Polymers

21 pages, 5724 KiB

Open AccessEditor’s ChoiceReview

Thermodynamics of the Glassy Polymer State: Equilibrium and Non-Equilibrium Aspects

by Costas Panayiotou

Polymers 2024, 16(2), 298; https://doi.org/10.3390/polym16020298 - 22 Jan 2024

Cited by 2 | Viewed by 1844

This work examines, first, the non-equilibrium character of the glassy state of polymer systems and its significance in the development of novel materials for important technological applications. Subsequently, it summarizes the essentials of the generalized lattice fluid approach for the description of this [...] Read more.

This work examines, first, the non-equilibrium character of the glassy state of polymer systems and its significance in the development of novel materials for important technological applications. Subsequently, it summarizes the essentials of the generalized lattice fluid approach for the description of this highly complex non-equilibrium behavior with an approximate and simple, yet analytically powerful formalism. The working equations are derived in a straightforward and consistent manner by clearly defining the universal and specific variables needed to describe the discussed properties. The role of the non-random distribution of molecular species and free volume in the glassy system is also examined, as is the role of strong specific interactions, such as hydrogen-bonding networks. This work also reports examples of applications in a variety of representative systems, including glass densification, retrograde vitrification, increase in glass-transition temperature in hydrogen-bonded polymer mixtures, and hysteresis phenomena in sorption–desorption from glassy polymer matrices. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece: 2nd Edition)

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15 pages, 5982 KiB

Open AccessEditor’s ChoiceArticle

Catalyst-Free Amino-Yne Click Reaction: An Efficient Way for Immobilizing Amoxicillin onto Polymeric Surfaces

by Julia Sánchez-Bodón, Maria Diaz-Galbarriatu, Rebeca Sola-Llano, Leire Ruiz-Rubio, José Luis Vilas-Vilela and Isabel Moreno-Benitez

Polymers 2024, 16(2), 246; https://doi.org/10.3390/polym16020246 - 15 Jan 2024

Cited by 2 | Viewed by 1989

Abstract

Surface modifications play a crucial role in enhancing the functionality of biomaterials. Different approaches can be followed in order to achieve the bioconjugation of drugs and biological compounds onto polymer surfaces. In this study, we focused on the immobilization of an amoxicillin antibiotic [...] Read more.

Surface modifications play a crucial role in enhancing the functionality of biomaterials. Different approaches can be followed in order to achieve the bioconjugation of drugs and biological compounds onto polymer surfaces. In this study, we focused on the immobilization of an amoxicillin antibiotic onto the surface of poly-L-lactic acid (PLLA) using a copper-free amino-yne click reaction. The utilization of this reaction allowed for a selective and efficient bioconjugation of the amoxicillin moiety onto the PLLA surface, avoiding copper-related concerns and ensuring biocompatibility. The process involved sequential steps that included surface activation via alkaline hydrolysis followed by an amidation reaction with ethylendiamine, functionalization with propiolic groups, and subsequent conjugation with amoxicillin via a click chemistry approach. Previous amoxicillin immobilization using tryptophan and fluorescent amino acid conjugation was carried out in order to determine the efficacy of the proposed methodology. Characterization techniques such as X-ray photoelectron spectroscopy (XPS), Attenuated Total Reflection (ATR)–Fourier Transform Infrared (FTIR) spectroscopy, surface imaging, water contact angle determination, and spectroscopic analysis confirmed the successful immobilization of both tryptophan and amoxicillin while maintaining the integrity of the PLLA surface. This tailored modification not only exhibited a novel method for surface functionalization but also opens avenues for developing antimicrobial biomaterials with improved drug-loading capacity. Full article

(This article belongs to the Special Issue Biomaterials in Medical Applications II)

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15 pages, 3109 KiB

Open AccessEditor’s ChoiceArticle

Potentiating Gilteritinib Efficacy Using Nanocomplexation with a Hyaluronic Acid–Epigallocatechin Gallate Conjugate

by Ki Hyun Bae, Fritz Lai, Qingfeng Chen and Motoichi Kurisawa

Polymers 2024, 16(2), 225; https://doi.org/10.3390/polym16020225 - 12 Jan 2024

Viewed by 1913

Abstract

Acute myeloid leukemia carrying FMS-like tyrosine kinase receptor-3 (FLT3) mutations is a fatal blood cancer with a poor prognosis. Although the FLT3 inhibitor gilteritinib has recently been approved, it still suffers from limited efficacy and relatively high nonresponse rates. In this study, we [...] Read more.

Acute myeloid leukemia carrying FMS-like tyrosine kinase receptor-3 (FLT3) mutations is a fatal blood cancer with a poor prognosis. Although the FLT3 inhibitor gilteritinib has recently been approved, it still suffers from limited efficacy and relatively high nonresponse rates. In this study, we report the potentiation of gilteritinib efficacy using nanocomplexation with a hyaluronic acid–epigallocatechin gallate conjugate. The self-assembly, colloidal stability, and gilteritinib loading capacity of the nanocomplex were characterized by reversed-phase high-performance liquid chromatography and dynamic light scattering technique. Flow cytometric analysis revealed that the nanocomplex efficiently internalized into FLT3-mutated leukemic cells via specific interactions between the surface-exposed hyaluronic acid and CD44 receptor overexpressed on the cells. Moreover, this nanocomplex was found to induce an eradication of the leukemic cells in a synergistic manner by elevating the levels of reactive oxygen species and caspase-3/7 activities more effectively than free gilteritinib. This study may provide a useful strategy to design nanomedicines capable of augmenting the therapeutic efficacy of FLT3 inhibitors for effective leukemia therapy. Full article

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

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18 pages, 5060 KiB

Open AccessEditor’s ChoiceArticle

Gas Permeability through Polyimides: Unraveling the Influence of Free Volume, Intersegmental Distance and Glass Transition Temperature

by Alba Torres, Cenit Soto, Javier Carmona, Bibiana Comesaña-Gandara, Mónica de la Viuda, Laura Palacio, Pedro Prádanos, María Teresa Simorte, Inmaculada Sanz, Raúl Muñoz, Alberto Tena and Antonio Hernández

Polymers 2024, 16(1), 13; https://doi.org/10.3390/polym16010013 - 19 Dec 2023

Cited by 3 | Viewed by 2340

Abstract

The relationships between gas permeability and free volume fraction, intersegmental distance, and glass transition temperature, are investigated. They are analyzed for He, CO₂, O₂, CH₄, and N₂ gases and for five similar polyimides with a wide [...] Read more.

The relationships between gas permeability and free volume fraction, intersegmental distance, and glass transition temperature, are investigated. They are analyzed for He, CO₂, O₂, CH₄, and N₂ gases and for five similar polyimides with a wide range of permeabilities, from very low to extremely high ones. It has been established here that there is an exponential relationship between permeability and the free volume fraction, and between permeability and the most probable intersegmental distance as measured by WAXS; in both cases, with an exponential coefficient that depends on the kinetic gas diameter as a quadratic polynomial and with a preexponential positive constant. Moreover, it has been proven that the intersegmental distance increases linearly with the free volume fraction. Finally, it has been established that the free volume fraction increases with the glass transition temperature for the polymers tested, and that they depend on each other in an approximate linear way. Full article

(This article belongs to the Special Issue Polymers for Membrane Separation Process)

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23 pages, 2297 KiB

Open AccessEditor’s ChoiceArticle

Bringing Light into the Dark—Overview of Environmental Impacts of Carbon Fiber Production and Potential Levers for Reduction

by Tobias Manuel Prenzel, Andrea Hohmann, Tim Prescher, Kerstin Angerer, Daniel Wehner, Robert Ilg, Tjark von Reden, Klaus Drechsler and Stefan Albrecht

Polymers 2024, 16(1), 12; https://doi.org/10.3390/polym16010012 - 19 Dec 2023

Cited by 3 | Viewed by 7863

Abstract

Carbon fibers (CFs) are a crucial material for lightweight structures with advanced mechanical performance. However, there is still a paucity of detailed understanding regarding the environmental impacts of production. Previously, mostly singled-out scenarios for CF production have been assessed, often based on scarce [...] Read more.

Carbon fibers (CFs) are a crucial material for lightweight structures with advanced mechanical performance. However, there is still a paucity of detailed understanding regarding the environmental impacts of production. Previously, mostly singled-out scenarios for CF production have been assessed, often based on scarce transparent inventory data. To expand the current knowledge and create a robust database for future evaluation, a life cycle assessment (LCA) was carried out. To this end, a detailed industry-approved LCI is published, which also proved plausible against the literature. Subsequently, based on a global scenario representing the market averages for precursor and CF production, the most relevant contributors to climate change (EF3.1 climate change, total) and the depletion of fossil energy carriers (EF3.1 resource use, fossil) were identified. The energy consumption in CF manufacturing was found to be responsible for 59% of the climate change and 48% of the fossil resource use. To enable a differentiated discussion of manufacturing locations and process energy consumption, 24 distinct scenarios were assessed. The findings demonstrate the significant dependence of the results on the scenarios’ boundary conditions: climate change ranges from 13.0 to 34.1 kg CO₂ eq./kg CF and resource use from 262.3 to 497.9 MJ/kg CF. Through the investigated scenarios, the relevant reduction potentials were identified. The presented results help close an existing data gap for high-quality, regionalized, and technology-specific LCA results for the production of CF. Full article

(This article belongs to the Special Issue Manufacturing of Polymer-Matrix Composites)

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14 pages, 5169 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of the Mechanical and Tribological Behavior of Polyether Ether Ketone Fiber-Reinforced Resin-Based Friction Materials Fabricated by Wet Granulation

by Lekai Li, Zichao Ma, Guoqin Liu, Wei Song, Lili Ren, Shengwang Yuan, Xiao Yang, Qifeng Zhang and Yunhai Ma

Polymers 2023, 15(24), 4732; https://doi.org/10.3390/polym15244732 - 18 Dec 2023

Cited by 1 | Viewed by 1616

Abstract

Resin-based friction materials (RBFMs) strengthened by polyether ether ketone (PEEK) fiber were designed and prepared in this study. Specimens incorporating PEEK fiber of 2–8 wt.% were fabricated based on wet granulation, and then the effects of the PEEK fiber content on the mechanical [...] Read more.

Resin-based friction materials (RBFMs) strengthened by polyether ether ketone (PEEK) fiber were designed and prepared in this study. Specimens incorporating PEEK fiber of 2–8 wt.% were fabricated based on wet granulation, and then the effects of the PEEK fiber content on the mechanical and tribological properties of RBFMs were systematically investigated. The results showed that PEEK fiber can sense the braking temperature and then effectively regulate the comprehensive properties of RBFMs. The specimen incorporating 6 wt.% PEEK fiber obtained the optimal comprehensive performance with a stable friction coefficient (COF), excellent fade resistance and recovery properties, and better wear resistance. The worn surface was inspected using a scanning electron microscope. After the friction–wear test, the specimen with 6 wt.% PEEK fiber presented a number of primary and secondary plateaus and a reduced number of pits with wear debris on the worn surface. The study indicated that PEEK fiber could not only enhance the mechanical and tribological properties of RBFMs at low temperatures because of their high strength and self-lubrication but also adhere to wear debris to reduce abrasive wear at high temperatures; furthermore, the adhered wear debris could form a secondary plateau under normal pressure, which could alleviate abrasion. Full article

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

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22 pages, 8253 KiB

Open AccessEditor’s ChoiceArticle

Development of an Electroactive and Thermo-Reversible Diels–Alder Epoxy Nanocomposite Doped with Carbon Nanotubes

by Isaac Lorero, Álvaro Rodríguez, Mónica Campo and Silvia G. Prolongo

Polymers 2023, 15(24), 4715; https://doi.org/10.3390/polym15244715 - 15 Dec 2023

Cited by 4 | Viewed by 1710

Abstract

The manufacturing of Diels–Alder (D-A) crosslinked epoxy nanocomposites is an emerging field with several challenges to overcome: the synthesis is complex due to side reactions, the mechanical properties are hindered by the brittleness of these bonds, and the content of carbon nanotubes (CNT) [...] Read more.

