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Polymers, Volume 14, Issue 8 (April-2 2022) – 138 articles

Cover Story (view full-size image): The attractive properties of poly(L-lactic acid) (PLA) and its aliphatic polyesters [poly(ethylene adipate) (PEAd) and poly(butylene adipate) (PBAd)] render them ideal co-formulants for the preparation of modified release pharmaceutical formulations. In this report, the in vitro modified release of the chronobiotic hormone melatonin (MLT) from PLA and the aforementioned copolymer matrix tablets is reported. It was found that, depending on the composition and the relevant content of these excipients in the matrix tablets, the release of MLT satisfied the sought targets for fast sleep onset and sleep maintenance. View this paper.
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16 pages, 17581 KiB  
Article
Improved Mechanical Properties and Bioactivity of Silicate Based Bioceramics Reinforced Poly(ether-ether-ketone) Nanocomposites for Prosthetic Dental Implantology
by Noha Taymour, Amal E. Fahmy, Mohamed Abdel Hady Gepreel, Sherif Kandil and Ahmed Abd El-Fattah
Polymers 2022, 14(8), 1632; https://doi.org/10.3390/polym14081632 - 18 Apr 2022
Cited by 12 | Viewed by 2654
Abstract
Polyether-ether-ketone (PEEK) biomaterial has been increasingly employed for orthopedic, trauma, spinal, and dental implants due to its biocompatibility and in vivo stability. However, a lack of bioactivity and binding ability to natural bone tissue has significantly limited PEEK for many challenging dental implant [...] Read more.
Polyether-ether-ketone (PEEK) biomaterial has been increasingly employed for orthopedic, trauma, spinal, and dental implants due to its biocompatibility and in vivo stability. However, a lack of bioactivity and binding ability to natural bone tissue has significantly limited PEEK for many challenging dental implant applications. In this work, nanocomposites based on PEEK reinforced with bioactive silicate-based bioceramics (forsterite or bioglass) as nanofillers were prepared using high energy ball milling followed by melt blending and compression molding. The influence of nanofillers type and content (10, 20 and 30 wt.%) on the crystalline structure, morphology, surface roughness, hydrophilicity, microhardness, elastic compression modulus, and flexural strength of the nanocomposites was investigated. The scanning electron microscopy images of the nanocomposites with low nanofillers content showed a homogenous surface with uniform dispersion within the PEEK matrix with no agglomerates. All nanocomposites showed an increased surface roughness compared to pristine PEEK. It was found that the incorporation of 20 wt.% forsterite was the most effective in the nanocomposite formulation compared with bioglass-based nanocomposites; it has significantly improved the elastic modulus, flexural strength, and microhardness. In vitro bioactivity evaluation, which used biomimetic simulated body fluid indicated the ability of PEEK nanocomposites loaded with forsterite or bioglass nanofillers to precipitate calcium and phosphate bone minerals on its surface. These nanocomposites are expected to be used in long-term load-bearing implant applications and could be recommended as a promising alternative to titanium and zirconia when used as a dental implant material. Full article
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28 pages, 18210 KiB  
Article
A Comparison of Numerical and Actual Measurements of Large-Scale Rib-Structured Pallet Flatness Using Recycled Polypropylene in Injection Molding
by Yi-Ling Liao and Hsi-Hsun Tsai
Polymers 2022, 14(8), 1631; https://doi.org/10.3390/polym14081631 - 18 Apr 2022
Cited by 2 | Viewed by 1720
Abstract
Many challenges are associated with the injection molding process for forming a rib-structured pallet (1100 mm × 1100 mm × 140 mm, length × width × height) because greater flowing resistance through the rib channels within the pallet can induce insufficient filling. Essentially, [...] Read more.
Many challenges are associated with the injection molding process for forming a rib-structured pallet (1100 mm × 1100 mm × 140 mm, length × width × height) because greater flowing resistance through the rib channels within the pallet can induce insufficient filling. Essentially, multi-gate filling involves a sequential valve gate system, which helps to spread the filling front with fewer weld lines. Based on the presetting of the sequential scheme of the valve gates, actual measurements of pallet flatness using the ATOS scan system were compared to numerical warpage measurements of a pallet derived by Moldex3D 2020. In this study, we propose a sequential scheme by actuating the valve gates to open once the flow front spreads towards them; then, actual warpage measurements of a pallet are compared with numerical measurements. The results show that the warpage of the top surface of the pallet is 5.144 mm in actual measurements and 5.729 mm in simulation. The results all indicated small warpage with respect to the pallet size. The simulation and actual measurements of flatness are in excellent agreement; the difference in top flatness between the simulated and actual pallet is 0.59 mm, while the bottom flatness difference is 0.035 mm. By adjusting the cooling water temperature, increasing the mold temperature, and decreasing the material temperature, overall flatness and warpage displacement can be reduced. Full article
(This article belongs to the Special Issue In-Situ Polymer Characterization in Polymer Processing)
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15 pages, 5240 KiB  
Article
Facile Preparation of Cellulose Fiber Reinforced Polypropylene Using Hybrid Filler Method
by Safarul Mustapha, Jacqueline Lease, Kubra Eksiler, Siew Teng Sim, Hidayah Ariffin and Yoshito Andou
Polymers 2022, 14(8), 1630; https://doi.org/10.3390/polym14081630 - 18 Apr 2022
Cited by 3 | Viewed by 2792
Abstract
Dried hybrid fillers comprised of silica/CNF were successfully synthesized in ethanol/water mixed solvents at room temperature without the usage of any precursor. The as-prepared fillers were incorporated with polypropylene (PP) as a polymer matrix through a twin-screw extruder. From surface morphology analysis, the [...] Read more.
Dried hybrid fillers comprised of silica/CNF were successfully synthesized in ethanol/water mixed solvents at room temperature without the usage of any precursor. The as-prepared fillers were incorporated with polypropylene (PP) as a polymer matrix through a twin-screw extruder. From surface morphology analysis, the agglomeration of the silica/CNF hybrid fillers was prevented in the PP matrix and they exhibited moderate transparency, around 17.9% and 44.6% T at 660 nm. Further, the chemical structures of the polymer composites were identified by Fourier transform infrared (FT-IR) analysis. According to thermogravimetric analysis (TGA), the insertion of silica as a co-filler to the PP matrix resulted in an increase in its degradation onset temperature and also thermal stability. In addition, the mechanical properties of the PP composites also increased after the blending process with the hybrid fillers. Overall, sample PP-SS/CNF exhibited the highest tensile strength, which was 36.8 MPa, or around 73.55% compared to the pristine PP. The improvements in tensile strength were attributed to good dispersion and enhanced efficiency of the stress transfer mechanism between the silica and the cellulose within the PP matrix. However, elongation of the sample was reduced sharply due to the stiffening effect of the filler. Full article
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21 pages, 13508 KiB  
Review
Application of Red Cabbage Anthocyanins as pH-Sensitive Pigments in Smart Food Packaging and Sensors
by Reza Abedi-Firoozjah, Shima Yousefi, Mahshid Heydari, Faezeh Seyedfatehi, Shima Jafarzadeh, Reza Mohammadi, Milad Rouhi and Farhad Garavand
Polymers 2022, 14(8), 1629; https://doi.org/10.3390/polym14081629 - 18 Apr 2022
Cited by 61 | Viewed by 14141
Abstract
Anthocyanins are excellent antioxidant/antimicrobial agents as well as pH-sensitive indicators that provide new prospects to foster innovative smart packaging systems due to their ability to improve food shelf life and detect physicochemical and biological changes in packaged food. Compared with anthocyanins from other [...] Read more.
