date, in achieving end functionalization to mimic the structure of natural rubber. In this study, we demonstrate an efficient in situ method to realize end-functionalizing polyisoprene by introducing epoxide compounds into a CCTP system. The end functionalization efficiency was 92.7%, and the obtained polymers were systematically characterized by ¹H NMR, ¹H,¹H-COSY NMR, DOSY NMR, and MALDI TOF. NMR studies revealed that a maximum of two EO units were introduced to the chain ends, and based on density functional theory (DFT) studies, an energy barrier of 33.3 kcal/mol was required to be overcome to open the ring of the EO monomer. Increasing the ratio of [Ip]/[Nd] resulted in gradually increased viscosities for the reaction medium and therefore gave rise to an end functionalization efficiency that decreased from 92.7% to 74.2%. The end hydroxyl group can also be readily converted to other functionalities, as confirmed by NMR spectroscopy. Full article

(This article belongs to the Section Polymer Chemistry)

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20 pages, 5663 KiB

Open AccessArticle

Cross-Linked Metathesis Polynorbornenes Based on Nadimides Bearing Hydrocarbon Substituents: Synthesis and Physicochemical Properties

by Kirill S. Sadovnikov, Ivan V. Nazarov, Vsevolod A. Zhigarev, Anastasia A. Danshina, Igor S. Makarov and Maxim V. Bermeshev

Polymers 2024, 16(18), 2671; https://doi.org/10.3390/polym16182671 - 22 Sep 2024

Viewed by 696

Abstract

Metathesis homo- and copolymerization of bifunctional monomers bearing two norbornene moieties was studied. The monomers were synthesized from cis-5-norbornene-exo-2,3-dicarboxylic anhydride and various diamines (hexamethylenediamine, decamethylenediamine, 1R,3S-isophoronediamine). The metathesis homopolymerization of these bis(nadimides) in the presence of the second-generation Grubbs catalyst afforded glassy cross-linked [...] Read more.

Metathesis homo- and copolymerization of bifunctional monomers bearing two norbornene moieties was studied. The monomers were synthesized from cis-5-norbornene-exo-2,3-dicarboxylic anhydride and various diamines (hexamethylenediamine, decamethylenediamine, 1R,3S-isophoronediamine). The metathesis homopolymerization of these bis(nadimides) in the presence of the second-generation Grubbs catalyst afforded glassy cross-linked polymers in more than 90% yields. The metathesis copolymerization of the bis(nadimides) and a monofunctional norbornene derivative containing the β-pinene fragment also resulted in insoluble cross-linked polymers in nearly quantitative yields. The structures and purity of the synthesized polymers were confirmed via IR spectroscopy and CP/MAS NMR spectroscopy. Conditions for the fabrication of mechanically strong solution-cast thin films based on copolymers synthesized from the comonomers mentioned above were determined by varying the content of the cross-linking agent. It was shown that the films made in this way are stable in a range of organic solvents and could be useful as semipermeable or membrane materials for use in liquid organic media. The permeability of the polymer films in question to 1-phenylethanol and mandelic acid was studied. The results obtained are discussed along with the data from the DSC, TGA, and powder X-ray diffraction studies of the properties of the synthesized metathesis homo- and copolymers. Full article

(This article belongs to the Special Issue Preparation and Application of Functional Polymer Materials)

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35 pages, 3113 KiB

Open AccessReview

Unlocking the Potential of Food Waste: A Review of Multifunctional Pectins

by Marta Tsirigotis-Maniecka, Ewa Górska, Aleksandra Mazurek-Hołys and Izabela Pawlaczyk-Graja

Polymers 2024, 16(18), 2670; https://doi.org/10.3390/polym16182670 - 22 Sep 2024

Viewed by 1139

Abstract

This review comprehensively explores the multifunctional applications of pectins derived from food waste and by-products, emphasizing their role as versatile biomaterials in the medical-related sectors. Pectins, known for their polyelectrolytic nature and ability to form hydrogels, influence the chemical composition, sensory properties, and [...] Read more.

This review comprehensively explores the multifunctional applications of pectins derived from food waste and by-products, emphasizing their role as versatile biomaterials in the medical-related sectors. Pectins, known for their polyelectrolytic nature and ability to form hydrogels, influence the chemical composition, sensory properties, and overall acceptability of food and pharmaceutical products. The study presents an in-depth analysis of molecular parameters and structural features of pectins, such as the degree of esterification (DE), monosaccharide composition, galacturonic acid (GalA) content, and relative amounts of homogalacturonan (HG) and rhamnogalacturonan I (RG-I), which are critical for their technofunctional properties and biological activity. Emphasis is placed on pectins obtained from various waste sources, including fruits, vegetables, herbs, and nuts. The review also highlights the importance of structure–function relationships, especially with respect to the interfacial properties and rheological behavior of pectin solutions and gels. Biological applications, including antioxidant, immunomodulatory, anticancer, and antimicrobial activities, are also discussed, positioning pectins as promising biomaterials for various functional and therapeutic applications. Recalled pectins can also support the growth of probiotic bacteria, thus increasing the health benefits of the final product. This detailed review highlights the potential of using pectins from food waste to develop advanced and sustainable biopolymer-based products. Full article