The manufacturing of Diels–Alder (D-A) crosslinked epoxy nanocomposites is an emerging field with several challenges to overcome: the synthesis is complex due to side reactions, the mechanical properties are hindered by the brittleness of these bonds, and the content of carbon nanotubes (CNT) added to achieve electroactivity is much higher than the percolation thresholds of other conventional resins. In this work, we develop nanocomposites with different D-A crosslinking ratios (0, 0.6, and 1.0) and CNT contents (0.1, 0.3, 0.5, 0.7, and 0.9 wt.%), achieving a simplified route and avoiding the use of solvents and side reactions by selecting a two-step curing method (100 °C-6 h + 60 °C-12 h) that generates the thermo-reversible resins. These reversible nanocomposites show ohmic behavior and effective Joule heating, reaching the dissociation temperatures of the D-A bonds. The fully reversible nanocomposites (ratio 1.0) present more homogeneous CNT dispersion compared to the partially reversible nanocomposites (ratio 0.6), showing higher electrical conductivity, as well as higher brittleness. For this study, the nanocomposite with a partially reversible matrix (ratio 0.6) doped with 0.7 CNT wt.% was selected to allow us to study its new smart functionalities and performance due to its reversible network by analyzing self-healing and thermoforming. Full article

(This article belongs to the Special Issue Epoxy Thermoset Polymer Composites)

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31 pages, 2191 KiB

Open AccessEditor’s ChoiceReview

Metal and Metal Oxide Nanoparticle Incorporation in Polyurethane Foams: A Solution for Future Antimicrobial Materials?

by Radu Claudiu Fierascu, Eduard-Marius Lungulescu, Irina Fierascu, Miruna S. Stan, Ionela C. Voinea and Silviu Ionel Dumitrescu

Polymers 2023, 15(23), 4570; https://doi.org/10.3390/polym15234570 - 29 Nov 2023

Cited by 4 | Viewed by 2263

Abstract

With the technological developments witnessed in recent decades, nanotechnology and nanomaterials have found uses in several common applications and products we encounter daily. On the other hand, polyurethane (PU) foams represent an extremely versatile material, being widely recognized for their extensive application possibilities [...] Read more.

With the technological developments witnessed in recent decades, nanotechnology and nanomaterials have found uses in several common applications and products we encounter daily. On the other hand, polyurethane (PU) foams represent an extremely versatile material, being widely recognized for their extensive application possibilities and possessing a multitude of fundamental attributes that enhance their broad usability across various application fields. By combining the versatility of PU with the antimicrobial properties of nanoparticles, this emerging field holds promise for addressing the urgent need for effective antimicrobial materials in various applications. In this comprehensive review, we explore the synthesis methods, properties and applications of these nanocomposite materials, shedding light on their potential role in safeguarding public health and environmental sustainability. The main focus is on PU foams containing metal and metal oxide nanoparticles, but a brief presentation of the progress documented in the last few years regarding other antimicrobial nanomaterials incorporated into such foams is also given within this review in order to obtain a larger image of the possibilities to develop improved PU foams. Full article

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

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15 pages, 3395 KiB

Open AccessEditor’s ChoiceArticle

Simultaneous Enhancement of the Mechanical Properties, Performance and Insensitivity of an Energetic Elastomeric Polyurethane Binder by Kinetically Grafting Reactive Spiranes

by Mingyang Ma and Younghwan Kwon

Polymers 2023, 15(23), 4564; https://doi.org/10.3390/polym15234564 - 28 Nov 2023

Viewed by 1198

Abstract

A series of robust energetic polyurethane binders was developed by in situ grafting reactive spiranes to achieve the migration-resistant processing aid and compensate for the energy output. The reactive grafting spiranes (RGSs), bearing two highly ring-strained spiranes, were synthesized sequentially to provide a [...] Read more.

A series of robust energetic polyurethane binders was developed by in situ grafting reactive spiranes to achieve the migration-resistant processing aid and compensate for the energy output. The reactive grafting spiranes (RGSs), bearing two highly ring-strained spiranes, were synthesized sequentially to provide a promising ring strain energy up to a maximum value of 290 kJ mol⁻¹. The thermodynamic compatibility of the RGS with uncured glycidyl azido polymer (GAP) was studied quantitatively by analyzing the glass transition temperature of their blendings. The reactivity study of the catalyst-free click reaction with respect to spacer-dependent species was amplified by tracing the extent of the reaction and measuring the activation energy. The faster reactivity of propargyl species was evident from two experimental approaches, which were verified further by theoretical predictions. Interestingly, the energy gap difference in the frontier molecular orbitals agreed well with the difference in activation energy between the two types of spacer-dependent species. The mechanical and thermochemical enhancements of GAP-based polyurethane with RGS were basically gained from those highly ring-strained moieties. Full article

(This article belongs to the Section Polymer Chemistry)

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19 pages, 16138 KiB

Open AccessEditor’s ChoiceArticle

Self-Assembly of Symmetric Copolymers in Slits with Inert and Attractive Walls

by Tomáš Blovský, Karel Šindelka, Zuzana Limpouchová and Karel Procházka

Polymers 2023, 15(22), 4458; https://doi.org/10.3390/polym15224458 - 18 Nov 2023

Viewed by 1164

Abstract

Although the behavior of the confined semi-dilute solutions of self-assembling copolymers represents an important topic of basic and applied research, it has eluded the interest of scientists. Extensive series of dissipative particle dynamics simulations have been performed on semi-dilute solutions of A₅ [...] Read more.

Although the behavior of the confined semi-dilute solutions of self-assembling copolymers represents an important topic of basic and applied research, it has eluded the interest of scientists. Extensive series of dissipative particle dynamics simulations have been performed on semi-dilute solutions of A₅B₅ chains in a selective solvent for A in slits using a DL-MESO simulation package. Simulations of corresponding bulk systems were performed for comparison. This study shows that the associates in the semi-dilute bulk solutions are partly structurally organized. Mild steric constraints in slits with non-attractive walls hardly affect the size of the associates, but they promote their structural arrangement in layers parallel to the slit walls. Attractive walls noticeably affect the association process. In slits with mildly attractive walls, the adsorption competes with the association process. At elevated concentrations, the associates start to form in wide slits when the walls are sparsely covered by separated associates, and the association process prevents the full coverage of the surface. In slits with strongly attractive walls, adsorption is the dominant behavior. The associates form in wide slits at elevated concentrations only after the walls are completely and continuously covered by the adsorbed chains. Full article

(This article belongs to the Special Issue Molecular Dynamics Simulation of Polymer for Absorption and Separation Applications)

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19 pages, 10734 KiB

Open AccessEditor’s ChoiceArticle

Novel Polyurethane-Based Systems Modified with Starch and Phase Change Materials for Bone Tissue Regeneration

by Klaudia Ordon, Piotr Szatkowski, Wojciech Piekarczyk, Elżbieta Pamuła and Kinga Pielichowska

Polymers 2023, 15(22), 4414; https://doi.org/10.3390/polym15224414 - 15 Nov 2023

Cited by 2 | Viewed by 1581

Abstract

Novel polyurethane-based materials have been synthesized by a two-step process using poly(ε–caprolactone) diol (PCL) and 1,3–propanediol/starch (PDO/ST) systems as chain extenders/cross-linkers and 1,6–hexamethylane diisocyante (HDI) as a potential material for bone tissue replacement or bone cements. A poly(ethylene glycol)/starch (PEG/ST) system has been [...] Read more.

Novel polyurethane-based materials have been synthesized by a two-step process using poly(ε–caprolactone) diol (PCL) and 1,3–propanediol/starch (PDO/ST) systems as chain extenders/cross-linkers and 1,6–hexamethylane diisocyante (HDI) as a potential material for bone tissue replacement or bone cements. A poly(ethylene glycol)/starch (PEG/ST) system has been applied as a form-stable phase change material (PCM) to decrease the maximum setting temperature, while hydroxyapatite (HAp) has been used as a bioactive nanofiller. FTIR and SEM-EDX analyses were performed to investigate the structure, surface morphology, and thermal properties of the obtained polyurethanes. FTIR spectroscopy confirmed the chemical structure of the synthesized polyurethanes. SEM-EDX analysis confirmed the incorporation of starch/hydroxyapatite into the polyurethane matrix. Modification with PCMs based on PEG or PEG/starch systems allowed for a decrease in the maximum setting temperature of PUs from 6 to 7.6 °C, depending on the type of PCM used. Thus, the obtained polyurethanes show a good energy storage effect and a good application potential for the synthesis of multifunctional bioactive materials for future use as bone cements. Full article

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12 pages, 2939 KiB

Open AccessEditor’s ChoiceArticle

Ring-Opening Polymerization of rac-β-Butyrolactone Promoted by New Tetradentate Thioether-Amide Ligand-Type Zinc Complexes

by Salvatore Impemba, Gabriele Manca, Irene Tozio and Stefano Milione

Polymers 2023, 15(22), 4366; https://doi.org/10.3390/polym15224366 - 9 Nov 2023

Cited by 4 | Viewed by 1500

Abstract

In this work, thioether-amide ligands featuring a combination of hard amide groups with soft donor groups have been employed to develop new zinc catalysts for the ring-opening polymerization of cyclic esters. All complexes were prepared in high yields through alkane elimination reactions with [...] Read more.

In this work, thioether-amide ligands featuring a combination of hard amide groups with soft donor groups have been employed to develop new zinc catalysts for the ring-opening polymerization of cyclic esters. All complexes were prepared in high yields through alkane elimination reactions with diethyl zinc and characterized using nuclear magnetic resonance (NMR) spectroscopy. Density functional theory (DFT) characterization provided insight into the parameters that influence catalytic activity, such as steric hindrance at the metal center, Lewis acidity and electronic density of thioether-amide ligands. In the presence of one equivalent of isopropanol, all complexes were active in the ring-opening polymerization of rac-β-butyrolactone. Quantitative conversion of 100 monomer equivalents was achieved within 1 h at 80 °C in a toluene solution. Number-average molecular weights increased linearly with monomer conversion; the values were in optimal agreement with those expected, and polydispersity index values were narrow and relatively constant throughout the course of polymerization. The most active complex was also effective in the ring-opening polymerization of ε-caprolactone and L-lactide. To propose a reliable reaction path, DFT calculations were undertaken. In the first step of the reaction, the acidic proton of the alcohol is transferred to the basic nitrogen atom of the amide ligand coordinated to the zinc ion. This leads to the alcoholysis of the Zn-N bond and the formation of an alcoholate derivative that starts the polymerization. In subsequent steps, the reaction follows the classical coordination–insertion mechanism. Full article

(This article belongs to the Special Issue Advances in Polymerization and Kinetic Studies)

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24 pages, 7503 KiB

Open AccessEditor’s ChoiceArticle

Mechanisms of Shock Dissipation in Semicrystalline Polyethylene

by John P. Mikhail and Gregory C. Rutledge

Polymers 2023, 15(21), 4262; https://doi.org/10.3390/polym15214262 - 30 Oct 2023

Cited by 1 | Viewed by 1585

Abstract

Semicrystalline polymers are lightweight, multiphase materials that exhibit attractive shock dissipation characteristics and have potential applications as protective armor for people and equipment. For shocks of 10 GPa or less, we analyzed various mechanisms for the storage and dissipation of shock wave energy [...] Read more.

Semicrystalline polymers are lightweight, multiphase materials that exhibit attractive shock dissipation characteristics and have potential applications as protective armor for people and equipment. For shocks of 10 GPa or less, we analyzed various mechanisms for the storage and dissipation of shock wave energy in a realistic, united atom (UA) model of semicrystalline polyethylene. Systems characterized by different levels of crystallinity were simulated using equilibrium molecular dynamics with a Hugoniostat to ensure that the resulting states conform to the Rankine–Hugoniot conditions. To determine the role of structural rearrangements, order parameters and configuration time series were collected during the course of the shock simulations. We conclude that the major mechanisms responsible for the storage and dissipation of shock energy in semicrystalline polyethylene are those associated with plastic deformation and melting of the crystalline domain. For this UA model, plastic deformation occurs primarily through fine crystallographic slip and the formation of kink bands, whose long period decreases with increasing shock pressure. Full article

(This article belongs to the Special Issue Modeling and Simulation of Polymer Composites)

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13 pages, 2657 KiB

Open AccessEditor’s ChoiceArticle

Synthesis and Structural Insight into poly(dimethylsiloxane)-b-poly(2-vinylpyridine) Copolymers

by Gkreti-Maria Manesi, Ioannis Moutsios, Dimitrios Moschovas, Georgios Papadopoulos, Christos Ntaras, Martin Rosenthal, Loic Vidal, Georgiy G. Ageev, Dimitri A. Ivanov and Apostolos Avgeropoulos

Polymers 2023, 15(21), 4227; https://doi.org/10.3390/polym15214227 - 25 Oct 2023

Viewed by 1959

Abstract

In this study, the use of anionic polymerization for the synthesis of living poly(dimethylsiloxane) or PDMS-Li⁺, as well as poly(2-vinylpyridine) or P2VP-Li⁺ homopolymers, and the subsequent use of chlorosilane chemistry in order for the two blocks to be covalently joined [...] Read more.