Anthocyanins are excellent antioxidant/antimicrobial agents as well as pH-sensitive indicators that provide new prospects to foster innovative smart packaging systems due to their ability to improve food shelf life and detect physicochemical and biological changes in packaged food. Compared with anthocyanins from other natural sources, red cabbage anthocyanins (RCAs) are of great interest in food packaging because they represent an acceptable color spectrum over a broad range of pH values. The current review addressed the recent advances in the application of RCAs in smart bio-based food packaging systems and sensors. This review was prepared based on the scientific reports found on Web of Science, Scopus, and Google Scholar from February 2000 to February 2022. The studies showed that the incorporation of RCAs in different biopolymeric films could affect their physical, mechanical, thermal, and structural properties. Moreover, the use of RCAs as colorimetric pH-responsive agents can reliably monitor the qualitative properties of the packaged food products in a real-time assessment. Therefore, the development of smart biodegradable films using RCAs is a promising approach to the prospect of food packaging. Full article
(This article belongs to the Special Issue Biopolymers for Food Packaging Films and Coatings)
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15 pages, 3063 KiB  
Article
Green and Rapid Preparation of Fluorosilicone Rubber Foam Materials with Tunable Chemical Resistance for Efficient Oil–Water Separation
by Wan-Jun Hu, Qiao-Qi Xia, Hong-Tao Pan, Hai-Yang Chen, Yong-Xiang Qu, Zuan-Yu Chen, Guo-Dong Zhang, Li Zhao, Li-Xiu Gong, Chang-Guo Xue and Long-Cheng Tang
Polymers 2022, 14(8), 1628; https://doi.org/10.3390/polym14081628 - 18 Apr 2022
Cited by 21 | Viewed by 2840
Abstract
Polydimethylsiloxane (PDMS) foam materials with lightweight, excellent oil resistance and mechanical flexibility are highly needed for various practical applications in aerospace, transportation, and oil/water separation. However, traditional PDMS foam materials usually present poor chemical resistance and easily swell in various solvents, which greatly [...] Read more.
Polydimethylsiloxane (PDMS) foam materials with lightweight, excellent oil resistance and mechanical flexibility are highly needed for various practical applications in aerospace, transportation, and oil/water separation. However, traditional PDMS foam materials usually present poor chemical resistance and easily swell in various solvents, which greatly limits their potential application. Herein, novel fluorosilicone rubber foam (FSiRF) materials with different contents of trifluoropropyl lateral groups were designed and fabricated by a green (no solvents used) and rapid (<10 min foaming process) foaming/crosslinking approach at ambient temperature. Typically, vinyl-terminated poly(dimethyl-co-methyltrifluoropropyl) siloxanes with different fluorine contents of 0–50 mol% were obtained through ring-opening polymerization to effectively adjust the chemical resistance of the FSiRFs. Notably, the optimized FSiRF samples exhibit lightweight (~0.25 g/cm−3), excellent hydrophobicity/oleophilicity (WCA > 120°), reliable mechanical flexibility (complete recovery ability after stretching of 130% strain or compressing of >60%), and improved chemical resistance and structural stability in various solvents, making them promising candidates for efficient and continuous oil–water separation. This work provides an innovative concept to design and prepare advanced fluorosilicone rubber foam materials with excellent chemical resistance for potential oil–water separation application. Full article
(This article belongs to the Section Polymer Chemistry)
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20 pages, 27432 KiB  
Review
Can 3D-Printed Bioactive Glasses Be the Future of Bone Tissue Engineering?
by Amey Dukle, Dhanashree Murugan, Arputharaj Joseph Nathanael, Loganathan Rangasamy and Tae-Hwan Oh
Polymers 2022, 14(8), 1627; https://doi.org/10.3390/polym14081627 - 18 Apr 2022
Cited by 22 | Viewed by 4414
Abstract
According to the Global Burden of Diseases, Injuries, and Risk Factors Study, cases of bone fracture or injury have increased to 33.4% in the past two decades. Bone-related injuries affect both physical and mental health and increase the morbidity rate. Biopolymers, metals, ceramics, [...] Read more.
According to the Global Burden of Diseases, Injuries, and Risk Factors Study, cases of bone fracture or injury have increased to 33.4% in the past two decades. Bone-related injuries affect both physical and mental health and increase the morbidity rate. Biopolymers, metals, ceramics, and various biomaterials have been used to synthesize bone implants. Among these, bioactive glasses are one of the most biomimetic materials for human bones. They provide good mechanical properties, biocompatibility, and osteointegrative properties. Owing to these properties, various composites of bioactive glasses have been FDA-approved for diverse bone-related and other applications. However, bone defects and bone injuries require customized designs and replacements. Thus, the three-dimensional (3D) printing of bioactive glass composites has the potential to provide customized bone implants. This review highlights the bottlenecks in 3D printing bioactive glass and provides an overview of different types of 3D printing methods for bioactive glass. Furthermore, this review discusses synthetic and natural bioactive glass composites. This review aims to provide information on bioactive glass biomaterials and their potential in bone tissue engineering. Full article
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44 pages, 8852 KiB  
Review
Tailoring the Barrier Properties of PLA: A State-of-the-Art Review for Food Packaging Applications
by Stefania Marano, Emiliano Laudadio, Cristina Minnelli and Pierluigi Stipa
Polymers 2022, 14(8), 1626; https://doi.org/10.3390/polym14081626 - 18 Apr 2022
Cited by 53 | Viewed by 7854
Abstract
It is now well recognized that the production of petroleum-based packaging materials has created serious ecological problems for the environment due to their resistance to biodegradation. In this context, substantial research efforts have been made to promote the use of biodegradable films as [...] Read more.
It is now well recognized that the production of petroleum-based packaging materials has created serious ecological problems for the environment due to their resistance to biodegradation. In this context, substantial research efforts have been made to promote the use of biodegradable films as sustainable alternatives to conventionally used packaging materials. Among several biopolymers, poly(lactide) (PLA) has found early application in the food industry thanks to its promising properties and is currently one of the most industrially produced bioplastics. However, more efforts are needed to enhance its performance and expand its applicability in this field, as packaging materials need to meet precise functional requirements such as suitable thermal, mechanical, and gas barrier properties. In particular, improving the mass transfer properties of materials to water vapor, oxygen, and/or carbon dioxide plays a very important role in maintaining food quality and safety, as the rate of typical food degradation reactions (i.e., oxidation, microbial development, and physical reactions) can be greatly reduced. Since most reviews dealing with the properties of PLA have mainly focused on strategies to improve its thermal and mechanical properties, this work aims to review relevant strategies to tailor the barrier properties of PLA-based materials, with the ultimate goal of providing a general guide for the design of PLA-based packaging materials with the desired mass transfer properties. Full article
(This article belongs to the Topic Polymers from Renewable Resources)
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18 pages, 3274 KiB  
Article
Hydrophobic Ag-Containing Polyoctylmethylsiloxane-Based Membranes for Ethylene/Ethane Separation in Gas-Liquid Membrane Contactor
by Evgenia Grushevenko, Alexey Balynin, Ruslan Ashimov, Stepan Sokolov, Sergey Legkov, Galina Bondarenko, Ilya Borisov, Morteza Sadeghi, Stepan Bazhenov and Alexey Volkov
Polymers 2022, 14(8), 1625; https://doi.org/10.3390/polym14081625 - 18 Apr 2022
Cited by 4 | Viewed by 1994
Abstract
The application of gas-liquid membrane contactors for ethane-ethylene separation seems to offer a good alternative to conventional energy-intensive processes. This work aims to develop new hydrophobic composite membranes with active ethylene carriers and to demonstrate their potential for ethylene/ethane separation in gas-liquid membrane [...] Read more.
