Next Issue
Volume 14, April-2
Previous Issue
Volume 14, March-2
 
 

Polymers, Volume 14, Issue 7 (April-1 2022) – 224 articles

Cover Story (view full-size image): In this study, polycaprolactone (PCL) and gelatin were electrospun to carry out a comparison study between blends and coating protocols. In order to overcome the hydrophobicity of synthetic polymers, natural polymers were introduced to enhance cellular proliferation and attachment, as both coating or blending methods. After electrospinning nanofibrous scaffolds, morphological and mechanical studies were carried out via SEM and traction studies, respectively. Blended PCL/gelatin scaffolds showed a variation in their mechanical properties, while the coated one remained equal. Moreover, mouse embryonic fibroblasts showed better proliferation and viability results on blended PCL/gelatin scaffolds. View this paper.
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Select all
Export citation of selected articles as:
13 pages, 6094 KiB  
Article
Ternary Electrical Memory Devices Based on Polycarbazole: SnO2 Nanoparticles Composite Material
by Yingna Zhang, Feng Dou, Yijia Zhou, Xiaofeng Zhao, Jiangshan Chen, Cheng Wang and Shuhong Wang
Polymers 2022, 14(7), 1494; https://doi.org/10.3390/polym14071494 - 6 Apr 2022
Cited by 2 | Viewed by 1888
Abstract
In this paper, a D–A polymer (PIB) containing carbazole as the donor group in the main chain and benzimidazole benzisoindolinone as the acceptor group was synthesized by Suzuki reaction. The Suzuki reaction, also known as the Suzuki coupling reaction, is a relatively new [...] Read more.
In this paper, a D–A polymer (PIB) containing carbazole as the donor group in the main chain and benzimidazole benzisoindolinone as the acceptor group was synthesized by Suzuki reaction. The Suzuki reaction, also known as the Suzuki coupling reaction, is a relatively new organic coupling reaction in which aryl or alkenyl boronic acids or boronic acid esters react with chlorine, bromine, iodoaromatic hydrocarbons or alkenes under the catalysis of zerovalent palladium complexes cross-coupling. A series of devices were fabricated by a spin-coating approach, and the devices all exhibited ternary resistance switching storage behavior. Among them, the composite device with the mass fraction of SnO2 NPs of 5 wt% has the best storage performance, with a threshold voltage of −0.4 V and a switching current ratio of 1:101.5:104.5. At the same time, the current of the device remained stable after a 3-h test. Furthermore, after 103 cycles, the current has no obvious attenuation. The device has good stability and continuity. Moreover, the conduction mechanism is further revealed. Inorganic nanoparticle composite devices have splendid memory performances and exhibit underlying application significance in storing data. Full article
(This article belongs to the Special Issue Polymeric Biosensors: Fabrication, Characterization, and Applications)
Show Figures

Graphical abstract

9 pages, 1677 KiB  
Communication
Thermoset/Thermoplastic Interphases: The Role of Initiator Concentration in Polymer Interdiffusion
by Ozan Erartsın, Jamal Sayyed Monfared Zanjani and Ismet Baran
Polymers 2022, 14(7), 1493; https://doi.org/10.3390/polym14071493 - 6 Apr 2022
Cited by 2 | Viewed by 1841
Abstract
In the co-bonding of thermoset and thermoplastic polymers, the interdiffusion of the polymers results in the formation of an interphase between them. Understanding the factors influencing the interdiffusion and the resulting interphase is crucial in order to optimize the mechanical performance of the [...] Read more.
In the co-bonding of thermoset and thermoplastic polymers, the interdiffusion of the polymers results in the formation of an interphase between them. Understanding the factors influencing the interdiffusion and the resulting interphase is crucial in order to optimize the mechanical performance of the bond. Herein, for the first time, the effect of the initiator concentration of the thermoset resin-initiator mixture on the interphase thickness of co-bonded thermoset-thermoplastic polymers is investigated. The dependence of the gelation time on the initiator concentration is determined by rheometer measurements. Differential scanning calorimetry measurements are carried out to determine the speed of cure. To co-bond the polymers, pieces of already-manufactured thermoplastic plates are embedded in a resin-initiator mixture. The interphase thickness of the co-bonded polymers is measured with an optical microscope. The results of this study show that the gelation time decreases as the initiator concentration increases. This decrease leads to a significant reduction in both interphase thickness and diffusivity. For instance, increasing the initiator/resin weight ratio from 1% to 3% reduces the gelation time by 74% and the interphase thickness by 63%. Full article
(This article belongs to the Special Issue Advanced Thermoplastic Polymers and Composites)
Show Figures

Figure 1

29 pages, 6024 KiB  
Article
A New Kinetic Modeling Approach for Predicting the Lifetime of ATH-Filled Silane Cross-Linked Polyethylene in a Nuclear Environment
by Sarah Hettal, Sébastien Roland, Konsta Sipila, Harri Joki and Xavier Colin
Polymers 2022, 14(7), 1492; https://doi.org/10.3390/polym14071492 - 6 Apr 2022
Cited by 5 | Viewed by 1650
Abstract
This study focuses on the degradation of a silane cross-linked polyethylene (Si-XLPE) matrix filled with three different contents of aluminum tri-hydrate (ATH): 0, 25, and 50 phr. These three materials were subjected to radiochemical ageing at three different dose rates (8.5, 77.8, and [...] Read more.
This study focuses on the degradation of a silane cross-linked polyethylene (Si-XLPE) matrix filled with three different contents of aluminum tri-hydrate (ATH): 0, 25, and 50 phr. These three materials were subjected to radiochemical ageing at three different dose rates (8.5, 77.8, and 400 Gy·h−1) in air at low temperatures close to ambient (47, 47, and 21 °C, respectively). Changes due to radio-thermal ageing were investigated according to both a multi-scale and a multi-technique approach. In particular, the changes in the chemical composition, the macromolecular network structure, and the crystallinity of the Si-XLPE matrix were monitored by FTIR spectroscopy, swelling measurements in xylene, differential scanning calorimetry, and density measurements. A more pronounced degradation of the Si-XLPE matrix located in the immediate vicinity of the ATH fillers was clearly highlighted by the swelling measurements. A very fast radiolytic decomposition of the covalent bonds initially formed at the ATH/Si-XLPE interface was proposed to explain the higher concentration of chain scissions. If, as expected, the changes in the elastic properties of the three materials under study are mainly driven by the crystallinity of the Si-XLPE matrix, in contrast, the changes in their fracture properties are also significantly impacted by the degradation of the interfacial region. As an example, the lifetime was found to be approximately halved for the two composite materials compared to the unfilled Si-XLPE matrix under the harshest ageing conditions (i.e., under 400 Gy·h−1 at 21 °C). The radio-thermal oxidation kinetic model previously developed for the unfilled Si-XLPE matrix was extended to the two composite materials by taking into account both the diluting effect of the ATH fillers (i.e., the ATH content) and the interfacial degradation. Full article
(This article belongs to the Section Polymer Physics and Theory)
Show Figures