(This article belongs to the Special Issue Biocompatible and Biodegradable Polymers for Medical Applications, 2nd Edition)

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13 pages, 9306 KiB

Open AccessArticle

Coniferous Bark as Filler for Polylactic Acid-Based Biocomposites

by Wojciech Jasiński, Radosław Auriga, Seng Hua Lee, Łukasz Adamik and Piotr Borysiuk

Polymers 2024, 16(18), 2669; https://doi.org/10.3390/polym16182669 - 22 Sep 2024

Viewed by 586

Abstract

This study explores the possibilities of utilisation of coniferous bark as a filler in wood–polymer composites (WPCs), its impact on properties such as the modulus of rupture (MOR), modulus of elasticity (MOE), thickness swelling (TS) and water absorption (WA) after 2 h and [...] Read more.

This study explores the possibilities of utilisation of coniferous bark as a filler in wood–polymer composites (WPCs), its impact on properties such as the modulus of rupture (MOR), modulus of elasticity (MOE), thickness swelling (TS) and water absorption (WA) after 2 h and 24 h of immersion in water and the significance of this impact compared to other factors. Six variants of bark–polylactic acid (PLA) WPCs were manufactured, differentiated by their filler content and filler particle size. As a comparison, analogous composites filled with coniferous sawdust were also manufactured. Bark-filled composites were characterised by lower TS and WA after both 2 h and 24 h of immersion, as well as lower water contact angles and surface free energy. The bark filler decreased the composites’ MORs and MOEs, while greater differences were noticed for variants filled with small particles. The type of filler was the second most important factor contributing to variance in this study, with the filler content being the most important one. Full article

(This article belongs to the Special Issue Advances in Functional Polymers and Composites)

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36 pages, 1539 KiB

Open AccessReview

Collagen and Its Derivatives Serving Biomedical Purposes: A Review

by Hanna Wosicka-Frąckowiak, Kornelia Poniedziałek, Stanisław Woźny, Mateusz Kuprianowicz, Martyna Nyga, Barbara Jadach and Bartłomiej Milanowski

Polymers 2024, 16(18), 2668; https://doi.org/10.3390/polym16182668 - 22 Sep 2024

Viewed by 2976

Abstract

Biomaterials have been the subject of extensive research, and their applications in medicine and pharmacy are expanding rapidly. Collagen and its derivatives stand out as valuable biomaterials due to their high biocompatibility, biodegradability, and lack of toxicity and immunogenicity. This review comprehensively examines [...] Read more.

Biomaterials have been the subject of extensive research, and their applications in medicine and pharmacy are expanding rapidly. Collagen and its derivatives stand out as valuable biomaterials due to their high biocompatibility, biodegradability, and lack of toxicity and immunogenicity. This review comprehensively examines collagen from various sources, its extraction and processing methods, and its structural and functional properties. Preserving the native state of collagen is crucial for maintaining its beneficial characteristics. The challenges associated with chemically modifying collagen to tailor its properties for specific clinical needs are also addressed. The review discusses various collagen-based biomaterials, including solutions, hydrogels, powders, sponges, scaffolds, and thin films. These materials have broad applications in regenerative medicine, tissue engineering, drug delivery, and wound healing. Additionally, the review highlights current research trends related to collagen and its derivatives. These trends may significantly influence future developments, such as using collagen-based bioinks for 3D bioprinting or exploring new collagen nanoparticle preparation methods and drug delivery systems. Full article

(This article belongs to the Special Issue Advanced Biodegradable Polymers for Drug Delivery)

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5 pages, 195 KiB

Open AccessEditorial

Advanced Polymeric Scaffolds for Stem Cell Engineering and Regenerative Medicine

by João Carlos Silva and Frederico Castelo Ferreira

Polymers 2024, 16(18), 2667; https://doi.org/10.3390/polym16182667 - 22 Sep 2024

Cited by 1 | Viewed by 2336

Abstract

Polymeric scaffolds play a pivotal role in tissue engineering (TE) and regenerative medicine strategies, as they offer the possibility to closely mimic the architectural features of the native tissues’ extracellular matrix (ECM) and support cell performance both in vitro and in vivo, creating [...] Read more.

