Polymers

19 pages, 8167 KiB

Open AccessArticle

Low Molecular Weight Bio-Polyamide 11 Composites Reinforced with Flax and Intraply Flax/Basalt Hybrid Fabrics for Eco-Friendlier Transportation Components

by Claudia Sergi, Libera Vitiello, Patrick Dang, Pietro Russo, Jacopo Tirillò and Fabrizio Sarasini

Polymers 2022, 14(22), 5053; https://doi.org/10.3390/polym14225053 - 21 Nov 2022

Cited by 3 | Viewed by 1551

Abstract

The transportation sector is striving to meet the more severe European legislation which encourages all industrial fields to embrace more eco-friendly policies by exploiting constituents from renewable resources. In this framework, the present work assessed the potential of a bio-based, low molecular weight [...] Read more.

The transportation sector is striving to meet the more severe European legislation which encourages all industrial fields to embrace more eco-friendly policies by exploiting constituents from renewable resources. In this framework, the present work assessed the potential of a bio-based, low molecular weight PA11 matrix reinforced with flax and intraply flax/basalt hybrid fabrics. To this aim, both quasi-static and impact performance were addressed through three-point bending and low-velocity impact tests, respectively. For hybrid composites, the effect of stacking sequence, i.e., [0/0] and [0/90], and fiber orientation were considered, while the effect of temperature, i.e., −40 °C, room temperature and +45 °C, was investigated for laminates’ impact response. The mechanical experimental campaign was supported by thermal and morphological analyses. The results disclosed an improved processability of the low molecular weight PA11, which ensured a manufacturing temperature of 200 °C, which is fundamental to minimize flax fibers’ thermal degradation. Both quasi-static and impact properties demonstrated that hybridization is a good solution for obtaining good mechanical properties while preserving laminates’ lightness and biodegradability. The [0/90] configuration proved to be the best solution, providing satisfying flexural performance, with an increase between 62% and 83% in stiffness and between 19.6% and 37.6% in strength compared to flax-based laminates, and the best impact performance, with a reduction in permanent indentation and back crack extent. Full article

(This article belongs to the Special Issue Progress in Polymer Composites for Different Applications)

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17 pages, 5527 KiB

Open AccessArticle

Norbornene as Key for a Possible Efficient Chemical Recycling in Structures Based on Ethylene

by Antonio F. Calles-Valero, Alberto García-Peñas, María L. Cerrada and José M. Gómez-Elvira

Polymers 2022, 14(22), 5052; https://doi.org/10.3390/polym14225052 - 21 Nov 2022

Viewed by 1134

Abstract

Different circular strategies attempt to increase the energy efficiency or reduce the accumulation of plastic in landfills through the development of circular polymers. Chemical recycling is essential to recover the initial monomers from plastic residues for obtaining new goods showing the same properties [...] Read more.

Different circular strategies attempt to increase the energy efficiency or reduce the accumulation of plastic in landfills through the development of circular polymers. Chemical recycling is essential to recover the initial monomers from plastic residues for obtaining new goods showing the same properties as those using virgin monomers from the initial feedstocks. This work addresses the preparation of poly(ethylene-co-norbornene) copolymers for a promising generation of materials for energy applications that could be treated by chemical recycling. The thermal and thermo-oxidative stability for these copolymers with norbornene is higher than for the neat PE, while their degradation exhibits an activation energy lower than that observed in PE, pointing out that chemical recycling would require a lower energy consumption. Full article

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

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16 pages, 3270 KiB

Open AccessArticle

Dynamic Response of Components Containing Polymer Composites in the Resonance Region for Vibration Amplitudes up to 5g

by Zuzana Murčinková, Pavel Adamčík and Dominik Sabol

Polymers 2022, 14(22), 5051; https://doi.org/10.3390/polym14225051 - 21 Nov 2022

Cited by 3 | Viewed by 1225

Abstract

This paper focuses on high-speed-operation textile machines with the aim of increasing the rotational speed by operating within the resonance region to vibration amplitudes up to 5g. The native design does not allow keeping the vibration amplitude under 5g, which is a safe [...] Read more.

This paper focuses on high-speed-operation textile machines with the aim of increasing the rotational speed by operating within the resonance region to vibration amplitudes up to 5g. The native design does not allow keeping the vibration amplitude under 5g, which is a safe operation mode, for revolutions more than 120,000 min⁻¹. The innovative modification of the design was made by the incorporation of polymer composite materials with carbon dust, glass hollow microspheres, and silica sand fillers to the rotor-bearing casing; moreover, through the incorporation of a multilayered foam composite structure and particle damper to the pressure plate of the mechanical machine system. By using the approach of supplementing with high-damping composites, the existing native design can be used, thus avoiding the costly production of new components and subassemblies with modified shapes and dimensions. Twelve possible combinations of mentioned modifications were tested, evaluated and compared with the native design made of steel, as standard structure material in mechanical engineering. The average vibration amplitudes were evaluated in the region before the resonance peak and in the range of the resonance peak, i.e., 120,000–135,000 min⁻¹. Significant vibration amplitude reductions in the range from 30 to 70% of the average vibration amplitude were obtained. The vibration amplitude reduction results were evaluated considering the mass through the amplitude reduction efficiency coefficient. Full article

(This article belongs to the Special Issue Advanced Polymer-Based Composites)

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20 pages, 7236 KiB

Open AccessArticle

A Systematic Investigation of Polymer Influence on Core Scale Wettability Aided by Positron Emission Tomography Imaging

by Bergit Brattekås, Martine Folgerø Sandnes, Marianne Steinsbø and Jacquelin E. Cobos

Polymers 2022, 14(22), 5050; https://doi.org/10.3390/polym14225050 - 21 Nov 2022

Cited by 1 | Viewed by 1078

Abstract

Polymers have been used as viscosifying agents in enhanced oil recovery applications for decades, but their influence on rock surface wettability is rarely discussed relative to its importance: wettability largely controls fluid flow in porous media and changes in wettability may significantly influence [...] Read more.

Polymers have been used as viscosifying agents in enhanced oil recovery applications for decades, but their influence on rock surface wettability is rarely discussed relative to its importance: wettability largely controls fluid flow in porous media and changes in wettability may significantly influence subsequent system performance. This paper presents a two-part systematic investigation of wettability alteration during polymer injection into oil-wet limestone. The first part of the paper determines wettability and wetting stability on the core scale. The well-established Amott–Harvey method is used, and five full cycles performed with repeated spontaneous imbibition and forced displacements. Wettability alterations are measured in a polymer/oil system, to determine polymer influence on wettability, and evaluated towards simpler brine/oil and glycerol/oil systems, to determine reproducibility and uncertainty related to the method and fluid/rock system. Polymer injection into oil-wet limestone core plugs is shown to repeatedly and reproducibly reverse the core wettability towards water-wet. Wettability changed both quicker and towards stronger water-wet conditions with polymer solution as the aqueous phase compared to brine and glycerol. The second part of the paper attempts to explain the observed behavior; by utilizing in situ imaging by Positron Emission Tomography, an emerging imaging technology within the geosciences. High resolution imaging provides insight into fluid flow dynamics during water and polymer injections, identifying uneven displacement fronts and significant polymer adsorption. Full article

(This article belongs to the Special Issue Polymer Applications for Enhanced Oil Recovery: Challenges and Opportunities)

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22 pages, 7035 KiB

Open AccessArticle

Electrospun Sound-Absorbing Nanofibrous Webs from Recycled Poly(vinyl butyral)

by Petr Filip, Tomas Sedlacek, Petra Peer and Martin Juricka

Polymers 2022, 14(22), 5049; https://doi.org/10.3390/polym14225049 - 21 Nov 2022

Cited by 1 | Viewed by 1552

Abstract

The amount of poly(vinyl butyral) (PVB) foils added to car windscreens to suppress glass shattering represents a huge worldwide volume of the material, and once a vehicle is end-of-life it also becomes a significance contributor to landfill. The recycling of PVB materials from [...] Read more.

