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Polymers, Volume 14, Issue 15 (August-1 2022) – 260 articles

Cover Story (view full-size image): Fibers with diameters in the lower micrometer range for textile and biomedical applications are produced by solution electrospinning, but this process is environmentally harmful because toxic solvents are used. Melt electrospinning is a sustainable alternative but the high viscosity and low electrical conductivity of molten polymers produces thicker fibers. Here, we used multifunctional potentially bio-based dyes as additives to produce antibacterial fibers in the lower micrometer range using pilot-scale melt electrospinning for interesting applications in the biomedical field. View this paper
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14 pages, 2226 KiB  
Article
Accelerating the Layup Sequences Design of Composite Laminates via Theory-Guided Machine Learning Models
by Zhenhao Liao, Cheng Qiu, Jun Yang, Jinglei Yang and Lei Yang
Polymers 2022, 14(15), 3229; https://doi.org/10.3390/polym14153229 - 8 Aug 2022
Cited by 11 | Viewed by 3243
Abstract
Experimental and numerical investigations are presented for a theory-guided machine learning (ML) model that combines the Hashin failure theory (HFT) and the classical lamination theory (CLT) to optimize and accelerate the design of composite laminates. A finite element simulation with the incorporation of [...] Read more.
Experimental and numerical investigations are presented for a theory-guided machine learning (ML) model that combines the Hashin failure theory (HFT) and the classical lamination theory (CLT) to optimize and accelerate the design of composite laminates. A finite element simulation with the incorporation of the HFT and CLT were used to generate the training dataset. Instead of directly mapping the relationship between the ply angles of the laminate and its strength and stiffness, a multi-layer interconnected neural network (NN) system was built following the logical sequence of composite theories. With the forward prediction by the NN system and the inverse optimization by genetic algorithm (GA), a benchmark case of designing a composite tube subjected to the combined loads of bending and torsion was studied. The ML models successfully provided the optimal layup sequences and the required fiber modulus according to the preset design targets. Additionally, it shows that the machine learning models, with the guidance of composite theories, realize a faster optimization process and requires less training data than models with direct simple NNs. Such results imply the importance of domain knowledge in helping improve the ML applications in engineering problems. Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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13 pages, 2954 KiB  
Article
On-the-Fly Formation of Polymer Film at Water Surface
by Veronica Vespini, Sara Coppola and Pietro Ferraro
Polymers 2022, 14(15), 3228; https://doi.org/10.3390/polym14153228 - 8 Aug 2022
Cited by 3 | Viewed by 2521
Abstract
The self-propulsion of bodies floating in water is of great interest for developing new robotic and intelligent systems at different scales, and whenever possible, Marangoni propulsion is an attractive candidate for the locomotion of untethered micro-robots. Significant cases have been shown using liquid [...] Read more.
The self-propulsion of bodies floating in water is of great interest for developing new robotic and intelligent systems at different scales, and whenever possible, Marangoni propulsion is an attractive candidate for the locomotion of untethered micro-robots. Significant cases have been shown using liquid and solid surfactants that allow an effective propulsion for bodies floating on water to be achieved. Here, we show for the first time a strategy for activating a twofold functionality where the self-propulsion of a floating body is combined with the formation of a polymer thin film at the water surface. In fact, we demonstrate that by using polymer droplets with an appropriate concentration of solvent and delivering such drops at specific locations onto freely floating objects, it is possible to form “on-the-fly” thin polymer films at the free water surface. By exploiting self-propulsion, a polymer thin film can be formed that could cover quite extensive areas with different shapes depending on the motion of the floating object. This intriguing twice-functionality activated though a single phenomenon, i.e., film formation and related locomotion, could be used in perspective to perform complex operations at water surfaces, such as dynamic liquid packaging, cleaning, and moving away floating particles, monolayer films, or macro-sized objects, as discussed in the text. Full article
(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)
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18 pages, 5872 KiB  
Review
Fabrication, Property and Application of Calcium Alginate Fiber: A Review
by Xiaolin Zhang, Xinran Wang, Wei Fan, Yi Liu, Qi Wang and Lin Weng
Polymers 2022, 14(15), 3227; https://doi.org/10.3390/polym14153227 - 8 Aug 2022
Cited by 54 | Viewed by 10199
Abstract
As a natural linear polysaccharide, alginate can be gelled into calcium alginate fiber and exploited for functional material applications. Owing to its high hygroscopicity, biocompatibility, nontoxicity and non-flammability, calcium alginate fiber has found a variety of potential applications. This article gives a comprehensive [...] Read more.
As a natural linear polysaccharide, alginate can be gelled into calcium alginate fiber and exploited for functional material applications. Owing to its high hygroscopicity, biocompatibility, nontoxicity and non-flammability, calcium alginate fiber has found a variety of potential applications. This article gives a comprehensive overview of research on calcium alginate fiber, starting from the fabrication technique of wet spinning and microfluidic spinning, followed by a detailed description of the moisture absorption ability, biocompatibility and intrinsic fire-resistant performance of calcium alginate fiber, and briefly introduces its corresponding applications in biomaterials, fire-retardant and other advanced materials that have been extensively studied over the past decade. This review assists in better design and preparation of the alginate bio-based fiber and puts forward new perspectives for further study on alginate fiber, which can benefit the future development of the booming eco-friendly marine biomass polysaccharide fiber. Full article
(This article belongs to the Special Issue Smart Textile and Polymer Materials)
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16 pages, 3883 KiB  
Article
Rheological Properties and Melt Spinning Application of Controlled-Rheology Polypropylenes via Pilot-Scale Reactive Extrusion
by Ho Suk Ji, Geunyeop Park and Hyun Wook Jung
Polymers 2022, 14(15), 3226; https://doi.org/10.3390/polym14153226 - 8 Aug 2022
Cited by 1 | Viewed by 3435
Abstract
Based on pilot-scale twin-screw reactive extrusion, the structural and rheological properties of controlled-rheology polypropylenes (CR-PPs) are investigated, where the effects of peroxide content and extrusion conditions such as screw configuration, extrusion temperature, and screw speed are prioritized. The active chain cleavage reaction by [...] Read more.
Based on pilot-scale twin-screw reactive extrusion, the structural and rheological properties of controlled-rheology polypropylenes (CR-PPs) are investigated, where the effects of peroxide content and extrusion conditions such as screw configuration, extrusion temperature, and screw speed are prioritized. The active chain cleavage reaction by a small peroxide content of less than 600 ppm inside the extruder gradually increases the melt index and narrows the molecular weight distribution of CR-PPs, thereby affording favorable properties that are applicable to the fiber spinning process. The mechanical properties of CR-PPs are slightly degraded owing to the generation of unsaturated chain ends during the reactive extrusion, which suppresses crystal growth. Under all extrusion conditions, the chain scission and thermal degradation of polypropylene samples occur actively in the harsh twin-screw extruder compared with those in the mild twin-screw extruder. Finally, it is confirmed that CR-PPs can be suitably applied to the melt-spinning process for staple fiber production, thereby guaranteeing a more stable spinning process window against draw resonance instability. Full article
(This article belongs to the Special Issue Rheology and Processing of Polymer Materials)
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15 pages, 5260 KiB  
Article
Experimental Study of Yield Surface in Polypropylene Considering Rate Effect: Stress Path Dependence
by Hang Zheng, Xiaofei Yi, Zhiping Tang, Kai Zhao and Yongliang Zhang
Polymers 2022, 14(15), 3225; https://doi.org/10.3390/polym14153225 - 8 Aug 2022
Viewed by 2111
Abstract
In order to investigate the yield surface evolution of polypropylene (PP) under dynamic impact and the relationship between yield surface parameters and the strain rate, five shear-compression specimens (SCSs) with different inclination angles are designed and produced to explore the yield behavior of [...] Read more.