The application of gas-liquid membrane contactors for ethane-ethylene separation seems to offer a good alternative to conventional energy-intensive processes. This work aims to develop new hydrophobic composite membranes with active ethylene carriers and to demonstrate their potential for ethylene/ethane separation in gas-liquid membrane contactors. For the first time, hybrid membrane materials based on polyoctylmethylsiloxane (POMS) and silver tetrafluoroborate, with a Si:Ag ratio of 10:0.11 and 10:2.2, have been obtained. This technique allowed us to obtain POMS-based membranes with silver nanoparticles (8 nm), which are dispersed in the polymer matrix. The dispersion of silver in the POMS matrix is confirmed by the data IR-spectroscopy, wide-angle X-ray diffraction, and X-ray fluorescence analyses. These membranes combine the hydrophobicity of POMS and the selectivity of silver ions toward ethylene. It was shown that ethylene sorption at 600 mbar rises from 0.89 cm3(STP)/g to 3.212 cm3(STP)/g with an increase of Ag content in POMS from 0 to 9 wt%. Moreover, the membrane acquires an increased sorption affinity for ethylene. The ethylene/ethane sorption selectivity of POMS is 0.64; for the membrane with 9 wt% silver nanoparticles, the ethylene/ethane sorption selectivity was 2.46. Based on the hybrid material, POMS-Ag, composite membranes were developed on a polyvinylidene fluoride (PVDF) porous support, with a selective layer thickness of 5–10 µm. The transport properties of the membranes were studied by separating a binary mixture of ethylene/ethane at 20/80% vol. It has been shown that the addition of silver nanoparticles to the POMS matrix leads to a decrease in the ethylene permeability, but ethylene/ethane selectivity increases from 0.9 (POMS) to 1.3 (9 wt% Ag). It was noted that when the POMS-Ag membrane is exposed to the gas mixture flow for 3 h, the selectivity increases to 1.3 (0.5 wt% Ag) and 2.3 (9 wt% Ag) due to an increase in ethylene permeability. Testing of the obtained membranes in a gas-liquid contactor showed that the introduction of silver into the POMS matrix makes it possible to intensify the process of ethylene mass transfer by more than 1.5 times. Full article
(This article belongs to the Special Issue Polymers for Membrane Separation: Properties and Applications)
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15 pages, 2154 KiB  
Article
Mechanics of a Biomimetic Moisture Sensitive Actuator Based on Compression Wood
by Gerhard Sinn, Elisabeth Fizek, Rupert Wimmer and Helga Lichtenegger
Polymers 2022, 14(8), 1624; https://doi.org/10.3390/polym14081624 - 18 Apr 2022
Cited by 1 | Viewed by 1532
Abstract
Various mechanisms of plant organ movements have been reported, including the close association of two layers with expressed differences in hygroscopic properties. Following this principle, actuator beams composed of thin veneers out of normal and compression wood cut from Scots pine (Pinus [...] Read more.
Various mechanisms of plant organ movements have been reported, including the close association of two layers with expressed differences in hygroscopic properties. Following this principle, actuator beams composed of thin veneers out of normal and compression wood cut from Scots pine (Pinus sylvestris L.) were prepared by using two types of adhesives. The mismatch of the swelling properties of the two layers in tight combination resulted in an expressed bending deflection in response to set humidity changes. The resulting curvatures were measured and analyzed by the Timoshenko bi-metal-model, as well as with an enhanced three-layer model, with the latter also considering the mechanical influence of the glueline on the actuator bending. The thermally induced strain in the original model was replaced by another strain due to moisture changes. The strain was modelled as a function of wood density, along with changes in wood moisture. Experiments with free movement of the bilayer to measure curvature, and with constraints to determine forces, were performed as well. Deformation and magnitude of actuators movements were in close agreement with the enhanced bilayer-model for the phenol-resorcinol-formaldehyde adhesive, which deviated substantially from the casein adhesive glued actuators. The obtained results are seen as critical for wood-based actuator systems that are potentially used in buildings or other applications. Full article
(This article belongs to the Special Issue Advances in Wood-Based Materials and Wood Polymer Composites)
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10 pages, 4476 KiB  
Article
Novel Mutations in Putative Nicotinic Acid Phosphoribosyltransferases of Mycobacterium tuberculosis and Their Effect on Protein Thermodynamic Properties
by Yu-Juan Zhang, Muhammad Tahir Khan, Madeeha Shahzad Lodhi, Hadba Al-Amrah, Salma Saleh Alrdahe, Hanan Ali Alatawi and Doaa Bahaa Eldin Darwish
Polymers 2022, 14(8), 1623; https://doi.org/10.3390/polym14081623 - 18 Apr 2022
Viewed by 1679
Abstract
pncB1 and pncB2 are two putative nicotinic acid phosphoribosyltransferases, playing a role in cofactor salvage and drug resistance in Mycobacterium tuberculosis. Mutations have been reported in first- and second-line drug targets, causing resistance. However, pncB1 and pncB2 mutational data are not available, [...] Read more.
pncB1 and pncB2 are two putative nicotinic acid phosphoribosyltransferases, playing a role in cofactor salvage and drug resistance in Mycobacterium tuberculosis. Mutations have been reported in first- and second-line drug targets, causing resistance. However, pncB1 and pncB2 mutational data are not available, and neither of their mutation effects have been investigated in protein structures. The current study has been designed to investigate mutations and also their effects on pncB1 and pncB2 structures. A total of 287 whole-genome sequenced data of drug-resistant Mycobacterium tuberculosis isolates from Khyber Pakhtunkhwa of Pakistan were retrieved (BioSample PRJEB32684, ERR2510337-ERR2510445, ERR2510546-ERR2510645) from NCBI. The genomic data were analyzed for pncB1 and pncB2 mutations using PhyResSE. All the samples harbored numerous synonymous and non-synonymous mutations in pncB1 and pncB2 except one. Mutations Pro447Ser, Arg286Arg, Gly127Ser, and delTCAGGCCG1499213>1499220 in pncB1 are novel and have not been reported in literature and TB databases. The most common non-synonymous mutations exhibited stabilizing effects on the pncB1 structure. Moreover, 36 out of 287 samples harbored two non-synonymous and 34 synonymous mutations in pncB2 among which the most common was Phe204Phe (TTT/TTC), present in 8 samples, which may have an important effect on the usage of specific codons that may increase the gene expression level or protein folding effect. Mutations Ser120Leu and Pro447Ser, which are present in the loop region, exhibited a gain in flexibility in the surrounding residues while Gly429Ala and Gly127Ser also demonstrated stabilizing effects on the protein structure. Inhibitors designed based on the most common pncB1 and pncB2 mutants may be a more useful strategy in high-burden countries. More studies are needed to elucidate the effect of synonymous mutations on organism phenotype. Full article
(This article belongs to the Special Issue Nucleic Acids as Polymers)
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14 pages, 3537 KiB  
Article
Melting Temperature Depression of Polymer Single Crystals: Application to the Eco-Design of Tie-Layers in Polyolefinic-Based Multilayered Films
by Juan F. Vega, Virginia Souza-Egipsy, M. Teresa Expósito and Javier Ramos
Polymers 2022, 14(8), 1622; https://doi.org/10.3390/polym14081622 - 17 Apr 2022
Cited by 2 | Viewed by 1883
Abstract
In this paper, we describe a method for determining polymer compatibility, which will aid in establishing the requirements of polyolefinic materials for the eco-design of multilayer films for mechanical recycling while avoiding the use of reactive tie layers. Our ultimate goal is to [...] Read more.