Polymeric scaffolds play a pivotal role in tissue engineering (TE) and regenerative medicine strategies, as they offer the possibility to closely mimic the architectural features of the native tissues’ extracellular matrix (ECM) and support cell performance both in vitro and in vivo, creating a favourable regenerative microenvironment [...] Full article

(This article belongs to the Special Issue Advanced Polymeric Scaffolds for Stem Cell Engineering and Regenerative Medicine)

12 pages, 2529 KiB

Open AccessArticle

Prediction of Wear Rate of Glass-Filled PTFE Composites Based on Machine Learning Approaches

by Abhijeet R. Deshpande, Atul P. Kulkarni, Namrata Wasatkar, Vaibhav Gajalkar and Masuk Abdullah

Polymers 2024, 16(18), 2666; https://doi.org/10.3390/polym16182666 - 22 Sep 2024

Viewed by 873

Abstract

Wear is induced when two surfaces are in relative motion. The wear phenomenon is mostly data-driven and affected by various parameters such as load, sliding velocity, sliding distance, interface temperature, surface roughness, etc. Hence, it is difficult to predict the wear rate of [...] Read more.

Wear is induced when two surfaces are in relative motion. The wear phenomenon is mostly data-driven and affected by various parameters such as load, sliding velocity, sliding distance, interface temperature, surface roughness, etc. Hence, it is difficult to predict the wear rate of interacting surfaces from fundamental physics principles. The machine learning (ML) approach has not only made it possible to establish the relation between the operating parameters and wear but also helps in predicting the behavior of the material in polymer tribological applications. In this study, an attempt is made to apply different machine learning algorithms to the experimental data for the prediction of the specific wear rate of glass-filled PTFE (Polytetrafluoroethylene) composite. Orthogonal array L25 is used for experimentation for evaluating the specific wear rate of glass-filled PTFE with variations in the operating parameters such as applied load, sliding velocity, and sliding distance. The experimental data are analysed using ML algorithms such as linear regression (LR), gradient boosting (GB), and random forest (RF). The R² value is obtained as 0.91, 0.97, and 0.94 for LR, GB, and RF, respectively. The R² value of the GB model is the highest among the models, close to 1.0, indicating an almost perfect fit on the experimental data. Pearson’s correlation analysis reveals that load and sliding distance have a considerable impact on specific wear rate as compared to sliding velocity. Full article

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20 pages, 8606 KiB

Open AccessArticle

Effects of Polymer–Curing Agent Ratio on Rheological, Mechanical Properties and Chemical Characterization of Epoxy-Modified Cement Composite Grouting Materials

by Yuxuan Wang and Jiehao Wu

Polymers 2024, 16(18), 2665; https://doi.org/10.3390/polym16182665 - 22 Sep 2024

Viewed by 699

Abstract

This study designs and uses water-borne epoxy resin (WBER) and curing agent (CA) to modify traditional cement-based grouting for tunnels. The purpose of this paper is to analyze the rheological and mechanical properties of composite grouting with different ratios of WBER and CA [...] Read more.

This study designs and uses water-borne epoxy resin (WBER) and curing agent (CA) to modify traditional cement-based grouting for tunnels. The purpose of this paper is to analyze the rheological and mechanical properties of composite grouting with different ratios of WBER and CA and analyze the modification mechanism by means of chemical characterization to explore the feasibility of WBER as a high-performance modifier for tunnel construction. The composite grouting is prepared by mixing cement paste with polymer emulsion. A series of experiments was carried out to investigate the effects of WBER and CA, including the slump test, viscosity, rheological curve, setting time, bleeding rate, grain size distribution, zeta potential, compressive and splitting tensile strength, X-ray diffraction(XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), on the composite grout. The results show that WBER improves grout fluidity, which decreases in combination with CA, while also reducing the average particle size of the composite grout for a more rational size distribution. Optimal uniaxial (38.9%) and splitting tensile strength (48.7%) of the grout are achieved with a WBER to CA mass ratio of 2:1. WBER accelerates cement hydration, with the modification centered on the reaction between free Ca²⁺ and polymer-OH, significantly enhancing the strength, fluidity, and stability of the polymer-modified composite grout compared to traditional cement-based grouting. Full article

(This article belongs to the Special Issue New Technologies of Epoxy Resin)

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10 pages, 2710 KiB

Open AccessArticle

Construction of Thick Myocardial Tissue through Layered Seeding in Multi-Layer Nanofiber Scaffolds

by Yuru You, Feng Xu, Lingling Liu, Songyue Chen, Zhengmao Ding and Daoheng Sun

Polymers 2024, 16(18), 2664; https://doi.org/10.3390/polym16182664 - 22 Sep 2024

Viewed by 914

Abstract

A major challenge in myocardial tissue engineering is replicating the heart’s highly complex three-dimensional (3D) anisotropic structure. Heart-on-a-chip (HOC) is an emerging technology for constructing myocardial tissue in vitro in recent years, but most existing HOC systems face difficulties in constructing 3D myocardial [...] Read more.

