Polymers

24 pages, 9841 KiB

Open AccessArticle

Preparation and Characterization of High-Density Polyethylene with Alternating Lamellar Stems Using Molecular Dynamics Simulations

by Mohammed Althaf Hussain, Takashi Yamamoto, Syed Farooq Adil and Shigeru Yao

Polymers 2024, 16(2), 304; https://doi.org/10.3390/polym16020304 - 22 Jan 2024

Cited by 1 | Viewed by 849

Abstract

Mechanical recycling is the most efficient way to reduce plastic pollution due to its ability to maintain the intrinsic properties of plastics as well as provide economic benefits involved in other types of recycling. On the other hand, molecular dynamics (MD) simulations provide [...] Read more.

Mechanical recycling is the most efficient way to reduce plastic pollution due to its ability to maintain the intrinsic properties of plastics as well as provide economic benefits involved in other types of recycling. On the other hand, molecular dynamics (MD) simulations provide key insights into structural deformation, lamellar crystalline axis (c-axis) orientations, and reorganization, which are essential for understanding plastic behavior during structural deformations. To simulate the influence of structural deformations in high-density polyethylene (HDPE) during mechanical recycling while paying attention to obtaining an alternate lamellar orientation, the authors examine a specific way of preparing stacked lamella-oriented HDPE united atom (UA) models, starting from a single 1000 UA (C₁₀₀₀) chain of crystalline conformations and then packing such chain conformations into 2-chain, 10-chain, 15-chain, and 20-chain semi-crystalline models. The 2-chain, 10-chain, and 15-chain models yielded HDPE microstructures with the desired alternating lamellar orientations and entangled amorphous segments. On the other hand, the 20-chain model displayed multi-nucleus crystal growth instead of the lamellar-stack orientation. Structural characterization using a one-dimensional density profile and local order parameter {P₂(r)} analyses demonstrated lamellar-stack orientation formation. All semi-crystalline models displayed the total density (ρ) and degree of crystallinity (χ) range of 0.90–0.94 g/cm⁻³ and ≥42–45%, respectively. A notable stress yield (σ_yield) ≈ 100–120 MPa and a superior elongation at break (ε_break) ~250% was observed under uniaxial strain deformation along the lamellar-stack orientation. Similarly, during the MD simulations, the microstructure phase change represented the average number of entanglements per chain (<Z>). From the present study, it can be recommended that the 10-chain alternate lamellar-stack orientation model is the most reliable miniature model for HDPE that can mimic industrially relevant plastic behavior in various conditions. Full article

(This article belongs to the Special Issue Advanced Recycling of Plastic Waste: An Approach for Circular Economy)

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15 pages, 4187 KiB

Open AccessArticle

Synthesis and Characterization of DOPO-Containing Poly(2,6-dimethyl-1,4-phenylene oxide)s by Oxidative Coupling Polymerization

by Cheng-Hao Lu, Chi Chang, Yu-Chen Huang, Jun-Xiang You and Mong Liang

Polymers 2024, 16(2), 303; https://doi.org/10.3390/polym16020303 - 22 Jan 2024

Viewed by 744

Abstract

A set of polyphenylene oxides incorporating DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) functionality, denoted as DOPO−R−PPO, was synthesized by copolymerization of 2,6-dimethylphenol (2,6-DMP) with various DOPO-substituted tetramethyl bisphenol monomers. In the initial step, a Friedel–Crafts acylation reaction was employed to react 2,6-DMP with different acyl chlorides, leading [...] Read more.

A set of polyphenylene oxides incorporating DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) functionality, denoted as DOPO−R−PPO, was synthesized by copolymerization of 2,6-dimethylphenol (2,6-DMP) with various DOPO-substituted tetramethyl bisphenol monomers. In the initial step, a Friedel–Crafts acylation reaction was employed to react 2,6-DMP with different acyl chlorides, leading to the formation of ketone derivatives substituted with 2,6-dimethylphenyl groups. Subsequently, the ketones, along with DOPO and 2,6-DMP, underwent a condensation reaction to yield a series of DOPO-substituted bisphenol derivatives. Finally, polymerizations of 2,6-dimethylphenol with these DOPO-substituted bisphenols were carried out in organic solvents using copper(I) bromide/N-butyldimethylamine catalysts (CuBr/DMBA) under a continuous flow of oxygen, yielding telechelic PPO oligomers with DOPO moieties incorporated into the polymer backbone. The chemical structures of the synthesized compounds were characterized using various analytical techniques, including Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H NMR), phosphorus nuclear magnetic resonance (³¹P NMR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). When compared to conventional poly(2,6-dimethyl-1,4-phenylene oxide)s with a similar molecular weight range, all DOPO−PPOs exhibited higher glass transition temperatures, enhanced thermal degradability, and increased char yield formation at 800 °C without compromising solubility in organic solvents. Full article

(This article belongs to the Special Issue Advanced Resin Matrix Composites: Synthesis, Characterization, Processing and Applications)

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13 pages, 3793 KiB

Open AccessArticle

Properties of Heat-Treated Wood Fiber–Polylactic Acid Composite Filaments and 3D-Printed Parts Using Fused Filament Fabrication

by Yu-Chen Chien and Teng-Chun Yang

Polymers 2024, 16(2), 302; https://doi.org/10.3390/polym16020302 - 22 Jan 2024

Cited by 1 | Viewed by 729

Abstract

Wood fibers (WFs) were treated at a fixed heat temperature (180 °C) for 2−6 h and added to a polylactic acid (PLA) matrix to produce wood−PLA composite (WPC) filaments. Additionally, the effects of the heat-treated WFs on the physicomechanical properties and impact strength [...] Read more.

Wood fibers (WFs) were treated at a fixed heat temperature (180 °C) for 2−6 h and added to a polylactic acid (PLA) matrix to produce wood−PLA composite (WPC) filaments. Additionally, the effects of the heat-treated WFs on the physicomechanical properties and impact strength of the WPC filaments and 3D-printed WPC parts using fused filament fabrication (FFF) were examined. The results revealed that heat-treated WFs caused an increase in crystallinity and a significant reduction in the number of pores on the failure cross section of the WPC filament, resulting in a higher tensile modulus and lower elongation at break. Additionally, the printed WPC parts with heat-treated WFs had higher tensile strength and lower water absorption compared to untreated WPC parts. However, most of the mechanical properties and impact strength of 3D-printed WPC parts were not significantly influenced by adding heat-treated WFs. As described above, at the fixed fiber addition amount, adding heat-treated WFs improved the dimensional stability of the WPC parts and it enabled a high retention ratio of mechanical properties and impact strength of the WPC parts. Full article

(This article belongs to the Special Issue Advanced FFF-Printed Polymeric Composites: Characterization, Modification, and Application)

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17 pages, 3516 KiB

Open AccessArticle

Water-Soluble Star Polymer as a Potential Photoactivated Nanotool for Lysozyme Degradation

by Lidia Mezzina, Angelo Nicosia, Laura Barone, Fabiana Vento and Placido Giuseppe Mineo

Polymers 2024, 16(2), 301; https://doi.org/10.3390/polym16020301 - 22 Jan 2024

Viewed by 707

Abstract

The development of nanotools for chemical sensing and macromolecular modifications is a new challenge in the biomedical field, with emphasis on artificial peptidases designed to cleave peptide bonds at specific sites. In this landscape, metal porphyrins are attractive due to their ability to [...] Read more.