The amount of poly(vinyl butyral) (PVB) foils added to car windscreens to suppress glass shattering represents a huge worldwide volume of the material, and once a vehicle is end-of-life it also becomes a significance contributor to landfill. The recycling of PVB materials from windscreens has been expensive and despite improvements in recycling technologies, the landfill burden still increases. However, an increase in oil prices can shift the economic balance and stimulates the possible applicability of recycled PVB. As PVB is a relatively easy electrospinnable material, it is shown that nanofibrous mats produced from recycled PVB blends in ethanol exhibit very good sound-absorbing properties. To achieve an optimal composition between virgin and recycled PVB blends, a series of their ratios was consecutively characterized using various techniques (rheometry, SEM, FTIR, DSC, TGA, DMA, an impedance tube for determining sound absorbance). The best result was obtained with two wt. portions of 8 wt.% solution of virgin PVB in ethanol and one wt. portion of 12 wt.% solution of recycled PVB in ethanol. Full article

(This article belongs to the Special Issue Electrospinning Technology to Produce Innovative Nanostructured Polymer Materials: Current Applications and Future Perspectives)

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12 pages, 2305 KiB

Open AccessArticle

The Electrical Conductivity and Mechanical Properties of Monolayer and Multilayer Nanofibre Membranes from Different Fillers: Calculated Based on Parallel Circuit

by Lijian Wang, Chuanhe Li, Jishu Zhang, Chunhong Wang, Qi Zuo, Wenting He and Ligang Lin

Polymers 2022, 14(22), 5048; https://doi.org/10.3390/polym14225048 - 21 Nov 2022

Cited by 5 | Viewed by 1400

Abstract

Advanced research on improving the performance of conductive polymer composites is essential to exploring their potential in various applications. Thus, in this study, the electrical conductivity of multilayer nanofibre membranes composed of polyvinyl alcohol (PVA) with different electroconductive fillers content including zinc oxide [...] Read more.

Advanced research on improving the performance of conductive polymer composites is essential to exploring their potential in various applications. Thus, in this study, the electrical conductivity of multilayer nanofibre membranes composed of polyvinyl alcohol (PVA) with different electroconductive fillers content including zinc oxide (ZnO), multiwalled carbon nanotubes (MWNTs), and Ferro ferric oxide (Fe₃O₄), were produced via electrospinning. The tensile property and electrical conductivity of monolayer membranes were explored. The results showed that PVA with 2 wt.% MWNTs nanofibre membrane has the best conductivity (1.0 × 10⁻⁵ S/cm) and tensile strength (29.36 MPa) compared with other fillers. Meanwhile, the combination of multilayer membrane ZnO/Fe₃O₄/Fe₃O₄/MWNTs/ZnO showed the highest conductivity (1.39 × 10⁻⁵ S/cm). The parallel circuit and calculation of parallel resistance were attempted to demonstrate the conductive mechanism of multilayer membranes, which can predict the conductivity of other multilayer films. The production of multilayer composites that enhance electrical conductivity and improve conductive predictions was successfully explored. Full article

(This article belongs to the Section Polymer Fibers)

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18 pages, 14431 KiB

Open AccessArticle

Development and Mechanical Characterization of Short Curauá Fiber-Reinforced PLA Composites Made via Fused Deposition Modeling

by Daniel K. K. Cavalcanti, Jorge S. S. Neto, Henrique F. M. de Queiroz, Yiyun. Wu, Victor F. S. Neto and Mariana D. Banea

Polymers 2022, 14(22), 5047; https://doi.org/10.3390/polym14225047 - 21 Nov 2022

Cited by 5 | Viewed by 1461

Abstract

The increase in the use of additive manufacturing (AM) has led to the need for filaments with specific and functional properties in face of requirements of structural parts production. The use of eco-friendly reinforcements (i.e., natural fibers) as an alternative to those more [...] Read more.

The increase in the use of additive manufacturing (AM) has led to the need for filaments with specific and functional properties in face of requirements of structural parts production. The use of eco-friendly reinforcements (i.e., natural fibers) as an alternative to those more traditional synthetic counterparts is still scarce and requires further investigation. The main objective of this work was to develop short curauá fiber-reinforced polylactic acid (PLA) composites made via fused deposition modeling. Three different fiber lengths (3, 6, and 8 mm), and three concentrations in terms of weight percentage (2, 3.5, and 5 wt.%) were used to fabricate reinforced PLA filaments. Tensile and flexural tests in accordance with their respective American Society for Testing and Materials (ASTM) standards were performed. A thermal analysis was also carried out in order to investigate the thermal stability of the new materials. It was found that the main driving factor for the variation in mechanical properties was the fiber weight fraction. The increase in fiber length did not provide any significant benefit on the mechanical properties of the curauá fiber-reinforced PLA composite printed parts. The composites produced with PLA filaments reinforced by 3 mm 2% curauá fiber presented the overall best mechanical and thermal properties of all studied groups. The curauá fiber-reinforced PLA composites made via fused deposition modeling may be a promising innovation to improve the performance of these materials, which might enable them to serve for new applications. Full article

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21 pages, 2044 KiB

Open AccessReview

One-Part Alkali-Activated Materials: State of the Art and Perspectives

by Yongjun Qin, Changwei Qu, Cailong Ma and Lina Zhou

Polymers 2022, 14(22), 5046; https://doi.org/10.3390/polym14225046 - 21 Nov 2022

Cited by 6 | Viewed by 3486

Abstract

Alkali-activated materials (AAM) are recognized as potential alternatives to ordinary Portland cement (OPC) to limit CO₂ emissions and beneficiate several wastes into useful products. Compared with its counterparts involving the concentrated aqueous alkali solutions, the development of “just add water” one-part alkali-activated [...] Read more.

Alkali-activated materials (AAM) are recognized as potential alternatives to ordinary Portland cement (OPC) to limit CO₂ emissions and beneficiate several wastes into useful products. Compared with its counterparts involving the concentrated aqueous alkali solutions, the development of “just add water” one-part alkali-activated materials (OP-AAM) has drawn much attention, mainly attributed to their benefits in overcoming the hazardous, irritating, and corrosive nature of activator solutions. This study starts with a comprehensive overview of the OP-AAM; 89 published studies reported on mortar or concrete with OP-AAM were collected and concluded in this paper. Comprehensive comparisons and discussions were conducted on raw materials, preparation, working performance, mechanical properties, and durability, and so on. Moreover, an in-depth comparison of different material pretreatment methods, fiber types, and curing methods was presented, and their potential mechanisms were discussed. It is found that ground granulated blast-furnace slag (GGBS) provides the best mechanical properties, and the reuse of most aluminosilicate materials can improve the utilization efficiency of solid waste. The curing temperature can be improved significantly for precursor materials with low calcium contents. In order to overcome the brittleness of the AAM, fiber reinforcement might be an efficient way, and steel fiber has the best chemical stability. It is not recommended to use synthetic fiber with poor chemical stability. Based on the analysis of current limitations, both the recommendations and perspectives are laid down to be the lighthouse for further research. Full article

(This article belongs to the Section Smart and Functional Polymers)

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12 pages, 3278 KiB

Open AccessArticle

Moisture-Related Shrinkage Behavior of Wood at Macroscale and Cellular Level

by Yufa Gao, Zongying Fu, Yongdong Zhou, Xin Gao, Fan Zhou and Huimin Cao

Polymers 2022, 14(22), 5045; https://doi.org/10.3390/polym14225045 - 21 Nov 2022

Cited by 4 | Viewed by 1632

Abstract

Due to wood moisture sensitivity, shrinkage cracks tend to present wooden structures. These failures are caused by moisture-related shrinkage behavior. In order to avoid it, it is necessary to have a better understanding of shrinkage behavior. In this respect, studying the dimension changes [...] Read more.