Graphical abstract

19 pages, 5584 KiB  
Article
A Modified Mean Stress Criterion for Considering Size Effects on Mode I Fracture Estimation of Rounded-Tip V-Notched Polymeric Specimens
by Ali Reza Torabi, Mahdi Jabbari, Javad Akbardoost and Sergio Cicero
Polymers 2022, 14(7), 1491; https://doi.org/10.3390/polym14071491 - 6 Apr 2022
Viewed by 1592
Abstract
The aim of this paper is to assess the size and geometry effects on the mode I notch fracture toughness of polymeric samples containing rounded-tip V-shaped (RV) notches (V-notch with a finite radius at the notch tip). First, using a large number of [...] Read more.
The aim of this paper is to assess the size and geometry effects on the mode I notch fracture toughness of polymeric samples containing rounded-tip V-shaped (RV) notches (V-notch with a finite radius at the notch tip). First, using a large number of fracture tests on an RV-notched Brazilian disk and semi-circular bending polymeric samples with four different sizes, the size-dependent values of the notch fracture toughness are obtained. Then, the mean stress criterion is modified for characterizing the size-dependency of notch fracture toughness in polymeric samples. The resulting modified mean stress criterion considers higher order terms of the stress field when calculating the fracture process zone length around the tip of the defect. Additionally, the critical distance rc is assumed to be associated with the specimen size and a formula containing fitting parameters is utilized for considering this trend of rc. The comparison between the values of notch fracture toughness obtained from experiments and those predicted by the modified mean stress criterion shows that the suggested approach can provide accurate estimations of size-dependent values of notch fracture toughness in polymeric specimens containing RV notches. Full article
(This article belongs to the Special Issue Structural Integrity Assessment on Polymers and Composites)
Show Figures

Graphical abstract

16 pages, 5397 KiB  
Article
Development of PVA–Psyllium Husk Meshes via Emulsion Electrospinning: Preparation, Characterization, and Antibacterial Activity
by Fatma Nur Parın, Azeem Ullah, Ayşenur Yeşilyurt, Uğur Parın, Md. Kaiser Haider and Davood Kharaghani
Polymers 2022, 14(7), 1490; https://doi.org/10.3390/polym14071490 - 6 Apr 2022
Cited by 11 | Viewed by 2638
Abstract
In this study, polyvinyl alcohol (PVA) and psyllium husk (PSH)/D-limonene electrospun meshes were produced by emulsion electrospinning for use as substrates to prevent the growth of bacteria. D-limonene and modified microcrystalline cellulose (mMCC) were preferred as antibacterial agents. SEM micrographs showed that PVA–PSH [...] Read more.
In this study, polyvinyl alcohol (PVA) and psyllium husk (PSH)/D-limonene electrospun meshes were produced by emulsion electrospinning for use as substrates to prevent the growth of bacteria. D-limonene and modified microcrystalline cellulose (mMCC) were preferred as antibacterial agents. SEM micrographs showed that PVA–PSH electrospun mesh with a 4% amount of D-limonene has the best average fiber distribution with 298.38 ± 62.8 nm. Moreover, the fiber morphology disrupts with the addition of 6% D-limonene. FT-IR spectroscopy was used to analyze the chemical structure between matrix–antibacterial agents (mMCC and D-limonene). Although there were some partial physical interactions in the FT-IR spectrum, no chemical reactions were seen between the matrixes and the antibacterial agents. The thermal properties of the meshes were determined using thermal gravimetric analysis (TGA). The thermal stability of the samples increased with the addition of mMCC. Further, the PVA–PSH–mMCC mesh had the highest value of contact angle (81° ± 4.05). The antibacterial activity of functional meshes against Gram (−) (Escherichia coli, Pseudomonas aeruginosa) and Gram (+) bacteria (Staphylococcus aureus) was specified based on a zone inhibition test. PPMD6 meshes had the highest antibacterial results with 21 mm, 16 mm, and 15 mm against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, respectively. While increasing the amount of D-limonene enhanced the antibacterial activity, it significantly decreased the amount of release in cases of excess D-limonene amount. Due to good fiber morphology, the highest D-limonene release value (83.1%) was observed in PPMD4 functional meshes. The developed functional meshes can be utilized as wound dressing material based on our data. Full article
(This article belongs to the Special Issue Advanced Electrospinning Fibers)
Show Figures

Figure 1

12 pages, 1573 KiB  
Article
Formulation and Characterization of Carbopol-934 Based Kojic Acid-Loaded Smart Nanocrystals: A Solubility Enhancement Approach
by Barkat Ali Khan, Maryam Waheed, Khaled M. Hosny, Waleed Y. Rizg, Samar S. Murshid, Majed Alharbi and Muhammad Khalid Khan
Polymers 2022, 14(7), 1489; https://doi.org/10.3390/polym14071489 - 6 Apr 2022
Cited by 1 | Viewed by 1961
Abstract
Kojic acid (KA) is a BCS class II drug having low solubility and high permeability. This study was designed to enhance the aqueous solubility of KA, as well as its dissolution rate and, in turn, bioavailability, by formulating its smart nanocrystals. Nanocrystals of [...] Read more.
Kojic acid (KA) is a BCS class II drug having low solubility and high permeability. This study was designed to enhance the aqueous solubility of KA, as well as its dissolution rate and, in turn, bioavailability, by formulating its smart nanocrystals. Nanocrystals of pure KA were formulated by the top-down method under high-pressure homogenization followed by freeze drying. The nanocrystals were evaluated for stability and other physical characteristics, including zeta sizer analysis, DSC, surface morphology, XRD, drug content, solubility, FTIR and in vitro drug release. The KA nanocrystals were found to be stable when kept at exaggerated conditions. The particle size of the nanocrystals was 137.5 ± 1.7, 150 ± 2.8, and 110 ± 3.0 nm for the F1, F2 and F3 formulations, respectively. There was negative zeta potential for all the formulations. The dispersity index was 0.45 ± 0.2, 0.36 ± 0.4 and 0.41 ± 1.5 for the F1, F2 and F3, respectively. The DSC studies showed that there was no interaction between the KA and the excipients of the nanocrystals. The morphological studies confirmed the presence of rough crystalline surfaces on the nanosized particles. XRD studies showed the successful preparation of nanocrystals. The drug content was in the official range of 90 ± 10%. The solubility of KA was significantly (p < 0.05) enhanced in the formulations of its nanocrystals as compared with pure KA powder. The ATR-FTIR studies revealed the presence of functional groups in both KA and KA-loaded nanocrystals, and no interaction was found between them. The nanocrystals released 83.93 ± 1.22% of KA in 24 h. The study concluded that the nanocrystals were successfully formulated using the top-down method followed by high-pressure homogenization. The solubility, as well as the dissolution, of the KA was enhanced, and this could improve the therapeutic effects of KA. Full article
(This article belongs to the Special Issue Polymers and Drug Delivery)
Show Figures