The development of nanotools for chemical sensing and macromolecular modifications is a new challenge in the biomedical field, with emphasis on artificial peptidases designed to cleave peptide bonds at specific sites. In this landscape, metal porphyrins are attractive due to their ability to form stable complexes with amino acids and to generate reactive oxygen species when irradiated by light of appropriate wavelengths. The issues of hydrophobic behavior and aggregation in aqueous environments of porphyrins can be solved by using its PEGylated derivatives. This work proposes the design of an artificial photo-protease agent based on a PEGylated mercury porphyrin, able to form a stable complex with l-Tryptophan, an amino acid present also in the lysozyme structure (a well-known protein model). The sensing and photodegradation features of PEGylated mercury porphyrin were exploited to detect and degrade both l-Trp and lysozyme using ROS, generated under green (532 nm) and red (650 nm) light lasers. The obtained system (Star3600_Hg) and its behavior as a photo-protease agent were studied by means of several spectroscopies (UV-Vis, fluorescence and circular dichroism), and MALDI-TOF mass spectrometry, showing the cleavage of lysozyme and the appearance of several short-chain residues. The approach of this study paves the way for potential applications in theranostics and targeted bio-medical therapies. Full article

(This article belongs to the Section Polymer Chemistry)

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13 pages, 2415 KiB

Open AccessArticle

Estimation of Digital Porosity of Electrospun Veils by Image Analysis

by Guadalupe Cuahuizo-Huitzil, Octavio Olivares-Xometl, Paulina Arellanes-Lozada, José Oscar Laguna Cortés, Janette Arriola Morales, Claudia Santacruz-Vázquez and Verónica Santacruz-Vázquez

Polymers 2024, 16(2), 300; https://doi.org/10.3390/polym16020300 - 22 Jan 2024

Viewed by 735

Abstract

The present work reports on an empirical mathematical expression for predicting the digital porosity (DP) of electrospun nanofiber veils, employing emulsions of poly(vinyl alcohol) (PVOH) and olive and orange oils. The electrospun nanofibers were analyzed by scanning electron microscopy (SEM), observing orientation and [...] Read more.

The present work reports on an empirical mathematical expression for predicting the digital porosity (DP) of electrospun nanofiber veils, employing emulsions of poly(vinyl alcohol) (PVOH) and olive and orange oils. The electrospun nanofibers were analyzed by scanning electron microscopy (SEM), observing orientation and digital porosity (DP) in the electrospun veils. To determine the DP of the veils, the SEM micrographs were transformed into a binary system, and then the threshold was established, and the nanofiber solid surfaces were emphasized. The relationship between the experimental results and those obtained with the empirical mathematical expression displayed a correlation coefficient (R²) of 0.97 by employing threshold II. The mathematical expression took into account experimental variables such as the nanofiber humidity and emulsion conductivity prior to electrospinning, in addition to the corresponding operation conditions. The results produced with the proposed expression showed that the prediction of the DP of the electrospun veils was feasible with the considered thresholds. Full article

(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)

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17 pages, 6929 KiB

Open AccessArticle

Application of Polymeric CO₂ Thickener Polymer-Viscosity-Enhance in Extraction of Low-Permeability Tight Sandstone

by Hong Fu, Kaoping Song, Yiqi Pan, Hanxuan Song, Senyao Meng, Mingxi Liu, Runfei Bao, Hongda Hao, Longxin Wang and Xindong Fu

Polymers 2024, 16(2), 299; https://doi.org/10.3390/polym16020299 - 22 Jan 2024

Viewed by 749

Abstract

The conventional production technique employed for low-permeability tight reservoirs exhibits limited productivity. To solve the problem, an acetate-type supercritical carbon dioxide (scCO₂) thickener, PVE, which contains a large number of microporous structures, was prepared using the atom transfer radical polymerization (ATRP) [...] Read more.

The conventional production technique employed for low-permeability tight reservoirs exhibits limited productivity. To solve the problem, an acetate-type supercritical carbon dioxide (scCO₂) thickener, PVE, which contains a large number of microporous structures, was prepared using the atom transfer radical polymerization (ATRP) method. The product exhibited an ability to decrease the minimum miscibility pressure of scCO₂ during a solubility test and demonstrated a favorable extraction efficiency in a low-permeability tight core displacement test. At 15 MPa and 70 °C, PVE-scCO₂ at a concentration of 0.2% exhibits effective oil recovery rates of 5.61% for the 0.25 mD core and 2.65% for the 5 mD core. The result demonstrates that the incorporation of the thickener PVE can effectively mitigate gas channeling, further improve oil displacement efficiency, and inflict minimal damage to crude oil. The mechanism of thickening was analyzed through molecular simulation. The calculated trend of thickening exhibited excellent agreement with the experimental measurement rule. The simulation results demonstrate that the contact area between the polymer and CO₂ increases in direct proportion to both the number of thickener molecules and the viscosity of the system. The study presents an effective strategy for mitigating gas channeling during scCO₂ flooding and has a wide application prospect. Full article

(This article belongs to the Section Polymer Applications)

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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

Viewed by 764

Abstract

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 II)

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17 pages, 4451 KiB

Open AccessArticle

Enhanced Mechanical and Thermal Properties of Polyimide Films Using Hydrophobic Fumed Silica Fillers

by Jongin Yeob, Sung Woo Hong, Won-Gun Koh and In Park

Polymers 2024, 16(2), 297; https://doi.org/10.3390/polym16020297 - 22 Jan 2024

Viewed by 881

Abstract

Polyimide (PI) composite films with enhanced mechanical properties were prepared by incorporating modified fumed silica (FS) particles while preserving their optical and thermal characteristics. The PI matrix was synthesized using a fluorinated diamine, a fluorinated dianhydride, and a rigid biphenyl dianhydride via chemical [...] Read more.

Polyimide (PI) composite films with enhanced mechanical properties were prepared by incorporating modified fumed silica (FS) particles while preserving their optical and thermal characteristics. The PI matrix was synthesized using a fluorinated diamine, a fluorinated dianhydride, and a rigid biphenyl dianhydride via chemical imidization. Commercially available FS particles, including unmodified FS particles (0-FS) and particles modified with dimethyl (2-FS), trimethyl (3-FS), octyl (8-FS), octamethylcyclotetrasiloxane (D4-FS), and polydimethylsiloxane (PDMS-FS) were used. Scanning electron microscope images and nitrogen adsorption–desorption isotherms revealed well-defined porous structures in the FS particles. The water contact angles on the composite films increased compared to those of the pristine PI films, indicating improved water resistance. The PI/0-FS films exhibited a typical trade-off relationship between tensile modulus and elongation at break, as observed in conventional composites. Owing to the poor compatibility and agglomeration of the PDMS-FS particles, the PI/PDMS-FS composite films exhibited poor mechanical performance and diminished optical characteristics. Although the longer-chained FS particles (8- and D4-FS) improved the tensile modulus of the PI film by up to 12%, a reduction of more than 20% in toughness was observed. The PI composite films containing the methylated FS particles (2- and 3-FS) outperformed 8- and D4-FS in terms of mechanical properties, with PI/3-FS films showing an over 10% increased tensile modulus (from 4.07 to 4.42 GPa) and 15% improved toughness (from 6.97 to 8.04 MJ/m³) at 7 wt. % silica loading. Except for the PI/PDMS-FS composites, all composite film samples exhibited more than 86% transmittance at 550 nm. Regarding thermal properties, the glass transition temperature (T_g) and thermal stability remained stable for most composite films. In addition, PI/3-FS films demonstrated enhanced dimensional stability with lower coefficients of thermal expansion (from 47.3 to 34.5 ppm/°C). Overall, this study highlights the potential of incorporating specific modified FS particles to tailor the mechanical, optical, and thermal properties of PI composite films. Full article