In order to investigate the yield surface evolution of polypropylene (PP) under dynamic impact and the relationship between yield surface parameters and the strain rate, five shear-compression specimens (SCSs) with different inclination angles are designed and produced to explore the yield behavior of PP under dynamic loading. Dynamic combined stress loading paths with different compression-shear ratios are achieved by the split Hopkinson pressure bar (SHPB). The evolution laws of the compressive stress and shear stress in the measurement region during the PP SCS compressive deformation process are analyzed. In terms of mechanical response, PP under combined compression-shear loading is of visco-elasticity plasticity and its deformation undergoes a three-stage transition, namely “unyield→yield→failure”. The yield characteristics of PP are found to be affected not only by the hydrostatic pressure but also by the stress path. According to the Hu–Pae yield criterion, the dynamic yield surface and model parameters of PP are obtained, and the relationship between the yield surface and the strain rate is ascertained. These findings contribute to deepening the research on the mechanical response characteristics of PP-based materials. Full article
(This article belongs to the Special Issue Polymer-Metal Composites)
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15 pages, 3178 KiB  
Article
Advanced “Green” Prebiotic Composite of Bacterial Cellulose/Pullulan Based on Synthetic Biology-Powered Microbial Coculture Strategy
by Sirina Zhantlessova, Irina Savitskaya, Aida Kistaubayeva, Ludmila Ignatova, Aizhan Talipova, Alexander Pogrebnjak and Ilya Digel
Polymers 2022, 14(15), 3224; https://doi.org/10.3390/polym14153224 - 8 Aug 2022
Cited by 20 | Viewed by 3091 | Correction
Abstract
Bacterial cellulose (BC) is a biopolymer produced by different microorganisms, but in biotechnological practice, Komagataeibacter xylinus is used. The micro- and nanofibrillar structure of BC, which forms many different-sized pores, creates prerequisites for the introduction of other polymers into it, including those synthesized [...] Read more.
Bacterial cellulose (BC) is a biopolymer produced by different microorganisms, but in biotechnological practice, Komagataeibacter xylinus is used. The micro- and nanofibrillar structure of BC, which forms many different-sized pores, creates prerequisites for the introduction of other polymers into it, including those synthesized by other microorganisms. The study aims to develop a cocultivation system of BC and prebiotic producers to obtain BC-based composite material with prebiotic activity. In this study, pullulan (PUL) was found to stimulate the growth of the probiotic strain Lactobacillus rhamnosus GG better than the other microbial polysaccharides gellan and xanthan. BC/PUL biocomposite with prebiotic properties was obtained by cocultivation of Komagataeibacter xylinus and Aureobasidium pullulans, BC and PUL producers respectively, on molasses medium. The inclusion of PUL in BC is proved gravimetrically by scanning electron microscopy and by Fourier transformed infrared spectroscopy. Cocultivation demonstrated a composite effect on the aggregation and binding of BC fibers, which led to a significant improvement in mechanical properties. The developed approach for “grafting” of prebiotic activity on BC allows preparation of environmentally friendly composites of better quality. Full article
(This article belongs to the Special Issue Cellulose Based Composites)
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12 pages, 2370 KiB  
Article
Novel Immobilized Biocatalysts Based on Cysteine Proteases Bound to 2-(4-Acetamido-2-sulfanilamide) Chitosan and Research on Their Structural Features
by Svetlana S. Olshannikova, Nataliya V. Malykhina, Maria S. Lavlinskaya, Andrey V. Sorokin, Nikolay E. Yudin, Yulia M. Vyshkvorkina, Anatoliy N. Lukin, Marina G. Holyavka and Valeriy G. Artyukhov
Polymers 2022, 14(15), 3223; https://doi.org/10.3390/polym14153223 - 8 Aug 2022
Cited by 11 | Viewed by 2011
Abstract
Briefly, 2-(4-Acetamido-2-sulfanilamide) chitosan, which is a chitosan water-soluble derivative, with molecular weights of 200, 350, and 600 kDa, was successfully synthesized. The immobilization of ficin, papain, and bromelain was carried out by complexation with these polymers. The interaction mechanism of 2-(4-acetamido-2-sulfanilamide) chitosan with [...] Read more.
Briefly, 2-(4-Acetamido-2-sulfanilamide) chitosan, which is a chitosan water-soluble derivative, with molecular weights of 200, 350, and 600 kDa, was successfully synthesized. The immobilization of ficin, papain, and bromelain was carried out by complexation with these polymers. The interaction mechanism of 2-(4-acetamido-2-sulfanilamide) chitosan with bromelain, ficin, and papain was studied using FTIR spectroscopy. It was found that the hydroxy, thionyl, and amino groups of 2-(4-acetamido-2-sulfanilamide) chitosan were involved in the complexation process. Molecular docking research showed that all amino acid residues of the active site of papain formed hydrogen bonds with the immobilization matrix, while only two catalytically valuable amino acid residues took part in the H-bond formation for bromelain and ficin. The spectral and in silico data were in good agreement with the catalytic activity evaluation data. Immobilized papain was more active compared to the other immobilized proteases. Moreover, the total and specific proteolytic activity of papain immobilized on the carrier with a molecular weight of 350 kDa were higher compared to the native one due to the hyperactivation. The optimal ratio of protein content (mg × g −1 of carrier), total activity (U × mL−1 of solution), and specific activity (U × mg−1 of protein) was determined for the enzymes immobilized on 2-(4-acetamido-2-sulfanilamide) chitosan with a molecular weight of 350 kDa. Full article
(This article belongs to the Special Issue Immobilization of Enzyme in Polymers)
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29 pages, 1162 KiB  
Review
In Vivo Bone Tissue Engineering Strategies: Advances and Prospects
by Ilya L. Tsiklin, Aleksey V. Shabunin, Alexandr V. Kolsanov and Larisa T. Volova
Polymers 2022, 14(15), 3222; https://doi.org/10.3390/polym14153222 - 8 Aug 2022
Cited by 33 | Viewed by 4455
Abstract
Reconstruction of critical-sized bone defects remains a tremendous challenge for surgeons worldwide. Despite the variety of surgical techniques, current clinical strategies for bone defect repair demonstrate significant limitations and drawbacks, including donor-site morbidity, poor anatomical match, insufficient bone volume, bone graft resorption, and [...] Read more.