Figure 1

13 pages, 3760 KiB  
Article
Fire Resistance Performance of Steel–Polymer Prefabricated Composite Floors Using Standard Fire Tests
by Min Jae Park, Robel Wondimu Alemayehu and Young K. Ju
Polymers 2022, 14(7), 1488; https://doi.org/10.3390/polym14071488 - 6 Apr 2022
Cited by 5 | Viewed by 2097
Abstract
In this study, the fire resistance performance of steel–polymer prefabricated composite floors, which have a sandwich-type structure, was assessed via standard fire tests and analyzed using finite element analysis. This form of analysis should consider two aspects, namely the thermal and structural fields, [...] Read more.
In this study, the fire resistance performance of steel–polymer prefabricated composite floors, which have a sandwich-type structure, was assessed via standard fire tests and analyzed using finite element analysis. This form of analysis should consider two aspects, namely the thermal and structural fields, so as to simulate complicated material properties and large deformations. As previous studies have already conducted analysis in the thermal field, this study entailed only the structural analysis based on the temperature distributions obtained from the thermal analysis. The variables of the specimens were the thicknesses of the top and bottom steel plates and polymers. According to the analysis results, the top steel plate thickness had no impact on the stability ratings, a criterion for fire resistance performance, whereas the bottom steel plate showed a linear correlation with the stability rating. An equation for the stability rating of composite floors was proposed, and an equation for fire resistance performance was devised based on the insulation ratings, which were obtained from the thermal analysis results. Full article
(This article belongs to the Special Issue Polymer Composites for Structural Applications)
Show Figures

Figure 1

14 pages, 3864 KiB  
Article
Impact of the Liquid Crystal Order of Poly(azomethine-sulfone)s on the Semiconducting Properties
by Oana Dumbravă, Dumitru Popovici, Decebal Vasincu, Ovidiu Popa, Lăcrămioara Ochiuz, Ștefan-Andrei Irimiciuc, Maricel Agop and Anca Negură
Polymers 2022, 14(7), 1487; https://doi.org/10.3390/polym14071487 - 6 Apr 2022
Cited by 1 | Viewed by 1544
Abstract
Organic semiconductors are an attractive class of materials with large application in various fields, from optoelectronics to biomedicine. Usually, organic semiconductors have low electrical conductivity, and different routes towards improving said conductivity are being investigated. One such method is to increase their ordering [...] Read more.
Organic semiconductors are an attractive class of materials with large application in various fields, from optoelectronics to biomedicine. Usually, organic semiconductors have low electrical conductivity, and different routes towards improving said conductivity are being investigated. One such method is to increase their ordering degree, which not only improves electrical conduction but promotes cell growth, adhesion, and proliferation at the polymer–tissue interface. The current paper proposes a mathematical model for understanding the influence of the ordering state on the electrical properties of the organic semiconductors. To this end, a series of aromatic poly(azomethine)s were prepared as thin films in both amorphous and ordered states, and their supramolecular and electrical properties were analyzed by polarized light microscopy and surface type cells, respectively. Furthermore, the film surface characteristics were investigated by atomic force microscopy. It was established that the manufacture of thin films from mesophase state induced an electrical conductivity improvement of one order of magnitude. A mathematical model was developed in the framework of a multifractal theory of motion in its Schrodinger representation. The model used the order degree of the thin films as a fractality measure of the physical system’s representation in the multifractal space. It proposed two types of conductivity, which manifest at different ranges of fractalization degrees. The mathematical predictions were found to be in line with the empirical data. Full article
(This article belongs to the Special Issue Conducting Polymer Nanocomposites and Their Potential Applications)
Show Figures

Figure 1

10 pages, 3019 KiB  
Article
Polydopamine-Coated Natural Rubber Sponge for Highly Efficient Vapor Generation
by Han Yu, Yuqi Shi, Aiwu Ding, Jianhe Liao, Hongxing Gui and Yongping Chen
Polymers 2022, 14(7), 1486; https://doi.org/10.3390/polym14071486 - 6 Apr 2022
Cited by 11 | Viewed by 2045
Abstract
The global water crisis is becoming more and more serious, and solar steam generation has recently been investigated for clean water production and wastewater treatment. However, the efficiency of solar vapor transfer is still low. It is a great challenge to find photothermal [...] Read more.
The global water crisis is becoming more and more serious, and solar steam generation has recently been investigated for clean water production and wastewater treatment. However, the efficiency of solar vapor transfer is still low. It is a great challenge to find photothermal materials which simultaneously have high energy transfer efficiency, facile production, and are low cost. To address this, we propose a method which is simple, low cost and suitable for large-scale preparation to fabricate the photothermal materials based on using recycled natural rubber sponge (NRS) coated with polydopamine (PDA). X-ray photoelectron spectroscopy analysis confirmed that when the PDA coated the surface of the NRS, the hydrophilicity of the sponge was significantly improved. Scanning electron microscopy characterization showed that the PDA-coated natural rubber sponge (PNRS) maintained the porous 3D skeleton of the pristine sponge. As a result, PNRS exhibits excellent photothermal properties, a very high evaporation rate of 1.35 kg m−2 h−1, and an energy transfer efficiency of 84.6% can be achieved under a light intensity of 1 sun (1 kW m−2). It is worth noting that the vapor generation of PNRS is still at a high level with 1.06 and 1.09 kg m−2 h−1 in the corrosive liquids of 1 M H2SO4 and 0.5 M NaOH, respectively. The photothermal materials based on using recycled NRS have good application prospects in seawater desalination and the purification of wastewater, which also provides a new method for the recycling of waste NRS. Full article
(This article belongs to the Section Polymer Applications)
Show Figures

Figure 1

25 pages, 6643 KiB  
Review
Cement-Based Repair Materials and the Interface with Concrete Substrates: Characterization, Evaluation and Improvement
by Xuemin Song, Xiongfei Song, Hao Liu, Haoliang Huang, Kasimova Guzal Anvarovna, Nurmirzayev Azizbek Davlatali Ugli, Yi Huang, Jie Hu, Jiangxiong Wei and Qijun Yu
Polymers 2022, 14(7), 1485; https://doi.org/10.3390/polym14071485 - 6 Apr 2022
Cited by 19 | Viewed by 4507
Abstract
Surface damages usually occur in concrete structures. In order to restore the functions and prolong the service life of concrete structures, their surface damages should be repaired in time. This paper reviews the main requirements for repair materials for concrete structures and the [...] Read more.
Surface damages usually occur in concrete structures. In order to restore the functions and prolong the service life of concrete structures, their surface damages should be repaired in time. This paper reviews the main requirements for repair materials for concrete structures and the most used inorganic repair materials, such as cement-based materials, alkali-activated materials and polymer modified inorganic repair materials. Moreover, techniques to characterize and even improve the interfaces between these repair materials and concrete substrate are summarized. Cement-based material has the advantages of good mechanical properties and consistency with concrete substrate while having the problems of high shrinkage and low flexibility. Polymer modified materials were found as having lower shrinkage and higher flexural strength. Increasing the roughness or humidity of the surface, adding fibers and applying interfacial agents can improve the bond strength between cement-based repair materials and concrete substrates. All of these repair materials and techniques can help to build a good interfacial bonding, and mechanisms of how they improve the interface are discussed in this article. These are of great importance in guaranteeing the effectiveness of the repair of the concrete surface and to guide the research and development of new repair materials. Full article
(This article belongs to the Special Issue Cement-Based Polymeric Composites: Design, Synthesis and Properties)
Show Figures