(This article belongs to the Special Issue Carbon-Based Polymer Nanocomposites: Preparation, Characterization, and Applications)

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11 pages, 2135 KiB

Open AccessArticle

Bottlebrush Elastomers with Crystallizable Side Chains: Monolayer-like Structure of Backbones Segregated in Intercrystalline Regions

by Evgeniia A. Nikitina, Erfan Dashtimoghadam, Sergei S. Sheiko and Dimitri A. Ivanov

Polymers 2024, 16(2), 296; https://doi.org/10.3390/polym16020296 - 22 Jan 2024

Viewed by 741

Abstract

Bottlebrush (BB) elastomers with water-soluble side chains and tissue-mimetic mechanical properties are promising for biomedical applications like tissue implants and drug depots. This work investigates the microstructure and phase transitions of BB elastomers with crystallizable polyethylene oxide (PEO) side chains by real-time synchrotron [...] Read more.

Bottlebrush (BB) elastomers with water-soluble side chains and tissue-mimetic mechanical properties are promising for biomedical applications like tissue implants and drug depots. This work investigates the microstructure and phase transitions of BB elastomers with crystallizable polyethylene oxide (PEO) side chains by real-time synchrotron X-ray scattering. In the melt, the elastomers exhibit the characteristic BB peak corresponding to the backbone-to-backbone correlation. This peak is a distinct feature of BB systems and is observable in small- or medium-angle X-ray scattering curves. In the systems studied, the position of the BB peak ranges from 3.6 to 4.8 nm in BB elastomers. This variation is associated with the degree of polymerization of the polyethylene oxide (PEO) side chains, which ranges from 19 to 40. Upon crystallization of the side chains, the intensity of the peak decays linearly with crystallinity and eventually vanishes due to BB packing disordering within intercrystalline amorphous gaps. This behavior of the bottlebrush peak differs from an earlier study of BBs with poly(ε-caprolactone) side chains, explained by stronger backbone confinement in the case of PEO, a high-crystallinity polymer. Microstructural models based on 1D SAXS correlation function analysis suggest crystalline lamellae of PEO side chains separated by amorphous gaps of monolayer-like BB backbones. Full article

(This article belongs to the Section Polymer Chemistry)

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11 pages, 3447 KiB

Open AccessArticle

Flat-Silk-Cocoon-Based Wearable Flexible Piezoresistive Sensor and Its Performance

by Zulan Liu, Mengyao Cai, Rui Jia, Xiang Xu, Mengting Xu, Guotao Cheng, Lan Cheng and Fangyin Dai

Polymers 2024, 16(2), 295; https://doi.org/10.3390/polym16020295 - 22 Jan 2024

Viewed by 888

Abstract

Flexible sensors are becoming the focus of research because they are very vital for intelligent products, real-time data monitoring, and recording. The flat silk cocoon (FSC), as a special form of cocoon, has all the advantages of silk, which is an excellent biomass [...] Read more.

Flexible sensors are becoming the focus of research because they are very vital for intelligent products, real-time data monitoring, and recording. The flat silk cocoon (FSC), as a special form of cocoon, has all the advantages of silk, which is an excellent biomass carbon-based material and a good choice for preparing flexible sensors. In this work, a flexible piezoresistive sensor was successfully prepared by encapsulating carbonized flat silk cocoons (CFSCs) using an elastic matrix polydimethylsiloxane (PDMS). The sensing performance of the material is 0.01 kPa⁻¹, and the monitoring range can reach 680.57 kPa. It is proved that the sensor can detect human motion and has excellent durability (>800 cycles). In addition, a sensor array for a keyboard based on CFSCs was explored. The sensor has a low production cost and a simple preparation process, and it is sustainable and environmentally friendly. Thus, it may have potential applications in wearable devices and human–computer interactions. Full article

(This article belongs to the Special Issue Smart Polymeric Materials for Soft Electronics)

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34 pages, 8372 KiB

Open AccessReview

Biopolymeric Nanocomposites for Wastewater Remediation: An Overview on Recent Progress and Challenges

by Annu, Mona Mittal, Smriti Tripathi and Dong Kil Shin

Polymers 2024, 16(2), 294; https://doi.org/10.3390/polym16020294 - 21 Jan 2024

Cited by 1 | Viewed by 2146

Abstract

Essential for human development, water is increasingly polluted by diverse anthropogenic activities, containing contaminants like organic dyes, acids, antibiotics, inorganic salts, and heavy metals. Conventional methods fall short, prompting the exploration of advanced, cost-effective remediation. Recent research focuses on sustainable adsorption, with nano-modifications [...] Read more.

Essential for human development, water is increasingly polluted by diverse anthropogenic activities, containing contaminants like organic dyes, acids, antibiotics, inorganic salts, and heavy metals. Conventional methods fall short, prompting the exploration of advanced, cost-effective remediation. Recent research focuses on sustainable adsorption, with nano-modifications enhancing adsorbent efficacy against persistent waterborne pollutants. This review delves into recent advancements (2020–2023) in sustainable biopolymeric nanocomposites, spotlighting the applications of biopolymers like chitosan in wastewater remediation, particularly as adsorbents and filtration membranes along with their mechanism. The advantages and drawbacks of various biopolymers have also been discussed along with their modification in synthesizing biopolymeric nanocomposites by combining the benefits of biodegradable polymers and nanomaterials for enhanced physiochemical and mechanical properties for their application in wastewater treatment. The important functions of biopolymeric nanocomposites by adsorbing, removing, and selectively targeting contaminants, contributing to the purification and sustainable management of water resources, have also been elaborated on. Furthermore, it outlines the reusability and current challenges for the further exploration of biopolymers in this burgeoning field for environmental applications. Full article

(This article belongs to the Special Issue Biopolymer Nanocomposites: Biomedical, Food and Environmental Applications)

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12 pages, 2830 KiB

Open AccessArticle

Differences in the Residual Behavior of a Bumetrizole-Type Ultraviolet Light Absorber during the Degradation of Various Polymers

by Hisayuki Nakatani, Taishi Uchiyama, Suguru Motokucho, Anh Thi Ngoc Dao, Hee-Jin Kim, Mitsuharu Yagi and Yusaku Kyozuka

Polymers 2024, 16(2), 293; https://doi.org/10.3390/polym16020293 - 21 Jan 2024

Viewed by 847

Abstract

The alteration of an ultraviolet light absorber (UVA: UV-326) in polymers (PP, HDPE, LDPE, PLA, and PS) over time during degradation was studied using an enhanced degradation method (EDM) involving sulfate ion radicals in seawater. The EDM was employed to homogeneously degrade the [...] Read more.