In this study, the use of anionic polymerization for the synthesis of living poly(dimethylsiloxane) or PDMS-Li⁺, as well as poly(2-vinylpyridine) or P2VP-Li⁺ homopolymers, and the subsequent use of chlorosilane chemistry in order for the two blocks to be covalently joined leading to PDMS-b-P2VP copolymers is proposed. High vacuum manipulations enabled the synthesis of well-defined materials with different molecular weights (

{\bar{Μ}}_{n}

, from 9.8 to 36.0 kg/mol) and volume fraction ratios (φ, from 0.15 to 0.67). The

{\bar{Μ}}_{n}

values, dispersity indices, and composition were determined through membrane/vapor pressure osmometry (MO/VPO), size exclusion chromatography (SEC), and proton nuclear magnetic resonance spectroscopy (¹H NMR), respectively, while the thermal transitions were determined via differential scanning calorimetry (DSC). The morphological characterization results suggested that for common composition ratios, lamellar, cylindrical, and spherical phases with domain periodicities ranging from approximately 15 to 39 nm are formed. A post-polymerization chemical modification reaction to quaternize the nitrogen atom in some of the P2VP monomeric units in the copolymer with the highest P2VP content, and the additional characterizations through ¹H NMR, infrared spectroscopy, DSC, and contact angle are reported. The synthesis, characterization, and quaternization of the copolymer structure are important findings toward the preparation of functional materials with enhanced properties suitable for various nanotechnology applications. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece: 2nd Edition)

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21 pages, 39738 KiB

Open AccessEditor’s ChoiceArticle

Biodegradability Assessment of Prickly Pear Waste–Polymer Fibers under Soil Composting

by Zormy Nacary Correa-Pacheco, Silvia Bautista-Baños, José Jesús Benítez-Jiménez, Pedro Ortega-Gudiño, Erick Omar Cisneros-López and Mónica Hernández-López

Polymers 2023, 15(20), 4164; https://doi.org/10.3390/polym15204164 - 20 Oct 2023

Cited by 4 | Viewed by 1790

Abstract

Nowadays, solving the problems associated with environmental pollution is of special interest. Therefore, in this work, the morphology and thermal and mechanical properties of extruded fibers based on polylactic acid (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) added to prickly pear flour (PPF) under composting [...] Read more.

Nowadays, solving the problems associated with environmental pollution is of special interest. Therefore, in this work, the morphology and thermal and mechanical properties of extruded fibers based on polylactic acid (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) added to prickly pear flour (PPF) under composting for 3 and 6 months were evaluated. The highest weight loss percentage (92 ± 7%) was obtained after 6-month degradation of the PLA/PBAT/PPF/CO/AA blend, in which PPF, canola oil (CO), and adipic acid (AA) were added. Optical and scanning electron microscopy (SEM) revealed structural changes in the fibers as composting time increased. The main changes in the absorption bands observed by Fourier transform infrared spectroscopy (FTIR) were related to the decrease in -C=O (1740 cm⁻¹) and -C-O (1100 cm⁻¹) groups and at 1269 cm⁻¹, associated with hemicellulose in the blends with PPF. Differential scanning calorimetry (DSC) showed an increase in the cold crystallization and melting point with degradation time, being more evident in the fibers with PPF, as well as a decrease in the mechanical properties, especially Young’s modulus. The obtained results suggest that PPF residues could promote the biodegradability of PLA/PBAT-based fiber composites. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Mexico)

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20 pages, 5610 KiB

Open AccessEditor’s ChoiceArticle

Atomic Force Microscopy of Hydrolysed Polyacrylamide Adsorption onto Calcium Carbonate

by Jin Hau Lew, Omar K. Matar, Erich A. Müller, Paul F. Luckham, Adrielle Sousa Santos and Maung Maung Myo Thant

Polymers 2023, 15(20), 4037; https://doi.org/10.3390/polym15204037 - 10 Oct 2023

Cited by 1 | Viewed by 1649

Abstract

In this work, the interaction of hydrolysed polyacrylamide (HPAM) of two molecular weights (F3330, 11–13 MDa; F3530, 15–17 MDa) with calcium carbonate (CaCO₃) was studied via atomic force microscopy (AFM). In the absence of polymers at 1.7 mM and 1 M [...] Read more.

In this work, the interaction of hydrolysed polyacrylamide (HPAM) of two molecular weights (F3330, 11–13 MDa; F3530, 15–17 MDa) with calcium carbonate (CaCO₃) was studied via atomic force microscopy (AFM). In the absence of polymers at 1.7 mM and 1 M NaCl, good agreement with DLVO theory was observed. At 1.7 mM NaCl, repulsive interaction during approach at approximately 20 nm and attractive adhesion of approximately 400 pN during retraction was measured, whilst, at 1 M NaCl, no repulsion during approach was found. Still, a significantly larger adhesion of approximately 1400 pN during retraction was observed. In the presence of polymers, results indicated that F3330 displayed higher average adhesion (450–625 pN) and interaction energy (43–145 aJ) with CaCO₃ than F3530’s average adhesion (85–88 pN) and interaction energy (8.4–11 aJ). On the other hand, F3530 exerted a longer steric repulsion distance (70–100 nm) than F3330 (30–70 nm). This was likely due to the lower molecular weight. F3330 adopted a flatter configuration on the calcite surface, creating more anchor points with the surface in the form of train segments. The adhesion and interaction energy of both HPAM with CaCO₃ can be decreased by increasing the salt concentration. At 3% NaCl, the average adhesion and interaction energy of F3330 was 72–120 pN and 5.6–17 aJ, respectively, while the average adhesion and interaction energy of F3530 was 11.4–48 pN and 0.3–2.98 aJ, respectively. The reduction of adhesion and interaction energy was likely due to the screening of the COO⁻ charged group of HPAM by salt cations, leading to a reduction of electrostatic attraction between the negatively charged HPAM and the positively charged CaCO₃. Full article

(This article belongs to the Special Issue Surfaces and Interfaces of Polymer Composites)

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17 pages, 4074 KiB

Open AccessEditor’s ChoiceArticle

PEDOT-Coated PLA Fibers Electrospun from Solutions Incorporating Fe(III)Tosylate in Different Solvents by Vapor-Phase Polymerization for Neural Regeneration

by Laura S. Pires, Diogo S. Melo, João P. Borges and Célia R. Henriques

Polymers 2023, 15(19), 4004; https://doi.org/10.3390/polym15194004 - 5 Oct 2023

Cited by 1 | Viewed by 1547

Abstract

Therapeutic solutions for injuries in the peripheral nervous system are limited and not existing in the case of the central nervous system. The electrical stimulation of cells through a cell-supporting conductive scaffold may contribute to new therapeutic solutions for nerve regeneration. In this [...] Read more.

Therapeutic solutions for injuries in the peripheral nervous system are limited and not existing in the case of the central nervous system. The electrical stimulation of cells through a cell-supporting conductive scaffold may contribute to new therapeutic solutions for nerve regeneration. In this work, biocompatible Polylactic acid (PLA) fibrous scaffolds incorporating Fe(III)Tosylate (FeTos) were produced by electrospinning a mixture of PLA/FeTos solutions towards a rotating cylinder, inducing fiber alignment. Fibers were coated with the conductive polymer Poly(3,4 ethylenedioxythiophene) (PEDOT) formed by vapor-phase polymerization of EDOT at 70 °C for 2 h. Different solvents (ETH, DMF and THF) were used as FeTos solvents to investigate the impact on the scaffold’s conductivity. Scaffold conductivity was estimated to be as high as 1.50 × 10⁻¹ S/cm when FeTos was dissolved in DMF. In vitro tests were performed to evaluate possible scaffold cytotoxicity, following ISO 10993-5, revealing no cytotoxic effects. Differentiation and growth of cells from the neural cell line SH-SY5Y seeded on the scaffolds were also assessed, with neuritic extensions observed in cells differentiated in neurons with retinoic acid. These extensions tended to follow the preferential alignment of the scaffold fibers. Full article

(This article belongs to the Special Issue Polymer Scaffold for Tissue Engineering Applications)

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23 pages, 4307 KiB

Open AccessEditor’s ChoiceArticle

Biodegradation of Choline NTF₂ by Pantoea agglomerans in Different Osmolarity. Characterization and Environmental Implications of the Produced Exopolysaccharide

by Abrusci Concepción, Amils Ricardo and Sánchez-León Enrique

Polymers 2023, 15(19), 3974; https://doi.org/10.3390/polym15193974 - 3 Oct 2023

Cited by 2 | Viewed by 1719

Abstract

A specific microorganism, Pantoea agglomerans uam8, was isolated from the ionic liquid (IL) Choline NTF₂ and identified by molecular biology. A biodegradation study was performed at osmolarity conditions (0.2, 0.6, 1.0 M). These had an important influence on the growth of the [...] Read more.

A specific microorganism, Pantoea agglomerans uam8, was isolated from the ionic liquid (IL) Choline NTF₂ and identified by molecular biology. A biodegradation study was performed at osmolarity conditions (0.2, 0.6, 1.0 M). These had an important influence on the growth of the strain, exopolysaccharide (EPS) production, and biodegradation (1303 mg/L max production and 80% biodegradation at 0.6 M). These conditions also had an important influence on the morphology of the strain and its EPSs, but not in the chemical composition. The EPS (glucose, mannose and galactose (6:0.5:2)) produced at 0.6 M was further characterized using different techniques. The obtained EPSs presented important differences in the behavior of the emulsifying activity for vegetable oils (olive (86%), sunflower (56%) and coconut (90%)) and hydrocarbons (diesel (62%), hexane (60%)), and were compared with commercial emulsifiers. The EPS produced at 0.6 M had the highest emulsifying activity overall. This EPS did not show cytotoxicity against the tested cell line (<20%) and presented great advantages as an antioxidant (1,1-diphenyl-2-picryl-hydrazyl radical (DPPH) (85%), hydroxyl radical (OH) (99%), superoxide anion (O₂⁻) (94%), chelator (54%), and antimicrobial product (15 mm). The osmolarity conditions directly affected the capacity of the strain to biodegrade IL and the subsequently produced EPS. Furthermore, the EPS produced at 0.6 M has potential for environmental applications, such as the removal of hazardous materials by emulsification, whilst resulting in positive health effects such as antioxidant activity and non-toxicity. Full article

(This article belongs to the Special Issue Microbial Biopolymers: Trends in Synthesis, Modification, and Applications (2nd Edition))

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76 pages, 7024 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Recent Advancements and Strategies for Overcoming the Blood–Brain Barrier Using Albumin-Based Drug Delivery Systems to Treat Brain Cancer, with a Focus on Glioblastoma

by Camelia-Elena Tincu (Iurciuc), Călin Vasile Andrițoiu, Marcel Popa and Lăcrămioara Ochiuz

Polymers 2023, 15(19), 3969; https://doi.org/10.3390/polym15193969 - 2 Oct 2023

Cited by 7 | Viewed by 4941

Abstract

Glioblastoma multiforme (GBM) is a highly aggressive malignant tumor, and the most prevalent primary malignant tumor affecting the brain and central nervous system. Recent research indicates that the genetic profile of GBM makes it resistant to drugs and radiation. However, the main obstacle [...] Read more.

Glioblastoma multiforme (GBM) is a highly aggressive malignant tumor, and the most prevalent primary malignant tumor affecting the brain and central nervous system. Recent research indicates that the genetic profile of GBM makes it resistant to drugs and radiation. However, the main obstacle in treating GBM is transporting drugs through the blood–brain barrier (BBB). Albumin is a versatile biomaterial for the synthesis of nanoparticles. The efficiency of albumin-based delivery systems is determined by their ability to improve tumor targeting and accumulation. In this review, we will discuss the prevalence of human glioblastoma and the currently adopted treatment, as well as the structure and some essential functions of the BBB, to transport drugs through this barrier. We will also mention some aspects related to the blood–tumor brain barrier (BTBB) that lead to poor treatment efficacy. The properties and structure of serum albumin were highlighted, such as its role in targeting brain tumors, as well as the progress made until now regarding the techniques for obtaining albumin nanoparticles and their functionalization, in order to overcome the BBB and treat cancer, especially human glioblastoma. The albumin drug delivery nanosystems mentioned in this paper have improved properties and can overcome the BBB to target brain tumors. Full article

(This article belongs to the Special Issue Polymeric Drug Delivery Systems: Design, Synthesis and Applications)

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15 pages, 5806 KiB

Open AccessEditor’s ChoiceArticle

Suitability of Mycelium-Reinforced Nanofiber Mats for Filtration of Different Dyes

by Angela Heide, Philip Wiebe, Lilia Sabantina and Andrea Ehrmann

Polymers 2023, 15(19), 3951; https://doi.org/10.3390/polym15193951 - 29 Sep 2023

Cited by 3 | Viewed by 1911

Abstract

Electrospun nanofiber mats have a high specific surface area and very small pores which can be tailored by the spinning process. They are thus highly suitable as filters for small particles and molecules, such as organic dyes. On the other hand, they are [...] Read more.