Figure 1

22 pages, 42790 KiB  
Article
Improvement in Thermochromic Offset Print UV Stability by Applying PCL Nanocomposite Coatings
by Marina Vukoje, Rahela Kulčar, Katarina Itrić Ivanda, Josip Bota and Tomislav Cigula
Polymers 2022, 14(7), 1484; https://doi.org/10.3390/polym14071484 - 6 Apr 2022
Cited by 10 | Viewed by 2486
Abstract
Thermochromic (TC) printing inks change their colouration as a response to a change in temperature. This ability renders them attractive for various applications such as smart packaging, security printing, and marketing, but their application is limited due to their low UV stability, i.e., [...] Read more.
Thermochromic (TC) printing inks change their colouration as a response to a change in temperature. This ability renders them attractive for various applications such as smart packaging, security printing, and marketing, but their application is limited due to their low UV stability, i.e., loss of their thermochromic effect when exposed to UV radiation. In order to improve the UV stability of TC prints, one offset TC printing ink was printed and coated with nanomodified polycaprolactone (PCL) coating. The coating was prepared with the incorporation of 1%, 2%, and 3% mass ratios of ZnO and TiO2 nanoparticles in the PCL matrix. The prepared nanocomposite coatings were applied onto the TC print and exposed to UV radiation; afterwards, they were characterized by the colour properties of prints, SEM microscopy, FTIR, and fluorescence spectroscopy. SEM microscopy, FTIR, and fluorescence spectroscopy showed higher rates of polymer degradation, and the results of colour stability indicated that 3% TiO2 in PCL matrix gave the best UV stability and protection of TC prints. Full article
(This article belongs to the Special Issue Advances in Biocompatible and Biodegradable Polymers)
Show Figures

Figure 1

11 pages, 13818 KiB  
Communication
Biocompatible Films of Calcium Alginate Inactivate Enveloped Viruses Such as SARS-CoV-2
by Alba Cano-Vicent, Rina Hashimoto, Kazuo Takayama and Ángel Serrano-Aroca
Polymers 2022, 14(7), 1483; https://doi.org/10.3390/polym14071483 - 6 Apr 2022
Cited by 19 | Viewed by 2908
Abstract
The current pandemic is urgently demanding the development of alternative materials capable of inactivating the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes the coronavirus 2019 (COVID-19) disease. Calcium alginate is a crosslinked hydrophilic biopolymer with an immense range of biomedical applications [...] Read more.
The current pandemic is urgently demanding the development of alternative materials capable of inactivating the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes the coronavirus 2019 (COVID-19) disease. Calcium alginate is a crosslinked hydrophilic biopolymer with an immense range of biomedical applications due to its excellent chemical, physical, and biological properties. In this study, the cytotoxicity and antiviral activity of calcium alginate in the form of films were studied. The results showed that these films, prepared by solvent casting and subsequent crosslinking with calcium cations, are biocompatible in human keratinocytes and are capable of inactivating enveloped viruses such as bacteriophage phi 6 with a 1.43-log reduction (94.92% viral inactivation) and SARS-CoV-2 Delta variant with a 1.64-log reduction (96.94% viral inactivation) in virus titers. The antiviral activity of these calcium alginate films can be attributed to its compacted negative charges that may bind to viral envelopes inactivating membrane receptors. Full article
(This article belongs to the Special Issue Physical and Biological Properties of Polymeric Biomaterials)
Show Figures

Graphical abstract

10 pages, 11294 KiB  
Article
In-Depth Sulfhydryl-Modified Cellulose Fibers for Efficient and Rapid Adsorption of Cr(VI)
by Wenxuan Wang, Feihan Yu, Zhichen Ba, Hongbo Qian, Shuai Zhao, Jie Liu, Wei Jiang, Jian Li and Daxin Liang
Polymers 2022, 14(7), 1482; https://doi.org/10.3390/polym14071482 - 6 Apr 2022
Cited by 13 | Viewed by 2301
Abstract
As one of the hazardous heavy metal ion pollutants, Cr(VI) has attracted much attention in the sewage treatment research field due to its wide distribution range and serious toxicity. In this paper, cellulose fibers were prepared by wet spinning and followed by freeze [...] Read more.
As one of the hazardous heavy metal ion pollutants, Cr(VI) has attracted much attention in the sewage treatment research field due to its wide distribution range and serious toxicity. In this paper, cellulose fibers were prepared by wet spinning and followed by freeze drying, resulting in large porosity. Subsequently, in-depth sulfhydryl modification was applied with cellulose fibers for efficient and rapid adsorption of Cr(VI). The maximum adsorption capacity of sulfhydryl-modified cellulose fibers to Cr(VI) can reach 120.60 mg g−1, the adsorption equilibrium can be achieved within 300 s, and its adsorption rate can reach 0.319 mg g−1 s−1. The results show that the in-depth sulfhydryl-modified cellulose fibers perform excellent adsorption capacity for chromium, and are also available for other heavy metal ions. At the same time, the low cost and environmentally friendly property of the as-synthesized material also demonstrate its potential for practical usage for the treatment of heavy metal ion pollution in waste water. Full article
(This article belongs to the Special Issue Eco Polymeric Materials and Natural Polymer)
Show Figures

Figure 1

9 pages, 2805 KiB  
Article
Ultra-Broadband and Compact TM-Pass Polarizer Based on Graphene-Buried Polymer Waveguide
by Baizhu Lin, Tianhang Lian, Shijie Sun, Mu Zhu, Yuanhua Che, Xueqing Sun, Xibin Wang and Daming Zhang
Polymers 2022, 14(7), 1481; https://doi.org/10.3390/polym14071481 - 6 Apr 2022
Cited by 5 | Viewed by 1716
Abstract
We report an ultra-broadband and compact TM-pass polarizer based on graphene-buried polymer waveguides. The characteristic parameters of the polarizer were carefully designed and optimized. The standard microfabrication processes were employed to fabricate the device. The presented polarizers exhibit high polarization-dependent transmission imposing a [...] Read more.
We report an ultra-broadband and compact TM-pass polarizer based on graphene-buried polymer waveguides. The characteristic parameters of the polarizer were carefully designed and optimized. The standard microfabrication processes were employed to fabricate the device. The presented polarizers exhibit high polarization-dependent transmission imposing a TE mode cutoff while leaving the TM mode almost unaffected. We experimentally demonstrated the polarizer that has an ultra-high extinction ratio of more than 22.9 dB and 41.9 dB for the monolayer graphene film placed on the surface of core layer and buried in the center of core layer, respectively, and as low insertion loss as ~4.0 dB for the TM mode with the bandwidth over 110 nm. The presented polarizer has the advantages of high extinction ratio, ultra-broadband, low cost, and easy integration with other polymer-based planar lightwave devices. Full article
(This article belongs to the Section Polymer Applications)
Show Figures