The alteration of an ultraviolet light absorber (UVA: UV-326) in polymers (PP, HDPE, LDPE, PLA, and PS) over time during degradation was studied using an enhanced degradation method (EDM) involving sulfate ion radicals in seawater. The EDM was employed to homogeneously degrade the entire polymer samples containing the UVA. The PP and PS samples containing 5-phr (phr: per hundred resin) UVA films underwent rapid whitening, characterized by the formation of numerous grooves or crushed particles. Notably, the UVA loss rate in PS, with the higher glass transition temperature (Tg), was considerably slower. The behavior of crystalline polymers, with the exception of PS, was analogous in terms of the change in UVA loss rate over the course of degradation. The significant increase in the initial loss rate observed during EDM degradation was due to microplasticization. A similar increase in microplasticization rate occurred with PS; however, the intermolecular interaction between UVA and PS did not result in as pronounced an increase in loss rate as observed in other polymers. Importantly, the chemical structure of UVA remained unaltered during EDM degradation. These findings revealed that the primary cause of UVA loss was leaching from the polymer matrix. Full article

(This article belongs to the Special Issue Degradation and Recycling of Polymer Materials)

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16 pages, 7428 KiB

Open AccessArticle

Durable Surface Modification of Low-Density Polyethylene/Nano-Silica Composite Films with Bacterial Antifouling and Liquid-Repelling Properties for Food Hygiene and Safety

by Sang Ha Song, Michael Bae and Jun Kyun Oh

Polymers 2024, 16(2), 292; https://doi.org/10.3390/polym16020292 - 21 Jan 2024

Viewed by 1063

Abstract

The growing prevalence of antimicrobial resistance in bacterial strains has increased the demand for preventing biological deterioration on the surfaces of films used in applications involving food contact materials (FCMs). Herein, we prepared superhydrophobic film surfaces using a casting process that involved the [...] Read more.

The growing prevalence of antimicrobial resistance in bacterial strains has increased the demand for preventing biological deterioration on the surfaces of films used in applications involving food contact materials (FCMs). Herein, we prepared superhydrophobic film surfaces using a casting process that involved the combination of low-density polyethylene (LDPE) with solutions containing surface energy-reducing silica (SRS). The bacterial antifouling properties of the modified film surfaces were evaluated using Escherichia coli O157:H7 and Staphylococcus epidermidis via the dip-inoculation technique. The reduction in bacterial populations on the LDPE film embedded with SRS was confirmed to be more than 2 log-units, which equates to over 99%, when compared to the bare LDPE film. Additionally, the modified film demonstrated liquid-repelling properties against food-related contaminants, such as blood, beverages, and sauces. Moreover, the modified film demonstrated enhanced durability and robustness compared to one of the prevalent industry methods, dip-coating. We anticipate that the developed LDPE/nano-silica composite film represents a promising advancement in the multidisciplinary aspects of food hygiene and safety within the food industry, particularly concerning FCMs. Full article

(This article belongs to the Special Issue Advances in Functional Polymer Coatings and Surfaces)

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12 pages, 2351 KiB

Open AccessArticle

Statistical Analysis of the Role of Cavity Flexibility in Thermostability of Proteins

by So Yeon Hong, Jihyun Yoon, Young Joo An, Siseon Lee, Haeng-Geun Cha, Ashutosh Pandey, Young Je Yoo and Jeong Chan Joo

Polymers 2024, 16(2), 291; https://doi.org/10.3390/polym16020291 - 21 Jan 2024

Viewed by 1054

Abstract

Conventional statistical investigations have primarily focused on the comparison of the simple one-dimensional characteristics of protein cavities, such as number, surface area, and volume. These studies have failed to discern the crucial distinctions in cavity properties between thermophilic and mesophilic proteins that contribute [...] Read more.

Conventional statistical investigations have primarily focused on the comparison of the simple one-dimensional characteristics of protein cavities, such as number, surface area, and volume. These studies have failed to discern the crucial distinctions in cavity properties between thermophilic and mesophilic proteins that contribute to protein thermostability. In this study, the significance of cavity properties, i.e., flexibility and location, in protein thermostability was investigated by comparing structural differences between homologous thermophilic and mesophilic proteins. Three dimensions of protein structure were categorized into three regions (core, boundary, and surface) and a comparative analysis of cavity properties using this structural index was conducted. The statistical analysis revealed that cavity flexibility is closely related to protein thermostability. The core cavities of thermophilic proteins were less flexible than those of mesophilic proteins (averaged B’ factor values, −0.6484 and −0.5111), which might be less deleterious to protein thermostability. Thermophilic proteins exhibited fewer cavities in the boundary and surface regions. Notably, cavities in mesophilic proteins, across all regions, exhibited greater flexibility than those in thermophilic proteins (>95% probability). The increased flexibility of cavities in the boundary and surface regions of mesophilic proteins, as opposed to thermophilic proteins, may compromise stability. Recent protein engineering investigations involving mesophilic xylanase and protease showed results consistent with the findings of this study, suggesting that the manipulation of flexible cavities in the surface region can enhance thermostability. Consequently, our findings suggest that a rational or computational approach to the design of flexible cavities in surface or boundary regions could serve as an effective strategy to enhance the thermostability of mesophilic proteins. Full article

(This article belongs to the Special Issue Modelling and Simulation of Proteins, Biopolymers and Biocompatible Materials)

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13 pages, 3358 KiB

Open AccessArticle

Structure-Based Evaluation of Hybrid Lipid–Polymer Nanoparticles: The Role of the Polymeric Guest

by Maria Chountoulesi, Natassa Pippa, Aleksander Forys, Barbara Trzebicka and Stergios Pispas

Polymers 2024, 16(2), 290; https://doi.org/10.3390/polym16020290 - 20 Jan 2024

Cited by 1 | Viewed by 995

Abstract

The combination of phospholipids and block-copolymers yields advanced hybrid nanoparticles through the self-assembly process in an aqueous environment. The physicochemical features of the lipid/polymer components, like the lipid–polymer molar ratio, the macromolecular architecture of the block copolymer, the main transition temperature of the [...] Read more.