A major challenge in myocardial tissue engineering is replicating the heart’s highly complex three-dimensional (3D) anisotropic structure. Heart-on-a-chip (HOC) is an emerging technology for constructing myocardial tissue in vitro in recent years, but most existing HOC systems face difficulties in constructing 3D myocardial tissue aligned with multiple cell layers. Electrospun nanofibers are commonly used as scaffolds for cell growth in myocardial tissue engineering, which can structurally simulate the extracellular matrix to induce the aligned growth of myocardial cells. Here, we developed an HOC that integrates multi-layered aligned polycaprolactone (PCL) nanofiber scaffolds inside microfluidic chips, and constructed 3D thick and aligned tissue with a layered seeding approach. By culturing human-induced pluripotent stem-cell-derived cardiomyocytes (hiPSC-CMs) on chip, the myocardial tissue on the two layered nanofibers reached a thickness of ~53 μm compared with ~19 μm for single-layered nanofibers. The obtained myocardial tissue presented well-aligned structures, with densely distributed α-actinin. By the third day post seeding, the hiPSC-CMs contract highly synchronously, with a contraction frequency of 18 times/min. The HOC with multi-layered biomimetic scaffolds provided a dynamic in vitro culture environment for hiPSC-CMs. Together with the layered cell-seeding process, the designed HOC promoted the formation of thick, well-aligned myocardial tissue. Full article

(This article belongs to the Special Issue Eco-Friendly Coatings and Adhesive Technology, 2nd Edition)

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28 pages, 5111 KiB

Open AccessArticle

Chitosan-Polyaniline (Bio)Polymer Hybrids by Two Pathways: A Tale of Two Biocomposites

by Yuriy A. Anisimov, Heng Yang, Johnny Kwon, Duncan E. Cree and Lee D. Wilson

Polymers 2024, 16(18), 2663; https://doi.org/10.3390/polym16182663 - 22 Sep 2024

Viewed by 742

Abstract

Previous research highlights the potential of polyaniline-based biocomposites as unique adsorbents for humidity sensors. This study examines several preparative routes for creating polyaniline (PANI) and chitosan (CHT) composites: Type 1—in situ polymerization of aniline with CHT; Type 2—molecular association in acidic aqueous media; [...] Read more.

Previous research highlights the potential of polyaniline-based biocomposites as unique adsorbents for humidity sensors. This study examines several preparative routes for creating polyaniline (PANI) and chitosan (CHT) composites: Type 1—in situ polymerization of aniline with CHT; Type 2—molecular association in acidic aqueous media; and a control, Type 3—physical mixing of PANI and CHT powders (without solvent). The study aims to differentiate the bonding nature (covalent vs. noncovalent) within these composites, which posits that noncovalent composites should exhibit similar physicochemical properties regardless of the preparative route. The results indicate that Type 1 composites display features consistent with covalent and hydrogen bonding, which result in reduced water swelling versus Type 2 and 3 composites. These findings align with spectral and thermogravimetric data, suggesting more compact structure for Type 1 materials. Dye adsorption studies corroborate the unique properties for Type 1 composites, and ¹H NMR results confirm the role of covalent bonding for the in situ polymerized samples. The structural stability adopts the following trend: Type 1 (covalent and noncovalent) > Type 2 (possible trace covalent and mainly noncovalent) > Type 3 (noncovalent). Types 2 and 3 are anticipated to differ based on solvent-driven complex formation. This study provides greater understanding of structure-function relationships in PANI-biopolymer composites and highlights the role of CHT as a template that involves variable (non)covalent contributions with PANI, according to the mode of preparation. The formation of composites with tailored bonding modalities will contribute to the design of improved adsorbent materials for environmental remediation to versatile humidity sensor systems. Full article

(This article belongs to the Special Issue Sustainable Polymer Composite Adsorbents: Preparation, Characterization and Applications)

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25 pages, 9690 KiB

Open AccessReview

Chitosan: A Green Approach to Metallic Nanoparticle/Nanocomposite Synthesis and Applications

by Ilham Ben Amor, Hadia Hemmami, Nedjoud Grara, Omaima Aidat, Asma Ben Amor, Soumeia Zeghoud and Stefano Bellucci

Polymers 2024, 16(18), 2662; https://doi.org/10.3390/polym16182662 - 21 Sep 2024

Viewed by 1209

Abstract

Chitosan, a naturally occurring biopolymer derived from chitin, has emerged as a highly promising instrument for the production and application of metal nanoparticles. The present review delves into the several functions of chitosan in the development and operation of metal nanoparticles, emphasizing its [...] Read more.

