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Polymers, Volume 12, Issue 8 (August 2020) – 230 articles

Cover Story (view full-size image): There is a huge demand for multi-polymer-layered nanofibers but mass production is elusive. This paper describes a new scalable manufacturing process that fulfills this need. Core-sheath polymeric fibers were prepared with excellent process control using a simple, economical procedure; pressurized gyration, easily adaptable in industry, where rotational speed and applied pressure can control the core and sheath dimensions at the nanoscale, starting from polymer solutions contained in a twin reservoir vessel. This discovery creates new forming capabilities that can be exploited to advance the frontiers of many advanced technologies, for example, fibers with a strong core and functional (bioactive) sheath can be made in large quantities for tissue engineering, drug delivery, and antimicrobial filtration. View this paper.
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Article
Adsorption and Release of Rose Bengal on Layer-by-Layer Films of Poly(Vinyl Alcohol) and Poly(Amidoamine) Dendrimers Bearing 4-Carboxyphenylboronic Acid
Polymers 2020, 12(8), 1854; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081854 - 18 Aug 2020
Cited by 1 | Viewed by 1053
Abstract
Phenylboronic acid-bearing polyamidoamine dendrimer (PBA-PAMAM)/poly(vinyl alcohol) (PVA) multilayer films were prepared through the layer-by-layer (LbL) deposition of PBA-PAMAM solution and PVA solution. PBA-PAMAM/PVA films were constructed successfully through the formation of boronate ester bonds between the boronic acid moiety in PBA and 1,3-diol [...] Read more.
Phenylboronic acid-bearing polyamidoamine dendrimer (PBA-PAMAM)/poly(vinyl alcohol) (PVA) multilayer films were prepared through the layer-by-layer (LbL) deposition of PBA-PAMAM solution and PVA solution. PBA-PAMAM/PVA films were constructed successfully through the formation of boronate ester bonds between the boronic acid moiety in PBA and 1,3-diol units in PVA. When the (PBA-PAMAM/PVA)5 films were immersed in rose bengal (RB) solution, RB was adsorbed onto the LbL films. The amount of RB adsorbed was higher in the LbL films immersed in acidic solution than in basic solution. The release of RB from the LbL films was also promoted in the basic solution, while it was suppressed in the acidic solution. The boronic acid ester is oxidized to phenol by hydrogen peroxide (H2O2) and the carbon-boron bond is cleaved, so that the (PBA-PAMAM/PVA)5 films can be decomposed by immersion in H2O2 solution. Therefore, when RB-adsorbed (PBA-PAMAM/PVA)5 films were immersed in H2O2 solution, the release of RB was moderately promoted when the solution was weakly acidic. Full article
(This article belongs to the Section Polymer Applications)
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Article
In Vitro Degradation of Electrospun Poly(Lactic-Co-Glycolic Acid) (PLGA) for Oral Mucosa Regeneration
Polymers 2020, 12(8), 1853; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081853 - 18 Aug 2020
Cited by 4 | Viewed by 1058
Abstract
Poly(lactic-co-glycolic acid) (PLGA) has been used in the field of tissue engineering as a scaffold due to its good biocompatibility, biodegradability and mechanical strength. With the aim to explore the degradability of PLGA electrospun nonwoven structures for oral mucosa tissue engineering applications, non-irradiated [...] Read more.