The combination of phospholipids and block-copolymers yields advanced hybrid nanoparticles through the self-assembly process in an aqueous environment. The physicochemical features of the lipid/polymer components, like the lipid–polymer molar ratio, the macromolecular architecture of the block copolymer, the main transition temperature of the phospholipid, as well as the formulation and preparation protocol parameters, are some of the most crucial parameters for the formation of hybrid lipid/polymer vesicles and for the differentiation of their morphology. The morphology, along with other physicochemical nanoparticle characteristics are strictly correlated with the nanoparticle’s later biological behavior after being administered, affecting interactions with cells, biodistribution, uptake, toxicity, drug release, etc. In the present study, a structural evaluation of hybrid lipid–polymer nanoparticles based on cryo-TEM studies was undertaken. Different kinds of hybrid lipid–polymer nanoparticles were designed and developed using phospholipids and block copolymers with different preparation protocols. The structures obtained ranged from spherical vesicles to rod-shaped structures, worm-like micelles, and irregular morphologies. The obtained morphologies were correlated with the formulation and preparation parameters and especially the type of lipid, the polymeric guest, and their ratio. Full article

(This article belongs to the Special Issue Polymers in Pharmaceutical Technology II)

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14 pages, 8788 KiB

Open AccessArticle

Evaluation of Starch–Garlic Husk Polymeric Composites through Mechanical, Thermal, and Thermo-Mechanical Tests

by Cynthia Graciela Flores-Hernández, Juventino López-Barroso, Beatriz Adriana Salazar-Cruz, Verónica Saucedo-Rivalcoba, Armando Almendarez-Camarillo and José Luis Rivera-Armenta

Polymers 2024, 16(2), 289; https://doi.org/10.3390/polym16020289 - 20 Jan 2024

Viewed by 910

Abstract

The present work evaluates the influence of different properties of composite materials from natural sources. Films were prepared using the evaporative casting technique from corn starch reinforced with a waste material such as garlic husk (GH), using glycerin as a plasticizer. The results [...] Read more.

The present work evaluates the influence of different properties of composite materials from natural sources. Films were prepared using the evaporative casting technique from corn starch reinforced with a waste material such as garlic husk (GH), using glycerin as a plasticizer. The results of the syntheses carried out demonstrated the synergy between these materials. In the morphological analysis, the compatibility and adequate dispersion of the reinforcer in the matrix were confirmed. Using Fourier transform infrared spectroscopy (FTIR), the interaction and formation of bonds between the matrix and the reinforcer were confirmed by the presence of some signals such as S-S and C-S. Similarly, thermogravimetric analysis (TGA) revealed that even at low concentrations, GH can slightly increase the decomposition temperature. Finally, from the results of dynamic mechanical analysis (DMA), it was possible to identify that the storage modulus increases significantly, up to 115%, compared to pure starch, especially at low concentrations of the reinforcer. Full article

(This article belongs to the Special Issue Lignocellulosic Polymer Composites)

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22 pages, 16713 KiB

Open AccessArticle

Electrically Conductive Natural Rubber Composite Films Reinforced with Graphite Platelets

by Veerapat Kitsawat, Saranrat Siri and Muenduen Phisalaphong

Polymers 2024, 16(2), 288; https://doi.org/10.3390/polym16020288 - 20 Jan 2024

Viewed by 1250

Abstract

Green natural rubber (NR) composites reinforced with synthetic graphite platelets, using alginate as a thickening and dispersing agent, were successfully developed to improve mechanical properties, chemical resistance, and electrical conductivity. The fabrication was performed using a latex aqueous microdispersion process. The research demonstrated [...] Read more.

Green natural rubber (NR) composites reinforced with synthetic graphite platelets, using alginate as a thickening and dispersing agent, were successfully developed to improve mechanical properties, chemical resistance, and electrical conductivity. The fabrication was performed using a latex aqueous microdispersion process. The research demonstrated the effective incorporation of graphite platelets into the NR matrix up to 60 parts per hundred rubbers (phr) without causing agglomeration or phase separation. Graphite incorporation significantly improved the mechanical strength of the composite films. NR with 60 phr of graphite exhibited the highest Young’s modulus of 12.3 MPa, roughly 100 times that of the neat NR film. The reinforcement also strongly improved the hydrophilicity of the composite films, resulting in a higher initial water absorption rate compared to the neat NR film. Moreover, the incorporation of graphite significantly improved the chemical resistance of the composite films against nonpolar solvents, such as toluene. The composite films exhibited biodegradability at about 21% to 30% after 90 days in soil. The electrical conductivity of the composite films was considerably enhanced up to 2.18 × 10⁻⁴ S/cm at a graphite loading of 60 phr. According to the improved properties, the developed composites have potential applications in electronic substrates. Full article

(This article belongs to the Special Issue Advances in Functional Rubber and Elastomer Composites II)

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19 pages, 10372 KiB

Open AccessArticle

Polysaccharide Composite Alginate–Pectin Hydrogels as a Basis for Developing Wound Healing Materials

by Galina A. Davydova, Leonid L. Chaikov, Nikolay N. Melnik, Radmir V. Gainutdinov, Irina I. Selezneva, Elena V. Perevedentseva, Muhriddin T. Mahamadiev, Vadim A. Proskurin, Daniel S. Yakovsky, Aurel George Mohan and Julietta V. Rau

Polymers 2024, 16(2), 287; https://doi.org/10.3390/polym16020287 - 20 Jan 2024

Cited by 1 | Viewed by 1020

Abstract

This article presents materials that highlight the bioengineering potential of polymeric systems of natural origin based on biodegradable polysaccharides, with applications in creating modern products for localized wound healing. Exploring the unique biological and physicochemical properties of polysaccharides offers a promising avenue for [...] Read more.

This article presents materials that highlight the bioengineering potential of polymeric systems of natural origin based on biodegradable polysaccharides, with applications in creating modern products for localized wound healing. Exploring the unique biological and physicochemical properties of polysaccharides offers a promising avenue for the atraumatic, controlled restoration of damaged tissues in extensive wounds. The study focused on alginate, pectin, and a hydrogel composed of their mixture in a 1:1 ratio. Atomic force microscopy data revealed that the two-component gel exhibits greater cohesion and is characterized by the presence of filament-like elements. The dynamic light scattering method indicated that this structural change results in a reduction in the damping of acoustic modes in the gel mixture compared to the component gels. Raman spectroscopy research on these gels revealed the emergence of new bonds between the components’ molecules, contributing to the observed effects. The biocompatibility of the gels was evaluated using dental pulp stem cells, demonstrating that all the gels exhibit biocompatibility. Full article

(This article belongs to the Special Issue Advanced Polymers for Medical Applications)

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26 pages, 3788 KiB

Open AccessReview

Advancing Drug Delivery Paradigms: Polyvinyl Pyrolidone (PVP)-Based Amorphous Solid Dispersion for Enhanced Physicochemical Properties and Therapeutic Efficacy

by Agus Rusdin, Amirah Mohd Gazzali, Nur Ain Thomas, Sandra Megantara, Diah Lia Aulifa, Arif Budiman and Muchtaridi Muchtaridi

Polymers 2024, 16(2), 286; https://doi.org/10.3390/polym16020286 - 20 Jan 2024

Cited by 1 | Viewed by 1158

Abstract

Background: The current challenge in drug development lies in addressing the physicochemical issues that lead to low drug effectiveness. Solubility, a crucial physicochemical parameter, greatly influences various biopharmaceutical aspects of a drug, including dissolution rate, absorption, and bioavailability. Amorphous solid dispersion (ASD) has [...] Read more.