Reconstruction of critical-sized bone defects remains a tremendous challenge for surgeons worldwide. Despite the variety of surgical techniques, current clinical strategies for bone defect repair demonstrate significant limitations and drawbacks, including donor-site morbidity, poor anatomical match, insufficient bone volume, bone graft resorption, and rejection. Bone tissue engineering (BTE) has emerged as a novel approach to guided bone tissue regeneration. BTE focuses on in vitro manipulations with seed cells, growth factors and bioactive scaffolds using bioreactors. The successful clinical translation of BTE requires overcoming a number of significant challenges. Currently, insufficient vascularization is the critical limitation for viability of the bone tissue-engineered construct. Furthermore, efficacy and safety of the scaffolds cell-seeding and exogenous growth factors administration are still controversial. The in vivo bioreactor principle (IVB) is an exceptionally promising concept for the in vivo bone tissue regeneration in a predictable patient-specific manner. This concept is based on the self-regenerative capacity of the human body, and combines flap prefabrication and axial vascularization strategies. Multiple experimental studies on in vivo BTE strategies presented in this review demonstrate the efficacy of this approach. Routine clinical application of the in vivo bioreactor principle is the future direction of BTE; however, it requires further investigation for overcoming some significant limitations. Full article
(This article belongs to the Special Issue Biopolymers for Regenerative Medicine Applications)
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13 pages, 2143 KiB  
Article
The Separation of Chlorobenzene Compounds from Environmental Water Using a Magnetic Molecularly Imprinted Chitosan Membrane
by Guizhen Li, Jinyao Wang, Peng Zhu, Ying Han, Anqi Yu, Junhong Li, Zhaomei Sun and Kyung Ho Row
Polymers 2022, 14(15), 3221; https://doi.org/10.3390/polym14153221 - 8 Aug 2022
Cited by 3 | Viewed by 2368
Abstract
In this work, a magnetic molecularly imprinted chitosan membrane (MMICM) was synthesized for the extraction of chlorobenzene compounds in environmental water using the membrane separation method. The optimal extraction amount for chlorobenzene (9.64 mg·L−1) was found to be a 1:2 solid [...] Read more.
In this work, a magnetic molecularly imprinted chitosan membrane (MMICM) was synthesized for the extraction of chlorobenzene compounds in environmental water using the membrane separation method. The optimal extraction amount for chlorobenzene (9.64 mg·L−1) was found to be a 1:2 solid to liquid ratio, with a 20 min extraction time and 35 °C extraction temperature. This method proved to be successfully applied for the separation and trace quantification of chlorobenzene compounds in environmental water, with the limit of detection (LOD) (0.0016–0.057 ng·L−1), limit of quantification (LOQ) (0.0026–0.098 ng·L−1), and the recoveries ranging (89.02–106.97%). Full article
(This article belongs to the Special Issue Polymer Materials in Environmental Chemistry II)
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24 pages, 5897 KiB  
Article
A QbD Approach to Design and to Optimize the Self-Emulsifying Resveratrol–Phospholipid Complex to Enhance Drug Bioavailability through Lymphatic Transport
by Syed Abul Layes Gausuzzaman, Mithun Saha, Shahid Jaman Dip, Shaiful Alam, Arup Kumar, Harinarayan Das, Shazid Md. Sharker, Md Abdur Rashid, Mohsin Kazi and Hasan Mahmud Reza
Polymers 2022, 14(15), 3220; https://doi.org/10.3390/polym14153220 - 8 Aug 2022
Cited by 12 | Viewed by 2657
Abstract
Objectives: Despite having profound therapeutic value, the clinical application of resveratrol is restrained due to its <1% bioavailability, arising from the extensive fast-pass effect along with enterohepatic recirculation. This study aimed to develop a self-emulsifying formulation capable of increasing the bioavailability of resveratrol [...] Read more.
Objectives: Despite having profound therapeutic value, the clinical application of resveratrol is restrained due to its <1% bioavailability, arising from the extensive fast-pass effect along with enterohepatic recirculation. This study aimed to develop a self-emulsifying formulation capable of increasing the bioavailability of resveratrol via lymphatic transport. Methods: The resveratrol–phospholipid complex (RPC) was formed by the solvent evaporation method and characterized by FTIR, DSC, and XRD analyses. The RPC-loaded self-emulsifying drug delivery system (SEDDS) was designed, developed, and optimized using the QbD approach with an emphasis on resveratrol transport through the intestinal lymphatic pathway. The in vivo pharmacokinetic study was investigated in male Wister Albino rats. Results: The FTIR, DSC, and XRD analyses confirmed the RPC formation. The obtained design space provided robustness of prediction within the 95% prediction interval to meet the CQA specifications. An optimal formulation (desirability value of 7.24) provided Grade-A self-emulsion and exhibited a 48-fold bioavailability enhancement compared to the pure resveratrol. The cycloheximide-induced chylomicron flow blocking approach demonstrated that 91.14% of the systemically available resveratrol was transported through the intestinal lymphatic route. Conclusions: This study suggests that an optimal self-emulsifying formulation can significantly increase the bioavailability of resveratrol through lymphatic transport to achieve the desired pharmacological effects. Full article
(This article belongs to the Special Issue Polymeric Materials for Drug Delivery)
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1 pages, 150 KiB  
Correction
Correction: Bitsi et al. Supramolecular Triblock Copolymers through the Formation of Hydrogen Bonds: Synthesis, Characterization, Association Effects in Solvents of Different Polarity. Polymers 2020, 12, 468
by Spyridoula-Lida Bitsi, Margarita Droulia and Marinos Pitsikalis
Polymers 2022, 14(15), 3219; https://doi.org/10.3390/polym14153219 - 8 Aug 2022
Viewed by 916
Abstract
The authors wish to make the following corrections to the published paper [...] Full article
20 pages, 4396 KiB  
Article
Molecular Insights into the Wall Slip Behavior of Pseudoplastic Polymer Melt in Nanochannels during Micro Injection Molding
by Wangqing Wu, Fengnan Duan, Baishun Zhao, Yuanbao Qiang, Mingyong Zhou and Bingyan Jiang
Polymers 2022, 14(15), 3218; https://doi.org/10.3390/polym14153218 - 8 Aug 2022
Cited by 2 | Viewed by 2137
Abstract
Wall slip directly affects the molding quality of plastic parts by influencing the stability of the filling flow field during micro injection molding. The accurate modeling of wall slip in nanochannels has been a great challenge for pseudoplastic polymer melts. Here, an effective [...] Read more.