Graphical abstract

21 pages, 10044 KiB  
Article
Processing, Characterization of Furcraea foetida (FF) Fiber and Investigation of Physical/Mechanical Properties of FF/Epoxy Composite
by Abhishek Sadananda Madival, Deepak Doreswamy, Srinivasulu Maddasani, Manjunath Shettar and Raviraj Shetty
Polymers 2022, 14(7), 1476; https://doi.org/10.3390/polym14071476 - 6 Apr 2022
Cited by 14 | Viewed by 2716
Abstract
In recent days the rising concern over environmental pollution with excessive use of synthetic materials has led to various eco-friendly innovations. Due to the organic nature, abundance and higher strength, natural fibers are gaining a lot of interest among researchers and are also [...] Read more.
In recent days the rising concern over environmental pollution with excessive use of synthetic materials has led to various eco-friendly innovations. Due to the organic nature, abundance and higher strength, natural fibers are gaining a lot of interest among researchers and are also extensively used by various industries to produce ecological products. Natural fibers are widely used in the composite industry as an alternative to synthetic fibers for numerous applications and new sources of fiber are continuously being explored. In this study, a fiber extracted from the Furcraea foetida (FF) plant is characterized for its feasibility as a reinforcement to fabricate polymer composite. The results show that the fiber has a density of 0.903 ± 0.07 g/cm3, tensile strength (σt) of 170.47 ± 24.71 MPa and the fiber is thermally stable up to 250 °C. The chemical functional groups and elements present in the FF fiber are evaluated by conducting Fourier transform infrared spectroscopy (FT-IR) and energy dispersive spectroscopy (EDS). The addition of FF fibers in epoxy reduced the density (13.44%) and hardness (10.9%) of the FF/Epoxy (FF/E) composite. However, the void content (Vc < 8%) and water absorption (WA: < 6%) rate increased in the composite. The FF/E composite with 30% volume of FF fibers showed maximum σt (32.14 ± 5.54 MPa) and flexural strength (σf: 80.23 ± 11.3 MPa). Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
Show Figures

Figure 1

13 pages, 4243 KiB  
Article
Performance of Multilayer Composite Hollow Membrane in Separation of CO2 from CH4 in Mixed Gas Conditions
by Shahidah Zakariya, Yin Fong Yeong, Norwahyu Jusoh and Lian See Tan
Polymers 2022, 14(7), 1480; https://doi.org/10.3390/polym14071480 - 5 Apr 2022
Cited by 3 | Viewed by 2111
Abstract
Composite membranes comprising NH2-MIL-125(Ti)/PEBAX coated on PDMS/PSf were prepared in this work, and their gas separation performance for high CO2 feed gas was investigated under various operating circumstances, such as pressure and CO2 concentration, in mixed gas conditions. The [...] Read more.
Composite membranes comprising NH2-MIL-125(Ti)/PEBAX coated on PDMS/PSf were prepared in this work, and their gas separation performance for high CO2 feed gas was investigated under various operating circumstances, such as pressure and CO2 concentration, in mixed gas conditions. The functional groups and morphology of the prepared membranes were characterized by Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). CO2 concentration and feed gas pressure were demonstrated to have a considerable impact on the CO2 and CH4 permeance, as well as the CO2/CH4 mixed gas selectivity of the resultant membrane. As CO2 concentration was raised from 14.5 vol % to 70 vol %, a trade-off between permeance and selectivity was found, as CO2 permeance increased by 136% and CO2/CH4 selectivity reduced by 42.17%. The membrane produced in this work exhibited pressure durability up to 9 bar and adequate gas separation performance at feed gas conditions consisting of high CO2 content. Full article
Show Figures

Graphical abstract

19 pages, 4008 KiB  
Article
Non-Isothermal Crystallization of Titanium-Dioxide-Incorporated Rice Straw Fiber/Poly(butylene succinate) Biocomposites
by Tianqi Yue, Huanbo Wang, Yuan Fu, Shiyu Guo, Xuefeng Zhang and Tian Liu
Polymers 2022, 14(7), 1479; https://doi.org/10.3390/polym14071479 - 5 Apr 2022
Cited by 5 | Viewed by 2039
Abstract
In this work, titanium dioxide (TiO2)-incorporated rice straw fiber (RS)/poly(butylene succinate) (PBS) biocomposites were prepared by injection molding with different TiO2 powder loadings. The RS/PBS with 1 wt% TiO2 demonstrated the best mechanical properties, where the flexural strength and [...] Read more.
In this work, titanium dioxide (TiO2)-incorporated rice straw fiber (RS)/poly(butylene succinate) (PBS) biocomposites were prepared by injection molding with different TiO2 powder loadings. The RS/PBS with 1 wt% TiO2 demonstrated the best mechanical properties, where the flexural strength and modulus increased by 30.34% and 28.39%, respectively, compared with RS/PBS. The non-isothermal crystallization of neat PBS, RS/PBS composites, and titanium-dioxide-incorporated RS/PBS composites was investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The non-isothermal crystallization data were analyzed using several theoretical models. The Avrami and Mo kinetic models described the non-isothermal crystallization behavior of neat PBS and the composites; however, the Ozawa model was inapplicable. The crystallization temperature (Tc), half-time of crystallization (t1/2), and kinetic parameters (FT) showed that the crystallizability followed the order: TiO2-incorporated RS/PBS composites > RS/PBS > PBS. The RS/PBS with 1 wt% TiO2 showed the best crystallization properties. The Friedman model was used to evaluate the effective activation energy of the non-isothermal crystallization of PBS and its composites. Rice straw fiber and TiO2 acted as nucleating agents for PBS. The XRD results showed that the addition of rice straw fiber and TiO2 did not substantially affect the crystal parameters of the PBS matrix. Overall, this study shows that RS and TiO2 can significantly improve the crystallization and mechanical properties of PBS composites. Full article
(This article belongs to the Topic Sustainable Polymer Technologies)
Show Figures

Figure 1

14 pages, 2996 KiB  
Article
Synthetic Sulfated Polymers Control Amyloid Aggregation of Ovine Prion Protein and Decrease Its Toxicity
by Pavel Semenyuk, Diana Evstafyeva, Vladimir Izumrudov and Vladimir Muronetz
Polymers 2022, 14(7), 1478; https://doi.org/10.3390/polym14071478 - 5 Apr 2022
Cited by 2 | Viewed by 1839
Abstract
Amyloid aggregation, including aggregation and propagation of prion protein, is a key factor in numerous human diseases, so-called amyloidosis, with a very poor ability for treatment or prevention. The present work describes the effect of sulfated or sulfonated polymers (sodium dextran sulfate, polystyrene [...] Read more.
Amyloid aggregation, including aggregation and propagation of prion protein, is a key factor in numerous human diseases, so-called amyloidosis, with a very poor ability for treatment or prevention. The present work describes the effect of sulfated or sulfonated polymers (sodium dextran sulfate, polystyrene sulfonate, polyanethole sulfonate, and polyvinyl sulfate) on different stages of amyloidogenic conversion and aggregation of the prion protein, which is associated with prionopathies in humans and animals. All tested polymers turned out to induce amyloid conversion of the ovine prion protein. As suggested from molecular dynamics simulations, this effect probably arises from destabilization of the native prion protein structure by the polymers. Short polymers enhanced its further aggregation, whereas addition of high-molecular poly(styrene sulfonate) inhibited amyloid fibrils formation. According to the seeding experiments, the protein–polymer complexes formed after incubation with poly(styrene sulfonate) exhibited significantly lower amyloidogenic capacity compared with the control fibrils of the free prion protein. The cytotoxicity of soluble oligomers was completely inhibited by treatment with poly(styrene sulfonate). To summarize, sulfonated polymers are a promising platform for the formulation of a new class of anti-prion and anti-amyloidosis therapeutics. Full article
(This article belongs to the Special Issue Advances in Polyelectrolyte Complexes)
Show Figures