Chitosan, a naturally occurring biopolymer derived from chitin, has emerged as a highly promising instrument for the production and application of metal nanoparticles. The present review delves into the several functions of chitosan in the development and operation of metal nanoparticles, emphasizing its aptitudes as a green reducing agent, shape-directing agent, size-controlling agent, and stabilizer. Chitosan’s special qualities make it easier to manufacture metal nanoparticles and nanocomposites with desired characteristics. Furthermore, there is a lot of promise for chitosan-based nanocomposites in a number of fields, such as metal removal, water purification, and photoacoustic, photothermal, antibacterial, and photodynamic therapies. This thorough analysis highlights the potential application of chitosan in the advancement of nanotechnology and the development of medicinal and environmental solutions. Full article

(This article belongs to the Special Issue Polymeric Biomaterials: New Materials & Structure-Property-Application Relationship)

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33 pages, 5128 KiB

Open AccessReview

Electrolytes for High-Safety Lithium-Ion Batteries at Low Temperature: A Review

by Shuhong Yun, Xinghua Liang, Junjie Xi, Leyu Liao, Shuwan Cui, Lihong Chen, Siying Li and Qicheng Hu

Polymers 2024, 16(18), 2661; https://doi.org/10.3390/polym16182661 - 21 Sep 2024

Viewed by 2581

Abstract

As the core of modern energy technology, lithium-ion batteries (LIBs) have been widely integrated into many key areas, especially in the automotive industry, particularly represented by electric vehicles (EVs). The spread of LIBs has contributed to the sustainable development of societies, especially in [...] Read more.

As the core of modern energy technology, lithium-ion batteries (LIBs) have been widely integrated into many key areas, especially in the automotive industry, particularly represented by electric vehicles (EVs). The spread of LIBs has contributed to the sustainable development of societies, especially in the promotion of green transportation. However, the high demand for battery performance and safety in these fields has made the high viscosity, volatility, and potential leakage inherent in traditional organic liquid electrolytes a constraint on their further expansion. Especially at low temperature, the increased viscosity of the electrolyte, reduced solubility of lithium salts, crystallization or solidification of the electrolyte, increased resistance to charge transfer due to interfacial by-products, and short-circuiting due to the growth of anode lithium dendrites all affect the performance and safety of LIBs. Therefore, improving the safety performance of LIBs under low-temperature environments has become a focus of current research. This paper primarily reviews the progress made in utilizing different types of electrolytes in LIBs to enhance safety and optimize low temperature performance and discusses the current research progress as well as the future development direction of the field. Full article

(This article belongs to the Special Issue Functional Polymer Composites for Advanced Applications)

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28 pages, 8007 KiB

Open AccessReview

Stimuli-Responsive Polymer Actuator for Soft Robotics

by Seewoo Kim, Sang-Nam Lee, Ambrose Ashwin Melvin and Jeong-Woo Choi

Polymers 2024, 16(18), 2660; https://doi.org/10.3390/polym16182660 - 21 Sep 2024

Viewed by 678

Abstract

Polymer actuators are promising, as they are widely used in various fields, such as sensors and soft robotics, for their unique properties, such as their ability to form high-quality films, sensitivity, and flexibility. In recent years, advances in structural and fabrication processes have [...] Read more.

Polymer actuators are promising, as they are widely used in various fields, such as sensors and soft robotics, for their unique properties, such as their ability to form high-quality films, sensitivity, and flexibility. In recent years, advances in structural and fabrication processes have significantly improved the reliability of polymer sensing-based actuators. Polymer actuators have attracted considerable attention for use in artificial or biohybrid systems, as they have the potential to operate under diverse conditions with high durability. This review briefly describes different types of polymer actuators and provides an understanding of their working mechanisms. It focuses on actuation modes controlled by diverse or multiple stimuli. Furthermore, it discusses the fabrication processes of polymer actuators; the fabrication process is an important consideration in the development of high-quality actuators with sensing properties for a wide range of applications in soft robotics. Additionally, the high potential of polymer actuators for use in sensing technology is examined, and the latest developments in the field of polymer actuators, such as the development of biohybrid polymers and the use of polymer actuators in 4D printing, are briefly described. Full article

(This article belongs to the Special Issue Flexible Devices Based on Functional Polymers)

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13 pages, 4716 KiB

Open AccessArticle

Facile In Situ Building of Sulfonated SiO₂ Coating on Porous Skeletons of Lithium-Ion Battery Separators

by Lei Ding, Dandan Li, Sihang Zhang, Yuanjie Zhang, Shuyue Zhao, Fanghui Du and Feng Yang

Polymers 2024, 16(18), 2659; https://doi.org/10.3390/polym16182659 - 20 Sep 2024

Viewed by 745

Abstract

Polyolefin separators with worse porous structures and compatibilities mismatch the internal environment and deteriorate lithium-ion battery (LIB) combination properties. In this study, a sulfonated SiO₂ (SSD) composited polypropylene separator (PP@SSD) is prepared to homogenize pore sizes and in situ-built SSD coatings on [...] Read more.