Wall slip directly affects the molding quality of plastic parts by influencing the stability of the filling flow field during micro injection molding. The accurate modeling of wall slip in nanochannels has been a great challenge for pseudoplastic polymer melts. Here, an effective modeling method for polymer melt flow in nanochannels based on united-atom molecular dynamics simulations is presented. The effects of driving forces and wall–fluid interactions on the behavior of polyethylene melt under Poiseuille flow conditions were investigated by characterizing the slip velocity, dynamics information of the flow process, and spatial configuration parameters of molecular chains. The results indicated that the united-atom molecular dynamics model could better describe the pseudoplastic behavior in nanochannels than the commonly used finitely extensible nonlinear elastic (FENE) model. It was found that the slip velocity could be increased with increasing driving force and show completely opposite variation trends under different orders of magnitude of the wall–fluid interactions. The influence mechanism was interpreted by the density distribution and molecular chain structure parameters, including disentanglement and orientation, which also coincides with the change in the radius of gyration. Full article
(This article belongs to the Special Issue Molecular Simulation and Modeling of Polymers)
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21 pages, 2422 KiB  
Review
Natural Polysaccharide-Based Nanodrug Delivery Systems for Treatment of Diabetes
by Aijun Qiu, Yunyun Wang, Genlin Zhang and Hebin Wang
Polymers 2022, 14(15), 3217; https://doi.org/10.3390/polym14153217 - 8 Aug 2022
Cited by 39 | Viewed by 4419
Abstract
In recent years, natural polysaccharides have been considered as the ideal candidates for novel drug delivery systems because of their good biocompatibility, biodegradation, low immunogenicity, renewable source and easy modification. These natural polymers are widely used in the designing of nanocarriers, which possess [...] Read more.
In recent years, natural polysaccharides have been considered as the ideal candidates for novel drug delivery systems because of their good biocompatibility, biodegradation, low immunogenicity, renewable source and easy modification. These natural polymers are widely used in the designing of nanocarriers, which possess wide applications in therapeutics, diagnostics, delivery and protection of bioactive compounds or drugs. A great deal of studies could be focused on developing polysaccharide nanoparticles and promoting their application in various fields, especially in biomedicine. In this review, a variety of polysaccharide-based nanocarriers were introduced, including nanoliposomes, nanoparticles, nanomicelles, nanoemulsions and nanohydrogels, focusing on the latest research progress of these nanocarriers in the treatment of diabetes and the possible strategies for further study of polysaccharide nanocarriers. Full article
(This article belongs to the Special Issue Advanced Biopolymers from Natural Resources)
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13 pages, 3950 KiB  
Article
Basalt Fiber Composites with Reduced Thermal Expansion for Additive Manufacturing
by Daniel Moreno-Sanchez, Alberto Sanz de León, Daniel Moreno Nieto, Francisco J. Delgado and Sergio I. Molina
Polymers 2022, 14(15), 3216; https://doi.org/10.3390/polym14153216 - 8 Aug 2022
Cited by 11 | Viewed by 2437
Abstract
Fused filament fabrication (FFF) is gaining attention as an efficient way to create parts and replacements on demand using thermoplastics. This technology requires the development of new materials with a reliable printability that satisfies the requirement of final parts. In this context, a [...] Read more.
Fused filament fabrication (FFF) is gaining attention as an efficient way to create parts and replacements on demand using thermoplastics. This technology requires the development of new materials with a reliable printability that satisfies the requirement of final parts. In this context, a series of composites based on acrylonitrile styrene acrylate (ASA) reinforced with basalt fiber (BF) are reported in this work. First, several surface modification treatments are applied onto the BF to increase their compatibility with the ASA matrix. Then, once the best treatment is identified, the mechanical properties, coefficient of thermal expansion (CTE) and warping distortion of the different specimens designed and prepared by FFF are studied. It was found that the silanized BF is appropriate for an adequate printing, obtaining composites with higher stiffness, tensile strength, low CTE and a significant reduction in part distortion. These composites are of potential interest in the design and manufacturing of final products by FFF, as they show much lower CTE values than pure ASA, which is essential to successfully fabricate large objects using this technique. Full article
(This article belongs to the Special Issue Polymers and Polymer-Based Composites for Additive Manufacturing)
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17 pages, 6451 KiB  
Article
Laboratory Experiments and Numerical Simulation Study of Composite-Material-Modified Loess Improving High-Speed Railway Subgrade
by Li Luo, Xingang Wang, Chen Xue, Daozheng Wang and Baoqin Lian
Polymers 2022, 14(15), 3215; https://doi.org/10.3390/polym14153215 - 8 Aug 2022
Cited by 10 | Viewed by 2653
Abstract
Construction of high-speed railway subgrade on loess soils in the Loess Plateau is risky because such soil is susceptible to differential settlements. Various soil-improvement methods have been used to enhance the mechanical properties of loess. Lime-ash soil and cement-lime soil are the most [...] Read more.
Construction of high-speed railway subgrade on loess soils in the Loess Plateau is risky because such soil is susceptible to differential settlements. Various soil-improvement methods have been used to enhance the mechanical properties of loess. Lime-ash soil and cement-lime soil are the most commonly used methods in the improvement of loess subgrade, while few studies have been found on loess subgrade improvement by using composite material consisting of traditional materials and new materials. A series of direct shear tests and unconfined compressive tests were conducted on the loess specimen with the addition of three kinds of composite materials: traditional material cement, new material polypropylene fiber and SCA-2 soil curing agent. The numerical simulation was conducted on loess subgrade in an actual engineering practice. The experimental results show that cement, polypropylene fiber and SCA-2 soil curing agent can effectively improve the shear strength and compressive strength of loess, and the influence degree is cement > fiber > curing agent. Additionally, based on the relative strength characteristics of the improved loess, an optimal improvement scheme for the composite-material-modified loess was obtained: 16% cement content + 0.5% fiber content + 4% curing agent content. The numerical simulation results revealed that the compressive strength index of the improved loess has a significant impact on the subgrade settlement, and the optimal improvement scheme obtained from comprehensive analysis can effectively improve the settlement of high-speed railway subgrade under vibration load. Full article
(This article belongs to the Special Issue Polymeric Composites in Road and Bridge Engineering: Characterization, Production and Application)
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10 pages, 2093 KiB  
Article
Microfoamed Strands by 3D Foam Printing
by Daniele Tammaro, Massimiliano Maria Villone and Pier Luca Maffettone
Polymers 2022, 14(15), 3214; https://doi.org/10.3390/polym14153214 - 7 Aug 2022
Cited by 12 | Viewed by 2643
Abstract
We report the design, production, and characterization of microfoamed strands by means of a green and sustainable technology that makes use of CO2 to create ad-hoc innovative bubble morphologies. 3D foam-printing technology has been recently developed; thus, the foaming mechanism in the [...] Read more.