Electrospun nanofiber mats have a high specific surface area and very small pores which can be tailored by the spinning process. They are thus highly suitable as filters for small particles and molecules, such as organic dyes. On the other hand, they are usually very thin and thus have low mechanical properties. As a potential reinforcement, mycelium of Pleurotus ostreatus was grown on poly(acrylonitrile) nanofiber mats and thermally solidified after fully covering the nanofiber mats. This study investigates whether the filtration efficiency of the nanofiber mats is altered by the mycelium growing through it and whether the mechanical properties of the nanofibrous filters can be improved in this way. The study shows fast and reliable growth of the mycelium on the nanofiber mats and high filtration efficiency for astra blue and chlorophyll, while indigo carmine showed only very low filtration efficiency of up to 20%. For chlorophyll and safranin, membranes with mycelium showed higher filtration than pure nanofiber mats. In diffusion cell tests, especially astra blue was strongly adsorbed on the membranes with mycelium. Full article

(This article belongs to the Special Issue New Advances in Polymer Electrospun Fibers)

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12 pages, 6919 KiB

Open AccessEditor’s ChoiceArticle

Morphological Evolution of Hybrid Block Copolymer Particles: Toward Magnetic Responsive Particles

by Jaeman J. Shin

Polymers 2023, 15(18), 3689; https://doi.org/10.3390/polym15183689 - 7 Sep 2023

Viewed by 1428

Abstract

The co-assembly of block copolymers (BCPs) and inorganic nanoparticles (NPs) under emulsion confinement allows facile access to hybrid polymeric colloids with controlled hierarchical structures. Here, the effect of inorganic NPs on the structure of the hybrid BCP particles and the local distribution of [...] Read more.

The co-assembly of block copolymers (BCPs) and inorganic nanoparticles (NPs) under emulsion confinement allows facile access to hybrid polymeric colloids with controlled hierarchical structures. Here, the effect of inorganic NPs on the structure of the hybrid BCP particles and the local distribution of NPs are studied, with a particular focus on comparing Au and Fe₃O₄ NPs. To focus on the effect of the NP core, Au and Fe₃O₄ NPs stabilized with oleyl ligands were synthesized, having a comparable diameter and grafting density. The confined co-assembly of symmetric polystyrene-b-poly(1,4-butadiene) (PS-b-PB) BCPs and NPs in evaporative emulsions resulted in particles with various morphologies including striped ellipsoids, onion-like particles, and their intermediates. The major difference in PS-b-PB/Au and PS-b-PB/Fe₃O₄ particles was found in the distribution of NPs inside the particles that affected the overall particle morphology. Au NPs were selectively localized inside PB domains with random distributions regardless of the particle morphology. Above the critical volume fraction, however, Au NPs induced the morphological transition of onion-like particles into ellipsoids by acting as an NP surfactant. For PS-b-PB/Fe₃O₄ ellipsoids, Fe₃O₄ NPs clustered and segregated to the particle/surrounding interface of the ellipsoids even at a low volume fraction, while Fe₃O₄ NPs were selectively localized in the middle of PB domains in a string-like pattern for PS-b-PB/Fe₃O₄ onion-like particles. Full article

(This article belongs to the Special Issue Block Copolymers: Synthesis, Self-Assembly, and Biomedical Applications)

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20 pages, 6948 KiB

Open AccessEditor’s ChoiceArticle

An Investigation of the Healing Efficiency of Epoxy Vitrimer Composites Based on Zn²⁺ Catalyst

by Barbara Palmieri, Fabrizia Cilento, Eugenio Amendola, Teodoro Valente, Stefania Dello Iacono, Michele Giordano and Alfonso Martone

Polymers 2023, 15(17), 3611; https://doi.org/10.3390/polym15173611 - 31 Aug 2023

Cited by 8 | Viewed by 2241

Abstract

The need to recycle carbon-fibre-reinforced composite polymers (CFRP) has grown significantly to reduce the environmental impact generated by their production. To meet this need, thermoreversible epoxy matrices have been developed in recent years. This study investigates the performance of an epoxy vitrimer made [...] Read more.

The need to recycle carbon-fibre-reinforced composite polymers (CFRP) has grown significantly to reduce the environmental impact generated by their production. To meet this need, thermoreversible epoxy matrices have been developed in recent years. This study investigates the performance of an epoxy vitrimer made by introducing a metal catalyst (Zn²⁺) and its carbon fibre composites, focusing on the healing capability of the system. The dynamic crosslinking networks endow vitrimers with interesting rheological behaviour; the capability of the formulated resin (AV-5) has been assessed by creep tests. The analysis showed increased molecular mobility above a topology freezing temperature (T_v). However, the reinforcement phase inhibits the flow capability, reducing the flow. The fracture behaviour of CFRP made with the vitrimeric resin has been investigated by Mode I and Mode II tests and compared with the conventional system. The repairability of the vitrimeric CFRP has been investigated by attempting to recover the delaminated samples, which yielded unsatisfactory results. Moreover, the healing efficiency of the modified epoxy composites has been assessed using the vitrimer as an adhesive layer. The joints were able to recover about 84% of the lap shear strength of the pristine system. Full article

(This article belongs to the Special Issue Advances in Self-Healing Polymer Composites)

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13 pages, 2682 KiB

Open AccessEditor’s ChoiceArticle

Comparative Study of the Preparation of High-Molecular-Weight Fibroin by Degumming Silk with Several Neutral Proteases

by Xueping Liu, Qian Huang, Peng Pan, Mengqi Fang, Yadong Zhang, Shanlong Yang, Mingzhong Li and Yu Liu

Polymers 2023, 15(16), 3383; https://doi.org/10.3390/polym15163383 - 12 Aug 2023

Cited by 11 | Viewed by 1984

Abstract

Removing sericin from the periphery of silk without damage to silk fibroin (SF) to obtain high-molecular-weight SF is a major challenge in the field of SF-based biomaterials. In this study, four neutral proteases, subtilisin, trypsin, bromelain and papain, were used to degum silk, [...] Read more.

Removing sericin from the periphery of silk without damage to silk fibroin (SF) to obtain high-molecular-weight SF is a major challenge in the field of SF-based biomaterials. In this study, four neutral proteases, subtilisin, trypsin, bromelain and papain, were used to degum silk, and the degumming efficiency of the proteases and their influence on the molecular weight (MW) of regenerated silk fibroin were studied. The results indicated that all four neutral proteases could remove sericin from silk almost completely, and they caused less damage to SF fibers than Na₂CO₃ degumming did. The degumming efficiency of trypsin and papain was strong, but they caused relatively high damage to SF, whereas bromelain caused the least damage. The results of sodium dodecyl sulfate–polyacrylamide gel electrophoresis, gel permeation chromatography and shear viscosity showed that the MWs of regenerated SF derived from neutral protease degumming were significantly higher than that of SF derived from Na₂CO₃ degumming. The MW of regenerated SF derived from bromelain degumming was the highest, while the MWs of regenerated SF derived from papain and trypsin degumming were relatively low. This study provides an efficient and environmentally friendly biological degumming method for obtaining high-molecular-weight silk fibroin. Full article

(This article belongs to the Special Issue Biobased and Natural Polymers II)

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14 pages, 4712 KiB

Open AccessEditor’s ChoiceArticle

Molecular Dynamics Simulation of Polymer Nanocomposites with Supramolecular Network Constructed via Functionalized Polymer End-Grafted Nanoparticles

by Guanyi Hou, Runhan Ren, Wei Shang, Yunxuan Weng and Jun Liu

Polymers 2023, 15(15), 3259; https://doi.org/10.3390/polym15153259 - 31 Jul 2023

Cited by 3 | Viewed by 2039

Abstract

Since the proposal of self-healing materials, numerous researchers have focused on exploring their potential applications in flexible sensors, bionic robots, satellites, etc. However, there have been few studies on the relationship between the morphology of the dynamic crosslink network and the comprehensive properties [...] Read more.

Since the proposal of self-healing materials, numerous researchers have focused on exploring their potential applications in flexible sensors, bionic robots, satellites, etc. However, there have been few studies on the relationship between the morphology of the dynamic crosslink network and the comprehensive properties of self-healing polymer nanocomposites (PNCs). In this study, we designed a series of modified nanoparticles with different sphericity (η) to establish a supramolecular network, which provide the self-healing ability to PNCs. We analyzed the relationship between the morphology of the supramolecular network and the mechanical performance and self-healing behavior. We observed that as η increased, the distribution of the supramolecular network became more uniform in most cases. Examination of the segment dynamics of polymer chains showed that the completeness of the supramolecular network significantly hindered the mobility of polymer matrix chains. The mechanical performance and self-healing behavior of the PNCs showed that the supramolecular network mainly contributed to the mechanical performance, while the self-healing efficiency was dominated by the variation of η. We observed that appropriate grafting density is the proper way to effectively enhance the mechanical and self-healing performance of PNCs. This study provides a unique guideline for designing and fabricating self-healing PNCs with modified Nanoparticles (NPs). Full article

(This article belongs to the Special Issue Molecular Dynamics Simulation of Polymeric Materials)

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17 pages, 6666 KiB

Open AccessEditor’s ChoiceArticle

Enhancement of the Mechanical Performance of Glass-Fibre-Reinforced Composites through the Infusion Process of a Thermoplastic Recyclable Resin

by Raffaele Ciardiello, Dario Fiumarella and Giovanni Belingardi

Polymers 2023, 15(15), 3160; https://doi.org/10.3390/polym15153160 - 25 Jul 2023

Cited by 6 | Viewed by 2034

Abstract

Mechanical testing of glass-fibre-reinforced composite (GFRP) plates made of twill fabric and a thermoplastic recyclable infusion resin is presented. The considered thermoplastic resin, ELIUM^®, is made of poly-methylmethacrylate and can be infused with properly tuned vacuum techniques, in the same manner [...] Read more.

Mechanical testing of glass-fibre-reinforced composite (GFRP) plates made of twill fabric and a thermoplastic recyclable infusion resin is presented. The considered thermoplastic resin, ELIUM^®, is made of poly-methylmethacrylate and can be infused with properly tuned vacuum techniques, in the same manner as all liquid resin. Tensile, flexural, and drop-dart impact tests were carried out to assess the mechanical properties of the composites considering different fabrication conditions, such as the different degassing pressure before infusion and three different infusion vacuum pressures. The work reports a methodology to infuse ELIUM resin at a relatively high vacuum pressure of 0.8 bar. X-ray microtomography analysis showed that the produced laminates are free of defects, differently from what was reported in the literature, where void problems related to a vacuum infusion pressure higher than 0.3–0.5 bar were pointed out. Vacuum pressure values influence the mechanical characteristics of the laminate: when higher vacuum pressures are adopted, the mechanical properties of the GFRP laminates are enhanced and higher values of elastic modulus and strength are obtained. On the other hand, degassing the resin before infusion does not influence the mechanical properties of the laminates. A maximum bending and tensile strength of 420 and 305 MPa were reached by using the vacuum infusion of 0.8 bar with an elastic modulus of 18.5 and 20.6 GPa, respectively. The density of the produced laminates increases at higher vacuum infusion pressure up to a maximum value of 1.81 g/cm³ with the fibre volume fraction of each laminate. Full article

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

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15 pages, 4597 KiB

Open AccessEditor’s ChoiceArticle

A Novel UV Barrier Poly(lactic acid)/Poly(butylene succinate) Composite Biodegradable Film Enhanced by Cellulose Extracted from Coconut Shell

by Xiaoyan He, Lisheng Tang, Jun Zheng, Yuanyuan Jin, Ruobin Chang, Xiaoquan Yu, Yihu Song and Ran Huang

Polymers 2023, 15(14), 3000; https://doi.org/10.3390/polym15143000 - 10 Jul 2023

Cited by 3 | Viewed by 2114

Abstract

Cellulose was extracted from coconut shell powder (CSP) as a renewable biomass resource and utilized as a reinforcing material in poly(lactic acid)/poly(butylene succinate) (PLA/PBS) solvent casting films. The extraction process involved delignification and mercerization of CSP. Microscopic investigation of the extracted microfibers demonstrated [...] Read more.

Cellulose was extracted from coconut shell powder (CSP) as a renewable biomass resource and utilized as a reinforcing material in poly(lactic acid)/poly(butylene succinate) (PLA/PBS) solvent casting films. The extraction process involved delignification and mercerization of CSP. Microscopic investigation of the extracted microfibers demonstrated a reduction in diameter and a rougher surface characteristic compared to the raw CSP. The cellulose prepared in this study exhibited improved thermal stability and higher crystallinity (54.3%) compared to CSP. The morphology of the cycrofractured surface, thermal analysis, mechanical property, and UV transmittance of films were measured and compared. Agglomeration of 3 wt.% of cellulose was observed in PLA/PBS films. The presence of cellulose higher than 1 wt.% in the PLA/PBS decreased the onset decomposition temperature and maximum decomposition temperature of films. However, the films loading 3 wt.% of cellulose had a higher char formation (5.47%) compared to neat PLA/PBS films. The presence of cellulose promoted the formation of non-uniform crystals, while cellulose had a slightly negative impact on crystallinity due to the disruption of polymer chains at lower cellulose content (0.3, 0.5 wt.%). The mechanical strength of PLA/PBS films decreased as the cellulose content increased. Moreover, PLA/PBS film with 3 wt.% of cellulose appeared to show a 3% and 7.5% decrease in transmittance in UVC (275 nm) and UVA (335 nm) regions compared to neat PLA/PBS films while maintaining a certain transparency. Full article

(This article belongs to the Special Issue Biopolymer-Based Micro/Nanoparticles: Fabrication, Characterization and Applications)

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18 pages, 11808 KiB

Open AccessEditor’s ChoiceArticle

Electrically and Thermally Triggered Three-Dimensional Graphene-Foam-Reinforced Shape Memory Epoxy Composites

by Adeyinka Idowu, Tony Thomas, Jenniffer Bustillos, Benjamin Boesl and Arvind Agarwal

Polymers 2023, 15(13), 2903; https://doi.org/10.3390/polym15132903 - 30 Jun 2023

Cited by 5 | Viewed by 1837

Abstract

Shape memory polymer (SMP) epoxy composites have attracted significant attention due to their easy processing, lightweight nature, and ability to recover strain. However, their limited recovery rate and inferior mechanical properties have hindered their functional applications. This research explores the potential of three-dimensional [...] Read more.