Polyolefin separators with worse porous structures and compatibilities mismatch the internal environment and deteriorate lithium-ion battery (LIB) combination properties. In this study, a sulfonated SiO₂ (SSD) composited polypropylene separator (PP@SSD) is prepared to homogenize pore sizes and in situ-built SSD coatings on porous skeletons. Imported SSD uniformizes pore sizes owing to centralized interface distributions within casting films. Meanwhile, abundant cavitations enable the in situ SSD coating to facilely fix onto porous skeleton surfaces during separator fabrications, which feature simple techniques, low cost, environmental friendliness, and the capability for continuous fabrications. A sturdy SSD coating on the porous skeleton confines thermal shrinkages and offers a superior safety guarantee for LIBs. The abundant sulfonic acid groups of SSD endow PP@SSD with excellent electrolyte affinity, which lowers Li⁺ transfer barriers and optimizes interfacial compatibility. Therefore, assembled LIBs give the optimal C-rate capacity and cycling stability, holding a capacity retention of 82.7% after the 400th cycle at 0.5 C. Full article

(This article belongs to the Special Issue Polymer-Based Flexible Materials, 2nd Edition)

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13 pages, 3380 KiB

Open AccessArticle

Enhanced Feedstock Processability for the Indirect Additive Manufacturing of Metals by Material Extrusion through Ethylene–Propylene Copolymer Modification

by Thomas Forstner, Simon Cholewa and Dietmar Drummer

Polymers 2024, 16(18), 2658; https://doi.org/10.3390/polym16182658 - 20 Sep 2024

Viewed by 597

Abstract

Filament-based material extrusion (MEX) represents one of the most commonly used additive manufacturing techniques for polymer materials. In a special variation of this process, highly filled polymer filaments are used to create metal parts via a multi-step process. The challenges associated with creating [...] Read more.

Filament-based material extrusion (MEX) represents one of the most commonly used additive manufacturing techniques for polymer materials. In a special variation of this process, highly filled polymer filaments are used to create metal parts via a multi-step process. The challenges associated with creating a dense final part are versatile due to the different and partly contrary requirements of the individual processing steps. Especially for processing in MEX, the compound must show sufficiently low viscosity, which is often achieved by the addition of wax. However, wax addition also leads to a significant reduction in ductility. This can cause filaments to break, which leads to failure of the MEX process. Therefore, the present study investigates the influence of different ethylene–propylene copolymers (EPCs) with varying ethylene contents as a ductility-enhancing component within the feedstock to improve filament processing behavior. The resulting feedstock materials are evaluated regarding their mechanical, thermal and debinding behavior. In addition, the processability in MEX is assessed. This study shows that a rising ethylene content within the EPC leads to a higher ductility and an enhanced filament flexibility while also influencing the crystallization behavior of the feedstock. For the MEX process, an ethylene fraction of 12% within the EPC was found to be the optimum regarding processability for the highly filled filaments in MEX and the additional processing steps to create sintered metal parts. Full article

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

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11 pages, 1965 KiB

Open AccessArticle

The Influence of the Heat Flux of the Infrared Heater on the Charring Rate of Spruce Wood

by Alena Párničanová, Martin Zachar and Danica Kačíková

Polymers 2024, 16(18), 2657; https://doi.org/10.3390/polym16182657 - 20 Sep 2024

Viewed by 504

Abstract

The study investigates the determination of selected fire properties of spruce wood, specifically the charring rate, using a modified testing method described and registered at the Industrial Property Office of the Slovak Republic PUV 50121-2020, utility model no. 9373. The samples were exposed [...] Read more.

The study investigates the determination of selected fire properties of spruce wood, specifically the charring rate, using a modified testing method described and registered at the Industrial Property Office of the Slovak Republic PUV 50121-2020, utility model no. 9373. The samples were exposed to a square ceramic infrared heater, FTE-750W, with a power output of 750 W, using which we determined the heat flux as a function of voltage (V). Spruce wood specimens with dimensions of 75 mm × 75 mm × 50 mm (l × w × h) were subjected to thermal exposure under heat fluxes of 10, 15, 20, and 25 kW∙m⁻². The charring rate was evaluated using two distinct approaches: the first method measured the thickness of the char layer formed after a duration of 1800 s, while the second method was based on reaching a temperature threshold of 300 °C. The findings demonstrated a positive correlation between the thermal load and the charring rate. The charring rates obtained using the first method ranged from 0.2397 to 0.6933 mm∙min⁻¹, whereas those derived from the second method varied from 0 to 1.0344 mm∙min⁻¹. This suggests that the 300 °C temperature criterion may not be a reliable parameter for calculating the charring rate. The precision of the results was corroborated through numerical simulations. Full article

(This article belongs to the Special Issue New Challenges in Wood and Wood-Based Materials III)

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18 pages, 23576 KiB

Open AccessArticle

Mechanical Properties and Economic Analysis of Fused Filament Fabrication Continuous Carbon Fiber Reinforced Composites

by Damira Dairabayeva, Ulanbek Auyeskhan and Didier Talamona

Polymers 2024, 16(18), 2656; https://doi.org/10.3390/polym16182656 - 20 Sep 2024

Viewed by 1093

Abstract

Additive manufacturing of composites offers advantages over metals since composites are lightweight, fatigue and corrosion-resistant, and show high strength and stiffness. This work investigates the tensile and flexural performance of continuous carbon-fiber reinforced (CCF) composites with different guide angles and number of layers. [...] Read more.