We report the design, production, and characterization of microfoamed strands by means of a green and sustainable technology that makes use of CO2 to create ad-hoc innovative bubble morphologies. 3D foam-printing technology has been recently developed; thus, the foaming mechanism in the printer nozzle is not yet fully understood and controlled. We study the effects of the operating parameters of the 3D foam-printing process to control and optimize CO2 utilization through a maximization of the foaming efficiency. The strands’ mechanical properties were measured as a function of the foam density and explained by means of an innovative model that takes into consideration the polymer’s crystallinity content. The innovative microfoamed morphologies were produced using a bio-based and compostable polymer as well as polylactic acid and were then blown with CO2. The results of the extensive experimental campaigns show insightful maps of the bubble size, density, and crystallinity as a function of the process parameters, i.e., the CO2 concentration and temperature. A CO2 content of 15 wt% enables the acquirement of an incredibly low foam density of 40 kg/m3 and porosities from the macro-scale (100–900 μm) to the micro-scale (1–10 μm), depending on the temperature. The foam crystallinity content varied from 5% (using a low concentration of CO2) to 45% (using a high concentration of CO2). Indeed, we determined that the crystallinity content changes linearly with the CO2 concentration. In turn, the foamed strand’s elastic modulus is strongly affected by the crystallinity content. Hence, a corrected Egli’s equation was proposed to fit the strand mechanical properties as a function of foam density. Full article
(This article belongs to the Special Issue Advanced Cellular Polymers)
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24 pages, 17923 KiB  
Article
Mechanical Characteristics Evaluation of a Single Ply and Multi-Ply Carbon Fiber-Reinforced Plastic Subjected to Tensile and Bending Loads
by Anton Hadăr, Florin Baciu, Andrei-Daniel Voicu, Daniel Vlăsceanu, Daniela-Ioana Tudose and Cătălin Adetu
Polymers 2022, 14(15), 3213; https://doi.org/10.3390/polym14153213 - 7 Aug 2022
Cited by 14 | Viewed by 3135
Abstract
Carbon fiber-reinforced composites represent a broadly utilized class of materials in aeronautical applications, due to their high-performance capability. The studied CFRP is manufactured from a 3K carbon biaxial fabric 0°/90° with high tensile resistance, reinforced with high-performance thermoset molding epoxy vinyl ester resin. [...] Read more.
Carbon fiber-reinforced composites represent a broadly utilized class of materials in aeronautical applications, due to their high-performance capability. The studied CFRP is manufactured from a 3K carbon biaxial fabric 0°/90° with high tensile resistance, reinforced with high-performance thermoset molding epoxy vinyl ester resin. The macroscale experimental characterization has constituted the subject of various studies, with the scope of assessing overall structural performance. This study, on the other hand, aims at evaluating the mesoscopic mechanical behavior of a single-ply CFRP, by utilizing tensile test specimens with an average experimental study area of only 3 cm2. The single-ply tensile testing was accomplished using a small scale custom-made uniaxial testing device, powered by a stepper motor, with measurements recorded by two 5-megapixel cameras of the DIC Q400 system, mounted on a Leica M125 digital stereo microscope. The single-ply testing results illustrated the orthotropic nature of the CFRP and turned out to be in close correlation with the multi-ply CFRP tensile and bending tests, resulting in a comprehensive material characterization. The results obtained for the multi-ply tensile and flexural characteristics are adequate in terms of CFRP expectations, having a satisfactory precision. The results have been evaluated using a broad experimental approach, consisting of the Dantec Q400 standard digital image correlation system, facilitating the determination of Poisson’s ratio, correlated with the measurements obtained from the INSTRON 8801 servo hydraulic testing system’s load cell, for a segment of the tensile and flexural characteristics determination. Finite element analyses were realized to reproduce the tensile and flexural test conditions, based on the experimentally determined stress–strain evolution of the material. The FEA results match very well with the experimental results, and thus will constitute the basis for further FEA analyses of aeronautic structures. Full article
(This article belongs to the Special Issue Functional Polymer Composites: Design, Preparation and Applications)
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15 pages, 6194 KiB  
Article
Preparation and Properties of PED-TDI Polyurethane-Modified Silicone Coatings
by Xiaojun Xi, Zhanping Zhang and Yuhong Qi
Polymers 2022, 14(15), 3212; https://doi.org/10.3390/polym14153212 - 6 Aug 2022
Cited by 2 | Viewed by 2827
Abstract
To explore the influence mechanisms of polyurethane soft segments on modified silicone coatings, a series of modified coatings was prepared by introducing different contents of hydroxypropyl-terminated polydimethylsiloxane (PDMS2200) into the soft segment of polyurethane. ATR-FTIR, NMR, CLSM, AFM, contact angle measurement, the tensile [...] Read more.
To explore the influence mechanisms of polyurethane soft segments on modified silicone coatings, a series of modified coatings was prepared by introducing different contents of hydroxypropyl-terminated polydimethylsiloxane (PDMS2200) into the soft segment of polyurethane. ATR-FTIR, NMR, CLSM, AFM, contact angle measurement, the tensile test, bacterial adhesion, and the benthic diatom adhesion test were used to investigate the structure, morphology, roughness, degree of microphase separation, surface energy, tensile properties, and antifouling properties of the modified coatings. The results show that PDMS2200 could aggravate the microphase separation of the modified coatings, increase the surface-free energy, and reduce its elastic modulus; when the microphase separation exceeded a certain degree, increasing PDMS2200 would decrease the tensile properties. The PED-TDI polyurethane-modified silicone coating prepared with the formula of PU-Si17 had the best tensile properties and antifouling properties among all modified coatings. Full article
(This article belongs to the Collection Silicon-Containing Polymeric Materials)
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14 pages, 3830 KiB  
Article
Fabrication of Low-Molecular-Weight Hyaluronic Acid–Carboxymethyl Cellulose Hybrid to Promote Bone Growth in Guided Bone Regeneration Surgery: An Animal Study
by Chun-Yu Lin, Po-Jan Kuo, Ya-Hui Lin, Chi-Yu Lin, Jerry Chin-Yi Lin, Hsien-Chung Chiu, Tsung-Fu Hung, Hung-Yun Lin and Haw-Ming Huang
Polymers 2022, 14(15), 3211; https://doi.org/10.3390/polym14153211 - 6 Aug 2022
Cited by 4 | Viewed by 2011
Abstract
Guided bone regeneration surgery is an important dental operation used to regenerate enough bone to successfully heal dental implants. When this technique is performed on maxilla sinuses, hyaluronic acid (HLA) can be used as an auxiliary material to improve the graft material handling [...] Read more.
Guided bone regeneration surgery is an important dental operation used to regenerate enough bone to successfully heal dental implants. When this technique is performed on maxilla sinuses, hyaluronic acid (HLA) can be used as an auxiliary material to improve the graft material handling properties. Recent studies have indicated that low-molecular hyaluronic acid (L-HLA) provides a better regeneration ability than high-molecular-weight (H-HLA) analogues. The aim of this study was to fabricate an L-HLA-carboxymethyl cellulose (CMC) hybrid to promote bone regeneration while maintaining viscosity. The proliferation effect of fabricated L-HLA was tested using dental pulp stem cells (DPSCs). The mitogen-activated protein kinase (MAPK) pathway was examined using cells cultured with L-HLA combined with extracellular-signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 inhibitors. The bone growth promotion of fabricated L-HLA/CMC hybrids was tested using an animal model. Micro-computer tomography (Micro-CT) and histological images were evaluated quantitatively to compare the differences in the osteogenesis between the H-HLA and L-HLA. Our results show that the fabricated L-HLA can bind to CD44 on the DPSC cell membranes and affect MAPK pathways, resulting in a prompt proliferation rate increase. Micro CT images show that new bone formation in rabbit calvaria defects treated with L-HLA/CMC was almost two times higher than in defects filled with H-HLA/CMC (p < 0.05) at 4 weeks, a trend that remained at 8 weeks and was confirmed by HE-stained images. According to these findings, it is reasonable to conclude that L-HLA provides better bone healing than H-HLA, and that the L-HLA/CMC fabricated in this study is a potential candidate for improving bone healing efficiency when a guided bone regeneration surgery was performed. Full article
(This article belongs to the Special Issue Medical Application of Polymer-Based Composites III)
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15 pages, 4540 KiB  
Article
Influence of Biofillers on the Properties of Regrind Crystalline Poly(ethylene terephthalate) (CPET)
by Victor S. Cecon, Greg W. Curtzwiler and Keith L. Vorst
Polymers 2022, 14(15), 3210; https://doi.org/10.3390/polym14153210 - 6 Aug 2022
Cited by 2 | Viewed by 2549
Abstract
As the demand for plastics only increases, new methods are required to economically and sustainably increase plastic usage without landfill and environmental accumulation. In addition, the use of biofillers is encouraged as a way to reduce the cost of the final resin by [...] Read more.