Due to wood moisture sensitivity, shrinkage cracks tend to present wooden structures. These failures are caused by moisture-related shrinkage behavior. In order to avoid it, it is necessary to have a better understanding of shrinkage behavior. In this respect, studying the dimension changes in wood at different scales is of utmost significance for a better understanding of the shrinkage properties. Herein, the shrinkage behavior of Masson pines (Pinus massoniana) wood was investigated at macroscopic and cellular levels during moisture loss via digital image correlation using VIC-3D and digital microscopic systems, respectively. According to the full-field strain maps, shrinkage strain near the external face was higher than that at the internal face, which increased susceptibility to cracking at the external face of lumber. Additionally, the anisotropic shrinkage of wood was explored. The shrinkage ratio at the end of drying was about 5.5% in the tangential (T) direction and 3.5% in the radial (R) direction. However, at a cellular level, the shrinkage ratios in the T and R directions of earlywood tracheids were 7.13% and 2.46%, whereas the corresponding values for latewood tracheid were 9.27% and 5.52%, respectively. Furthermore, the maximum T/R shrinkage ratio at the macroscopic level (1.7) was found to be similar to the value of latewood tracheid (1.72). The earlywood showed high anisotropic, its T/R shrinkage ratio was 2.75. The macroscopic shrinkage was the result of the interaction of the tracheids of earlywood and latewood and was mainly dominated by latewood tracheids. Full article

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

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22 pages, 4215 KiB

Open AccessArticle

The EDLC Energy Storage Device Based on a Natural Gelatin (NG) Biopolymer: Tuning the Capacitance through Plasticizer Variation

by Shujahadeen B. Aziz, Elham M. A. Dannoun, Sozan N. Abdullah, Hewa O. Ghareeb, Ranjdar M. Abdullah, Ari A. Abdalrahman, Muaffaq M. Nofal and Sunanda Kakroo

Polymers 2022, 14(22), 5044; https://doi.org/10.3390/polym14225044 - 21 Nov 2022

Cited by 2 | Viewed by 1266

Abstract

A solution casting method has been utilisedto fabricate plasticisednatural gelatin (NG)-based polymer electrolyte films. The NG electrolyte with 50 wt.% glycerol and 13 wt.% sodium nitrate (NaNO₃) attained the highest ionic conductivity of 1.67 × 10⁻⁴ S cm⁻¹. [...] Read more.

A solution casting method has been utilisedto fabricate plasticisednatural gelatin (NG)-based polymer electrolyte films. The NG electrolyte with 50 wt.% glycerol and 13 wt.% sodium nitrate (NaNO₃) attained the highest ionic conductivity of 1.67 × 10⁻⁴ S cm⁻¹. Numerous techniques were used to characterisethe NG films to assess their electrochemical performance. The data obtained from impedance spectroscopy for the plasticisedsystem, such as bulk resistance (Rb), arerelatively low. Thiscomprehensive study has been focused on dielectric characteristics and electric modulus parameters. The plasticisedsystem has shown eligibility for practice in energy storage devices with electrochemical strength up to 2.85 V. The TNM data based on ion transference number (tion) and electron transference number (te) determine the identity of the main charge carrier, ion. The redox peaks in the cyclic voltammograms have not been observed as evidence of charge accumulation other than the Faradaic process at the electrode–electrolyte interface. The GCD plot reveals a triangle shape and records arelatively low drop voltage. The high average efficiency of 90% with low ESR has been achieved over 500 cycles, indicating compatibility between electrolyte and electrode. The average power density and energy density of the plasticisedare 700 W/kg and 8 Wh/kg, respectively. Full article

(This article belongs to the Special Issue Advanced Polymer Composite for Energy Applications)

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14 pages, 8591 KiB

Open AccessArticle

Inkjet Printing of Electrodes on Electrospun Micro- and Nanofiber Hydrophobic Membranes for Flexible and Smart Textile Applications

by Zuzanna J. Krysiak, Hamed Abdolmaleki, Shweta Agarwala and Urszula Stachewicz

Polymers 2022, 14(22), 5043; https://doi.org/10.3390/polym14225043 - 21 Nov 2022

Cited by 5 | Viewed by 2251

Abstract

With the increasing demand for smart textile and sensor applications, the interest in printed electronics is rising. In this study, we explore the applicability of electrospun membranes, characterized by high porosity and hydrophobicity, as potential substrates for printed electronics. The two most common [...] Read more.

With the increasing demand for smart textile and sensor applications, the interest in printed electronics is rising. In this study, we explore the applicability of electrospun membranes, characterized by high porosity and hydrophobicity, as potential substrates for printed electronics. The two most common inks, silver and carbon, were used in inkjet printing to create a conductive paths on electrospun membranes. As substrates, we selected hydrophobic polymers, such as polyimide (PI), low- and high-molecular-weight poly (vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (PVB) and polystyrene (PS). Electrospinning of PI and PVB resulted in nanofibers in the range of 300–500 nm and PVB and PS microfibers (1–5 μm). The printed patterns were investigated with a scanning electron microscope (SEM) and resistance measurements. To verify the biocompatibility of printed electrodes on the membranes, an indirect cytotoxicity test with cells (MG-63) was performed. In this research, we demonstrated good printability of silver and carbon inks on flexible PI, PVB and PS electrospun membranes, leading to electrodes with excellent conductivity. The cytotoxicity study indicated the possibility of using manufactured printed electronics for various sensors and also as topical wearable devices. Full article

(This article belongs to the Special Issue Functionalised Fibers and Multifunctional Fabrics)

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18 pages, 54685 KiB

Open AccessArticle

Development of Smart Bilayer Alginate/Agar Film Containing Anthocyanin and Catechin-Lysozyme

by Orapan Romruen, Pimonpan Kaewprachu, Thomas Karbowiak and Saroat Rawdkuen

Polymers 2022, 14(22), 5042; https://doi.org/10.3390/polym14225042 - 21 Nov 2022

Cited by 5 | Viewed by 1958

Abstract

Smart packaging can provide real-time information about changes in food quality and impart a protective effect to the food product by using active agents. This study aimed to develop a smart bilayer film (alginate/agar) with a cellulose nanosphere (CNs) from corncob. The bilayer [...] Read more.