Graphical abstract

55 pages, 64781 KiB  
Review
Modification of Cellulose Micro- and Nanomaterials to Improve Properties of Aliphatic Polyesters/Cellulose Composites: A Review
by Mariia Stepanova and Evgenia Korzhikova-Vlakh
Polymers 2022, 14(7), 1477; https://doi.org/10.3390/polym14071477 - 5 Apr 2022
Cited by 36 | Viewed by 4917
Abstract
Aliphatic polyesters/cellulose composites have attracted a lot attention due to the perspectives of their application in biomedicine and the production of disposable materials, food packaging, etc. Both aliphatic polyesters and cellulose are biocompatible and biodegradable polymers, which makes them highly promising for the [...] Read more.
Aliphatic polyesters/cellulose composites have attracted a lot attention due to the perspectives of their application in biomedicine and the production of disposable materials, food packaging, etc. Both aliphatic polyesters and cellulose are biocompatible and biodegradable polymers, which makes them highly promising for the production of “green” composite materials. However, the main challenge in obtaining composites with favorable properties is the poor compatibility of these polymers. Unlike cellulose, which is very hydrophilic, aliphatic polyesters exhibit strong hydrophobic properties. In recent times, the modification of cellulose micro- and nanomaterials is widely considered as a tool to enhance interfacial biocompatibility with aliphatic polyesters and, consequently, improve the properties of composites. This review summarizes the main types and properties of cellulose micro- and nanomaterials as well as aliphatic polyesters used to produce composites with cellulose. In addition, the methods for noncovalent and covalent modification of cellulose materials with small molecules, polymers and nanoparticles have been comprehensively overviewed and discussed. Composite fabrication techniques, as well as the effect of cellulose modification on the mechanical and thermal properties, rate of degradation, and biological compatibility have been also analyzed. Full article
(This article belongs to the Special Issue Advances in Bio-Based and Biodegradable Polymeric Composites)
Show Figures

Figure 1

27 pages, 1755 KiB  
Review
Chitosan as a Tool for Sustainable Development: A Mini Review
by Soundouss Maliki, Gaurav Sharma, Amit Kumar, María Moral-Zamorano, Omid Moradi, Juan Baselga, Florian J. Stadler and Alberto García-Peñas
Polymers 2022, 14(7), 1475; https://doi.org/10.3390/polym14071475 - 5 Apr 2022
Cited by 42 | Viewed by 4787
Abstract
New developments require innovative ecofriendly materials defined by their biocompatibility, biodegradability, and versatility. For that reason, the scientific society is focused on biopolymers such as chitosan, which is the second most abundant in the world after cellulose. These new materials should show good [...] Read more.
New developments require innovative ecofriendly materials defined by their biocompatibility, biodegradability, and versatility. For that reason, the scientific society is focused on biopolymers such as chitosan, which is the second most abundant in the world after cellulose. These new materials should show good properties in terms of sustainability, circularity, and energy consumption during industrial applications. The idea is to replace traditional raw materials with new ecofriendly materials which contribute to keeping a high production rate but also reducing its environmental impact and the costs. The chitosan shows interesting and unique properties, thus it can be used for different purposes which contributes to the design and development of sustainable novel materials. This helps in promoting sustainability through the use of chitosan and diverse materials based on it. For example, it is a good sustainable alternative for food packaging or it can be used for sustainable agriculture. The chitosan can also reduce the pollution of other industrial processes such as paper production. This mini review collects some of the most important advances for the sustainable use of chitosan for promoting circular economy. Hence, the present review focuses on different aspects of chitosan from its synthesis to multiple applications. Full article
Show Figures

Figure 1

19 pages, 14996 KiB  
Article
Delivery of Mesenchymal Stem Cell in Dialdehyde Methylcellulose-Succinyl-Chitosan Hydrogel Promotes Chondrogenesis in a Porcine Model
by Yu-Chun Chen, Hsiu-Jung Liao, Yuan-Ming Hsu, Yi-Shan Shen and Chih-Hung Chang
Polymers 2022, 14(7), 1474; https://doi.org/10.3390/polym14071474 - 5 Apr 2022
Cited by 1 | Viewed by 2099
Abstract
Due to the limitation in the current treatment modalities, such as secondary surgery in ACI and fibrocartilage formation in microfracture surgery, various scaffolds or hydrogels have been developed for cartilage regeneration. In the present study, we used sodium periodate to oxidize methylcellulose and [...] Read more.
Due to the limitation in the current treatment modalities, such as secondary surgery in ACI and fibrocartilage formation in microfracture surgery, various scaffolds or hydrogels have been developed for cartilage regeneration. In the present study, we used sodium periodate to oxidize methylcellulose and formed dialdehyde methylcellulose (DAC) after dialysis and freeze-drying process, DAC was further mixed with succinyl-chitosan (SUC) to form an DAC-SUC in situ forming hydrogel. The hydrogel is a stiffness, elastic-like and porous hydrogel according to the observation of SEM and rheological analysis. DAC-SUC13 hydrogel possess well cell-compatibility as well as biodegradability. Most bone marrow mesenchymal stem cells (BM-pMSCs) were alive in the hydrogel and possess chondrogenesis potential. According to the results of animal study, we found DAC-SUC13 hydrogel can function as a stem cell carrier to promote glycosaminoglycans and type II collagen synthesis in the osteochondral defects of porcine knee. These findings suggested that DAC-SUC13 hydrogel combined with stem cell is a potential treatment for cartilage defects repair in the future. Full article
(This article belongs to the Special Issue Advanced Biopolymers for Disease Treatment)
Show Figures

Figure 1

17 pages, 9733 KiB  
Article
Adsorption of an Anionic Surfactant (Sodium Dodecyl Sulfate) from an Aqueous Solution by Modified Cellulose with Quaternary Ammonium
by Ming Zou, Haixin Zhang, Naoto Miyamoto, Naoki Kano and Hirokazu Okawa
Polymers 2022, 14(7), 1473; https://doi.org/10.3390/polym14071473 - 5 Apr 2022
Cited by 2 | Viewed by 2762
Abstract
In this study, a method of removing an anionic surfactant sodium dodecyl sulfate (SDS) from an aqueous solution by cellulose modified with quaternary ammonium cation was discussed. Cellulose, as the adsorbent, was obtained from medical cotton balls, and the quaternary ammonium cation (synthesized [...] Read more.
In this study, a method of removing an anionic surfactant sodium dodecyl sulfate (SDS) from an aqueous solution by cellulose modified with quaternary ammonium cation was discussed. Cellulose, as the adsorbent, was obtained from medical cotton balls, and the quaternary ammonium cation (synthesized from dodecyl dimethyl tertiary amine and epichlorohydrin) was grafted onto the sixth hydroxyl group of D-glucose in the cellulose by the Williamson reaction under alkaline conditions. The modified cellulose was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS); and the zeta potential of the material was also measured after confirmation of the synthesis of quaternary ammonium salts by nuclear magnetic resonance (NMR). From these analyses, a peak of the quaternary ammonium group was observed at 1637 cm−1; and it was found that the surface of the material exhibited a positive charge in pH 2–7. The optimal conditions for SDS adsorption by modified cellulose were pH of 7, contact time of 3 h, and temperature of 60 °C in this study. Typical adsorption isotherms (Langmuir and Freundlich) were determined for the adsorption process, and the maximal adsorption capacity was estimated as 32.5 mg g−1. The results of adsorption kinetics were more consistent with the pseudo-second-order equation, indicating that the adsorption process was mainly controlled by chemical adsorption. Furthermore, thermodynamic analysis indicated that the adsorption process of SDS on the modified cellulose was endothermic and spontaneous and that an increasing temperature was conducive to adsorption. Full article
Show Figures