As the demand for plastics only increases, new methods are required to economically and sustainably increase plastic usage without landfill and environmental accumulation. In addition, the use of biofillers is encouraged as a way to reduce the cost of the final resin by incorporating agricultural and industrial waste by-products, such as rice hulls and coffee chaff to further reduce waste being sent to landfills. Crystalline poly(ethylene terephthalate) (CPET) is a resin commonly used for microwave and ovenable food packaging containers that have not been fully explored for recycling. In this article, we investigate how the incorporation of biofillers at 5% wt. and 10% wt. impacts critical polymer properties. The thermal and mechanical properties were not significantly altered with the presence of rice hulls or coffee chaff in the polymer matrix at 5% wt. loading, but some reduction in melt temperature, thermal stability, and maximum stress and strain was more noticed at 10% wt. The complex viscosity was also reduced with the introduction of biofillers. The levels of heavy metals of concern, such as Cd, Cr, and Pb, were below the regulatory limits applicable in the United States and Europe. Additional studies are suggested to improve the performance of CPET/biofiller blends by pre-treating the biofiller and using compatibilizers. Full article
(This article belongs to the Special Issue Recycled Polymers: Eco-Design, Structure/Property Relationships and Compatibility)
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30 pages, 7034 KiB  
Article
Fresh, Mechanical, and Durability Behavior of Fly Ash-Based Self Compacted Geopolymer Concrete: Effect of Slag Content and Various Curing Conditions
by Aryan Far H. Sherwani, Khaleel H. Younis and Ralf W. Arndt
Polymers 2022, 14(15), 3209; https://doi.org/10.3390/polym14153209 - 6 Aug 2022
Cited by 18 | Viewed by 2732
Abstract
This investigation evaluates the influence of various curing conditions and slag inclusion on the fresh, mechanical, and durability properties of self-compacting geopolymer concrete (SCGC) based on fly ash (FA). Curing temperature and curing time have a vital role in the strength and microstructure [...] Read more.
This investigation evaluates the influence of various curing conditions and slag inclusion on the fresh, mechanical, and durability properties of self-compacting geopolymer concrete (SCGC) based on fly ash (FA). Curing temperature and curing time have a vital role in the strength and microstructure of geopolymer concrete. Therefore, to begin the research, the impacts of different curing conditions (curing temperature and curing time) and slag content on the compressive strength of FA-based SCGC were examined to determine the optimum curing method. A series of four SCGC mixes with a fixed binder content (450 kg/m3) and an alkaline/binder ratio of 0.5 was designated to conduct a parametric study. FA was replaced with slag at four different substitution percentages, including 0%, 30%, 50%, and 100% of the total weight of the binder. The fresh properties of the produced SCGC specimens were investigated in terms of slump flow diameter, T50 flow time, and L-box height ratio. Additionally, the following mechanical properties of SCGC specimens were investigated: modulus of elasticity and fracture parameters. The water permeability and freezing–thawing resistance were studied to determine the durability behavior of SCGC. In this study, the optimum curing temperature was 85 °C for the duration of 24 h, which provided the maximum compressive strength. The results confirmed that adding slag affected the workability of SCGC mixtures. However, the mechanical characteristics, fracture parameters, and durability performance of SCGC were improved for slag-rich mixtures. When using 50% slag instead of FA, the percentage increase in compressive, flexural, elastic module, and fracture energy test values were about 100%, 43%, 58%, and 55%, respectively, whilst the percentage decrease in water permeability was 65% and the resistance to freeze–thaw test in terms of surface scaling was enhanced by 79%. Full article
(This article belongs to the Special Issue Polymer and Geopolymer Concrete Composites for Sustainable Development)
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18 pages, 3895 KiB  
Article
Oil Palm Empty Fruit Bunches as Raw Material of Dissolving Pulp for Viscose Rayon Fiber in Making Textile Products
by Siti Nikmatin, Irmansyah Irmansyah, Bambang Hermawan, Teddy Kardiansyah, Frederikus Tunjung Seta, Irma Nur Afiah and Rofiqul Umam
Polymers 2022, 14(15), 3208; https://doi.org/10.3390/polym14153208 - 6 Aug 2022
Cited by 5 | Viewed by 3479
Abstract
The creative fashion industry produces several textile products that play an important role in the national economy. In various countries, this industry has continued to grow along with the strong flow of information technology and e-commerce. The development of textile products for fashion [...] Read more.
The creative fashion industry produces several textile products that play an important role in the national economy. In various countries, this industry has continued to grow along with the strong flow of information technology and e-commerce. The development of textile products for fashion is very dynamic and competitive. Competition is not only about price, but also the quality of organic/synthetic materials, the comfort provided, and designs that change every 4–6 months. Recently, creative fashion not only relies on natural and synthetic polymer-made fibers but also biomass-based waste materials. Therefore, this study aims to manufacture textile products from biomass-based waste materials that can be applied to the creative fashion industry. Two types of raw materials from oil palm empty fruit bunches (EFB), namely, whole-empty fruit bunches (WEFB) and stalk-empty fruit bunches (SEFB), are used as an excellent innovation of rayon viscose fiber (RVF), a noncotton organic yarn capable of providing a solution to the 99% import of global cotton needs. This is expected to increase competitiveness, as well as the added value of palm oil products and their derivatives. The process of manufacturing DP chemically includes prehydrolysis, cooking, bleaching to dissolve the lignin and noncellulosic materials as well as isolation to purify POEFB fiber. Furthermore, DP testing is carried out to determine product quality and compare it with the national product standards. The results show that the alpha-cellulose content reaches >94% with variations in the active alkali of 18%, 20% and 24%. This implies that the WEFB and SEFB are used to fulfill the first requirements of the national standard (SNI 938:2017). The WEFB with an active alkali variation of 24% meets the SNI standard for rayon pulp with a value of S10 = 3.07 and S18 = 7.14%, while all variations of SEFB show opposite results. The use of active alkali at 24% had a brighter color than between 18% and 20%. Additionally, the fiber density of WEFB appears to be higher than that of SEFB. These results correlate positively with DP prepared using 24% alkali as the optimum treatment for all products, as well as the morphological observations performed with scanning electron microscopy (SEM), which shows that WEFB fixated fiber had a larger diameter than SEFB. Full article
(This article belongs to the Section Polymer Fibers)
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17 pages, 33141 KiB  
Article
Durability and Long-Term Performance Prediction of Carbon Fiber Reinforced Polymer Laminates
by Eyad Alsuhaibani, Nur Yazdani and Eyosias Beneberu
Polymers 2022, 14(15), 3207; https://doi.org/10.3390/polym14153207 - 5 Aug 2022
Cited by 10 | Viewed by 2266
Abstract
The feasibility of strengthening deteriorated or under-capacity concrete structures with external carbon-fiber-reinforced polymer (CFRP) laminates has been widely validated in the literature. However, there is a lack of knowledge on the in situ long-term performance and age-related environmental degradation of the mechanical properties [...] Read more.