Background: The current challenge in drug development lies in addressing the physicochemical issues that lead to low drug effectiveness. Solubility, a crucial physicochemical parameter, greatly influences various biopharmaceutical aspects of a drug, including dissolution rate, absorption, and bioavailability. Amorphous solid dispersion (ASD) has emerged as a widely explored approach to enhance drug solubility. Objective: The objective of this review is to discuss and summarize the development of polyvinylpyrrolidone (PVP)-based amorphous solid dispersion in improving the physicochemical properties of drugs, with a focus on the use of PVP as a novel approach. Methodology: This review was conducted by examining relevant journals obtained from databases such as Scopus, PubMed, and Google Scholar, since 2018. The inclusion and exclusion criteria were applied to select suitable articles. Results: This study demonstrated the versatility and efficacy of PVP in enhancing the solubility and bioavailability of poorly soluble drugs. Diverse preparation methods, including solvent evaporation, melt quenching, electrospinning, coprecipitation, and ball milling are discussed for the production of ASDs with tailored characteristics. Conclusion: PVP-based ASDs could offer significant advantages in the formulation strategies, stability, and performance of poorly soluble drugs to enhance their overall bioavailability. The diverse methodologies and findings presented in this review will pave the way for further advancements in the development of effective and tailored amorphous solid dispersions. Full article

(This article belongs to the Special Issue Polymeric Materials for Drug Delivery II)

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15 pages, 6654 KiB

Open AccessArticle

The Performance of Cellulose Composite Membranes and Their Application in Drinking Water Treatment

by Rengui Weng, Guohong Chen, Xin He, Jie Qin, Shuo Dong, Junjiang Bai, Shaojie Li and Shikang Zhao

Polymers 2024, 16(2), 285; https://doi.org/10.3390/polym16020285 - 20 Jan 2024

Viewed by 923

Abstract

Water scarcity and water pollution have become increasingly severe, and therefore, the purification of water resources has recently garnered increasing attention. Given its position as a major water resource, the efficient purification of drinking water is of crucial importance. In this study, we [...] Read more.

Water scarcity and water pollution have become increasingly severe, and therefore, the purification of water resources has recently garnered increasing attention. Given its position as a major water resource, the efficient purification of drinking water is of crucial importance. In this study, we adopted a phase transition method to prepare ZrO₂/BCM (bamboo cellulose membranes), after which we developed IP-ZrO₂/BC-NFM (bamboo cellulose nanofiltration membranes) through interfacial polymerization using piperazine (PIP) and tricarbonyl chloride (TMC). Subsequently, we integrated these two membranes to create a combined “ultrafiltration + nanofiltration” membrane process for the treatment of drinking water. The membrane combination process was conducted at 25 °C, with ultrafiltration at 0.1 MPa and nanofiltration at 0.5 MPa. This membrane combination, featuring “ultrafiltration + nanofiltration,” had a significant impact on reducing turbidity, consistently maintaining the post-filtration turbidity of drinking water at or below 0.1 NTU. Furthermore, the removal rates for COD_MN and ammonia nitrogen reached 75% and 88.6%, respectively, aligning with the standards for high-quality drinking water. In a continuous 3 h experiment, the nanofiltration unit exhibited consistent retention rates for Na₂SO₄ and bovine serum protein (BSA), with variations of less than 5%, indicating exceptional separation performance. After 9 h of operation, the water flux of the nanofiltration unit began to stabilize, with a decrease rate of approximately 25%, demonstrating that the “ultrafiltration + nanofiltration” membrane combination can maintain consistent performance during extended use. In conclusion, the “ultrafiltration + nanofiltration” membrane combination exhibited remarkable performance in the treatment of drinking water, offering a viable solution to address issues related to water scarcity and water pollution. Full article

(This article belongs to the Section Polymer Membranes and Films)

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19 pages, 7233 KiB

Open AccessArticle

A Study of PLA Thin Film on SS 316L Coronary Stents Using a Dip Coating Technique

by Mariana Macías-Naranjo, Margarita Sánchez-Domínguez, J. F. Rubio-Valle, Ciro A. Rodríguez, J. E. Martín-Alfonso, Erika García-López and Elisa Vazquez-Lepe

Polymers 2024, 16(2), 284; https://doi.org/10.3390/polym16020284 - 19 Jan 2024

Viewed by 874

Abstract

The dip coating process is one of the recognized techniques used to generate polymeric coatings on stents in an easy and low-cost way. However, there is a lack of information about the influence of the process parameters of this technique on complex geometries [...] Read more.

The dip coating process is one of the recognized techniques used to generate polymeric coatings on stents in an easy and low-cost way. However, there is a lack of information about the influence of the process parameters of this technique on complex geometries such as stents. This paper studies the dip coating process parameters used to provide a uniform coating of PLA with a 4–10 µm thickness. A stainless-steel tube (AISI 316L) was laser-cut, electropolished, and dip-coated in a polylactic acid (PLA) solution whilst changing the process parameters. The samples were characterized to examine the coating’s uniformity, thickness, surface roughness, weight, and chemical composition. FTIR and Raman investigations indicated the presence of PLA on the stent’s surface, the chemical stability of PLA during the coating process, and the absence of residual chloroform in the coatings. Additionally, the water contact angle was measured to determine the hydrophilicity of the coating. Our results indicate that, when using entry and withdrawal speeds of 500 mm min⁻¹ and a 15 s immersion time, a uniform coating thickness was achieved throughout the tube and in the stent with an average thickness of 7.8 µm. Full article

(This article belongs to the Special Issue Polymer Films and Coatings: Preparation, Characterization, and Applications)

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12 pages, 2668 KiB

Open AccessArticle

The Toughness-Enhanced Atelocollagen Double-Network Gel for Biomaterials

by Atsushi Tsuyukubo, Riku Kubota, Yuzo Sato and Ichiro Fujimoto

Polymers 2024, 16(2), 283; https://doi.org/10.3390/polym16020283 - 19 Jan 2024

Viewed by 849

Abstract

A tough gel composed of atelocollagen, which lacks an immunogenetic site, is a promising material for biomedical application. In this study, we created a composite hydrogel composed of atelocollagen gel cross-linked with glutaraldehyde (GA) and poly-(N,N-dimethylacrylamide) gel exhibiting biocompatibility [...] Read more.

A tough gel composed of atelocollagen, which lacks an immunogenetic site, is a promising material for biomedical application. In this study, we created a composite hydrogel composed of atelocollagen gel cross-linked with glutaraldehyde (GA) and poly-(N,N-dimethylacrylamide) gel exhibiting biocompatibility based on the double-network (DN) gel principle. The tensile toughness of atelocollagen gel remained constant regardless of the amount of cross-linker (GA) used. In contrast, tensile tests of the DN gel indicated that mechanical properties, such as fracture stress and toughness, were significantly higher than those of the atelocollagen gel. Moreover, fibroblast cells adhered and spread on the gels, the Schiff bases of which were treated via reductive amination for detoxification from GA. These findings demonstrate the potential of the proposed gel materials as artificial alternative materials to soft tissues with sub-MPa fracture stress. Full article

(This article belongs to the Special Issue Polymer Materials for Biomedical Applications)

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15 pages, 5399 KiB

Open AccessArticle

Influence of Partially Carboxylated Powdered Lignocellulose from Oat Straw on Technological and Strength Properties of Water-Swelling Rubber

by Elena Cherezova, Yulia Karaseva, Abdirakym Nakyp, Airat Nuriev, Bakytbek Islambekuly and Nurgali Akylbekov

Polymers 2024, 16(2), 282; https://doi.org/10.3390/polym16020282 - 19 Jan 2024

Viewed by 729

Abstract

The work is aimed at the development of an energy-saving technique involving the partial carboxylation of powdered lignocellulose products from the straw of annual agricultural plants and the use of the obtained products in rubber compositions as a water-swelling filler. Lignocellulose powder from [...] Read more.