Additive manufacturing of composites offers advantages over metals since composites are lightweight, fatigue and corrosion-resistant, and show high strength and stiffness. This work investigates the tensile and flexural performance of continuous carbon-fiber reinforced (CCF) composites with different guide angles and number of layers. The cost and printing time analyses were also conducted. Tensile specimens with a contour-only specimen and one CCF layer with a 0° guide angle exhibited nearly comparable strength values. Increasing the number of CCF layers enhances the tensile properties. For the identical cost and reinforcement amount, 0°/0° provides a higher tensile strength and elastic modulus compared with 15°/−15°. The same phenomenon was observed for 15°/0°/−15° and 0°/0°/0°. The samples with one and two reinforcement layers had similar stiffness and maximum load values for flexural tests. For the samples with four layers, there was a considerable improvement in stiffness but a minor decrease in the maximum load. Full article

(This article belongs to the Special Issue Additive Manufacturing of Polymer-Based Materials and Lightweight Structures)

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11 pages, 78948 KiB

Open AccessArticle

The Catalytic Effect of Low Molecular Weight Acids on the Physicochemical and Dielectric Properties of Oil-Paper Insulation Systems

by Kakou D. Kouassi, Issouf Fofana, Yazid Hadjadj and Kouba M. Lucia Yapi

Polymers 2024, 16(18), 2655; https://doi.org/10.3390/polym16182655 - 20 Sep 2024

Viewed by 734

Abstract

In most industrialized countries, power transformers built several decades ago are approaching the end of their operational lifespan. The ongoing energy transition, focused on developing 100% renewable energy sources and accelerating global transportation electrification, further exacerbates these assets. Combined with rising electricity demand, [...] Read more.

In most industrialized countries, power transformers built several decades ago are approaching the end of their operational lifespan. The ongoing energy transition, focused on developing 100% renewable energy sources and accelerating global transportation electrification, further exacerbates these assets. Combined with rising electricity demand, there is an increasing risk of critical transformers’ degradation acceleration. In this context, understanding the aging mechanisms of the insulation system inside these essential assets, which form the core of every energy network, becomes paramount for today’s managers and engineers responsible for their operations. The acids generated through oil oxidation can be classified into two categories: low molecular weight acids (LMAs), which are inherently more hydrophilic and consequently have a greater impact on the degradation rate of solid insulation through hydrolysis, and high molecular weight acids (HMAs), which do not significantly contribute to the degradation of paper insulation. This study specifically addresses the impact of acids generated through oil oxidation—focusing on LMAs. New oil samples were infused with different ratios of LMAs before impregnation. The impregnated paper samples underwent thermal aging at 115 °C. Different physicochemical and dielectric properties were investigated. The investigations revealed that oils blended with formic acid exhibited more adverse effects on the insulation system compared to other LMAs. This information is essential for industry professionals seeking to mitigate the risks associated with transformer degradation and extend the lifespan of these critical assets during the energy transition. Full article

(This article belongs to the Special Issue Advances in the Preparation, Properties and Application of Polyurethane, Cellulose and Their Composites (2nd Edition))

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14 pages, 3050 KiB

Open AccessArticle

Performance Investigation of PSF-nAC Composite Ultrafiltration Membrane for Protein Separation

by Gunawan Setia Prihandana, Muslim Mahardika, Budi Arifvianto, Ario Sunar Baskoro, Yudan Whulanza, Tutik Sriani and Farazila Yusof

Polymers 2024, 16(18), 2654; https://doi.org/10.3390/polym16182654 - 20 Sep 2024

Cited by 1 | Viewed by 593

Abstract

As a promising wastewater treatment technology, ultrafiltration membranes face challenges related to fouling and flux reduction. To enhance these membranes, various strategies have been explored. Among them, the incorporation of nano-activated carbon (nAC) powder has emerged as an effective method. In this study, [...] Read more.

As a promising wastewater treatment technology, ultrafiltration membranes face challenges related to fouling and flux reduction. To enhance these membranes, various strategies have been explored. Among them, the incorporation of nano-activated carbon (nAC) powder has emerged as an effective method. In this study, composite polysulfone (PSF) ultrafiltration membranes were fabricated using nAC powder at concentrations ranging from 0 to 8 wt.%. These membranes underwent comprehensive investigation, including assessments of membrane morphology, hydrophilicity, pure water flux, equilibrium water content, porosity, average pore size, and protein separation. The addition of activated carbon improved several desirable properties. Specifically, the hydrophilicity of the PSF membranes was enhanced, with the contact angle reduced from 69° to 58° for 8 wt.% of nAC composite membranes compared to the pristine PSF membrane. Furthermore, the water flux test revealed that 6 wt.% activated carbon-based membranes exhibited the highest flux, with a nearly 3 times improvement at 2 bar. Importantly, this enhancement did not compromise the protein rejection. Additionally, the introduction of nAC had a significant effect on the membrane’s pore size by improving lysozyme rejection up to 40%. Overall, these findings will guide the selection of the optimal concentration of nAC for PSF ultrafiltration membranes. Full article