The feasibility of strengthening deteriorated or under-capacity concrete structures with external carbon-fiber-reinforced polymer (CFRP) laminates has been widely validated in the literature. However, there is a lack of knowledge on the in situ long-term performance and age-related environmental degradation of the mechanical properties of the laminates. The current study involved the immersion of coupons from a common new CFRP laminate in heated water at 23, 45, and 60 °C for 224 days. The coupons were then tested for residual tensile properties, such as tensile capacity and elastic modulus, using ASTM D3039 (2017) specifications. The CFRP tensile capacity and elastic modulus decreased by a maximum of 33% and 26%, respectively, for 224 days of exposure. Based on the test data, an age-based long-term prediction model with excellent reliability for CFRP laminate tensile capacity was developed. The model was then calibrated with test results from old CFRP coupons collected from an existing CFRP laminate retrofitted concrete bridge. The calibrated model output was then compared with the environmental reduction factor from ACI 440.2R-17 and a few other common sources. It was found that the ACI specified a reduction factor of 0.75, which does not consider the CFRP age and overestimates the design tensile strength of the CFRP laminate by approximately 13%, which may compromise the structural safety of retrofitted bridges. The reduction factors from the other guidelines varied between 0.51 and 0.85. Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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34 pages, 2663 KiB  
Review
A Review on the Modification of Cellulose and Its Applications
by Tariq Aziz, Arshad Farid, Fazal Haq, Mehwish Kiran, Asmat Ullah, Kechun Zhang, Cheng Li, Shakira Ghazanfar, Hongyue Sun, Roh Ullah, Amjad Ali, Muhammad Muzammal, Muddaser Shah, Nosheen Akhtar, Samy Selim, Nashwa Hagagy, Mennatalla Samy and Soad K. Al Jaouni
Polymers 2022, 14(15), 3206; https://doi.org/10.3390/polym14153206 - 5 Aug 2022
Cited by 149 | Viewed by 26977
Abstract
The latest advancements in cellulose and its derivatives are the subject of this study. We summarize the characteristics, modifications, applications, and properties of cellulose. Here, we discuss new breakthroughs in modified cellulose that allow for enhanced control. In addition to standard approaches, improvements [...] Read more.
The latest advancements in cellulose and its derivatives are the subject of this study. We summarize the characteristics, modifications, applications, and properties of cellulose. Here, we discuss new breakthroughs in modified cellulose that allow for enhanced control. In addition to standard approaches, improvements in different techniques employed for cellulose and its derivatives are the subject of this review. The various strategies for synthetic polymers are also discussed. The recent advancements in polymer production allow for more precise control, and make it possible to make functional celluloses with better physical qualities. For sustainability and environmental preservation, the development of cellulose green processing is the most abundant renewable substance in nature. The discovery of cellulose disintegration opens up new possibilities for sustainable techniques. Based on the review of recent scientific literature, we believe that additional chemical units of cellulose solubility should be used. This evaluation will evaluate the sustainability of biomass and processing the greenness for the long term. It appears not only crucial to dissolution, but also to the greenness of any process. Full article
(This article belongs to the Special Issue Biomass Conversion and Green Chemistry in Polymer Science)
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15 pages, 3392 KiB  
Article
In Vitro Evaluation of Kaempferol-Loaded Hydrogel as pH-Sensitive Drug Delivery Systems
by Qin Zhang, Xinying Yang, Yifang Wu, Chang Liu, Hongmei Xia, Xiaoman Cheng, Yongfeng Cheng, Ying Xia and Yu Wang
Polymers 2022, 14(15), 3205; https://doi.org/10.3390/polym14153205 - 5 Aug 2022
Cited by 14 | Viewed by 2516
Abstract
The purpose of this study was to prepare and evaluate kaempferol-loaded carbopol polymer (acrylic acid) hydrogel, investigate its antioxidant activity in vitro, and compare the effects on drug release under different pH conditions. Drug release studies were conducted in three different pH media [...] Read more.
The purpose of this study was to prepare and evaluate kaempferol-loaded carbopol polymer (acrylic acid) hydrogel, investigate its antioxidant activity in vitro, and compare the effects on drug release under different pH conditions. Drug release studies were conducted in three different pH media (pH 3.4, 5.4, and 7.4). The kaempferol-loaded hydrogel was prepared by using carbopol 934 as the hydrogel matrix. The morphology and viscosity of the preparation were tested to understand the fluidity of the hydrogel. The antioxidant activity of the preparation was studied by scavenging hydrogen peroxide and 2,2-diphenyl-1-picrilhidrazil (DPPH) radicals in vitro and inhibiting the production of malondialdehyde in mouse tissues. The results showed that kaempferol and its preparations had high antioxidant activity. In vitro release studies showed that the drug release at pH 3.4, 5.4, and 7.4 was 27.32 ± 3.49%, 70.89 ± 8.91%, and 87.9 ± 10.13%, respectively. Kaempferol-loaded carbopol hydrogel displayed greater swelling and drug release at higher pH values (pH 7.4). Full article
(This article belongs to the Special Issue Advances in Smart Polymers and Materials)
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15 pages, 3730 KiB  
Article
Printing Polymeric Convex Lenses to Boost the Sensitivity of a Graphene-Based UV Sensor
by Jonghyun Kim, Dongwoon Shin and Jiyoung Chang
Polymers 2022, 14(15), 3204; https://doi.org/10.3390/polym14153204 - 5 Aug 2022
Viewed by 2105
Abstract
Ultraviolet (UV) is widely used in daily life as well as in industrial manufacturing. In this study, a single-step postprocess to improve the sensitivity of a graphene-based UV sensor is studied. We leverage the advantage of electric-field-assisted on-demand printing, which is simply applicable [...] Read more.