Shape memory polymer (SMP) epoxy composites have attracted significant attention due to their easy processing, lightweight nature, and ability to recover strain. However, their limited recovery rate and inferior mechanical properties have hindered their functional applications. This research explores the potential of three-dimensional (3D) graphene foam (GrF) as a highly efficient reinforcement for SMP epoxy composites. We demonstrated that the incorporation of a mere 0.13 wt.% GrF into mold-cast SMP epoxy leads to a 19% increase in the glass transition temperature (T_g). To elucidate the reinforcing mechanism, we fabricated and extensively analyzed composites with varying weight percentages of GrF. The GrF-based SMP epoxy composite exhibits a 57% increase in thermal conductivity, measuring 0.296 W mK⁻¹ at 70 °C, due to the interconnected 3D graphene network within the matrix. Notably, this composite also demonstrates remarkable electrical conductivity, making it suitable for dual-triggering applications. The GrF-SMP epoxy composite achieves a maximum shape recovery ratio and a significant 23% improvement in the recovery rate, effectively addressing the issue of slow recovery associated with SMPs. We investigated the effect of switching temperatures on the shape recovery rate. We identified the optimal triggering temperature to initiate shape recovery for epoxy SMP and GrF-epoxy SMP as thermal energy equivalent to T_g + 20 °C. Additionally, we fabricated a bird-shaped composite using GrF reinforcement, which showcases self-healing capabilities through the crack opening and closure and serves as a tangible demonstration of the transformative potential of the composite. These GrF-epoxy SMP composites, responsive to stimuli, hold immense promise for diverse applications, such as mechanical systems, wearable sensors, morphing wings, foldable robots, and antennas. Full article

(This article belongs to the Special Issue Advanced Polymers and Composites: New Functionalities and Sustainability)

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13 pages, 5198 KiB

Open AccessEditor’s ChoiceArticle

Eco-Friendly Epoxy-Terminated Polyurethane-Modified Epoxy Resin with Efficient Enhancement in Toughness

by Kun Zhang, Jinrui Huang, Yigang Wang, Wenbin Li and Xiaoan Nie

Polymers 2023, 15(13), 2803; https://doi.org/10.3390/polym15132803 - 24 Jun 2023

Cited by 15 | Viewed by 3083

Abstract

Polyurethane is widely used to toughen epoxy resins due to its excellent comprehensive properties and compatibility. However, some demerits of polyurethanes limit their applications, such as the harsh storage condition of isocyanate-terminated polyurethane (ITPU), the limited amount of ITPU in epoxy resin, and [...] Read more.

Polyurethane is widely used to toughen epoxy resins due to its excellent comprehensive properties and compatibility. However, some demerits of polyurethanes limit their applications, such as the harsh storage condition of isocyanate-terminated polyurethane (ITPU), the limited amount of ITPU in epoxy resin, and using solvents during the preparation of polyurethane-modified epoxy resins. To address these issues, in this study, we reported a facile and green approach for preparing epoxy-terminated polyurethane (EPU)-modified epoxy resins with different EPU contents. It was found that the toughness of the epoxy resin was significantly improved after the addition of EPU. When the EPU content was 30 wt%, the elongation at break and toughness were improved by 358.36% and 73.56%, respectively. In comparison, the toughening effect of EPU outperformed that of ITPU. Moreover, the high content of EPU did not significantly decrease the glass transition temperature and had little effect on the thermal stability of the epoxy resin. Full article

(This article belongs to the Special Issue Development in Thermosetting Polymers)

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16 pages, 3437 KiB

Open AccessEditor’s ChoiceArticle

Nucleophilic Aromatic Substitution of Pentafluorophenyl-Substituted Quinoline with a Functional Perylene: A Route to the Modification of Semiconducting Polymers

by Stefania Aivali, Konstantinos C. Andrikopoulos and Aikaterini K. Andreopoulou

Polymers 2023, 15(12), 2721; https://doi.org/10.3390/polym15122721 - 18 Jun 2023

Cited by 1 | Viewed by 1812

Abstract

A systematic study of the influence of the chemical substitution pattern of semiconducting polymers carrying side chain perylene diimide (PDI) groups is presented. Semiconducting polymers based on perflurophenyl quinoline (5FQ) were modified via a readily accessible nucleophilic substitution reaction. The perfluorophenyl group was [...] Read more.

A systematic study of the influence of the chemical substitution pattern of semiconducting polymers carrying side chain perylene diimide (PDI) groups is presented. Semiconducting polymers based on perflurophenyl quinoline (5FQ) were modified via a readily accessible nucleophilic substitution reaction. The perfluorophenyl group was studied as an electron-withdrawing reactive functionality on semiconducting polymers that can undergo fast nucleophilic aromatic substitution. A PDI molecule, functionalized with one phenol group on the bay area, was used for the substitution of the fluorine atom at the para position in 6-vinylphenyl-(2-perfluorophenyl)-4-phenyl quinoline. The final product was polymerized under free radical polymerization providing polymers of 5FQ incorporated with PDI side groups. Alternatively, the post-polymerization modification of the fluorine atoms at the para position of the 5FQ homopolymer with the PhOH-di-EH-PDI was also successfully tested. In this case, the PDI units were partially introduced to the perflurophenyl quinoline moieties of the homopolymer. The para-fluoro aromatic nucleophilic substitution reaction was confirmed and estimated via ¹H and ¹⁹F NMR spectroscopies. The two different polymer architectures, namely, fully or partially modified with PDI units, were studied in terms of their optical and electrochemical properties, while their morphology was evaluated using TEM analysis, revealing polymers of tailor-made optoelectronic and morphological properties. This work provides a novel molecule-designing method for semiconducting materials of controlled properties. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Greece: 2nd Edition)

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19 pages, 2585 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of the Interface Strength in the Abaca-Fiber-Reinforced Bio-Polyethylene Composites

by Faust Seculi, Francesc X. Espinach, Fernando Julián, Marc Delgado-Aguilar, Pere Mutjé and Quim Tarrés

Polymers 2023, 15(12), 2686; https://doi.org/10.3390/polym15122686 - 15 Jun 2023

Cited by 4 | Viewed by 2347

Abstract

Bio-based polymers, with any of their constituents based on nonrenewable sources, can answer the demands of society and regulations regarding minimizing the environmental impact. The more similar such biocomposites are to oil-based composites, the easier the transition, especially for companies that do not [...] Read more.

Bio-based polymers, with any of their constituents based on nonrenewable sources, can answer the demands of society and regulations regarding minimizing the environmental impact. The more similar such biocomposites are to oil-based composites, the easier the transition, especially for companies that do not like the uncertainty. A BioPE matrix, with a structure similar to that of a high-density polyethylene (HDPE), was used to obtain abaca-fiber-reinforced composites. The tensile properties of these composites are displayed and compared with commercial glass-fiber-reinforced HDPE. Since the strength of the interface between the reinforcements and the matrix is responsible for the exploitation of the strengthening abilities of the reinforcements, several micromechanical models were used to obtain an estimation of the strength of the interface and the intrinsic tensile strength of the reinforcements. Biocomposites require the use of a coupling agent to strengthen their interface, and once an 8 wt.% of such coupling agent was added to the composites, these materials returned tensile properties in line with commercial glass-fiber-reinforced HDPE composites. Full article

(This article belongs to the Topic Polymers from Renewable Resources, 2nd Volume)

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15 pages, 6051 KiB

Open AccessEditor’s ChoiceArticle

Hybrid Device Fabrication Using Roll-to-Roll Printing for Personal Environmental Monitoring

by Thanh Huy Phung, Anton Nailevich Gafurov, Inyoung Kim, Sung Yong Kim, Kyoung Min Kim and Taik-Min Lee

Polymers 2023, 15(12), 2687; https://doi.org/10.3390/polym15122687 - 15 Jun 2023

Cited by 5 | Viewed by 2250

Abstract

Roll-to-roll (R2R) printing methods are well known as additive, cost-effective, and ecologically friendly mass-production methods for processing functional materials and fabricating devices. However, implementing R2R printing to fabricate sophisticated devices is challenging because of the efficiency of material processing, the alignment, and the [...] Read more.

Roll-to-roll (R2R) printing methods are well known as additive, cost-effective, and ecologically friendly mass-production methods for processing functional materials and fabricating devices. However, implementing R2R printing to fabricate sophisticated devices is challenging because of the efficiency of material processing, the alignment, and the vulnerability of the polymeric substrate during printing. Therefore, this study proposes the fabrication process of a hybrid device to solve the problems. The device was created so that four layers, composed of polymer insulating layers and conductive circuit layers, are entirely screen-printed layer by layer onto a roll of polyethylene terephthalate (PET) film to produce the circuit. Registration control methods were presented to deal with the PET substrate during printing, and then solid-state components and sensors were assembled and soldered to the printed circuits of the completed devices. In this way, the quality of the devices could be ensured, and the devices could be massively used for specific purposes. Specifically, a hybrid device for personal environmental monitoring was fabricated in this study. The importance of environmental challenges to human welfare and sustainable development is growing. As a result, environmental monitoring is essential to protect public health and serve as a basis for policymaking. In addition to the fabrication of the monitoring devices, a whole monitoring system was also developed to collect and process the data. Here, the monitored data from the fabricated device were personally collected via a mobile phone and uploaded to a cloud server for additional processing. The information could then be utilized for local or global monitoring purposes, moving one step toward creating tools for big data analysis and forecasting. The successful deployment of this system could be a foundation for creating and developing systems for other prospective uses. Full article

(This article belongs to the Special Issue Polymers in Roll to Roll Processes)

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13 pages, 1682 KiB

Open AccessEditor’s ChoiceArticle

Multi-Armed Star-Shaped Block Copolymers of Poly(ethylene glycol)-Poly(furfuryl glycidol) as Long Circulating Nanocarriers

by Yasuhiro Nakagawa, Kotaro Ushidome, Keita Masuda, Kazunori Igarashi, Yu Matsumoto, Tatsuya Yamasoba, Yasutaka Anraku, Madoka Takai and Horacio Cabral

Polymers 2023, 15(12), 2626; https://doi.org/10.3390/polym15122626 - 9 Jun 2023

Cited by 3 | Viewed by 2101

Abstract

Multi-arm star-shaped block copolymers with precisely tuned nano-architectures are promising candidates for drug delivery. Herein, we developed 4- and 6-arm star-shaped block copolymers consisting of poly(furfuryl glycidol) (PFG) as the core-forming segments and biocompatible poly(ethylene glycol) (PEG) as the shell-forming blocks. The polymerization [...] Read more.

Multi-arm star-shaped block copolymers with precisely tuned nano-architectures are promising candidates for drug delivery. Herein, we developed 4- and 6-arm star-shaped block copolymers consisting of poly(furfuryl glycidol) (PFG) as the core-forming segments and biocompatible poly(ethylene glycol) (PEG) as the shell-forming blocks. The polymerization degree of each block was controlled by adjusting the feeding ratio of a furfuryl glycidyl ether and ethylene oxide. The size of the series of block copolymers was found to be less than 10 nm in DMF. In water, the polymers showed sizes larger than 20 nm, which can be related to the association of the polymers. The star-shaped block copolymers effectively loaded maleimide-bearing model drugs in their core-forming segment with the Diels–Alder reaction. These drugs were rapidly released upon heating via a retro Diels–Alder step. When the star-shaped block copolymers were injected intravenously in mice, they showed prolonged blood circulation, with more than 80% of the injected dose remaining in the bloodstream at 6 h after intravenous injection. These results indicate the potential of the star-shaped PFG-PEG block copolymers as long-circulating nanocarriers. Full article

(This article belongs to the Special Issue Bioactivated Polymers for Nanomedicine)

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13 pages, 4655 KiB

Open AccessEditor’s ChoiceArticle

3D-Printed PLA Scaffold with Fibronectin Enhances In Vitro Osteogenesis

by Eisner Salamanca, Cheuk Sing Choy, Lwin Moe Aung, Ting-Chia Tsao, Pin-Han Wang, Wei-An Lin, Yi-Fan Wu and Wei-Jen Chang

Polymers 2023, 15(12), 2619; https://doi.org/10.3390/polym15122619 - 8 Jun 2023

Cited by 2 | Viewed by 2353

Abstract

Background: Tricalcium phosphate (TCP, Molecular formula: Ca₃(PO₄)₂) is a hydrophilic bone graft biomaterial extensively used for guided bone regeneration (GBR). However, few studies have investigated 3D-printed polylactic acid (PLA) combined with the osteo-inductive molecule fibronectin (FN) for [...] Read more.