Smart packaging can provide real-time information about changes in food quality and impart a protective effect to the food product by using active agents. This study aimed to develop a smart bilayer film (alginate/agar) with a cellulose nanosphere (CNs) from corncob. The bilayer films were prepared using 1.5% (w/w) sodium alginate with 0.25% (w/v) butterfly pea extract incorporated (indicator layer) and 2% (w/w) agar containing 0.5% (w/v) catechin–lysozyme (ratio 1:1) (active layer). The CNs were incorporated into the alginate layer at different concentrations (0, 5, 10, 20, and 30% w/w-based film) in order to improve the film’s properties. The thickness of smart bilayer film dramatically increased with the increase of CNs concentration. The inclusion of CNs reduced the transparency and elongation at break of the smart bilayer film while increasing its tensile strength (p < 0.05). The integration of CNs did not significantly affect the solubility and water vapor permeability of the smart bilayer film (p > 0.05). The smart bilayer film displayed a blue film with a glossy (without CNs) or matte surface (with CNs). The developed bilayer film shows excellent pH sensitivity, changing color at a wide range of pHs, and has a good response to ammonia and acetic acid gases. The film possesses exceptional antimicrobial and antioxidant activities. The integration of CNs did not influence the antibacterial activity of the film, despite the presence of a higher level of DPPH in film containing CNs. The smart bilayer film was effectively used to monitor shrimp freshness. These findings imply that smart bilayer films with and without CNs facilitate food safety and increase food shelf life by monitoring food quality. Full article

(This article belongs to the Special Issue Biopolymer-Based Films and Coatings for Packaging Applications)

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17 pages, 15422 KiB

Open AccessArticle

Characterization of the Mechanical and Morphological Properties of Cow Dung Fiber-Reinforced Polymer Composites: A Comparative Study with Corn Stalk Fiber Composites and Sisal Fiber Composites

by Siyang Wu, Mingzhuo Guo, Jiale Zhao, Qian Wu, Jian Zhuang and Xinming Jiang

Polymers 2022, 14(22), 5041; https://doi.org/10.3390/polym14225041 - 21 Nov 2022

Cited by 3 | Viewed by 2524

Abstract

Natural fibers and their composites have attracted much attention due to the growing energy crisis and environmental awareness. In this work, a natural lignocellulosic fiber was extracted from cow dung waste and its potential use as reinforcing material in resin-based polymer composites was [...] Read more.

Natural fibers and their composites have attracted much attention due to the growing energy crisis and environmental awareness. In this work, a natural lignocellulosic fiber was extracted from cow dung waste and its potential use as reinforcing material in resin-based polymer composites was evaluated. For this purpose, cow dung fiber-reinforced composites (CDFC) were fabricated, and their mechanical and morphological properties were systematically investigated and compared with corn stalk fiber composites (CSFC) and sisal fiber composites (SFC). The results showed that the addition of cow dung fibers reduced the density of the polymer composites, increased the water absorption, and enhanced the impact strength and shear strength. The highest impact and shear strengths were obtained at 6 wt.% and 9 wt.% of fiber loading, respectively, which increased by 23.8% and 34.6% compared to the composite without the fibers. Further comparisons revealed that at the same fiber addition level, the CDFC exhibited better mechanical properties than the CSFC; notably, the CDFC-3 (adding 3 wt.% of fiber loading) had an impact strength closer to the SFC-3. Furthermore, an SEM analysis suggested that the cow dung fibers exhibited a rough and crinkly surface with more node structures, and presented good interfacial bonding with the composite matrix. This work revealed that cow dung fibers are a promising candidate as reinforcement for resin-based polymer composites, which promotes an alternative application for cow dung waste resources in the automotive components field. Full article

(This article belongs to the Special Issue Fiber-Reinforced Composite)

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11 pages, 838 KiB

Open AccessArticle

Ascorbic Acid-Modified Silicones: Crosslinking and Antioxidant Delivery

by Guanhua Lu, Akop Yepremyen, Khaled Tamim, Yang Chen and Michael A. Brook

Polymers 2022, 14(22), 5040; https://doi.org/10.3390/polym14225040 - 21 Nov 2022

Cited by 1 | Viewed by 2352

Abstract

Vitamin C is widely used as an antioxidant in biological systems. The very high density of functional groups makes it challenging to selectively tether this molecule to other moieties. We report that, following protection of the enediol as benzyl ethers, the introduction of [...] Read more.

Vitamin C is widely used as an antioxidant in biological systems. The very high density of functional groups makes it challenging to selectively tether this molecule to other moieties. We report that, following protection of the enediol as benzyl ethers, the introduction of an acrylate ester at C1 is straightforward. Ascorbic acid-modified silicones were synthesized via aza-Michael reactions of aminoalkylsilicones with ascorbic acrylate. Viscous oils formed when the amine/acrylate ratios were <1. However, at higher amine/acrylate ratios with pendent silicones, a double reaction occurred to give robust elastomers whose modulus is readily tuned simply by controlling the ascorbic acid amine ratio that leads to crosslinks. Reduction with H₂/Pd removed the benzyl ethers and led to increased crosslinking, and either liberated the antioxidant small molecule or produced antioxidant elastomers. These pro-antioxidant elastomers show the power of exploiting natural materials as co-constituents of silicone polymers. Full article

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

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23 pages, 23581 KiB

Open AccessArticle

Warmforming Flow Pressing Characteristics of Continuous Fibre Reinforced Thermoplastic Composites

by Benjamin Gröger, David Römisch, Martin Kraus, Juliane Troschitz, René Füßel, Marion Merklein and Maik Gude

Polymers 2022, 14(22), 5039; https://doi.org/10.3390/polym14225039 - 21 Nov 2022

Cited by 3 | Viewed by 1522

Abstract

The paper presents research regarding a thermally supported multi-material clinching process (hotclinching) for metal and thermoplastic composite (TPC) sheets: an experimental approach to investigate the flow pressing phenomena during joining. Therefore, an experimental setup is developed to compress the TPC-specimens in out-of-plane direction [...] Read more.

The paper presents research regarding a thermally supported multi-material clinching process (hotclinching) for metal and thermoplastic composite (TPC) sheets: an experimental approach to investigate the flow pressing phenomena during joining. Therefore, an experimental setup is developed to compress the TPC-specimens in out-of-plane direction with different initial TPC thicknesses and varying temperature levels. The deformed specimens are analyzed with computed tomography to investigate the resultant inner material structure at different compaction levels. The results are compared in terms of force-compaction-curves and occurring phenomena during compaction. The change of the material structure is characterized by sliding phenomena and crack initiation and growth. Full article

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

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12 pages, 3030 KiB

Open AccessArticle

Novel Polymeric Nanomaterial Based on Poly(Hydroxyethyl Methacrylate-Methacryloylamidophenylalanine) for Hypertension Treatment: Properties and Drug Release Characteristics

by Fevzi Bardakci, Kevser Kusat, Mohd Adnan, Riadh Badraoui, Mohammad Jahoor Alam, Mousa M. Alreshidi, Arif Jamal Siddiqui, Manojkumar Sachidanandan and Sinan Akgöl

Polymers 2022, 14(22), 5038; https://doi.org/10.3390/polym14225038 - 21 Nov 2022

Viewed by 1347

Abstract

In this study, a novel polymeric nanomaterial was synthesized and characterized, and it its potential usability in hypertension treatment was demonstrated. For these purposes, a poly(hydroxyethyl methacrylate-methacryloylamidophenylalanine)-based polymeric nanomaterial (p(HEMPA)) was synthesized using a mini-emulsion polymerization technique. The nanomaterials were characterized using scanning [...] Read more.