In this paper, we describe a method for determining polymer compatibility, which will aid in establishing the requirements of polyolefinic materials for the eco-design of multilayer films for mechanical recycling while avoiding the use of reactive tie layers. Our ultimate goal is to define the molecular characteristics of the polyolefinic structural layer that improve compatibility with the tie layer during mechanical recycling. We have investigated the melting temperature depression of single crystals of various polyethylenes embedded in commercial polymeric matrices with various functionalities (ester, acrylate, acetate and methacrylic acid sodium ionomer), which can be potentially used as tie layers. We demonstrate how the concentration and molecular architecture of the matrices affect the melting temperature of the embedded single crystals differently depending on the latter’s molecular architecture. The main finding indicates that the tie layers are more compatible with linear polyethylene than with branched polyethylenes. Indeed, our results show that the heterogeneous Ziegler–Natta linear low-density polyethylene is incompatible with all of the tie layers tested. The depression of melting temperatures observed are in excellent agreement with the results obtained by investigating the rheological behaviour and morphological features of solution-mixed blends in which segmental interactions between polymeric chains have been, in theory, maximized. Because Ziegler–Natta linear density polyethylene is one of the most commonly used polymers as a structural layer in multi-layer applications, the findings of this study are useful as they clearly show the unsuitability of this type of polyethylene for recycling from an eco-design standpoint. The specific molecular requirements for polyethylene layers (branching content less than 0.5/100 carbon atoms) can be specified for use in packaging, guiding the eco-design and valorisation of recycled multi-layered films containing this material. Full article
(This article belongs to the Section Polymer Applications)
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15 pages, 1497 KiB  
Review
Liquefaction of Cellulose for Production of Advanced Porous Carbon Materials
by Arjeta Kryeziu, Václav Slovák and Alžběta Parchaňská
Polymers 2022, 14(8), 1621; https://doi.org/10.3390/polym14081621 - 16 Apr 2022
Cited by 6 | Viewed by 3951
Abstract
Cellulose is a renewable resource for the production of advanced carbonaceous materials for various applications. In addition to direct carbonization, attention has recently been paid to the preparation of porous carbons from liquid cellulose-based precursors. Possible pathways of cellulose conversion to a liquid [...] Read more.
Cellulose is a renewable resource for the production of advanced carbonaceous materials for various applications. In addition to direct carbonization, attention has recently been paid to the preparation of porous carbons from liquid cellulose-based precursors. Possible pathways of cellulose conversion to a liquid state suitable for the preparation of porous carbons are summarized in this review. Hydrothermal liquefaction leading to liquid mixtures of low-molecular-weight organics is described in detail together with less common decomposition techniques (microwave or ultrasound assisted liquefaction, decomposition in a strong gravitation field). We also focus on dissolution of cellulose without decomposition, with special attention paid to dissolution of nonderivatized cellulose. For this purpose, cold alkalines, hot acids, ionic liquids, or alcohols are commonly used. Full article
(This article belongs to the Topic Cellulose and Cellulose Derivatives)
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21 pages, 3082 KiB  
Review
Mechanical and Moisture Barrier Properties of Epoxy–Nanoclay and Hybrid Epoxy–Nanoclay Glass Fibre Composites: A Review
by Necar Merah, Farhan Ashraf and Mian M. Shaukat
Polymers 2022, 14(8), 1620; https://doi.org/10.3390/polym14081620 - 16 Apr 2022
Cited by 11 | Viewed by 2661
Abstract
Epoxy clay nanocomposites have been proven to have improved mechanical, thermal and physical properties over pristine matrix. Thus, the fields of application of epoxy–clay nanocomposites along with their hybrid glass/carbon fibre reinforced composites have grown tremendously during the last few decades. The present [...] Read more.
Epoxy clay nanocomposites have been proven to have improved mechanical, thermal and physical properties over pristine matrix. Thus, the fields of application of epoxy–clay nanocomposites along with their hybrid glass/carbon fibre reinforced composites have grown tremendously during the last few decades. The present review paper covers the research work performed on epoxy clay nanocomposites. It includes the influence of the processing techniques and parameters on the morphology of the nanocomposite, the methods of characterization and the effects of adding nanoclay on the mechanical and physical properties of composite. The improvements in the liquid barrier properties brought about by the addition of nanoclay platelets to epoxy resin are discussed. The variation of physical and mechanical properties with nanoclay type and content are reviewed along with the effects of moisture uptake on these properties. The advances in the development, characterization and applications of hybrid glass fibre reinforced epoxy–clay nanocomposites are discussed. Findings of the research work on the influence of nanoclay addition and exposure to water laden atmospheres on the behaviour of the hybrid glass fibre epoxy–nanoclay composites are presented. Finally, the potential health and environmental issues related to nanomaterials and their hybrid composites are reviewed. Full article
(This article belongs to the Special Issue Polymer Composite Analysis and Characterization)
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25 pages, 6045 KiB  
Article
Evaluation of Antimicrobial and Anti-Biofilm Formation Activities of Novel Poly(vinyl alcohol) Hydrogels Reinforced with Crosslinked Chitosan and Silver Nano-Particles
by Reem T. Alfuraydi, Fahad M. Alminderej and Nadia A. Mohamed
Polymers 2022, 14(8), 1619; https://doi.org/10.3390/polym14081619 - 16 Apr 2022
Cited by 23 | Viewed by 2773
Abstract
Novel hydrogels were prepared by blending chitosan and poly(vinyl alcohol), PVA, then crosslinking the resulting blends using trimellitic anhydride isothiocyanate at a concentration based on chitosan content in the blends. The weight ratios of chitosan: PVA in the blends were 1:3, 1:1, and [...] Read more.
Novel hydrogels were prepared by blending chitosan and poly(vinyl alcohol), PVA, then crosslinking the resulting blends using trimellitic anhydride isothiocyanate at a concentration based on chitosan content in the blends. The weight ratios of chitosan: PVA in the blends were 1:3, 1:1, and 3:1 to produce three hydrogels symbolized as H13, H11, and H31, respectively. For a comparison, H10 was also prepared by crosslinking pure chitosan with trimellitic anhydride isothiocyanate. For further modification, three H31/silver nanocomposites (AgNPs) were synthesized using three different concentrations of silver nitrate to obtain H31/AgNPs1%, H31/AgNPs3% and H31/AgNPs5%. The structures of the prepared samples were emphasized using various analytical techniques. PVA has no inhibition activity against the tested microbes and biofilms. The antimicrobial and anti-biofilm formation activities of the investigated samples was arranged as: H31/AgNPs5% ≥ H31/AgNPs3% > H31/AgNPs1% > H10 > H31 > H11 > H13 > chitosan. H31/AgNPs5% and H31/AgNPs3% were more potent than Vancomycin and Amphotericin B against most of the tested microbes. Interestingly, H31 and H31/AgNPs3% were safe on the normal human cells. Consequently, hydrogels resulting from crosslinked blends of chitosan and PVA loaded with AgNPs in the same structure have significantly reinforced the antimicrobial and inhibition activity against the biofilms of PVA. Full article
(This article belongs to the Topic Advances in Biomaterials)
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21 pages, 4258 KiB  
Article
Cold Plasma-Based Fabrication and Characterization of Active Films Containing Different Types of Myristica fragrans Essential Oil Emulsion
by Bara Yudhistira, Andi Syahrullah Sulaimana, Fuangfah Punthi, Chao-Kai Chang, Chun-Ta Lung, Shella Permatasari Santoso, Mohsen Gavahian and Chang-Wei Hsieh
Polymers 2022, 14(8), 1618; https://doi.org/10.3390/polym14081618 - 16 Apr 2022
Cited by 13 | Viewed by 2383
Abstract
Myristica fragrans essential oil (MFEO) is a potential active compound for application as an active packaging material. A new approach was developed using a cold plasma treatment to incorporate MFEO to improve the optical, physical, and bacterial inhibition properties of the film. The [...] Read more.