Ultraviolet (UV) is widely used in daily life as well as in industrial manufacturing. In this study, a single-step postprocess to improve the sensitivity of a graphene-based UV sensor is studied. We leverage the advantage of electric-field-assisted on-demand printing, which is simply applicable for mounting functional polymers onto various structures. Here, the facile printing process creates optical plano-convex geometry by accelerating and colliding a highly viscous droplet on a micropatterned graphene channel. The printed transparent lens refracts UV rays. The concentrated UV photon energy from a wide field of view enhances the photodesorption of electron-hole pairs between the lens and the graphene sensor channel, which is coupled with a large change in resistance. As a result, the one-step post-treatment has about a 4× higher sensitivity compared to bare sensors without the lenses. We verify the applicability of printing and the boosting mechanism by variation of lens dimensions, a series of UV exposure tests, and optical simulation. Moreover, the method contributes to UV sensing in acute angle or low irradiation. In addition, the catalytic lens provides about a 9× higher recovery rate, where water molecules inside the PEI lens deliver fast reassembly of the electron-hole pairs. The presented method with an ultimately simple fabrication step is expected to be applied to academic research and prototyping, including optoelectronic sensors, energy devices, and advanced manufacturing processes. Full article
(This article belongs to the Special Issue Polymer-Based Materials for Sensors)
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24 pages, 7842 KiB  
Article
Two-Dimensional Simulation of the Freezing Characteristics in PEMFCs during Cold Start Considering Ice Crystallization Kinetics
by Panxing Jiang, Zhigang Zhan, Di Zhang, Chenlong Wang, Heng Zhang and Mu Pan
Polymers 2022, 14(15), 3203; https://doi.org/10.3390/polym14153203 - 5 Aug 2022
Cited by 7 | Viewed by 2056
Abstract
Cold start is one of the major issues that hinders the commercialization of polymer electrolyte membrane fuel cells (PEMFCs). In this study, a 2D transient multi-physics model is developed to simulate the cold start processes in a PEMFC. The phase change between water [...] Read more.
Cold start is one of the major issues that hinders the commercialization of polymer electrolyte membrane fuel cells (PEMFCs). In this study, a 2D transient multi-physics model is developed to simulate the cold start processes in a PEMFC. The phase change between water vapor, liquid water, and ice in the catalyst layers (CLs), micro porous layer (MPLs), and gas diffusion layers (GDLs) is also investigated, particularly the effect of ice crystallization kinetics when supercooled liquid water changes into ice. The factors affecting the different operating conditions and structural features of the membrane electrode assembly (MEA) are investigated. The results show that when the start temperature is −20 °C or higher, ice formation is delayed and the formation rate is decreased, and supercooled liquid water permeates from the CL into the MPL. For an MEA with relatively high hydrophobicity, the water permeation rate is high. These results can enable a PEMFC to start at subzero temperatures. The effect of ice crystallization kinetics is negligible when the fuel cell is started at −30 °C or below. Full article
(This article belongs to the Special Issue Advance in New Energy Materials and Devices)
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12 pages, 2560 KiB  
Article
The Study of Manufacturing Thermal Insulation Materials Based on Inorganic Polymers under Microwave Exposure
by Tatyana Rymar, Halyna Tatarchenko, Oleksij Fomin, Václav Píštěk, Pavel Kučera, Martin Beran and Oleksij Burlutskyy
Polymers 2022, 14(15), 3202; https://doi.org/10.3390/polym14153202 - 5 Aug 2022
Cited by 5 | Viewed by 2317
Abstract
The work is devoted to the creation of an energy-saving microwave technology of composite materials for thermal insulation based on an inorganic polymer—liquid glass—and the establishment of the formation patterns of their structure and properties, depending on the parameters of microwave radiation. Due [...] Read more.
The work is devoted to the creation of an energy-saving microwave technology of composite materials for thermal insulation based on an inorganic polymer—liquid glass—and the establishment of the formation patterns of their structure and properties, depending on the parameters of microwave radiation. Due to volumetric heating and the mechanism of "non-thermal" action of microwave radiation on processed objects, the duration of their heating is significantly reduced, and the performance properties of products are improved due to the modification of the structure of the liquid glass matrix under the influence of its irradiation with this type of energy. In the course of the research, the relationship between the processing conditions and the obtained properties of heat-insulating materials was established. The prospects of using the microwave electromagnetic field in the production of new building materials, expanding their range, and improving quality and competitiveness are shown, which is a priority for the modernization and innovative development of the construction industry. Full article
(This article belongs to the Section Polymer Applications)
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32 pages, 8535 KiB  
Review
Spectroelectrochemistry of Electroactive Polymer Composite Materials
by Oxana L. Gribkova and Alexander A. Nekrasov
Polymers 2022, 14(15), 3201; https://doi.org/10.3390/polym14153201 - 5 Aug 2022
Cited by 5 | Viewed by 2893
Abstract
In this review, we have summarized the main advantages of the method of spectroelectrochemistry as applied to recent studies on electrosynthesis and redox processes of electroactive polymer composite materials, which have found wide application in designing organic optoelectronic devices, batteries and sensors. These [...] Read more.
In this review, we have summarized the main advantages of the method of spectroelectrochemistry as applied to recent studies on electrosynthesis and redox processes of electroactive polymer composite materials, which have found wide application in designing organic optoelectronic devices, batteries and sensors. These polymer composites include electroactive polymer complexes with large unmovable dopant anions such as polymer electrolytes, organic dyes, cyclodextrins, poly(β-hydroxyethers), as well as polymer-inorganic nanocomposites. The spectroelectrochemical methods reviewed include in situ electron absorption, Raman, infrared and electron spin resonance spectroscopies. Full article
(This article belongs to the Section Polymer Applications)
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13 pages, 2131 KiB  
Article
The Analysis of Acute and Subacute Toxicity of Silver Selenide Nanoparticles Encapsulated in Arabinogalactan Polymer Matrix
by Evgeniy A. Titov, Larisa M. Sosedova, Mikhail A. Novikov, Marina V. Zvereva, Viktor S. Rukavishnikov and Oleg L. Lakhman
Polymers 2022, 14(15), 3200; https://doi.org/10.3390/polym14153200 - 5 Aug 2022
Cited by 4 | Viewed by 1908
Abstract
The acute and subacute toxicity of a newly synthesized silver selenide nanoparticles encapsulated in a natural polymeric matrix of arabinogalactan study has been studied. The nanocomposite is a promising material for the design of diagnostic and therapeutic drugs. It can also be used [...] Read more.
The acute and subacute toxicity of a newly synthesized silver selenide nanoparticles encapsulated in a natural polymeric matrix of arabinogalactan study has been studied. The nanocomposite is a promising material for the design of diagnostic and therapeutic drugs. It can also be used for the preparation of fluorescent labels and in thermal oncotherapy. The employment of binary nanocomposites enables one to unveil the potential hidden in metals which constitute these composites. The study of acute toxicity, carried out by the oral administration of nanocomposites at a dose of 2000 mg/kg, has shown that the compound belongs to low-toxic substances of the 5th hazard class. With the subacute oral administration of nanocomposites at a dose of 500 μg/kg, slight changes are observed in the brain tissue and liver of experimental animals, indicating the development of compensatory–adaptive reactions. In the kidneys, the area of the Shumlyansky–Bowman chamber decreases by 40.5% relative to the control group. It is shown that the application of the protective properties of selenium, which is contained in the composite, helps to reduce the toxicity of silver. Full article
(This article belongs to the Special Issue Biomedical Applications of Polymeric Materials)
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