Figure 1

17 pages, 126492 KiB  
Article
Study of the Behavior of Square Concrete-Filled CFRP Steel Tubular under a Bending-Torsion Load
by Qing-Li Wang, Hang-Cheng Gao and Kuan Peng
Polymers 2022, 14(7), 1472; https://doi.org/10.3390/polym14071472 - 5 Apr 2022
Viewed by 1671
Abstract
To study the behavior of square concrete-filled CFRP (carbon fiber polymer) steel tubular under bending-torsional load, nine square section concrete-filled CFRP steel tubular specimens are designed. The T-θ curve and failure mode of square concrete-filled CFRP steel tubular are studied under a bending-torsional [...] Read more.
To study the behavior of square concrete-filled CFRP (carbon fiber polymer) steel tubular under bending-torsional load, nine square section concrete-filled CFRP steel tubular specimens are designed. The T-θ curve and failure mode of square concrete-filled CFRP steel tubular are studied under a bending-torsional load. Based on the test results, a finite element modeling method is proposed by using the finite element software ABAQUS, and the simulation results are compared with the experimental results. The results show that the simulation is in good agreement with the experimental results. On the basis of verifying the reliability of the model, the whole stress process and parameter analysis of the component are studied, and the calculation expression of bearing capacity of square concrete-filled CFRP steel tubular under bending-torsion load is proposed. The predicted specimen-bearing capacity of the proposed calculation expression of the bearing capacity of square concrete-filled CFRP steel tubular under bending-torsion load is basically consistent with the test results. Full article
(This article belongs to the Special Issue Mechanical Properties of Fiber Reinforced Polymer Composites)
Show Figures

Figure 1

17 pages, 7107 KiB  
Article
Prediction of the Damage Effect on Fiberglass-Reinforced Polymer Matrix Composites for Wind Turbine Blades
by Mariana Domnica Stanciu, Silviu Marian Nastac and Ionut Tesula
Polymers 2022, 14(7), 1471; https://doi.org/10.3390/polym14071471 - 4 Apr 2022
Cited by 5 | Viewed by 2321
Abstract
The structure of wind turbine blades (WTBs) is characterized by complex geometry and materials that must resist various loading over a long period. Because of the components’ exposure to highly aggressive environmental conditions, the blade material suffers cracks, delamination, or even ruptures. The [...] Read more.
The structure of wind turbine blades (WTBs) is characterized by complex geometry and materials that must resist various loading over a long period. Because of the components’ exposure to highly aggressive environmental conditions, the blade material suffers cracks, delamination, or even ruptures. The prediction of the damage effects on the mechanical behavior of WTBs, using finite element analysis, is very useful for design optimization, manufacturing processes, and for monitoring the health integrity of WTBs. This paper focuses on the sensitivity analysis of the effects of the delamination degree of fiberglass-reinforced polymer composites in the structure of wind turbine blades. Using finite element analysis, the composite was modeled as a laminated structure with five plies (0/45/90/45/0) and investigated regarding the stress states around the damaged areas. Thus, the normal and shear stresses corresponding to each element of delaminated areas were extracted from each ply of the composites. It was observed that the maximum values of normal and shear stresses occurred in relation to the orientation of the composite layer. Tensile stresses were developed along the WTB with maximum values in the upper and lower plies (Ply 1 and Ply 5), while the maximum tensile stresses were reached in the perpendicular direction (on the thickness of the composite), in the median area of the thickness, compared to the outer layers where compression stresses were obtained. Taking into account the delamination cases, there was a sinuous-type fluctuation of the shear stress distribution in relation to the thickness of the composite and the orientation of the layer. Full article
Show Figures

Figure 1

13 pages, 12457 KiB  
Article
High-Strength Heat-Elongated Thermoplastic Polyurethane Elastomer Consisting of a Stacked Domain Structure
by Mutsumi Takano, Koudai Takamatsu and Hiromu Saito
Polymers 2022, 14(7), 1470; https://doi.org/10.3390/polym14071470 - 4 Apr 2022
Cited by 8 | Viewed by 2055
Abstract
We found that a high-strength elastomer was obtained by the heat elongation of a thermoplastic polyurethane (TPU) film consisting of a high content of crystalline hard segments (HS). The stress upturn continuously increased with the elongation ratio without a decrease in the strain [...] Read more.
We found that a high-strength elastomer was obtained by the heat elongation of a thermoplastic polyurethane (TPU) film consisting of a high content of crystalline hard segments (HS). The stress upturn continuously increased with the elongation ratio without a decrease in the strain recovery by heat elongation, i.e., the stress at break of a quenched TPU film was increased from 55 to 136 MPa by heat elongation at an elongation ratio of 300%. The results of small-angle X-ray scattering, DSC, and AFM observations revealed that: (1) anisotropically shaped HS domains were stacked at a nanometer scale and the longer direction of the HS domains was arranged perpendicular to the elongated direction due to the heat elongation, (2) the densification of the HS domains increased with increases in the elongation ratio without a significant increase in the crystallinity, and (3) the stacked domain structure remained during the stretching at 23 °C. Thus, the strengthening of the elongated TPU might be attributed to the densification of the HS domains in the stacked structure, which prevents the fracture of the HS domains during the stretching. Full article
(This article belongs to the Special Issue Rubber Materials: Processes, Structures and Applications)
Show Figures

Figure 1

16 pages, 25539 KiB  
Article
Fire Retardancy of Cementitious Panels with Larch and Spruce Bark as Bio-Admixtures
by Thomas Pacher, Marius Cătălin Barbu, Johannes Urstöger, Alexander Petutschnigg and Eugenia Mariana Tudor
Polymers 2022, 14(7), 1469; https://doi.org/10.3390/polym14071469 - 4 Apr 2022
Cited by 2 | Viewed by 1797
Abstract
The aim of this study is to investigate the production of fire-resistant panels made out of bark from spruce (Picea abies), larch (Larix decidua Mill.) and cement. This research included test panels produced from bark, cement, water and cement-bonded recycling [...] Read more.
The aim of this study is to investigate the production of fire-resistant panels made out of bark from spruce (Picea abies), larch (Larix decidua Mill.) and cement. This research included test panels produced from bark, cement, water and cement-bonded recycling material aiming for the target density of 750 kg/m3. The physical (density, dimension stability, thickness swelling) and mechanical properties such as tensile strength and compressive strength together with fire resistance were tested. Considering the results, appealing values have been achieved: max. compressive strength: 3.42 N/mm2; max. thickness swelling: 5.48%; and density: 515 to 791 kg/m3. In principle, the properties of the produced panels depend not only on the density, but also on the hydration and, above all, on the compaction and the composition of the boards. The fire tests demonstrated that the produced panels have an enormous potential in terms of fire resistance and could be utilized for fire-retardant applications. Full article
(This article belongs to the Special Issue Wood Waste-Based Composites)
Show Figures