In this study, a novel polymeric nanomaterial was synthesized and characterized, and it its potential usability in hypertension treatment was demonstrated. For these purposes, a poly(hydroxyethyl methacrylate-methacryloylamidophenylalanine)-based polymeric nanomaterial (p(HEMPA)) was synthesized using a mini-emulsion polymerization technique. The nanomaterials were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and zeta size analysis. The synthesized p(HEMPA) nanomaterial had a diameter of about 113 nm. Amlodipine-binding studies were optimized by changing the reaction conditions. Under optimum conditions, amlodipine’s maximum adsorption value (Qmax) of the p(HEMPA) nanopolymer was found to be 145.8 mg/g. In vitro controlled drug release rates of amlodipine, bound to the nanopolymer at the optimum conditions, were studied with the dialysis method in a simulated gastrointestinal system with pH values of 1.2, 6.8 and 7.4. It was found that 99.5% of amlodipine loaded on the nanomaterial was released at pH 7.4 and 72 h. Even after 72 h, no difference was observed in the release of AML. It can be said that the synthesized nanomaterial is suitable for oral amlodipine release. In conclusion, the synthesized nanomaterial was studied for the first time in the literature as a drug delivery system for use in the treatment of hypertension. In addition, AML–p(HEMPA) nanomaterials may enable less frequent drug uptake, have higher bioavailability, and allow for prolonged release with minimal side effects. Full article

(This article belongs to the Special Issue Polymers for Drug Release and Drug Delivery)

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15 pages, 2608 KiB

Open AccessArticle

APTES-Modified Nanocellulose as the Formaldehyde Scavenger for UF Adhesive-Bonded Particleboard and Strawboard

by Jakub Kawalerczyk, Joanna Walkiewicz, Dorota Dziurka, Radosław Mirski and Jakub Brózdowski

Polymers 2022, 14(22), 5037; https://doi.org/10.3390/polym14225037 - 21 Nov 2022

Cited by 12 | Viewed by 2338

Abstract

This work examines the possibility of applying non-modified nanocellulose and nanocellulose functionalized with 3-aminopropyltriethoxysilane (APTES) as a formaldehyde scavenger for commonly used urea-formaldehyde (UF) adhesive. The effect of silanization was determined with the use of Fourier transform infrared spectroscopy (FTIR), flame atomic absorption [...] Read more.

This work examines the possibility of applying non-modified nanocellulose and nanocellulose functionalized with 3-aminopropyltriethoxysilane (APTES) as a formaldehyde scavenger for commonly used urea-formaldehyde (UF) adhesive. The effect of silanization was determined with the use of Fourier transform infrared spectroscopy (FTIR), flame atomic absorption spectrometry (FAAS), and elemental analysis. Moreover, the ability of cellulosic nanoparticles to absorb the formaldehyde from an aqueous solution was investigated. After homogenization, cured UF adhesives were examined with the use of FTIR, energy-dispersive spectroscopy (SEM-EDS), and the perforator method to determine the content of formaldehyde. Manufactured boards made of rape straw particles and wood particles were tested in terms of their physico-mechanical properties and formaldehyde emission. Studies have shown that the applied method of silanization was effective. Furthermore, in the case of non-modified nanocellulose, no sign of formaldehyde scavenging ability was found. However, the functionalization of cellulosic nanoparticles with APTES containing an amino group led to the significant reduction of formaldehyde content in both the aqueous solution and the UF adhesive. The mechanical properties of both strawboards and particleboards were improved due to the nanocellulose reinforcement; however, no effect of silanization was found. Nevertheless, functionalization with APTES contributed to a decrease in formaldehyde emission from boards, which was not found in the case of the introduction of non-modified cellulosic nanoparticles. Full article

(This article belongs to the Special Issue Research on Wood-Based Composites)

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20 pages, 5296 KiB

Open AccessArticle

Core/Double-Sheath Composite Fibers from Poly(ethylene oxide), Poly(L-lactide) and Beeswax by Single-Spinneret Electrospinning

by Selin Kyuchyuk, Dilyana Paneva, Nevena Manolova, Iliya Rashkov, Daniela Karashanova and Nadya Markova

Polymers 2022, 14(22), 5036; https://doi.org/10.3390/polym14225036 - 21 Nov 2022

Cited by 7 | Viewed by 1633

Abstract

The conventional approach for preparation of core-sheath fibers is coaxial electrospinning. Single-spinneret electrospinning of emulsions is a much less common method to obtain core-sheath fibers. Core-sheath structure may be generated by electrospinning of homogeneous blend solutions; however, reports on such cases are still [...] Read more.

The conventional approach for preparation of core-sheath fibers is coaxial electrospinning. Single-spinneret electrospinning of emulsions is a much less common method to obtain core-sheath fibers. Core-sheath structure may be generated by electrospinning of homogeneous blend solutions; however, reports on such cases are still scarce. Herein, the preparation of nanofibrous composites from poly(ethylene oxide) (PEO), poly(L-lactide) (PLA) and beeswax (BW) by single-spinneret electrospinning of their homogeneous blend solutions in chloroform is reported. The produced fibers had core/double-sheath structure with a PEO core, PLA inner sheath and BW outer sheath. This original fiber structure was evidenced by transmission electron microscopy, selective extraction of BW or PEO, and X-ray photoelectron spectroscopy. The PLA/BW double sheath led to hydrophobicity of the PEO/PLA/BW mats. The tensile tests revealed that PEO/PLA/BW mats had substantially improved mechanical behavior as compared to PEO, PLA and PEO/BW mats. PEO/PLA/BW mats can be used as drug carriers as evidenced by the one-pot incorporation of the model drug 5-nitro-8-hydroxyquinoline (NQ) into the fibrous materials. Microbiological tests showed that PEO/PLA/BW/NQ had antimicrobial activity. Therefore, the new materials are promising for wound healing applications. Full article

(This article belongs to the Special Issue Electrospinning Techniques and Advanced Textile Materials)

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9 pages, 2058 KiB

Open AccessArticle

Pyrolysis of Denim Jeans Waste: Pyrolytic Product Modification by the Addition of Sodium Carbonate

by Junghee Joo, Heeyoung Choi, Kun-Yi Andrew Lin and Jechan Lee

Polymers 2022, 14(22), 5035; https://doi.org/10.3390/polym14225035 - 21 Nov 2022

Viewed by 1541

Abstract

Quickly changing fashion trends generate tremendous amounts of textile waste globally. The inhomogeneity and complicated nature of textile waste make its recycling challenging. Hence, it is urgent to develop a feasible method to extract value from textile waste. Pyrolysis is an effective waste-to-energy [...] Read more.