Background: Tricalcium phosphate (TCP, Molecular formula: Ca₃(PO₄)₂) is a hydrophilic bone graft biomaterial extensively used for guided bone regeneration (GBR). However, few studies have investigated 3D-printed polylactic acid (PLA) combined with the osteo-inductive molecule fibronectin (FN) for enhanced osteoblast performance in vitro, and specialized bone defect treatments. Aim: This study evaluated PLA properties and efficacy following glow discharge plasma (GDP) treatment and FN sputtering for fused deposition modeling (FDM) 3D printed PLA alloplastic bone grafts. Methods: 3D trabecular bone scaffolds (8 × 1 mm) were printed by the 3D printer (XYZ printing, Inc. 3D printer da Vinci Jr. 1.0 3-in-1). After printing PLA scaffolds, additional groups for FN grafting were continually prepared with GDP treatment. Material characterization and biocompatibility evaluations were investigated at 1, 3 and 5 days. Results: SEM images showed the human bone mimicking patterns, and EDS illustrated the increased C and O after fibronectin grafting, XPS and FTIR results together confirmed the presence of FN within PLA material. Degradation increased after 150 days due to FN presence. 3D immunofluorescence at 24 h demonstrated better cell spreading, and MTT assay results showed the highest proliferation with PLA and FN (p < 0.001). Cells cultured on the materials exhibited similar alkaline phosphatase (ALP) production. Relative quantitative polymerase chain reaction (qPCR) at 1 and 5 days revealed a mixed osteoblast gene expression pattern. Conclusion: In vitro observations over a period of five days, it was clear that PLA/FN 3D-printed alloplastic bone graft was more favorable for osteogenesis than PLA alone, thereby demonstrating great potential for applications in customized bone regeneration. Full article

(This article belongs to the Special Issue Advances in Functional Polymer Coatings: Preparation and Application)

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21 pages, 7944 KiB

Open AccessEditor’s ChoiceArticle

Novel SMD Component and Module Interconnection and Encapsulation Technique for Textile Substrates Using 3D Printed Polymer Materials

by David Kalaš, Radek Soukup, Jan Řeboun, Michaela Radouchová, Pavel Rous and Aleš Hamáček

Polymers 2023, 15(11), 2526; https://doi.org/10.3390/polym15112526 - 30 May 2023

Cited by 3 | Viewed by 2989

Abstract

Nowadays, a range of sensors and actuators can be realized directly in the structure of textile substrates using metal-plated yarns, metal-filament yarns, or functionalized yarns with nanomaterials, such as nanowires, nanoparticles, or carbon materials. However, the evaluation or control circuits still depend upon [...] Read more.

Nowadays, a range of sensors and actuators can be realized directly in the structure of textile substrates using metal-plated yarns, metal-filament yarns, or functionalized yarns with nanomaterials, such as nanowires, nanoparticles, or carbon materials. However, the evaluation or control circuits still depend upon the use of semiconductor components or integrated circuits, which cannot be currently implemented directly into the textiles or substituted by functionalized yarns. This study is focused on a novel thermo-compression interconnection technique intended for the realization of the electrical interconnection of SMD components or modules with textile substrates and their encapsulation in one single production step using commonly widespread cost-effective devices, such as 3D printers and heat-press machines, intended for textile applications. The realized specimens are characterized by low resistance (median 21 mΩ), linear voltage–current characteristics, and fluid-resistant encapsulation. The contact area is comprehensively analyzed and compared with the theoretical Holm’s model. Full article

(This article belongs to the Special Issue Smart Textiles: Synthesis, Characterization and Application)

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12 pages, 2756 KiB

Open AccessEditor’s ChoiceArticle

Roll-Out Deployment Process Analysis of a Fiber Reinforced Polymer (FRP) Composite Tape-Spring Boom

by Sicong Wang, Shuhong Xu, Lei Lu and Lining Sun

Polymers 2023, 15(11), 2455; https://doi.org/10.3390/polym15112455 - 25 May 2023

Cited by 4 | Viewed by 2000

Abstract

Deployable extendable booms are widely used in aerospace technology due to many advantages they have, such as high folded-ratio, lightweight and self-deployable properties. A bistable FRP composite boom can not only extend its tip outwards with a corresponding rotation speed on the hub, [...] Read more.

Deployable extendable booms are widely used in aerospace technology due to many advantages they have, such as high folded-ratio, lightweight and self-deployable properties. A bistable FRP composite boom can not only extend its tip outwards with a corresponding rotation speed on the hub, but can also drive the hub rolling outwards with a fixed boom tip, which is commonly called roll-out deployment. In a bistable boom’s roll-out deployment process, the second stability can keep the coiled section from chaos without introducing a controlling mechanism. Because of this, the boom’s roll-out deployment velocity is not under control, and a high moving speed at the end will give the structure a big impact. Therefore, predicting the velocity in this whole deployment process is necessary to be researched. This paper aims to analyze the roll-out deployment process of a bistable FRP composite tape-spring boom. First, based on the Classical Laminate Theory, a dynamic analytical model of a bistable boom is established through the energy method. Afterwards, an experiment is introduced to produce some practical verification for comparison with the analytical results. According to the comparison with the experiment, the analytical model is verified for predicting the deployment velocity when the boom is relatively short, which can cover most booms using CubeSats. Finally, a parametric study reveals the relationship between the boom properties and the deployment behaviors. The research of this paper will give some guidance to the design of a composite roll-out deployable boom. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymers and Lightweight Structures)

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28 pages, 13650 KiB

Open AccessEditor’s ChoiceArticle

Globular Proteins and Where to Find Them within a Polymer Brush—A Case Study

by Aikaterini A. Galata and Martin Kröger

Polymers 2023, 15(10), 2407; https://doi.org/10.3390/polym15102407 - 22 May 2023

Cited by 1 | Viewed by 2373

Abstract

Protein adsorption by polymerized surfaces is an interdisciplinary topic that has been approached in many ways, leading to a plethora of theoretical, numerical and experimental insight. There is a wide variety of models trying to accurately capture the essence of adsorption and its [...] Read more.

Protein adsorption by polymerized surfaces is an interdisciplinary topic that has been approached in many ways, leading to a plethora of theoretical, numerical and experimental insight. There is a wide variety of models trying to accurately capture the essence of adsorption and its effect on the conformations of proteins and polymers. However, atomistic simulations are case-specific and computationally demanding. Here, we explore universal aspects of the dynamics of protein adsorption through a coarse-grained (CG) model, that allows us to explore the effects of various design parameters. To this end, we adopt the hydrophobic-polar (HP) model for proteins, place them uniformly at the upper bound of a CG polymer brush whose multibead-spring chains are tethered to a solid implicit wall. We find that the most crucial factor affecting the adsorption efficiency appears to be the polymer grafting density, while the size of the protein and its hydrophobicity ratio come also into play. We discuss the roles of ligands and attractive tethering surfaces to the primary adsorption as well as secondary and ternary adsorption in the presence of attractive (towards the hydrophilic part of the protein) beads along varying spots of the backbone of the polymer chains. The percentage and rate of adsorption, density profiles and the shapes of the proteins, alongside with the respective potential of mean force are recorded to compare the various scenarios during protein adsorption. Full article

(This article belongs to the Collection Progress in Theory of Polymers at Interfaces)

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15 pages, 13429 KiB

Open AccessEditor’s ChoiceArticle

On the Thermomechanical Behavior of 3D-Printed Specimens of Shape Memory R-PETG

by Ștefan-Dumitru Sava, Nicoleta-Monica Lohan, Bogdan Pricop, Mihai Popa, Nicanor Cimpoeșu, Radu-Ioachim Comăneci and Leandru-Gheorghe Bujoreanu

Polymers 2023, 15(10), 2378; https://doi.org/10.3390/polym15102378 - 19 May 2023

Cited by 7 | Viewed by 1911

Abstract

From commercial pellets of recycled polyethylene terephthalate glycol (R-PETG), 1.75 mm diameter filaments for 3D printing were produced. By varying the filament’s deposition direction between 10° and 40° to the transversal axis, parallelepiped specimens were fabricated by additive manufacturing. When bent at room [...] Read more.

From commercial pellets of recycled polyethylene terephthalate glycol (R-PETG), 1.75 mm diameter filaments for 3D printing were produced. By varying the filament’s deposition direction between 10° and 40° to the transversal axis, parallelepiped specimens were fabricated by additive manufacturing. When bent at room temperature (RT), both the filaments and the 3D-printed specimens recovered their shape during heating, either without any constraint or while lifting a load over a certain distance. In this way, free-recovery and work-generating shape memory effects (SMEs) were developed. The former could be repeated without any visible fatigue marks for as much as 20 heating (to 90 °C)-RT cooling–bending cycles, while the latter enabled the lifting of loads over 50 times heavier than the active specimens. Tensile static failure tests revealed the superiority of the specimens printed at larger angles over those printed at 10°, since the specimens printed at 40° had tensile failure stresses and strains over 35 MPa and 8.5%, respectively. Scanning electron microscopy (SEM) fractographs displayed the structure of the successively deposited layers and a shredding tendency enhanced by the increase in the deposition angle. Differential scanning calorimetry (DSC) analysis enabled the identification of the glass transition between 67.5 and 77.3 °C, which might explain the occurrence of SMEs in both the filament and 3D-printed specimens. Dynamic mechanical analysis (DMA) emphasized a local increase in storage modulus of 0.87–1.66 GPa that occurred during heating, which might explain the development of work-generating SME in both filament and 3D-printed specimens. These properties recommend 3D-printed parts made of R-PETG as active elements in low-price lightweight actuators operating between RT and 63 °C. Full article

(This article belongs to the Special Issue Dynamic Mechanical Analysis of Polymer Composites)

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20 pages, 3631 KiB

Open AccessEditor’s ChoiceArticle

Effects of Bitumen Thickness on the Aging Behavior of High-Content Polymer-Modified Asphalt Mixture

by Peng Lin, Xueyan Liu, Shisong Ren, Jian Xu, Yi Li and Mingliang Li

Polymers 2023, 15(10), 2325; https://doi.org/10.3390/polym15102325 - 16 May 2023

Cited by 12 | Viewed by 2849

Abstract

The film thickness of asphalt mixtures is critical for determining their performance and aging durability. However, understanding of the appropriate film thickness and its influence on performance and aging behavior for high-content polymer-modified asphalt (HCPMA) mixtures is still limited. This research aims to [...] Read more.

The film thickness of asphalt mixtures is critical for determining their performance and aging durability. However, understanding of the appropriate film thickness and its influence on performance and aging behavior for high-content polymer-modified asphalt (HCPMA) mixtures is still limited. This research aims to examine the relationship between film thickness, performance, and aging behavior of HCPMA mixtures in order to establish an optimal film thickness that ensures satisfactory performance and aging durability. HCPMA specimens with film thicknesses ranging from 6.9 μm to 17 μm were prepared using a 7.5% SBS-content-modified bitumen. Various tests, including Cantabro, SCB, SCB fatigue, and Hamburg wheel-tracking tests, were conducted to evaluate raveling, cracking, fatigue, and rutting resistance before and after aging. The key findings indicate that insufficient film thickness negatively affects aggregate bonding and performance, while excessive thickness reduces mixture stiffness and resistance to cracking and fatigue. A parabolic relationship between the aging index and film thickness was observed, suggesting that increasing film thickness improves aging durability up to a point, beyond which excessive thickness adversely impacts aging durability. The optimal film thickness for HCPMA mixtures, considering performance before and after aging and aging durability, falls within the 12.9 to 14.9 µm range. This range ensures the best balance between performance and aging durability, offering valuable insights for the pavement industry in designing and utilizing HCPMA mixtures. Full article

(This article belongs to the Special Issue Application of Polymer Materials in Pavement Design)

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12 pages, 2198 KiB

Open AccessEditor’s ChoiceArticle

Potential of Aligned Electrospun PLGA/SIS Blended Nanofibrous Membrane for Tendon Tissue Engineering

by Kihoon Kim, Hyosung Kim, Sunhee Do and Hwiyool Kim

Polymers 2023, 15(10), 2313; https://doi.org/10.3390/polym15102313 - 15 May 2023

Cited by 6 | Viewed by 2212

Abstract

Tendons are responsible for transmitting mechanical forces from muscles to bones for body locomotion and joint stability. However, tendons are frequently damaged with high mechanical forces. Various methods have been utilized for repairing damaged tendons, including sutures, soft tissue anchors, and biological grafts. [...] Read more.