The work is aimed at the development of an energy-saving technique involving the partial carboxylation of powdered lignocellulose products from the straw of annual agricultural plants and the use of the obtained products in rubber compositions as a water-swelling filler. Lignocellulose powder from oat straw (composition: α-cellulose—77.0%, lignin—3.8%, resins and fats—1.8%) was used for carboxylation without preliminary separation into components. Microwave radiation was used to activate the carboxylation process. This reduced the reaction time by 2–3 times. The synthesized products were analyzed by IR spectroscopy, thermogravimetry and scanning electron microscopy. Industrial product sodium carboxymethylcellulose (Na-CMC) was used as a swelling filler for comparison. The swelling fillers were fractionated by the sieve method; particles with the size of 0–1 mm were used for filling rubber compounds. The amount of swelling filler was 150 parts per 100 parts of rubber (phr). Due to the high filling of rubber compounds, plasticizer Oxal T-92 was added to the composition of a number of samples to facilitate the processing and uniform distribution of ingredients. The rubber composition was prepared in two stages. In the first stage, ingredients without swelling filler were mixed with rubber on a laboratory two-roll mill to create a base rubber compound (BRC). In the second stage, the BRC was mixed with the swelling filler in a closed laboratory plasti-corder rubber mixer, the Brabender Plasti-Corder^® Lab-Station. Vulcanization was carried out at 160 °C. For the obtained samples, the physical-mechanical and sorption properties were determined. It has been shown that the carboxylated powdered lignocellulose from oat straw increases the strength properties of rubber in comparison with Na-CMC. It has been shown that when the carboxylated powdered lignocellulose from oat straw is introduced into the rubber composition, the degree of rubber swelling in aqueous solutions of various mineralizations increases by 50 and 100% in comparison with a noncarboxylated lignocellulose. Full article

(This article belongs to the Special Issue Advances in Cellulose-Based Polymers and Composites)

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22 pages, 5967 KiB

Open AccessReview

Repair of Infected Bone Defects with Hydrogel Materials

by Zhenmin Cao, Zuodong Qin, Gregory J. Duns, Zhao Huang, Yao Chen, Sheng Wang, Ruqi Deng, Libo Nie and Xiaofang Luo

Polymers 2024, 16(2), 281; https://doi.org/10.3390/polym16020281 - 19 Jan 2024

Cited by 1 | Viewed by 1114

Abstract

Infected bone defects represent a common clinical condition involving bone tissue, often necessitating surgical intervention and antibiotic therapy. However, conventional treatment methods face obstacles such as antibiotic resistance and susceptibility to postoperative infections. Hydrogels show great potential for application in the field of [...] Read more.

Infected bone defects represent a common clinical condition involving bone tissue, often necessitating surgical intervention and antibiotic therapy. However, conventional treatment methods face obstacles such as antibiotic resistance and susceptibility to postoperative infections. Hydrogels show great potential for application in the field of tissue engineering due to their advantageous biocompatibility, unique mechanical properties, exceptional processability, and degradability. Recent interest has surged in employing hydrogels as a novel therapeutic intervention for infected bone repair. This article aims to comprehensively review the existing literature on the anti-microbial and osteogenic approaches utilized by hydrogels in repairing infected bones, encompassing their fabrication techniques, biocompatibility, antimicrobial efficacy, and biological activities. Additionally, the potential opportunities and obstacles in their practical implementation will be explored. Lastly, the limitations presently encountered and the prospective avenues for further investigation in the realm of hydrogel materials for the management of infected bone defects will be deliberated. This review provides a theoretical foundation and advanced design strategies for the application of hydrogel materials in the treatment of infected bone defects. Full article

(This article belongs to the Special Issue Advances in Functional Polymer Materials for Biomedical Applications)

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0 pages, 3546 KiB

Open AccessArticle

Comparison of Two Methods for Measuring the Temperature Dependence of H₂ Permeation Parameters in Nitrile Butadiene Rubber Polymer Composites Blended with Fillers: The Volumetric Analysis Method and the Differential Pressure Method

by Ji Hun Lee, Ye Won Kim, Do Jung Kim, Nak Kwan Chung and Jae Kap Jung

Polymers 2024, 16(2), 280; https://doi.org/10.3390/polym16020280 - 19 Jan 2024

Viewed by 665

Abstract

Hydrogen uptake/diffusivity in nitrile butadiene rubber (NBR) blended with carbon black (CB) and silica fillers was measured with a volumetric analysis method in the 258–323 K temperature range. The temperature-dependent H₂ diffusivity was obtained by assuming constant solubility with temperature variations. The [...] Read more.

Hydrogen uptake/diffusivity in nitrile butadiene rubber (NBR) blended with carbon black (CB) and silica fillers was measured with a volumetric analysis method in the 258–323 K temperature range. The temperature-dependent H₂ diffusivity was obtained by assuming constant solubility with temperature variations. The logarithmic diffusivity decreased linearly with increasing reciprocal temperature. The diffusion activation energies were calculated with the Arrhenius equation. The activation energies for NBR blended with high-abrasion furnace CB and silica fillers increased linearly with increasing filler content. For NBR blended with medium thermal CB filler, the activation energy decreased with increasing filler content. The activation energy filler dependency is similar to the glass transition temperature filler dependency, as determined with dynamic mechanical analysis. Additionally, the activation energy was compared with that obtained by the differential pressure method through permeability temperature dependence. The same activation energy between diffusion and permeation in the range of 33–39 kJ/mol was obtained, supporting the temperature-independent H₂ solubility and H₂ physisorption in polymer composites. Full article

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

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2 pages, 326 KiB

Open AccessCorrection

Correction: Zhu et al. Mineralized Collagen/Polylactic Acid Composite Scaffolds for Load-Bearing Bone Regeneration in a Developmental Model. Polymers 2023, 15, 4194

by Wenbo Zhu, Wenjing Li, Mengxuan Yao, Yan Wang, Wei Zhang, Chao Li, Xiumei Wang, Wei Chen and Hongzhi Lv

Polymers 2024, 16(2), 279; https://doi.org/10.3390/polym16020279 - 19 Jan 2024

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Abstract

In the original publication [...] Full article

(This article belongs to the Special Issue Stimuli Responsive Polymeric-Based Electroactive Biomaterials)

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15 pages, 6848 KiB

Open AccessArticle

Influence of Novel SrTiO₃/MnO₂ Hybrid Nanoparticles on Poly(methyl methacrylate) Thermal and Mechanical Behavior

by Houda Taher Elhmali, Ivana Stajcic, Aleksandar Stajcic, Ivan Pesic, Marija Jovanovic, Milos Petrovic and Vesna Radojevic

Polymers 2024, 16(2), 278; https://doi.org/10.3390/polym16020278 - 19 Jan 2024

Viewed by 728

Abstract

While dental poly methyl methacrylate(PMMA) possesses distinctive qualities such as ease of fabrication, cost-effectiveness, and favorable physical and mechanical properties, these attributes alone are inadequate to impart the necessary impact strength and hardness. Consequently, pure PMMA is less suitable for dental applications. This [...] Read more.