Quickly changing fashion trends generate tremendous amounts of textile waste globally. The inhomogeneity and complicated nature of textile waste make its recycling challenging. Hence, it is urgent to develop a feasible method to extract value from textile waste. Pyrolysis is an effective waste-to-energy option to processing waste feedstocks having an inhomogeneous and complicated nature. Herein, pyrolysis of denim jeans waste (DJW; a textile waste surrogate) was performed in a continuous flow pyrolyser. The effects of adding sodium carbonate (Na₂CO₃; feedstock/Na₂CO₃ = 10, weight basis) to the DJW pyrolysis on the yield and composition of pyrolysates were explored. For the DJW pyrolysis, using Na₂CO₃ as an additive increased the yields of gas and solid phase pyrolysates and decreased the yield of liquid phase pyrolysate. The highest yield of the gas phase pyrolysate was 34.1 wt% at 800 °C in the presence of Na₂CO₃. The addition of Na₂CO₃ could increase the contents of combustible gases such as H₂ and CO in the gas phase pyrolysate in comparison with the DJW pyrolysis without Na₂CO₃. The maximum yield of the liquid phase pyrolysate obtained with Na₂CO₃ was 62.5 wt% at 400 °C. The composition of the liquid phase pyrolysate indicated that the Na₂CO₃ additive decreased the contents of organic acids, which potentially improve its fuel property by reducing acid value. The results indicated that Na₂CO₃ can be a potential additive to pyrolysis to enhance energy recovery from DJW. Full article

(This article belongs to the Special Issue Recycled Polymers: Eco-Design, Structure/Property Relationships and Compatibility)

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13 pages, 3523 KiB

Open AccessArticle

Human Umbilical Vein Endothelial Cells Form a Network on a Hyaluronic Acid/Gelatin Composite Hydrogel Moderately Crosslinked and Degraded by Hydrogen Peroxide

by Kelum Chamara Manoj Lakmal Elvitigala, Wildan Mubarok and Shinji Sakai

Polymers 2022, 14(22), 5034; https://doi.org/10.3390/polym14225034 - 20 Nov 2022

Cited by 2 | Viewed by 1616

Abstract

The study of the capillary-like network formation of human umbilical vein endothelial cells (HUVECs) in vitro is important for understanding the factors that promote or inhibit angiogenesis. Here, we report the behavior of HUVECs on the composite hydrogels containing hyaluronic acid (HA) and [...] Read more.

The study of the capillary-like network formation of human umbilical vein endothelial cells (HUVECs) in vitro is important for understanding the factors that promote or inhibit angiogenesis. Here, we report the behavior of HUVECs on the composite hydrogels containing hyaluronic acid (HA) and gelatin with different degrees of degradation, inducing the different physicochemical properties of the hydrogels. The hydrogels were obtained through horseradish peroxidase (HRP)-catalyzed hydrogelation consuming hydrogen peroxide (H₂O₂, 16 ppm) supplied from the air, and the degradation degree was tuned by altering the exposure time to the air. The HUVECs on the composite hydrogel with intermediate stiffness (1.2 kPa) obtained through 120 min of the exposure were more elongated than those on the soft (0.4 kPa) and the stiff (2.4 kPa) composite hydrogels obtained through 15 min and 60 min of the exposure, respectively. In addition, HUVECs formed a capillary-like network only on the stiff composite hydrogel although those on the hydrogels with comparable stiffness but containing gelatin alone or alginate instead of HA did not form the network. These results show that the HA/gelatin composite hydrogels obtained through the H₂O₂-mediated crosslinking and degradation could be a tool for studies using HUVECs to understand the promotion and inhibition of angiogenesis. Full article

(This article belongs to the Special Issue Applications of Biocompatible and Biodegradable Polymers and Their Composites)

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23 pages, 8631 KiB

Open AccessArticle

Sustainable PHBH–Alumina Nanowire Nanocomposites: Properties and Life Cycle Assessment

by Julen Ibarretxe, Laura Alonso, Nora Aranburu, Gonzalo Guerrica-Echevarría, Amaia Orbea and Maider Iturrondobeitia

Polymers 2022, 14(22), 5033; https://doi.org/10.3390/polym14225033 - 20 Nov 2022

Cited by 1 | Viewed by 1696

Abstract

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) is a bio-based polyester with the potential to replace some common polymers of fossil origin. However, PHBH presents serious limitations, such as low stiffness, tendency to undergo crystallization over long time periods and low resistance to thermal degradation during processing. In [...] Read more.

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) is a bio-based polyester with the potential to replace some common polymers of fossil origin. However, PHBH presents serious limitations, such as low stiffness, tendency to undergo crystallization over long time periods and low resistance to thermal degradation during processing. In this work, we studied the use of alumina nanowires to generate PHBH–alumina nanocomposites, modifying the properties of PHBH to improve its usability. Solvent casting and melt blending were used to produce the nanocomposites. Then, their physicochemical properties and aquatic toxicity were measured. Finally, LCA was used to evaluate and compare the environmental impacts of several scenarios relevant to the processing and end of life (EoL) conditions of PHBHs. It was observed that, at low concentrations (3 wt.%), the alumina nanowires have a small positive impact on the stiffness and thermal degradation for the samples. However, for higher concentrations, the observed effects differed for each of the applied processing techniques (solvent casting or melt blending). The toxicity measurements showed that PHBH alone and in combination with alumina nanowires (10 wt.%) did not produce any impact on the survival of brine shrimp larvae after 24 and 48 h of exposure. The 18 impact categories evaluated by LCA allowed defining the most environmentally friendly conditions for the processing and EoL of PHBHs, and comparing the PHBH-related impacts to those of some of the most common fossil-based plastics. It was concluded that the preferable processing technique for PHBH is melt blending and that PHBH is unquestionably more environmentally friendly than every other analyzed plastic. Full article

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

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18 pages, 5120 KiB

Open AccessArticle

Molecular Dynamics Simulation of the Interfacial Shear Properties between Thermoplastic Polyurethane and Functionalized Graphene Sheet

by Yuyang Wang, Guangping Zou and Junpeng Liu

Polymers 2022, 14(22), 5032; https://doi.org/10.3390/polym14225032 - 20 Nov 2022

Cited by 3 | Viewed by 2203

Abstract

In this study, the effect of the type and content of functional groups on the interfacial shear properties of a functionalized graphene sheet (FGS)/thermoplastic polyurethane (TPU) nanocomposite are investigated by molecular dynamics (MD) simulations. The maximum pull-out force and separation energy were used [...] Read more.

In this study, the effect of the type and content of functional groups on the interfacial shear properties of a functionalized graphene sheet (FGS)/thermoplastic polyurethane (TPU) nanocomposite are investigated by molecular dynamics (MD) simulations. The maximum pull-out force and separation energy were used to characterize the interfacial strength of the FGS/TPU nanocomposite in sliding mode. To find out how the type and content of functional groups affect the interfacial shear properties of the TPU/FGS system from an atomic view, the details of interactions between FGS and TPU were characterized. Based on the results, stronger interfacial shear properties of the TPU/FGS system can be achieved by adding the carboxyl group or hydroxyl group on the surface of graphene than that between TPU and FGS modified by the amine group or epoxy group, because of the strong interaction of electrostatic forces and H-bonds. In addition, interfacial shear properties can also be enhanced by increasing the content of functional groups modified on the surface of graphene. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

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13 pages, 3700 KiB

Open AccessArticle

Swelling and Collapse of Cylindrical Polyelectrolyte Microgels

by Ivan V. Portnov, Alexandra A. Larina, Rustam A. Gumerov and Igor I. Potemkin

Polymers 2022, 14(22), 5031; https://doi.org/10.3390/polym14225031 - 20 Nov 2022

Viewed by 1423

Abstract

In this study, we propose computer simulations of charged cylindrical microgels. The effects of cross-linking density, aspect ratio, and fraction of charged groups on the microgel swelling and collapse with a variation in the solvent quality were studied. The results were compared with [...] Read more.