Tendons are responsible for transmitting mechanical forces from muscles to bones for body locomotion and joint stability. However, tendons are frequently damaged with high mechanical forces. Various methods have been utilized for repairing damaged tendons, including sutures, soft tissue anchors, and biological grafts. However, tendons experience a higher rate of retear post-surgery due to their low cellularity and vascularity. Surgically sutured tendons are vulnerable to reinjury due to their inferior functionality when compared with native tendons. Surgical treatment using biological grafts also has complications such as joint stiffness, re-rupture, and donor-site morbidity. Therefore, current research is focused on developing novel materials that can facilitate the regeneration of tendons with histological and mechanical characteristics similar to those of intact tendons. With respect to the complications in association with the surgical treatment of tendon injuries, electrospinning may be an alternative for tendon tissue engineering. Electrospinning is an effective method for fabrication of polymeric fibers with diameters ranging from nanometers to micrometers. Thus, this method produces nanofibrous membranes with an extremely high surface area-to-volume ratio, which is similar to the extracellular matrix structure, making them suitable candidates for application in tissue engineering. Moreover, it is possible to fabricate nanofibers with specific orientations that are similar to those of the native tendon tissue using an adequate collector. To increase the hydrophilicity of the electrospun nanofibers, natural polymers in addition to synthetic polymers are used concurrently. Therefore, in this study, aligned nanofibers composed of poly-d,l-lactide-co-glycolide (PLGA) and small intestine submucosa (SIS) were fabricated using electrospinning with rotating mandrel. The diameter of aligned PLGA/SIS nanofibers was 568.44 ± 135.594 nm, which closely resembles that of native collagen fibrils. Compared to the results of the control group, the mechanical strength exhibited by the aligned nanofibers was anisotropic in terms of break strain, ultimate tensile strength, and elastic modulus. Elongated cellular behavior was observed in the aligned PLGA/SIS nanofibers using confocal laser scanning microscopy, indicating that the aligned nanofibers were highly effective with regard to tendon tissue engineering. In conclusion, considering its mechanical properties and cellular behavior, aligned PLGA/SIS is a promising candidate for tendon tissue engineering. Full article

(This article belongs to the Section Polymer Fibers)

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18 pages, 2569 KiB

Open AccessEditor’s ChoiceArticle

Isotherm and Kinetic Study of Metal Ions Sorption on Mustard Waste Biomass Functionalized with Polymeric Thiocarbamate

by Dumitru Bulgariu, Lăcrămioara (Negrilă) Nemeş, Iftikhar Ahmad and Laura Bulgariu

Polymers 2023, 15(10), 2301; https://doi.org/10.3390/polym15102301 - 13 May 2023

Cited by 15 | Viewed by 1702

Abstract

The presence of high concentrations of metal ions in effluents resulting from industrial metal coatings is a well-known fact. Most of the time, such metal ions, once they reach the environment, significantly contribute to its degradation. Therefore, it is essential that the concentration [...] Read more.

The presence of high concentrations of metal ions in effluents resulting from industrial metal coatings is a well-known fact. Most of the time, such metal ions, once they reach the environment, significantly contribute to its degradation. Therefore, it is essential that the concentration of metal ions is reduced (as much as possible) before such effluents are discharged into the environment to minimize the negative impact on the quality of the ecosystems. Among all methods that can be used to reduce the concentration of metal ions, sorption is one of the most viable options due to its high efficiency and low cost. Moreover, due to the fact that many industrial wastes have sorbent properties, this method is in accordance with the principles of circular economy. Based on these considerations, in this study, mustard waste biomass (resulting from oil extraction) was functionalized with an industrial polymeric thiocarbamate (METALSORB) and used as a sorbent to remove Cu(II), Zn(II) and Co(II) ions from aqueous media. The best conditions for the functionalization of mustard waste biomass were found to be: mixing ratio biomass: METASORB = 1 g: 1.0 mL and a temperature of 30 °C. The experimental sorption capacities of functionalized sorbent (MET-MWB) were 0.42 mmol/g for Cu(II), 0.29 mmol/g for Zn(II) and 0.47 mmol/g for Co(II), which were obtained under the following conditions: pH of 5.0, 5.0 g sorbent/L and a temperature of 21 °C. The modeling of isotherms and kinetic curves as well as the analysis of the results obtained from desorption processes demonstrate the usefulness of this sorbent in the treatment of effluents contaminated with metal ions. In addition, tests on real wastewater samples highlight the potential of MET-MWB for large-scale applications. Full article

(This article belongs to the Special Issue Applications of Polymer-Based Absorbent Materials)

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18 pages, 11401 KiB

Open AccessEditor’s ChoiceArticle

Multifunctional Properties of Polyhedral Oligomeric Silsesquioxanes (POSS)-Based Epoxy Nanocomposites

by Liberata Guadagno, Andrea Sorrentino, Raffaele Longo and Marialuigia Raimondo

Polymers 2023, 15(10), 2297; https://doi.org/10.3390/polym15102297 - 13 May 2023

Cited by 10 | Viewed by 2409

Abstract

In this study, a tetrafunctional epoxy resin was loaded with 5 wt% of three different types of polyhedral oligomeric silsesquioxane (POSS) compounds, namely, DodecaPhenyl POSS (DPHPOSS), Epoxycyclohexyl POSS (ECPOSS), Glycidyl POSS (GPOSS), and 0.5 wt% of multi-walled carbon nanotubes (CNTs) in order to [...] Read more.

In this study, a tetrafunctional epoxy resin was loaded with 5 wt% of three different types of polyhedral oligomeric silsesquioxane (POSS) compounds, namely, DodecaPhenyl POSS (DPHPOSS), Epoxycyclohexyl POSS (ECPOSS), Glycidyl POSS (GPOSS), and 0.5 wt% of multi-walled carbon nanotubes (CNTs) in order to formulate multifunctional structural nanocomposites tailored for aeronautic and aerospace applications. This work aims to demonstrate how the skillful combination of desired properties, such as good electrical, flame-retardant, mechanical, and thermal properties, is obtainable thanks to the advantages connected with nanoscale incorporations of nanosized CNTs with POSS. The special hydrogen bonding-based intermolecular interactions between the nanofillers have proved to be strategic in imparting multifunctionality to the nanohybrids. All multifunctional formulations are characterized by a Tg centered at values close to 260 °C, fully satisfying structural requirements. Infrared spectroscopy and thermal analysis confirm the presence of a cross-linked structure characterized by a high curing degree of up to 94% and high thermal stability. Tunneling atomic force microscopy (TUNA) allows to detect the map of the electrical pathways at the nanoscale of the multifunctional samples, highlighting a good dispersion of the carbon nanotubes within the epoxy resin. The combined action of POSS with CNTs has allowed to obtain the highest values of self-healing efficiency if compared to those measured for samples containing only POSS in the absence of CNTs. Full article

(This article belongs to the Special Issue Polymeric Self-Healing Materials II)

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20 pages, 8356 KiB

Open AccessEditor’s ChoiceArticle

Thermo-Mechanical Recyclability of Additively Manufactured Polypropylene and Polylactic Acid Parts and Polypropylene Support Structures

by Niko Nagengast, Christian Bay, Frank Döpper, Hans-Werner Schmidt and Christian Neuber

Polymers 2023, 15(10), 2291; https://doi.org/10.3390/polym15102291 - 12 May 2023

Cited by 9 | Viewed by 2344

Abstract

Polymers have a reputation for several advantageous characteristics like chemical resistance, weight reduction, and simple form-giving processes. The rise of additive manufacturing technologies such as Fused Filament Fabrication (FFF) has introduced an even more versatile production process that supported new product design and [...] Read more.

Polymers have a reputation for several advantageous characteristics like chemical resistance, weight reduction, and simple form-giving processes. The rise of additive manufacturing technologies such as Fused Filament Fabrication (FFF) has introduced an even more versatile production process that supported new product design and material concepts. This led to new investigations and innovations driven by the individualization of customized products. The other side of the coin contains an increasing resource and energy consumption satisfying the growing demand for polymer products. This turns into a magnitude of waste accumulation and increased resource consumption. Therefore, appropriate product and material design, taking into account end-of-life scenarios, is essential to limit or even close the loop of economically driven product systems. In this paper, a comparison of virgin and recycled biodegradable (polylactic acid (PLA)) and petroleum-based (polypropylene (PP) & support) filaments for extrusion-based Additive Manufacturing is presented. For the first time, the thermo-mechanical recycling setup contained a service-life simulation, shredding, and extrusion. Specimens and complex geometries with support materials were manufactured with both, virgin and recycled materials. An empirical assessment was executed through mechanical (ISO 527), rheological (ISO 1133), morphological, and dimensional testing. Furthermore, the surface properties of the PLA and PP printed parts were analyzed. In summary, PP parts and parts from its support structure showed, in consideration of all parameters, suitable recyclability with a marginal parameter variance in comparison to the virgin material. The PLA components showed an acceptable decline in the mechanical values but through thermo-mechanical degradation processes, rheological and dimensional properties of the filament dropped decently. This results in significantly identifiable artifacts of the product optics, based on an increase in surface roughness. Full article

(This article belongs to the Special Issue Progress in 3D Printing)

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16 pages, 2680 KiB

Open AccessEditor’s ChoiceArticle

Behavior Characteristics and Thermal Energy Absorption Mechanism of Physical Blowing Agents in Polyurethane Foaming Process

by Haozhen Wang, Yingshu Liu and Lin Lin

Polymers 2023, 15(10), 2285; https://doi.org/10.3390/polym15102285 - 12 May 2023

Cited by 2 | Viewed by 2352

Abstract

Polyurethane rigid foam is a widely used insulation material, and the behavior characteristics and heat absorption performance of the blowing agent used in the foaming process are key factors that affect the molding performance of this material. In this work, the behavior characteristics [...] Read more.

Polyurethane rigid foam is a widely used insulation material, and the behavior characteristics and heat absorption performance of the blowing agent used in the foaming process are key factors that affect the molding performance of this material. In this work, the behavior characteristics and heat absorption of the polyurethane physical blowing agent in the foaming process were studied; this is something which has not been comprehensively studied before. This study investigated the behavior characteristics of polyurethane physical blowing agents in the same formulation system, including the efficiency, dissolution, and loss rates of the physical blowing agents during the polyurethane foaming process. The research findings indicate that both the physical blowing agent mass efficiency rate and mass dissolution rate are influenced by the vaporization and condensation process of physical blowing agent. For the same type of physical blowing agent, the amount of heat absorbed per unit mass decreases gradually as the quantity of physical blowing agent increases. The relationship between the two shows a pattern of initial rapid decrease followed by a slower decrease. Under the same physical blowing agent content, the higher the heat absorbed per unit mass of physical blowing agent, the lower the internal temperature of the foam when the foam stops expanding. The heat absorbed per unit mass of the physical blowing agents is a key factor affecting the internal temperature of the foam when it stops expanding. From the perspective of heat control of the polyurethane reaction system, the effects of physical blowing agents on the foam quality were ranked in order from good to poor as follows: HFC-245fa, HFC-365mfc, HFCO-1233zd(E), HFO-1336mzzZ, and HCFC-141b. Full article

(This article belongs to the Special Issue Advanced Study on Polyurethane)

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23 pages, 4836 KiB

Open AccessEditor’s ChoiceArticle

Parylene C as a Multipurpose Material for Electronics and Microfluidics

by Beatriz J. Coelho, Joana V. Pinto, Jorge Martins, Ana Rovisco, Pedro Barquinha, Elvira Fortunato, Pedro V. Baptista, Rodrigo Martins and Rui Igreja

Polymers 2023, 15(10), 2277; https://doi.org/10.3390/polym15102277 - 12 May 2023

Cited by 15 | Viewed by 7988

Abstract

Poly(p-xylylene) derivatives, widely known as Parylenes, have been considerably adopted by the scientific community for several applications, ranging from simple passive coatings to active device components. Here, we explore the thermal, structural, and electrical properties of Parylene C, and further present a variety [...] Read more.