Myristica fragrans essential oil (MFEO) is a potential active compound for application as an active packaging material. A new approach was developed using a cold plasma treatment to incorporate MFEO to improve the optical, physical, and bacterial inhibition properties of the film. The MFEO was added as coarse emulsion (CE), nanoemulsion (NE), and Pickering emulsion (PE) at different concentrations. The PE significantly affected (p < 0.05) the optical, physical, and chemical properties compared with CE and NE films. The addition of MFEO to low-density polyethylene (LDPE) film significantly reduced water vapor permeability (WVP) and oxygen permeability (OP) and showed marked activity against E. coli and S. aureus (p < 0.05). The release rate of PE films after 30 h was 70% lower than that of CE and NE films. Thus, it can be concluded that the fabrication of active packaging containing MFEO is a potential food packaging material. Full article
(This article belongs to the Special Issue Polymeric Materials for Food Packaging II)
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25 pages, 23380 KiB  
Review
TiO2 Containing Hybrid Composite Polymer Membranes for Vanadium Redox Flow Batteries
by Gowthami Palanisamy and Tae Hwan Oh
Polymers 2022, 14(8), 1617; https://doi.org/10.3390/polym14081617 - 15 Apr 2022
Cited by 10 | Viewed by 3593
Abstract
In recent years, vanadium redox flow batteries (VRFB) have captured immense attraction in electrochemical energy storage systems due to their long cycle life, flexibility, high-energy efficiency, time, and reliability. In VRFB, polymer membranes play a significant role in transporting protons for current transmission [...] Read more.
In recent years, vanadium redox flow batteries (VRFB) have captured immense attraction in electrochemical energy storage systems due to their long cycle life, flexibility, high-energy efficiency, time, and reliability. In VRFB, polymer membranes play a significant role in transporting protons for current transmission and act as barriers between positive and negative electrodes/electrolytes. Commercial polymer membranes (such as Nafion) are the widely used IEM in VRFBs due to their outstanding chemical stability and proton conductivity. However, the membrane cost and increased vanadium ions permeability limit its commercial application. Therefore, various modified perfluorinated and non-perfluorinated membranes have been developed. This comprehensive review primarily focuses on recent developments of hybrid polymer composite membranes with inorganic TiO2 nanofillers for VRFB applications. Hence, various fabrications are performed in the membrane with TiO2 to alter their physicochemical properties for attaining perfect IEM. Additionally, embedding the -SO3H groups by sulfonation on the nanofiller surface enhances membrane proton conductivity and mechanical strength. Incorporating TiO2 and modified TiO2 (sTiO2, and organic silica modified TiO2) into Nafion and other non-perfluorinated membranes (sPEEK and sPI) has effectively influenced the polymer membrane properties for better VRFB performances. This review provides an overall spotlight on the impact of TiO2-based nanofillers in polymer matrix for VRFB applications. Full article
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13 pages, 4728 KiB  
Article
Effects of Modified Layered Double Hydroxides on the Thermal Degradation and Combustion Behaviors of Intumescent Flame Retardant Polyethylene Nanocomposites
by Tiefeng Zhang, Chunfeng Wang, Yue Wang, Yongliang Wang and Zhidong Han
Polymers 2022, 14(8), 1616; https://doi.org/10.3390/polym14081616 - 15 Apr 2022
Cited by 15 | Viewed by 2020
Abstract
The flame retardancy of layered double hydroxides (LDHs) correlates with their structure and dispersion in a polymeric matrix. To improve the flame retardant effectiveness of Mg-Al LDH in polyethylene (PE), 2-carboxy ethyl (phenyl) phosphinic acid (CEPPA) was adopted as a flame retardant modifier [...] Read more.
The flame retardancy of layered double hydroxides (LDHs) correlates with their structure and dispersion in a polymeric matrix. To improve the flame retardant effectiveness of Mg-Al LDH in polyethylene (PE), 2-carboxy ethyl (phenyl) phosphinic acid (CEPPA) was adopted as a flame retardant modifier to prepare CEPPA-intercalated LDH (CLDH) by the regeneration method, which was then exfoliated in PE by melt blending in the form of a masterbatch prepared from solution mixing. By compounding CLDH with intumescent flame retardant (IFR) composed of ammonium polyphosphate (APP) and pentaerythritol (PER), the thermal degradation and combustion behaviors of the flame retardant PE-based composites were investigated to reveal the flame retardant mechanism between CLDH and IFR in PE. The reactions between CLDH and IFR were revealed to make a predominant contribution to the compact and fully developed char of PE/IFR/CLDH, which enhanced the flame retardancy of the composites. Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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16 pages, 2348 KiB  
Article
Thermal Degradation of Photoluminescence Poly(9,9-dioctylfluorene) Solvent-Tuned Aggregate Films
by Kang Wei Chew, Nor Azura Abdul Rahim, Pei Leng Teh, Nurfatin Syafiqah Abdul Hisam and Siti Salwa Alias
Polymers 2022, 14(8), 1615; https://doi.org/10.3390/polym14081615 - 15 Apr 2022
Cited by 4 | Viewed by 1889
Abstract
The progression of the green emission spectrum during the decomposition of polyfluorenes (PFs) has impeded the development and commercialization of the materials. Herein, we constructed a solvent-tuned aggregated PFO film with the aim of retarding the material’s thermal degradation behavior which causes a [...] Read more.
The progression of the green emission spectrum during the decomposition of polyfluorenes (PFs) has impeded the development and commercialization of the materials. Herein, we constructed a solvent-tuned aggregated PFO film with the aim of retarding the material’s thermal degradation behavior which causes a significant decline in optical properties as a result of phase transformation. The tuning of the aggregate amount and distribution was executed by applying a poor alcohol-based solvent in chloroform. It emerges that at a lower boiling point methanol evaporates quickly, limiting the aggregate propagation in the film which gives rise to a more transparent film. Furthermore, because of the modulated β-phase conformation, the absorption spectra of PFO films were red-shifted and broadened. The increase in methanol percentage also led to a rise in β-phase percentage. As for the thermal degradation reactions, both pristine and aggregated PFO films exhibited apparent changes in the UV-Vis spectra and PL spectra. In addition, a 97:3 (chloroform:methanol) aggregated PFO film showed a more defined emission spectrum, which demonstrates that the existence of β-phase is able to suppress the unwanted green emission. Full article
(This article belongs to the Collection Assessment of the Ageing and Durability of Polymers)
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16 pages, 2926 KiB  
Article
Investigation of XLPE Cable Insulation Using Electrical, Thermal and Mechanical Properties, and Aging Level Adopting Machine Learning Techniques
by Priya Selvamany, Gowri Sree Varadarajan, Naresh Chillu and Ramanujam Sarathi
Polymers 2022, 14(8), 1614; https://doi.org/10.3390/polym14081614 - 15 Apr 2022
Cited by 3 | Viewed by 3021
Abstract
Hydrothermal and chemical aging tests on a 230 kV cross-linked polyethylene (XLPE) insulation cable were carried out in the present study to evaluate the degradation and aging levels qualitatively. The samples were subjected to water aging at a temperature of 80 °C, and [...] Read more.