While dental poly methyl methacrylate(PMMA) possesses distinctive qualities such as ease of fabrication, cost-effectiveness, and favorable physical and mechanical properties, these attributes alone are inadequate to impart the necessary impact strength and hardness. Consequently, pure PMMA is less suitable for dental applications. This research focused on the incorporation of Strontium titanate (SrTiO₃-STO) and hybrid filler STO/Manganese oxide (MnO₂) to improve impact resistance and hardness. The potential of STO in reinforcing PMMA is poorly investigated, while hybrid filler STO/MnO₂ has not been presented yet. Differential scanning calorimetry is conducted in order to investigate the agglomeration influence on the PMMA glass transition temperature (T_g), as well as the leaching of residual monomer and volatile additives that could pose a threat to human health. It has been determined that agglomeration with 1 wt% loading had no influence on T_g, while the first scan revealed differences in evaporation of small molecules, in favor of composite PMMA-STO/MnO₂, which showed the trapping potential of volatiles. Investigations of mechanical properties have revealed the significant influence of hybrid STO/MnO₂ filler on microhardness and total absorbed impact energy, which were increased by 89.9% and 145.4%, respectively. Results presented in this study revealed the reinforcing potential of hybrid nanoparticles that could find application in other polymers as well. Full article

(This article belongs to the Special Issue Thermal Properties Analysis of Polymers)

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18 pages, 5748 KiB

Open AccessArticle

A Novel In-Line Measurement and Analysis Method of Bubble Growth-Dependent Strain and Deformation Rates during Foaming

by Tobias Schaible and Christian Bonten

Polymers 2024, 16(2), 277; https://doi.org/10.3390/polym16020277 - 19 Jan 2024

Cited by 1 | Viewed by 689

Abstract

Bubble growth processes are highly influenced by the elongational viscosity of the blowing agent-loaded polymer melt. Therefore, the elongational viscosity is an important parameter for the development of new polymers for foaming applications, as well as for the prediction of bubble growth processes. [...] Read more.

Bubble growth processes are highly influenced by the elongational viscosity of the blowing agent-loaded polymer melt. Therefore, the elongational viscosity is an important parameter for the development of new polymers for foaming applications, as well as for the prediction of bubble growth processes. Thus, knowledge of the initial expansion and deformation behavior in dependency on the polymer, the blowing agent concentration, and the process conditions is necessary. This study presents a novel method for the in-line observation and analysis of the initial expansion and deformation behavior within the bead foam extrusion process. For this purpose, nitrogen as the blowing agent was injected into the polymer melt (PS and PLA) during the extrusion process. The in-line observation system consists of a borescope equipped with a camera, which was integrated into the water box of an underwater pelletizer. The camera is controlled by a developed trigger by means of angular step signal analysis of a rotary encoder on the cutter shaft of the underwater pelletizer. Thus, images can be taken at any time during the foaming process depending on the cutter position to the die outlet. It is shown that the developed method provides reliable results and that the differences of the initial expansion and deformation behavior during bubble growth can be analyzed in-line in dependency on real foaming process conditions and the type of polymer used. Full article

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12 pages, 4713 KiB

Open AccessArticle

The Role of Lanthanum Stearate on Strain-Induced Crystallization and the Mechanical Properties of Whole Field Latex Rubber

by Changjin Yang, Yuhang Luo, Zechun Li, Chuanyu Wei and Shuangquan Liao

Polymers 2024, 16(2), 276; https://doi.org/10.3390/polym16020276 - 19 Jan 2024

Viewed by 546

Abstract

Natural rubber (NR) is extensively utilized in numerous industries, such as aerospace, military, and transportation, because of its exceptional elasticity and all-around mechanical qualities. However, commercial NR made using various techniques typically has distinct mechanical characteristics. For instance, whole field latex rubber (SCR-WF) [...] Read more.

Natural rubber (NR) is extensively utilized in numerous industries, such as aerospace, military, and transportation, because of its exceptional elasticity and all-around mechanical qualities. However, commercial NR made using various techniques typically has distinct mechanical characteristics. For instance, whole field latex rubber (SCR-WF) cured with accelerator 2-Mercaptobenzothiazole exhibits poor mechanical properties. This work attempts to enhance the mechanical property of SCR-WF via the addition of lanthanum stearate (LaSt). The influence of LaSt on strain-induced crystallization (SIC) and the mechanical properties of SCR-WF were investigated. The results of crosslinking density measured by the equilibrium swelling method demonstrate that the presence of LaSt significantly increases the crosslinking density of SCR-WF with lower loading of LaSt. The results of the mechanical properties show that the introduction of LaSt can enhance the tensile strength and fracture toughness of SCR-WF. To reveal the mechanism of LaSt improving the mechanical properties of SCR-WF, synchrotron radiation wide-angle X-ray diffraction (WAXD) experiments were used to investigate the SIC behaviors of SCR-WF. We found that the LaSt leads to higher crystallinity of SIC for the strain higher than 3.5. The tube model indicates the contribution of LaSt in both crosslinking and topological constraints. This work may provide an instruction for developing SCR-WF with superior mechanical properties. Full article

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

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15 pages, 5044 KiB

Open AccessArticle

Development of a UiO-66 Based Waterborne Flame-Retardant Coating for PC/ABS Material

by Shaojun Chen, Youhan Zeng, Weifeng Bi, Haitao Zhuo and Haiqiang Zhong

Polymers 2024, 16(2), 275; https://doi.org/10.3390/polym16020275 - 19 Jan 2024

Viewed by 679

Abstract

The flame-retardancy of polymeric materials has garnered great interest. Most of the flame retardants used in copolymers are functionalized additives, which can deteriorate the intrinsic properties of these materials. As a new type of flame retardant, functionalized metal–organic frameworks (MOFs) can be used [...] Read more.

The flame-retardancy of polymeric materials has garnered great interest. Most of the flame retardants used in copolymers are functionalized additives, which can deteriorate the intrinsic properties of these materials. As a new type of flame retardant, functionalized metal–organic frameworks (MOFs) can be used in surface coatings of polymers. To reduce the flammability, a mixture of phytic acid, multi-wall carbon nanotubes, zirconium-based MOFs, and UiO-66 was coated on a PC/ABS substrate. The structure of the UiO-66-based flame retardant was established by FT-IR, XRD, XPS, and SEM. The flammable properties of coated PC/ABS materials were assessed by LOI, a vertical combustion test, TGA, CCT, and Raman spectroscopy. The presence of a UiO-66-based coating on the PC/ABS surface resulted in a good flame-retardant performance. Heat release and smoke generation were significantly reduced. Importantly, the structure and mechanical properties of PC/ABS were less impacted by the presence of the flame-retardant coating. Hence, this work presents a new strategy for the development of high-performance PC/ABC materials with both excellent flame-retardancy and good mechanical properties. Full article

(This article belongs to the Special Issue Advance in Polymer Composites: Fire Protection and Thermal Management)

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