Poly(p-xylylene) derivatives, widely known as Parylenes, have been considerably adopted by the scientific community for several applications, ranging from simple passive coatings to active device components. Here, we explore the thermal, structural, and electrical properties of Parylene C, and further present a variety of electronic devices featuring this polymer: transistors, capacitors, and digital microfluidic (DMF) devices. We evaluate transistors produced with Parylene C as a dielectric, substrate, and encapsulation layer, either semitransparent or fully transparent. Such transistors exhibit steep transfer curves and subthreshold slopes of 0.26 V/dec, negligible gate leak currents, and fair mobilities. Furthermore, we characterize MIM (metal–insulator–metal) structures with Parylene C as a dielectric and demonstrate the functionality of the polymer deposited in single and double layers under temperature and AC signal stimuli, mimicking the DMF stimuli. Applying temperature generally leads to a decrease in the capacitance of the dielectric layer, whereas applying an AC signal leads to an increase in said capacitance for double-layered Parylene C only. By applying the two stimuli, the capacitance seems to suffer from a balanced influence of both the separated stimuli. Lastly, we demonstrate that DMF devices with double-layered Parylene C allow for faster droplet motion and enable long nucleic acid amplification reactions. Full article

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15 pages, 2750 KiB

Open AccessEditor’s ChoiceArticle

Enhancing Production of Medium-Chain-Length Polyhydroxyalkanoates from Pseudomonas sp. SG4502 by tac Enhancer Insertion

by Linxin Song, Ming Wang, Dengbin Yu, Yu Li, Hongwen Yu and Xuerong Han

Polymers 2023, 15(10), 2290; https://doi.org/10.3390/polym15102290 - 12 May 2023

Cited by 1 | Viewed by 1913

Abstract

Pseudomonas sp. SG4502 screened from biodiesel fuel by-products can synthesize medium-chain-length polyhydroxyalkanoates (mcl-PHAs) using glycerol as a substrate. It contains a typical PHA class II synthase gene cluster. This study revealed two genetic engineering methods for improving the mcl-PHA accumulation capacity of Pseudomonas [...] Read more.

Pseudomonas sp. SG4502 screened from biodiesel fuel by-products can synthesize medium-chain-length polyhydroxyalkanoates (mcl-PHAs) using glycerol as a substrate. It contains a typical PHA class II synthase gene cluster. This study revealed two genetic engineering methods for improving the mcl-PHA accumulation capacity of Pseudomonas sp. SG4502. One way was to knock out the PHA-depolymerase phaZ gene, the other way was to insert a tac enhancer into the upstream of the phaC1/phaC2 genes. Yields of mcl-PHAs produced from 1% sodium octanoate by +(tac-phaC2) and ∆phaZ strains were enhanced by 53.8% and 23.1%, respectively, compared with those produced by the wild-type strain. The increase in mcl-PHA yield from +(tac-phaC2) and ∆phaZ was due to the transcriptional level of the phaC2 and phaZ genes, as determined by RT-qPCR (the carbon source was sodium octanoate). ¹H-NMR results showed that the synthesized products contained 3-hydroxyoctanoic acid (3HO), 3-hydroxydecanoic acid (3HD) and 3-hydroxydodecanoic acid (3HDD) units, which is consistent with those synthesized by the wild-type strain. The size-exclusion chromatography by GPC of mcl-PHAs from the (∆phaZ), +(tac-phaC1) and +(tac-phaC2) strains were 2.67, 2.52 and 2.60, respectively, all of which were lower than that of the wild-type strain (4.56). DSC analysis showed that the melting temperature of mcl-PHAs produced by recombinant strains ranged from 60 °C to 65 °C, which was lower than that of the wild-type strain. Finally, TG analysis showed that the decomposition temperature of mcl-PHAs synthesized by the (∆phaZ), +(tac-phaC1) and +(tac-phaC2) strains was 8.4 °C, 14.7 °C and 10.1 °C higher than that of the wild-type strain, respectively. Full article

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16 pages, 6402 KiB

Open AccessEditor’s ChoiceArticle

Anti-Ballistic Performance of PPTA/UHMWPE Laminates

by Long Zhu, Weixiao Gao, Dmitriy A. Dikin, Simona Percec and Fei Ren

Polymers 2023, 15(10), 2281; https://doi.org/10.3390/polym15102281 - 12 May 2023

Cited by 5 | Viewed by 3318

Abstract

Poly(p-phenylene terephthalamide) (PPTA) and ultra-high-molecular-weight polyethylene (UHMWPE) are high-performance polymer materials largely used for body armor applications. Although composite structures from a combination of PPTA and UHMWPE have been created and described in the literature, the manufacture of layered composites from [...] Read more.

Poly(p-phenylene terephthalamide) (PPTA) and ultra-high-molecular-weight polyethylene (UHMWPE) are high-performance polymer materials largely used for body armor applications. Although composite structures from a combination of PPTA and UHMWPE have been created and described in the literature, the manufacture of layered composites from PPTA fabrics and UHMWPE films with UHMWPE film as an adhesive layer has not been reported. Such a new design can provide the obvious advantage of simple manufacturing technology. In this study, for the first time, we prepared PPTA fabrics/UHMWPE films laminate panels using plasma treatment and hot-pressing and examined their ballistic performance. Ballistic testing results indicated that samples with moderate interlayer adhesion between PPTA and UHMWPE layers exhibited enhanced performance. A further increase in interlayer adhesion showed a reverse effect. This finding implies that optimization of interface adhesion is essential to achieve maximum impact energy absorption through the delamination process. In addition, it was found that the stacking sequence of the PPTA and UHMWPE layers affected ballistic performance. Samples with PPTA as the outermost layer performed better than those with UHMWPE as the outermost layer. Furthermore, microscopy of the tested laminate samples showed that PPTA fibers exhibited shear cutting failure on the entrance side and tensile failure on the exit side of the panel. UHMWPE films exhibited brittle failure and thermal damage at high compression strain rate on the entrance side and tensile fracture on the exit side. For the first time, findings from this study reported in-field bullet testing results of PPTA/UHMWPE composite panels, which can provide important insights for designing, fabricating, and failure analysis of such composite structures for body armors. Full article

(This article belongs to the Special Issue Development in Fiber-Reinforced Polymer Composites)

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15 pages, 6550 KiB

Open AccessEditor’s ChoiceArticle

Free Vibration Analysis of a Tunable Micro-Fabrication Device Comprising Asymmetric L-Shaped Membranes

by Cheng-Hua Xiong, Lian-Gui He, Kao-Hao Chang and Chang-Wei Huang

Polymers 2023, 15(10), 2293; https://doi.org/10.3390/polym15102293 - 12 May 2023

Cited by 1 | Viewed by 1604

Abstract

Membrane sensors have been widely used in various fields owing to their multifunctionality and cost-effectiveness. However, few studies have investigated frequency-tunable membrane sensors, which could enable versatility in the face of different device requirements while retaining high sensitivity, fast response times, and high [...] Read more.

Membrane sensors have been widely used in various fields owing to their multifunctionality and cost-effectiveness. However, few studies have investigated frequency-tunable membrane sensors, which could enable versatility in the face of different device requirements while retaining high sensitivity, fast response times, and high accuracy. In this study, we propose a device comprising an asymmetric L-shaped membrane with tunable operating frequencies for microfabrication and mass sensing applications. The resonant frequency could be controlled by adjusting the membrane geometry. To fully understand the vibration characteristics of the asymmetric L-shaped membrane, the free vibrations of the membrane are first solved by a semi-analytical treatment combining domain decomposition and variable separation methods. The finite-element solutions confirmed the validity of the derived semi-analytical solutions. Parametric analysis results revealed that the fundamental natural frequency decreases monotonically with the increase in length or width of the membrane segment. Numerical examples revealed that the proposed model can be employed to identify suitable materials for membrane sensors with specific frequency requirements under a given set of L-shaped membrane geometries. The model can also achieve frequency matching by changing the length or width of membrane segments given a specified membrane material. Finally, performance sensitivity analyses for mass sensing were carried out, and the results showed that the performance sensitivity was up to 0.7 kHz/pg for polymer materials under certain conditions. Full article

(This article belongs to the Special Issue Polymeric Membranes: Design, Processing and Application)

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10 pages, 1887 KiB

Open AccessEditor’s ChoiceArticle

Electropositive Membrane Prepared via a Simple Dipping Process: Exploiting Electrostatic Attraction Using Electrospun SiO₂/PVDF Membranes with Electronegative SiO₂ Shell

by Dalsu Choi, Cheol Ho Lee, Han Bi Lee, Min Wook Lee and Seong Mu Jo

Polymers 2023, 15(10), 2270; https://doi.org/10.3390/polym15102270 - 11 May 2023

Cited by 3 | Viewed by 2383

Abstract

This research aimed to develop a simple and cost-effective method for fabricating electropositive membranes for highly efficient water filtration. Electropositive membranes are novel functional membranes with electropositive properties and can filter electronegative viruses and bacteria using electrostatic attraction. Because electropositive membranes do not [...] Read more.

This research aimed to develop a simple and cost-effective method for fabricating electropositive membranes for highly efficient water filtration. Electropositive membranes are novel functional membranes with electropositive properties and can filter electronegative viruses and bacteria using electrostatic attraction. Because electropositive membranes do not rely on physical filtration, they exhibit high flux characteristics compared with conventional membranes. This study presents a simple dipping process for fabricating boehmite/SiO₂/PVDF electropositive membranes by modifying an electrospun SiO₂/PVDF host membrane using electropositive boehmite nanoparticles (NPs). The surface modification enhanced the filtration performance of the membrane, as revealed by electronegatively charged polystyrene (PS) NPs as a bacteria model. The boehmite/SiO₂/PVDF electropositive membrane, with an average pore size of 0.30 μm, could successfully filter out 0.20 μm PS particles. The rejection rate was comparable to that of Millipore GSWP, a commercial filter with a pore size of 0.22 μm, which can filter out 0.20 μm particles via physical sieving. In addition, the water flux of the boehmite/SiO₂/PVDF electropositive membrane was twice that of Millipore GSWP, demonstrating the potential of the electropositive membrane in water purification and disinfection. Full article

(This article belongs to the Special Issue Functional Polymer Composites: Synthesis, Characterization and Application)

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19 pages, 7685 KiB

Open AccessEditor’s ChoiceArticle

Calculation of Strain Energy Density Function Using Ogden Model and Mooney–Rivlin Model Based on Biaxial Elongation Experiments of Silicone Rubber

by Yoshihiro Yamashita, Hideyuki Uematsu and Shuichi Tanoue

Polymers 2023, 15(10), 2266; https://doi.org/10.3390/polym15102266 - 11 May 2023

Cited by 11 | Viewed by 4604

Abstract

Strain energy density functions are used in CAE analysis of hyperelastic materials such as rubber and elastomers. This function can originally be obtained only by experiments using biaxial deformation, but the difficulty of such experiments has made it almost impossible to put the [...] Read more.

Strain energy density functions are used in CAE analysis of hyperelastic materials such as rubber and elastomers. This function can originally be obtained only by experiments using biaxial deformation, but the difficulty of such experiments has made it almost impossible to put the function to practical use. Furthermore, it has been unclear how to introduce the strain energy density function necessary for CAE analysis from the results of biaxial deformation experiments on rubber. In this study, parameters of the Ogden and Mooney–Rivlin approximations of the strain energy density function were derived from the results of biaxial deformation experiments on silicone rubber, and their validity was verified. These results showed that it is best to determine the coefficients of the approximate equations for the strain energy density function after 10 cycles of repeated elongation of rubber in an equal biaxial deformation state, followed by equal biaxial elongation, uniaxial constrained biaxial elongation, and uniaxial elongation to obtain these three stress–strain curves. Full article

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

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18 pages, 33150 KiB

Open AccessEditor’s ChoiceArticle

Additive Manufacturing of Biodegradable Hemp-Reinforced Polybutylene Succinate (PBS) and Its Mechanical Characterization

by Antonia Dönitz, Anton Köllner, Tim Richter, Oliver Löschke, Dietmar Auhl and Christina Völlmecke

Polymers 2023, 15(10), 2271; https://doi.org/10.3390/polym15102271 - 11 May 2023

Cited by 12 | Viewed by 3074

Abstract

The additive manufacturing of natural fibre-reinforced polymers is a pivotal method in developing sustainable engineering solutions. Using the fused filament fabrication method, the current study investigates the additive manufacturing of hemp-reinforced polybutylene succinate (PBS) alongside its mechanical characterization. Two types of hemp reinforcement [...] Read more.

The additive manufacturing of natural fibre-reinforced polymers is a pivotal method in developing sustainable engineering solutions. Using the fused filament fabrication method, the current study investigates the additive manufacturing of hemp-reinforced polybutylene succinate (PBS) alongside its mechanical characterization. Two types of hemp reinforcement are considered: short fibres (max. length smaller than 2 mm) and long fibres (max. length smaller than 10 mm), which are compared against non-reinforced (pure) PBS. A detailed analysis is performed regarding the determination of suitable 3D printing parameters (overlap, temperature, nozzle diameter). In a comprehensive experimental study, additionally to general analyses regarding the influence of hemp reinforcement on the mechanical behaviour, the effect of printing parameters is determined and discussed. Introducing an overlap in the additive manufacturing of the specimens results in improved mechanical performance. The study highlights that the Young’s modulus of PBS can be improved by 63% by introducing hemp fibres in conjunction with overlap. In contrast, hemp fibre reinforcement reduces the tensile strength of PBS, while this effect is less pronounced considering overlap in the additive manufacturing process. Full article

(This article belongs to the Special Issue Additive Manufacturing of (Bio) Polymeric Materials)

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