Hydrothermal and chemical aging tests on a 230 kV cross-linked polyethylene (XLPE) insulation cable were carried out in the present study to evaluate the degradation and aging levels qualitatively. The samples were subjected to water aging at a temperature of 80 °C, and in an aqueous ionic solution of CuSO4 at room temperature. The diffusion coefficient results indicated that the ion migration was not at the same rate in the aging conditions. The diffusion coefficient–D–of the sample immersed in an aqueous CuSO4 solution was lower than the hydrothermally aged specimens. The hydrophobicity of aged specimens decreased considerably compared to unaged samples. The distribution of trapped charges was quantitatively characterized. The presence of shallow trap energy states were observed in unaged XLPE, whereas the deep trap sites were noticed in aged specimens. In addition, the charge trap characteristics were different for positive and negative charge deposition. Various material characterization techniques, viz. dynamic mechanical analysis (DMA), tensile, contact angle, and LIBS, were further employed on the aged and virgin specimens. The tensile behavior of the hydrothermally aged specimen was degraded due to the oxidised regions, which had formed a weak spot against the mechanical stress. Reduced glass transition temperature and increased loss tangent measurements were noticed for aged specimens over their unaged counterparts. Machine learning techniques, such as the principal component analysis (PCA) and the artificial neural network (ANN) analysis, were performed on LIBS spectral data of the samples to classify the aging mechanisms qualitatively. Full article
(This article belongs to the Section Circular and Green Polymer Science)
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18 pages, 4170 KiB  
Article
Expandable Graphite as a Multifunctional Flame-Retarding Additive for Highly Filled Thermal Conductive Polymer Formulations
by Florian Tomiak, Kevin Schneider, Angelina Schoeffel, Klaus Rathberger and Dietmar Drummer
Polymers 2022, 14(8), 1613; https://doi.org/10.3390/polym14081613 - 15 Apr 2022
Cited by 8 | Viewed by 2163
Abstract
Expandable graphite (EG) and graphite (G) were assessed as multifunctional additives improving both flame retardancy and thermal conductivity in highly filled, thermal conductive polymeric materials based on polyamide 6 (PA6). Fire testing was conducted using modern UL-94, LOI and cone calorimeter test setups. [...] Read more.
Expandable graphite (EG) and graphite (G) were assessed as multifunctional additives improving both flame retardancy and thermal conductivity in highly filled, thermal conductive polymeric materials based on polyamide 6 (PA6). Fire testing was conducted using modern UL-94, LOI and cone calorimeter test setups. It is demonstrated that thermal conductivity can significantly influence the time to ignition, although offering little fire resistance once ignited even in highly filled systems. Thus, for PA6 formulations containing solely 70 wt.% G, the peak heat release rate (pHRR) measured in cone calorimeter tests was 193 kW/m², whereas PA6 formulations containing 20 wt.% EG/50 wt.% G did not exhibit a measurable heat development. Particular attention was paid to effect separation between thermal conductivity and residue formation. Good thermal conductivity properties are proven to be particularly effective in test scenarios where the heat impact is comparatively low and the testing environment provides good heat dissipation and convective cooling possibilities. For candle-like ignition scenarios (e.g., LOI), filling levels of >50 wt.% (G or EG/G) are shown to be sufficient to suppress ignition exclusively by thermal conductivity. V0 classifications in UL-94 vertical burning tests were achieved for PA6 formulations containing ≥70 wt.% G, ≥25 wt.% EG and ≥20 wt.% EG/25 wt.% G. Full article
(This article belongs to the Special Issue Reinforced Polymer Composites III)
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20 pages, 7489 KiB  
Article
Implementation of Microwave Circuits Using Stereolithography
by Germán Torregrosa-Penalva, Héctor García-Martínez, Ángela E. Ortega-Argüello, Alberto Rodríguez-Martínez, Arnau Busqué-Nadal and Ernesto Ávila-Navarro
Polymers 2022, 14(8), 1612; https://doi.org/10.3390/polym14081612 - 15 Apr 2022
Cited by 3 | Viewed by 2391
Abstract
In this work, the use of additive manufacturing techniques through stereolithography for the manufacture of high-frequency circuits and devices is presented. Both the resin and the 3D printer used in this research are general-purpose commercial materials, not specifically intended for the implementation of [...] Read more.
In this work, the use of additive manufacturing techniques through stereolithography for the manufacture of high-frequency circuits and devices is presented. Both the resin and the 3D printer used in this research are general-purpose commercial materials, not specifically intended for the implementation of microwave networks. The manufacturing and metallization procedures used to produce substrates for the design of planar microwave circuits are described, introducing the characterization process carried out to determine the electrical properties of the resin used. The ultrasonic techniques that allow the structural analysis of the manufactured substrates are also described. The electrical characterization provides a relative dielectric permittivity of 3.25 and a loss tangent of 0.03 for the resin used. In addition, the structural analysis shows a homogeneity and a finish of the manufactured parts that is not achievable using fused deposition modeling techniques. Finally, as a proof of concept, the design and manufacture of a complex geometry stepped impedance filter on a multi-height substrate using stereolithography techniques is presented, which allows for reducing the size of the traditional implementation of the same filter while maintaining its high-frequency response performance. Full article
(This article belongs to the Special Issue Applications of 3D Printing for Polymers)
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35 pages, 2910 KiB  
Review
Polymeric Coatings and Antimicrobial Peptides as Efficient Systems for Treating Implantable Medical Devices Associated-Infections
by Irina Negut, Bogdan Bita and Andreea Groza
Polymers 2022, 14(8), 1611; https://doi.org/10.3390/polym14081611 - 15 Apr 2022
Cited by 16 | Viewed by 4456
Abstract
Many infections are associated with the use of implantable medical devices. The excessive utilization of antibiotic treatment has resulted in the development of antimicrobial resistance. Consequently, scientists have recently focused on conceiving new ways for treating infections with a longer duration of action [...] Read more.
Many infections are associated with the use of implantable medical devices. The excessive utilization of antibiotic treatment has resulted in the development of antimicrobial resistance. Consequently, scientists have recently focused on conceiving new ways for treating infections with a longer duration of action and minimum environmental toxicity. One approach in infection control is based on the development of antimicrobial coatings based on polymers and antimicrobial peptides, also termed as “natural antibiotics”. Full article
(This article belongs to the Special Issue Advances in Polymer Devices for Cell Transplantation)
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18 pages, 10020 KiB  
Article
Phase Behaviors of ABA Star Polymer and Nanoparticles Confined in a Sphere with Soft Inner Surface
by Minna Sun, Zhiwei Zhang, Ying Li, Wen Li, Qingwei Liao and Lei Qin
Polymers 2022, 14(8), 1610; https://doi.org/10.3390/polym14081610 - 15 Apr 2022
Viewed by 1279
Abstract
The phase behaviors of an ABA star polymer and nanoparticles confined in a sphere with soft inner surface, which is grafted with homopolymer brushes have been studied by the self-consistent field theory (SCFT). The morphologies of mixture in the center slice of sphere [...] Read more.