In this study, we propose computer simulations of charged cylindrical microgels. The effects of cross-linking density, aspect ratio, and fraction of charged groups on the microgel swelling and collapse with a variation in the solvent quality were studied. The results were compared with those obtained for equivalent neutral cylindrical microgels. The study demonstrated that microgels’ degree of swelling strongly depends on the fraction of charged groups. Polyelectrolyte microgels under adequate solvent conditions are characterized by a larger length and thickness than their neutral analogues: the higher the fraction of charged groups, the longer their length and greater their thickness. Microgels’ collapse upon solvent quality decline is characterized by a decrease in length and non-monotonous behavior of its thickness. First, the thickness decreases due to the attraction of monomer units (beads) upon collapse. The further thickness increase is related to the surface tension, which tends to reduce the anisotropy of collapsed objects (the minimum surface energy is known to be achieved for the spherical objects). This reduction is opposed by the network elasticity. The microgels with a low cross-linking density and/or a low enough aspect ratio reveal a cylinder-to-sphere collapse. Otherwise, the cylindrical shape is preserved in the course of the collapse. Aspect ratio as a function of the solvent quality (interaction parameter) demonstrates the maximum, which is solely due to the electrostatics. Finally, we plotted radial concentration profiles for network segments, their charged groups, and counterions. Full article

(This article belongs to the Special Issue Polymer Materials in Sensors, Actuators and Energy Conversion II)

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10 pages, 2315 KiB

Open AccessArticle

Facile Fabrication of a Bio-Inspired Leaf Vein-Based Ultra-Sensitive Humidity Sensor with a Hygroscopic Polymer

by Pin-Hsuan Li, Govindasamy Madhaiyan, Ying-Yi Shin, Hsu-Yang Tsai, Hsin-Fei Meng, Sheng-Fu Horng and Hsiao-Wen Zan

Polymers 2022, 14(22), 5030; https://doi.org/10.3390/polym14225030 - 20 Nov 2022

Cited by 3 | Viewed by 1898

Abstract

Bio-inspired materials have received significant interest in the development of flexible electronics due to their natural grid structures, especially natural leaf vein networks. In this work, a bio-inspired leaf vein-based flexible humidity sensor is demonstrated. The proposed sensor is composed of a leaf/Al/glycerin/Ag [...] Read more.

Bio-inspired materials have received significant interest in the development of flexible electronics due to their natural grid structures, especially natural leaf vein networks. In this work, a bio-inspired leaf vein-based flexible humidity sensor is demonstrated. The proposed sensor is composed of a leaf/Al/glycerin/Ag paste. The Al-deposited leaf vein networks are used as a bottom electrode with a resistance of around 100 Ω. The humidity sensor responds well to relative humidity (RH) levels ranging from 15% to 70% at room temperature. The fabricated humidity sensor exhibits an ultra-sensitive response to different humidity conditions due to the biodegradable insulating hygroscopic polymer (glycerin), specifically the ionic conductivity reaction. To further verify the presence of ionic conduction, the device performance is tested by doping NaCl salt into the hygroscopic polymer sensing layer. In addition, both the repeatability and flexibility of the sensor are tested under different bending angles (0°, 90°, 180°, and 360°). The bioinspired ultrasensitive humidity sensor with a biocompatible and biodegradable sensing layer holds great potential, especially for health care applications (e.g., respiratory monitoring) without causing any body harm. Full article

(This article belongs to the Special Issue Polymer-Based Materials for Sensors)

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12 pages, 4401 KiB

Open AccessArticle

Synthesis and Characterization of PU/PLCL/CMCS Electrospun Scaffolds for Skin Tissue Engineering

by Xiang Gao, Meiling Wen, Yang Liu, Tian Hou, Bin Niu and Meiwen An

Polymers 2022, 14(22), 5029; https://doi.org/10.3390/polym14225029 - 19 Nov 2022

Cited by 6 | Viewed by 1561

Abstract

As tissue regeneration material, electrospun fibers can mimic the microscale and nanoscale structure of the natural extracellular matrix (ECM), which provides a basis for cell growth and achieves organic integration with surrounding tissues. At present, the challenge for researchers is to develop a [...] Read more.

As tissue regeneration material, electrospun fibers can mimic the microscale and nanoscale structure of the natural extracellular matrix (ECM), which provides a basis for cell growth and achieves organic integration with surrounding tissues. At present, the challenge for researchers is to develop a bionic scaffold for the regeneration of the wound area. In this paper, polyurethane (PU) is a working basis for the subsequent construction of tissue-engineered skin. poly(L-lactide-co-caprolactone) (PLCL)/carboxymethyl chitosan (CMCS) composite fibers were prepared via electrospinning and cross-linked by glutaraldehyde. The effect of CMCS content on the surface morphology, mechanical properties, hydrophilicity, swelling degree, and cytocompatibility were explored, aiming to assess the possibility of composite scaffolds for tissue engineering applications. The results showed that randomly arranged electrospun fibers presented a smooth surface. All scaffolds exhibited sufficient tensile strength (5.30–5.60 MPa), Young’s modulus (2.62–4.29 MPa), and swelling degree for wound treatment. The addition of CMCS improved the hydrophilicity and cytocompatibility of the scaffolds. Full article

(This article belongs to the Special Issue Polymers and Biopolymers for Tissue Engineering)

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27 pages, 7506 KiB

Open AccessArticle

Poly(Glycerol Succinate) as Coating Material for 1393 Bioactive Glass Porous Scaffolds for Tissue Engineering Applications

by Eirini A. Nakiou, Maria Lazaridou, Georgia K. Pouroutzidou, Anna Michopoulou, Ioannis Tsamesidis, Liliana Liverani, Marcela Arango-Ospina, Anastasia Beketova, Aldo R. Boccaccini, Eleana Kontonasaki and Dimitrios N. Bikiaris

Polymers 2022, 14(22), 5028; https://doi.org/10.3390/polym14225028 - 19 Nov 2022

Cited by 6 | Viewed by 4003

Abstract

Background: Aliphatic polyesters are widely used for biomedical, pharmaceutical and environmental applications due to their high biodegradability and cost-effective production. Recently, star and hyperbranched polyesters based on glycerol and ω-carboxy fatty diacids have gained considerable interest. Succinic acid and bio-based diacids similar to [...] Read more.

Background: Aliphatic polyesters are widely used for biomedical, pharmaceutical and environmental applications due to their high biodegradability and cost-effective production. Recently, star and hyperbranched polyesters based on glycerol and ω-carboxy fatty diacids have gained considerable interest. Succinic acid and bio-based diacids similar to glycerol are regarded as safe materials according to the US Food and Drug Administration (FDA). Bioactive glass scaffolds utilized in bone tissue engineering are relatively brittle materials. However, their mechanical properties can be improved by using polymer coatings that can further control their degradation rate, tailor their biocompatibility and enhance their performance. The purpose of this study is to explore a new biopolyester poly(glycerol succinate) (PGSuc) reinforced with mesoporous bioactive nanoparticles (MSNs) as a novel coating material to produce hybrid scaffolds for bone tissue engineering. Methods: Bioactive glass scaffolds were coated with neat PGSuc, PGSuc loaded with dexamethasone sodium phosphate (DexSP) and PGSuc loaded with DexSP-laden MSNs. The physicochemical, mechanical and biological properties of the scaffolds were also evaluated. Results: Preliminary data are provided showing that polymer coatings with and without MSNs improved the physicochemical properties of the 1393 bioactive glass scaffolds and increased the ALP activity and alizarin red staining, suggesting osteogenic differentiation potential when cultured with adipose-derived mesenchymal stem cells. Conclusions: PGSuc with incorporated MSNs coated onto 1393 bioactive glass scaffolds could be promising candidates in bone tissue engineering applications. Full article