(This article belongs to the Special Issue Polymeric Materials in Wastewater Treatment)

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18 pages, 4252 KiB

Open AccessArticle

Statistical-Based Optimization of Modified Mangifera indica Fruit Starch as Substituent for Pharmaceutical Tableting Excipient

by Prin Chaksmithanont, Ketsana Bangsitthideth, Kwanputtha Arunprasert, Prasopchai Patrojanasophon and Chaiyakarn Pornpitchanarong

Polymers 2024, 16(18), 2653; https://doi.org/10.3390/polym16182653 - 20 Sep 2024

Viewed by 909

Abstract

This study aimed to optimize modified starch from Mangifera indica (mango) fruit using acid hydrolysis and pre-gelatinization via computer-assisted techniques as a substituent for pharmaceutical tableting excipients. The hydrolysis and microwave-assisted pre-gelatinization time and temperature were optimized using a three-level factorial design. The [...] Read more.

This study aimed to optimize modified starch from Mangifera indica (mango) fruit using acid hydrolysis and pre-gelatinization via computer-assisted techniques as a substituent for pharmaceutical tableting excipients. The hydrolysis and microwave-assisted pre-gelatinization time and temperature were optimized using a three-level factorial design. The modified starches were characterized for flowability, compressibility, and swelling properties. It was found that all parameters fit a quadratic model, which can be used to predict the properties of the modified starch. The optimized hydrolysis reaction was 3.8 h at 56.4 °C, while the pre-gelatinization reaction was 3 min at 150 °C. Structural changes were found, ascertaining that starch modification was successful. The optimized hydrolyzed starch showed superior properties in relative to unmodified M. indica fruit starch and comparable characteristics to conventional excipients. The optimized pre-gelatinized starch presented an excellent enhancement in the flow and compression properties, with %swelling greatly augmented 3.95-fold and 1.24-fold compared to unmodified starch and SSG, respectively. Additionally, the pre-gelatinized starch presented comparable binding effect, while the hydrolyzed powder had reduced binding capacity due to shorter chains. The findings revealed that the use of software-assisted design of experiment facilitated a data-driven approach to optimize the modifications. The optimized modified mango starch demonstrated potential as a multifunctional excipient, capable of functioning as binder, disintegrant, and diluent. Full article

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

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18 pages, 2573 KiB

Open AccessArticle

Natural Rubber Films Reinforced with Cellulose and Chitosan Prepared by Latex Aqueous Microdispersion

by Naipaporn Sutipanwihan, Veerapat Kitsawat, Praewpakun Sintharm and Muenduen Phisalaphong

Polymers 2024, 16(18), 2652; https://doi.org/10.3390/polym16182652 - 20 Sep 2024

Viewed by 693

Abstract

In this paper, green composite films comprising natural rubber (NR), cellulose (CE), and chitosan (CS) were successfully fabricated through a simple, facile, cost-effective method in order to improve mechanical, chemical, and antimicrobial properties of NR composite films. Chitosan with a low molecular weight [...] Read more.

In this paper, green composite films comprising natural rubber (NR), cellulose (CE), and chitosan (CS) were successfully fabricated through a simple, facile, cost-effective method in order to improve mechanical, chemical, and antimicrobial properties of NR composite films. Chitosan with a low molecular weight of 30,000–50,000 g/mol (CS-L) and a medium molecular weight of 300,000–500,000 g/mol (CS-M) was used for the fabrication. The composite films were prepared via a latex aqueous microdispersion method with different weight ratios of NR:CE:CS-L/CS-M. Fourier transform infrared spectroscopy (FTIR) results demonstrated strong interactions of hydrogen bonds between CE and CS-L/CS-M in the composite films. The tensile strength and the modulus of the composite films in dried form were found to significantly increase with the reinforcement of CE and CS-L/CS-M. The maximum tensile strength (13.8 MPa) and Young’s modulus (12.7 MPa) were obtained from the composite films reinforced with CE at 10 wt.% and CS-L at 10 wt.%. The high elongation of 500–526% was obtained from the composite films reinforced with CE at 10 wt.% and CS (CS-L or CS-M) at 5.0 wt.%. The modification could also significantly promote antimicrobial activities and chemical resistance against non-polar solvents in the composite films. The NR composite films have potential uses as flexible films for sustainable green packaging. Full article

(This article belongs to the Special Issue Renewable, Degradable, and Recyclable Polymer Composites)

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