The phase behaviors of an ABA star polymer and nanoparticles confined in a sphere with soft inner surface, which is grafted with homopolymer brushes have been studied by the self-consistent field theory (SCFT). The morphologies of mixture in the center slice of sphere were focused. Two cases are considered: one is that the nanoparticles interact with the B blocks and the other is that the nanoparticles preferentially wet the B blocks. Under the two conditions, through changing the block ratio of the ABA star polymer, the concentration and radius of the nanoparticles, the phase behaviors of the mixtures confined the soft sphere are studied systematically. With increasing the concentration of nanoparticles, the entropy and the steric repulsive interaction of nanoparticles, and the nanoparticle density distributions along the perpendicular line through the center of sphere are plotted. The phase diagram is also constructed to analyze the effects of the nanoparticle volume fraction and radius on morphologies of ABA star polymers, and to study the effect of confinement on the phase behaviors. The results in this work provide a useful reference for controlling the ordered structures in experiment, which is an effective way to fabricate the newly multifunctional materials. Full article
(This article belongs to the Section Polymer Physics and Theory)
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12 pages, 1447 KiB  
Article
Inhibition of Carrageenan-Induced Acute Inflammation in Mice by the Microgramma vacciniifolia Frond Lectin (MvFL)
by Leydianne Leite de Siqueira Patriota, Dalila de Brito Marques Ramos, Mariana Gama e Silva, Angela Caroline Lima Amorim dos Santos, Yasmym Araújo Silva, Patrícia Maria Guedes Paiva, Emmanuel Viana Pontual, Lidiane Pereira de Albuquerque, Rosemairy Luciane Mendes and Thiago Henrique Napoleão
Polymers 2022, 14(8), 1609; https://doi.org/10.3390/polym14081609 - 15 Apr 2022
Cited by 6 | Viewed by 2501
Abstract
Most anti-inflammatory drugs used nowadays have an excessive cost and their prolonged use has been connected with several injurious effects. Thus, the search for new anti-inflammatory agents is increasing. Lectins are carbohydrate-interacting proteins that can modulate immune response and the release of inflammation [...] Read more.
Most anti-inflammatory drugs used nowadays have an excessive cost and their prolonged use has been connected with several injurious effects. Thus, the search for new anti-inflammatory agents is increasing. Lectins are carbohydrate-interacting proteins that can modulate immune response and the release of inflammation mediators. The Microgramma vacciniifolia frond lectin (MvFL) was previously reported to be an immunomodulatory agent in vitro. This work aimed to evaluate the effects of MvFL on the in vivo inflammatory status in the carrageenan-induced peritonitis and paw edema, using female Swiss mice. The animals were pretreated intraperitoneally with MvFL (5 and 10 mg/kg). In the peritonitis assay, the total and differential migration of white blood cells was evaluated, as well as the levels of cytokines, nitric oxide (NO), and total proteins in the peritoneal fluid. In the paw edema evaluation, the paw volume was measured in the early (from 30 min–2 h) and late (3–4 h) phases of edema formation. MvFL (5 and 10 mg/kg) was efficient in reducing neutrophil infiltration, pro-inflammatory cytokines (IL-6, IL-17, and TNF-α), NO, and protein content in the peritoneal fluid. It also repressed the edema formation in the late phase of the assay. In conclusion, MvFL showed inhibitory effects in in vivo acute inflammation, which encouraged future studies exploiting its immunomodulatory ability. Full article
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15 pages, 1678 KiB  
Review
Microneedles in Action: Microneedling and Microneedles-Assisted Transdermal Delivery
by Dong-Jin Lim and Hong-Jun Kim
Polymers 2022, 14(8), 1608; https://doi.org/10.3390/polym14081608 - 15 Apr 2022
Cited by 17 | Viewed by 4534
Abstract
Human skin is a multilayered physiochemical barrier protecting the human body. The stratum corneum (SC) is the outermost keratinized layer of skin through which only molecules with less or equal to 500 Da (Dalton) in size can freely move through the skin. Unfortunately, [...] Read more.
Human skin is a multilayered physiochemical barrier protecting the human body. The stratum corneum (SC) is the outermost keratinized layer of skin through which only molecules with less or equal to 500 Da (Dalton) in size can freely move through the skin. Unfortunately, the conventional use of a hypothermic needle for large therapeutic agents is susceptible to needle phobia and the risk of acquiring infectious diseases. As a new approach, a microneedle (MN) can deliver therapeutically significant molecules without apparent limitations associated with its molecular size. Microneedles can create microchannels through the skin’s SC without stimulating the proprioceptive pain nerves. With recent technological advancements in both fabrication and drug loading, MN has become a versatile platform that improves the efficacy of transdermally applied therapeutic agents (TAs) and associated treatments for various indications. This review summarizes advanced fabrication techniques for MN and addresses numerous TA coating and TA elution strategies from MN, offering a comprehensive perspective on the current microneedle technology. Lastly, we discuss how microneedling and microneedle technologies can improve the clinical efficacy of a variety of skin diseases. Full article
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19 pages, 8555 KiB  
Article
Development of an Online Quality Control System for Injection Molding Process
by Ming-Hong Tsai, Jia-Chen Fan-Jiang, Guan-Yan Liou, Feng-Jung Cheng, Sheng-Jye Hwang, Hsin-Shu Peng and Hsiao-Yeh Chu
Polymers 2022, 14(8), 1607; https://doi.org/10.3390/polym14081607 - 15 Apr 2022
Cited by 7 | Viewed by 2630
Abstract
This research developed an adaptive control system for injection molding process. The purpose of this control system is to adaptively maintain the consistency of product quality by minimize the mass variation of injection molded parts. The adaptive control system works with the information [...] Read more.
This research developed an adaptive control system for injection molding process. The purpose of this control system is to adaptively maintain the consistency of product quality by minimize the mass variation of injection molded parts. The adaptive control system works with the information collected through two sensors installed in the machine only—the injection nozzle pressure sensor and the temperature sensor. In this research, preliminary experiments are purposed to find master pressure curve that relates to product quality. Viscosity index, peak pressure, and timing of the peak pressure are used to characterize the pressure curve. The correlation between product quality and parameters such as switchover position and injection speed were used to produce a training data for back propagation neural network (BPNN) to compute weight and bias which are applied on the adaptive control system. By using this system, the variation of part weight is maintained to be as low as 0.14%. Full article
(This article belongs to the Special Issue Recent Advances in Polymer Rheology)
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19 pages, 8529 KiB  
Article
Multiscale Thermal Investigations of Graphite Doped Polystyrene Thermal Insulation
by Ákos Lakatos and Attila Csík
Polymers 2022, 14(8), 1606; https://doi.org/10.3390/polym14081606 - 14 Apr 2022
Cited by 8 | Viewed by 2392
Abstract
Nowadays, to improve quality of life, to have a more comfortable life, in internal spaces we try to maintain conditions that are free from external environmental influences. Thus, existing as well as newly built houses have adequate interiors maintaining their temperature, warming, or [...] Read more.