Graphical abstract

14 pages, 5174 KiB  
Article
Characterizing the Diffusion Property of Hydrogen Sorption and Desorption Processes in Several Spherical-Shaped Polymers
by Jae-Kap Jung, Kyu-Tae Kim, Nak-Kwan Chung, Un-Bong Baek and Seung-Hoon Nahm
Polymers 2022, 14(7), 1468; https://doi.org/10.3390/polym14071468 - 4 Apr 2022
Viewed by 1625
Abstract
We developed a method for characterizing permeation parameters in hydrogen sorption and desorption processes in polymers using the volumetric measurement technique. The technique was utilized for three polymers: nitrile butadiene rubber (NBR), ethylene propylene diene monomer (EPDM), and fluoroelastomer (FKM). The total uptake [...] Read more.
We developed a method for characterizing permeation parameters in hydrogen sorption and desorption processes in polymers using the volumetric measurement technique. The technique was utilized for three polymers: nitrile butadiene rubber (NBR), ethylene propylene diene monomer (EPDM), and fluoroelastomer (FKM). The total uptake (C), total desorbed content (C0), diffusivity in sorption (Ds), and diffusivity in desorption (Dd) of hydrogen in the polymers were determined versus the sample diameter used in both processes. For all the polymers, the diameter dependence was not detected for C and C0. The average C and C0 at 5.75 MPa were 316 wt∙ppm and 291 wt∙ppm for NBR, 270 wt∙ppm and 279 wt∙ppm for EPDM, and 102 wt∙ppm and 93 wt∙ppm for FKM. The coincidence of C and C0 in the sorption and desorption process indicated physisorption upon introducing hydrogen molecules into the polymers. The larger Dd in the desorption process than Ds could be attributed to an increased amorphous phase and volume swelling after decompression. The equilibrium time to reach the saturation of the hydrogen content in both processes was experimentally confirmed as proportional to the squared radius and consistent with the COMSOL simulation. This method could be used to predict the equilibrium time of the sorption time, depending on the radius of the polymers without any measurement. Full article
(This article belongs to the Section Polymer Analysis and Characterization)
Show Figures

Figure 1

22 pages, 5954 KiB  
Article
Optimal Processing Parameters of Transmission Parts of a Flapping-Wing Micro-Aerial Vehicle Using Precision Injection Molding
by Huei-Yu Huang, Fang-Yu Fan, Wei-Chun Lin, Chiung-Fang Huang, Yung-Kang Shen, Yi Lin and Muhammad Ruslin
Polymers 2022, 14(7), 1467; https://doi.org/10.3390/polym14071467 - 4 Apr 2022
Cited by 4 | Viewed by 1837
Abstract
In this study, we designed and fabricated transmission parts for a flapping-wing micro-aerial vehicle (FW-MAV), which was fabricated by precision injection molding, and analyzed its warpage phenomena. First, a numerical simulation (Moldflow) was used to analyze the runner balance and temperature, pressure, and [...] Read more.
In this study, we designed and fabricated transmission parts for a flapping-wing micro-aerial vehicle (FW-MAV), which was fabricated by precision injection molding, and analyzed its warpage phenomena. First, a numerical simulation (Moldflow) was used to analyze the runner balance and temperature, pressure, and stress distributions of the base, gears, and linkage of the transmission structures in an FW-MAV. These data were then applied to fabricate a steel mold for an FW-MAV. Various process parameters (i.e., injection temperature, mold temperature, injection pressure, and packing time) for manufacturing transmission parts for the FW-MAV by precision injection molding were compared. The Taguchi method was employed to determine causes of warpage in the transmission parts. The experimental results revealed that the causes of warpage in the transmission parts were, in order of importance, the mold temperature, injection pressure, packing time, and injection temperature. After the transmission parts were assembled on the FW-MAV, experiments revealed that the MAV could achieve a flight time of 180 s. Mass production of the FW-MAV by precision injection molding could potentially produce substantial savings in time, manpower, and cost. Full article
(This article belongs to the Special Issue Injection Molding of Polymers)
Show Figures

Figure 1

11 pages, 2245 KiB  
Communication
Designing Soft Mobile Machines Enabled by Dielectric Elastomer Minimum Energy Structures
by Fan Liu, Ning An, Wenjie Sun and Jinxiong Zhou
Polymers 2022, 14(7), 1466; https://doi.org/10.3390/polym14071466 - 4 Apr 2022
Cited by 6 | Viewed by 1973
Abstract
Dielectric elastomers (DE) are ideal electro-active polymers with large voltage-induced deformation for the design and realization of soft machines. Among the diversity of configurations of DE-based soft machines, dielectric elastomer minimum energy structures (DEMES) are unique due to their ease of fabrication, readiness [...] Read more.
Dielectric elastomers (DE) are ideal electro-active polymers with large voltage-induced deformation for the design and realization of soft machines. Among the diversity of configurations of DE-based soft machines, dielectric elastomer minimum energy structures (DEMES) are unique due to their ease of fabrication, readiness to extend into multiple segments, and versatility of design configurations. Despite many successful demonstrations of DEMES actuators, these DEMES devices are limited to immobile use. We report several possible implementations of soft mobile machines through the combination of DEMES design, finite element simulation, and experiment. Our designs mimic the biomimetic locomotion of inchworms and marry complex components such as ratchet wheels with soft DEMES actuators. We even elucidate that buckling of DE can be harnessed to achieve asymmetric feet, which is otherwise realized via more complicated means. The examples presented here enrich DE devices’ design and provide valuable insights into the design and fabrication of soft machines that other soft-active materials enable. All the codes and files used in this paper can be downloaded from GitHub. Full article
Show Figures

Figure 1

15 pages, 4468 KiB  
Article
Effects of Freeze–Thaw Cycles on Strength and Wave Velocity of Lime-Stabilized Basalt Fiber-Reinforced Loess
by Wensong Wang, Guansen Cao, Ye Li, Yuxi Zhou, Ting Lu, Binbin Zheng and Weile Geng
Polymers 2022, 14(7), 1465; https://doi.org/10.3390/polym14071465 - 4 Apr 2022
Cited by 13 | Viewed by 1890
Abstract
Basalt fiber is a new environmentally-friendly material with excellent potential for soil reinforcement in geotechnical engineering construction. This study explores the effects of freeze–thaw cycles on the unconfined compressive strength (UCS) and P-wave velocity (Vp) of lime-stabilized basalt fiber-reinforced loess. [...] Read more.
Basalt fiber is a new environmentally-friendly material with excellent potential for soil reinforcement in geotechnical engineering construction. This study explores the effects of freeze–thaw cycles on the unconfined compressive strength (UCS) and P-wave velocity (Vp) of lime-stabilized basalt fiber-reinforced loess. Reinforced loess samples with different proportions of basalt fiber and lime were subjected to 0, 1, 5, and 10 freeze–thaw cycles, and their UCS and Vp were subsequently measured. The test results showed that the addition of basalt fiber and lime to loess could enhance strength and improve resistance against freeze–thaw damage, and the freeze–thaw damage of reinforced loess decreases with the increase of basalt fiber content and length. A relationship between UCS and Vp of the reinforced samples was obtained for the same number of freeze–thaw cycles, and this relationship exhibited linear characteristics. The fitting results indicate that the Vp can be used to estimate the UCS after freeze–thaw damage. The research results not only have important practical significance in the application of basalt fiber in geotechnical engineering but also provide a reference for the non-destructive testing of the strength of loess after freeze–thaw cycles. Full article
Show Figures

Figure 1

Previous Issue
Next Issue
Back to TopTop