(This article belongs to the Special Issue Thermomechanical Development of Bio-Based Polymer Materials)

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16 pages, 2748 KiB

Open AccessArticle

Impact of Particle and Crystallite Size of Ba_0.6Sr_0.4TiO₃ on the Dielectric Properties of BST/P(VDF-TrFE) Composites in Fully Printed Varactors

by Tim P. Mach, Yingfang Ding and Joachim R. Binder

Polymers 2022, 14(22), 5027; https://doi.org/10.3390/polym14225027 - 19 Nov 2022

Cited by 3 | Viewed by 1734

Abstract

In the field of printed electronics, electronic components such as varactors are of special interest. As ferroelectric materials, Ba_0.6Sr_0.4TiO₃ (BST) and poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) are promising compounds to be used in functional inks for the fabrication [...] Read more.

In the field of printed electronics, electronic components such as varactors are of special interest. As ferroelectric materials, Ba_0.6Sr_0.4TiO₃ (BST) and poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) are promising compounds to be used in functional inks for the fabrication of fully inkjet-printed dielectric layers. In BST/P(VDF-TrFE) composite inks, the influence of the particle and crystallite size is investigated by using different grinding media sizes and thermal treatments at varying temperatures. It was found that with an increasing particle and crystallite size, both the relative permittivity and tunability increase as well. However, the thermal treatment which impacts both the particle and crystallite size has a greater effect on the dielectric properties. An additional approach is the reduction in the dielectric layer thickness, which has a significant effect on the maximal tunability. Here, with a thickness of 0.9 µm, a tunability of 29.6% could be achieved in an external electric field of 34 V µm⁻¹. Full article

(This article belongs to the Special Issue Multifunctional Polymer (Nano)Composites: Structure-Property Relationships)

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14 pages, 30131 KiB

Open AccessArticle

Design and Ballistic Performance of Hybrid Plates Manufactured from Aramid Composites for Developing Multilayered Armor Systems

by Cheng-Hung Shih, Jhu-Lin You, Yung-Lung Lee, An-Yu Cheng, Chang-Pin Chang, Yih-Ming Liu and Ming-Der Ger

Polymers 2022, 14(22), 5026; https://doi.org/10.3390/polym14225026 - 19 Nov 2022

Cited by 8 | Viewed by 2168

Abstract

In this study, the impact resistance of aramid fabric reinforced with shear thickening fluids (STFs), epoxy or polyurea elastomers is examined through ballistic tests. According to the ballistic test results, the aramid composite structure treated with polyurea elastomers absorbs the most impact energy [...] Read more.

In this study, the impact resistance of aramid fabric reinforced with shear thickening fluids (STFs), epoxy or polyurea elastomers is examined through ballistic tests. According to the ballistic test results, the aramid composite structure treated with polyurea elastomers absorbs the most impact energy per unit area density and has the best impact resistance. However, the occurrence of stress concentration during ballistic impact reduces the impact resistance of the aramid composite structure treated with epoxy. On the other hand, aramid fabric impregnated with STF improves structural protection, but it also increases the weight of the composite structure and reduces the specific energy absorption (SEA). The results of this study analyze the energy absorption properties, deformation characteristics, and damage modes of different aramid composites, which will be of interest to future researchers developing next-generation protective equipment. Full article

(This article belongs to the Special Issue Polymer-Based Hybrid Composites)

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20 pages, 6314 KiB

Open AccessArticle

Development of Water Repellent, Non-Friable Tannin-Furanic-Fatty Acids Biofoams

by Elham Azadeh, Ummi Hani Abdullah, Nurul Basirah Md Ali, Antonio Pizzi, Christine Gerardin-Charbonnier, Philippe Gerardin, Wan Sarah Samiun and Siti Efliza Ashari

Polymers 2022, 14(22), 5025; https://doi.org/10.3390/polym14225025 - 19 Nov 2022

Cited by 2 | Viewed by 1374

Abstract

Tannin-furanic foams were prepared with a good yield using the addition of relatively small proportions of a polyflavonoid tannin extract esterified with either palmitic acid, oleic acid, or lauric acid by its reaction with palmitoyl chloride, oleyl chloride, or lauryl chloride. FTIR analysis [...] Read more.

Tannin-furanic foams were prepared with a good yield using the addition of relatively small proportions of a polyflavonoid tannin extract esterified with either palmitic acid, oleic acid, or lauric acid by its reaction with palmitoyl chloride, oleyl chloride, or lauryl chloride. FTIR analysis allowed us to ascertain the esterification of the tannin, and MALDI-TOF analysis allowed us to identify a number of multi-esterified flavonoid oligomers as well as some linked to residual carbohydrates related to the equally esterified tannin. These foams presented a markedly decreased surface friability or no friability at all, and at densities lower than the standard foam they were compared to. Equally, these experimental foams presented a much-improved water repellence, as indicated by their initial wetting angle, its small variation over time, and its stabilization at a high wetting angle value, while the wetting angle of the standard foam control went to zero very rapidly. This conclusion was supported by the calculation of the total surface energy of their surfaces as well as of their dispersive and polar components. Full article

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

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15 pages, 4893 KiB

Open AccessArticle

Temperature Controlled Mechanical Reinforcement of Polyacrylate Films Containing Nematic Liquid Crystals

by Latifa Zair, Abdelkader Berrayah, Khadidja Arabeche, Zohra Bouberka, Andreas Best, Kaloian Koynov and Ulrich Maschke

Polymers 2022, 14(22), 5024; https://doi.org/10.3390/polym14225024 - 19 Nov 2022

Cited by 2 | Viewed by 1110

Abstract

This investigation reports on the thermomechanical properties of Poly-tripropyleneglycoldiacrylate (Poly-TPGDA)/liquid crystal (LC) blends, developed via free radical polymerization processes, which are induced by Electron Beam (EB) and Ultraviolet (UV) radiation. The EB-cured Poly-TPGDA network exhibits a higher glass transition temperature (T_g [...] Read more.

This investigation reports on the thermomechanical properties of Poly-tripropyleneglycoldiacrylate (Poly-TPGDA)/liquid crystal (LC) blends, developed via free radical polymerization processes, which are induced by Electron Beam (EB) and Ultraviolet (UV) radiation. The EB-cured Poly-TPGDA network exhibits a higher glass transition temperature (T_g), a higher tensile storage, and Young moduli than the corresponding UV-cured sample, indicating a lower elasticity and a shorter distance between the two adjacent crosslinking points. Above T_g of Poly-TPGDA/LC blends, the LC behaves as a plasticizing agent, whereas, for EB-cured networks, at temperatures below T_g, the LC shows a strong temperature dependence on the storage tensile modulus: the LC reinforces the polymer due to the presence of nano-sized phase separated glassy LC domains, confirmed by electron microscopy observations. In the case of the UV-cured TPGDA/LC system, the plasticizing effect of the LC remains dominant in both the whole composition and the temperature ranges explored. The rubber elasticity and T_g of Poly-TPGDA/LC films were investigated using mechanical measurements. Full article

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

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