Nowadays, to improve quality of life, to have a more comfortable life, in internal spaces we try to maintain conditions that are free from external environmental influences. Thus, existing as well as newly built houses have adequate interiors maintaining their temperature, warming, or cooling due to the environment compensation. One way to create this is to reduce the heat loss in buildings. An option to achieve this is the application of thermal insulations. Nowadays, the use of super insulation materials such as aerogel and vacuum insulation panels and other nano-structured insulations, such as graphite doped expanded polystyrene, is becoming increasingly justified. These are relatively new materials, and we know only a little about them. This paper presents research results based on temperature-induced investigations of nanostructured graphite expanded polystyrene, to reveal its thermal stability after long-term and short-term thermal annealing, simulating the ageing of the material. Firstly, with a differential scanning calorimeter, we will explore the thermal stability profile of the specimens. After this, the paper will present temperature-induced changes in both the thermal properties and the structure of the samples. We will also present changes in the thermal conductivity, modifications in the surface, and compressive property variation induced by thermal annealing. The samples were thermal annealed at 70 °C for 6 weeks, at 100 and 110 °C for 1 h. Besides the thermal conductivity measurements with Netzsch 446 heat flow meter equipment, we will present specific heat capacity measurement results executed with the same equipment. Moreover, sorption isotherms of the as-received and annealed samples were registered and completed with hydrophobic experiments, too. Furthermore, from the measurements, we showed that temperature should affect a significant change in the thermal conductivity of materials. Moreover, the changes in the graphite expanded polystyrene before and after thermal annealing were investigated by Scanning Electron Microscopy, as well as optical microscopy. The structural changes were further followed by an X-ray diffractometer and the IR absorption capability was tested, too. Full article
(This article belongs to the Special Issue Application of Polymeric Materials in the Building Industry)
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17 pages, 4810 KiB  
Article
Polymer Composites Based on Glycol-Modified Poly(Ethylene Terephthalate) Applied to Additive Manufacturing Using Melted and Extruded Manufacturing Technology
by Katarzyna Bulanda, Mariusz Oleksy and Rafał Oliwa
Polymers 2022, 14(8), 1605; https://doi.org/10.3390/polym14081605 - 14 Apr 2022
Cited by 4 | Viewed by 2042
Abstract
As part of the work, innovative polymer composites dedicated to 3D printing applications were developed. For this purpose, the influence of modified fillers, such as silica modified with alumina, bentonite modified with quaternary ammonium salt, and hybrid filler lignin/silicon dioxide, on the functional [...] Read more.
As part of the work, innovative polymer composites dedicated to 3D printing applications were developed. For this purpose, the influence of modified fillers, such as silica modified with alumina, bentonite modified with quaternary ammonium salt, and hybrid filler lignin/silicon dioxide, on the functional properties of composites based on glycol-modified poly(ethylene terephthalate) (PET-G) was investigated. In the first part of the work, using the proprietary technological line, filaments from unfilled polymer and its composites were obtained, which contained modified fillers in an amount from 1.5% to 3.0% by weight. The fittings for the testing of functional properties were obtained using the 3D printing technique in the Melted and Extruded Manufacturing (MEM) technology and the injection molding technique. In a later part of the work, rheological properties such as mass melt flow rate (MFR) and viscosity, and mechanical properties such as Rockwell hardness, Charpy impact strength, and static tensile strength with Young’s modulus were presented. The structure of the obtained composites was also described and determined using scanning electron microscopy with an attachment for the microanalysis of chemical composition (SEM/EDS) and the atomic force microscope (AFM). The correct dispersion of the fillers in the polymer matrix was confirmed by wide-angle X-ray scattering analysis (WAXS). In turn, the physicochemical properties were presented on the basis of the research results: thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR). On the basis of the obtained results, it was found that both the amount and the type of fillers used significantly affected the functional properties of the tested composites. Full article
(This article belongs to the Special Issue Synthesis, Characterization and Structure of Polymer Nanomaterials)
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44 pages, 2783 KiB  
Review
Pervaporation as a Successful Tool in the Treatment of Industrial Liquid Mixtures
by Kadavil Subhash Lakshmy, Devika Lal, Anandu Nair, Allan Babu, Haritha Das, Neethu Govind, Mariia Dmitrenko, Anna Kuzminova, Aleksandra Korniak, Anastasia Penkova, Abhimanyu Tharayil and Sabu Thomas
Polymers 2022, 14(8), 1604; https://doi.org/10.3390/polym14081604 - 14 Apr 2022
Cited by 11 | Viewed by 4127
Abstract
Pervaporation is one of the most active topics in membrane research, and it has time and again proven to be an essential component for chemical separation. It has been employed in the removal of impurities from raw materials, separation of products and by-products [...] Read more.
Pervaporation is one of the most active topics in membrane research, and it has time and again proven to be an essential component for chemical separation. It has been employed in the removal of impurities from raw materials, separation of products and by-products after reaction, and separation of pollutants from water. Given the global problem of water pollution, this approach is efficient in removing hazardous substances from water bodies. Conventional processes are based on thermodynamic equilibria involving a phase transition such as distillation and liquid–liquid extraction. These techniques have a relatively low efficacy and nowadays they are not recommended because it is not sustainable in terms of energy consumption and/or waste generation. Pervaporation emerged in the 1980s and is now becoming a popular membrane separation technology because of its intrinsic features such as low energy requirements, cheap separation costs, and good quality product output. The focus of this review is on current developments in pervaporation, mass transport in membranes, material selection, fabrication and characterization techniques, and applications of various membranes in the separation of chemicals from water. Full article
(This article belongs to the Special Issue Advanced Polymeric Materials for Membrane Technology II)
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14 pages, 1596 KiB  
Article
Effectiveness and Applications of a Metal-Coated HNT/Polylactic Acid Antimicrobial Filtration System
by Antwine W. McFarland, Jr., Anusha Elumalai, Christopher C. Miller, Ahmed Humayun and David K. Mills
Polymers 2022, 14(8), 1603; https://doi.org/10.3390/polym14081603 - 14 Apr 2022
Cited by 9 | Viewed by 2354
Abstract
A broad-spectrum antimicrobial respiration apparatus designed to fight bacteria, viruses, fungi, and other biological agents is critical in halting the current pandemic’s trajectory and containing future outbreaks. We applied a simple and effective electrodeposition method for metal (copper, silver, and zinc) coating the [...] Read more.
A broad-spectrum antimicrobial respiration apparatus designed to fight bacteria, viruses, fungi, and other biological agents is critical in halting the current pandemic’s trajectory and containing future outbreaks. We applied a simple and effective electrodeposition method for metal (copper, silver, and zinc) coating the surface of halloysite nanotubes (HNTs). These nanoparticles are known to possess potent antiviral and antimicrobial properties. Metal-coated HNTs (mHNTs) were then added to polylactic acid (PLA) and extruded to form an mHNT/PLA 3D composite printer filament. Our composite 3D printer filament was then used to fabricate an N95-style mask with an interchangeable/replaceable filter with surfaces designed to inactivate a virus and kill bacteria on contact, thus reducing deadly infections. The filter, made of a multilayered antimicrobial/mHNT blow spun polymer and fabric, is disposable, while the mask can be sanitized and reused. We used several in vitro means of assessing critical clinical features and assessed the bacterial growth inhibition against commonly encountered bacterial strains. These tests demonstrated the capability of our antimicrobial filament to fabricate N95 masks and filters that possessed antibacterial capabilities against both Gram-negative and Gram-positive bacteria. Full article
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