Poly(lactic-co-glycolic acid) (PLGA) has been used in the field of tissue engineering as a scaffold due to its good biocompatibility, biodegradability and mechanical strength. With the aim to explore the degradability of PLGA electrospun nonwoven structures for oral mucosa tissue engineering applications, non-irradiated and gamma irradiated nonwovens were immersed in three different solutions, in which simulated body fluid (SBF) and artificial saliva are important for future oral mucosa tissue engineering. The nonwovens were immersed for 7, 15 and 30 days in SBF, culture media (DMEM) and artificial saliva at 37 °C. Before immersion in the solutions, the dosage of 15 kGy was applied for sterilization in one assay and compared with non-irradiated samples at the same timepoints. Samples were characterized using different techniques such as scanning electron microscopy (SEM), differential scanning calorimetric (DSC) and gel permeation chromatography (GPC) to evaluate the nonwoven degradation and Fourier-transform infrared spectroscopy (FTIR) to evaluate the chain scissions. Our results showed that PLGA nonwovens were constituted by semicrystalline fibers with moderate degradation properties up to thirty days. The non-irradiated samples exhibited slower kinetics of degradation than irradiated nonwovens. For immersion times longer than 7 days in the three different solutions, the mean diameter of irradiated fibers stayed in the same range, but significantly different from the control sample. On non-irradiated samples, the degradation kinetics was slower and the plateau in the diameter value was only attained after 30 days of immersion in the fluids. Plasticization (fluid absorption into the fiber structure) occurred in the bulk material, as confirmed by a decrease in Tg observed by DSC analyses of non-irradiated and irradiated nonwovens, in comparison with the respective controls. In addition, artificial saliva showed a higher capacity of influencing PLGA crystallization than SBF and DMEM. FTIR analyses showed typical PLGA chemical functional groups changes. These results will be important for future application of those PLGA electrospun nonwovens for oral mucosa regeneration. Full article
(This article belongs to the Special Issue Polymer-Based Biocompatible System)
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Article
Long-Term Formaldehyde Emission Potential from UF- and NAF-Bonded Particleboards
Polymers 2020, 12(8), 1852; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081852 - 18 Aug 2020
Viewed by 758
Abstract
As a result of the dominance of urea formaldehyde (UF)-bonded particleboard, it seemed worthwhile to examine formaldehyde emissions years after production. A California Air Resources Board (CARB) phase II-compliant commercial particleboard produced with a UF resin adhesive was compared to a no-added formaldehyde [...] Read more.
As a result of the dominance of urea formaldehyde (UF)-bonded particleboard, it seemed worthwhile to examine formaldehyde emissions years after production. A California Air Resources Board (CARB) phase II-compliant commercial particleboard produced with a UF resin adhesive was compared to a no-added formaldehyde (NAF)-particleboard produced with Soyad™ adhesive resin for formaldehyde emissions during exposure to elevated humidity and temperature conditions after being in a room at 21 ± 1.9 °C, 50 ± 3.3% relative humidity for 3.5 years. A modified version of EN 717-3 was used to collect formaldehyde emissions under typical along with higher temperature and humidity conditions. The formaldehyde emissions from the commercial particleboard panel bonded with a UF adhesive even after the 3.5 years of exposure greatly increased only during exposure of the panels to elevated heat and humidity compared to typical testing conditions. The amounts were the same as those with the previous shorter-term study. In contrast, formaldehyde emissions from the NAF-bonded particleboard were not as susceptible (in absolute terms) to increases in temperature and relative humidity conditions. Full article
(This article belongs to the Collection Polymeric Adhesives)
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Article
Preparation and Electrochemical Properties of Porous Carbon Nanofiber Electrodes Derived from New Precursor Polymer: 6FDA-TFMB
Polymers 2020, 12(8), 1851; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081851 - 18 Aug 2020
Cited by 2 | Viewed by 989
Abstract
Porous carbon nanofibers (CNFs) with high energy storage performance were fabricated with a single precursor polymer, 6FDA-TFMB, without the use of any pore-generating materials. 6FDA-TFMB was synthesized, electrospun, and thermally treated to produce binder-free CNF electrodes for electrochemical double-layer capacitors (EDLCs). Highly porous [...] Read more.
Porous carbon nanofibers (CNFs) with high energy storage performance were fabricated with a single precursor polymer, 6FDA-TFMB, without the use of any pore-generating materials. 6FDA-TFMB was synthesized, electrospun, and thermally treated to produce binder-free CNF electrodes for electrochemical double-layer capacitors (EDLCs). Highly porous CNFs with a surface area of 2213 m2 g−1 were prepared by steam-activation. CNFs derived from 6FDA-TFMB showed rectangular cyclic voltammograms with a specific capacitance of 292.3 F g−1 at 10 mV s−1. It was also seen that CNFs exhibit a maximum energy density of 13.1 Wh kg−1 at 0.5 A g−1 and power density of 1.7 kW kg−1 at 5 A g−1, which is significantly higher than those from the common precursor polymer, polyacrylonitrile (PAN). Full article
(This article belongs to the Special Issue Polymer-Based Electrodes)
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Review
State of the Art on Biomaterials for Soft Tissue Augmentation in the Oral Cavity. Part I: Natural Polymers-Based Biomaterials
Polymers 2020, 12(8), 1850; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081850 - 18 Aug 2020
Cited by 8 | Viewed by 1150
Abstract
Oral soft tissue thickening or grafting procedures are often necessary to cover tooth recession, re-establish an adequate width of keratinized tissue, correct mucogingival deformities improving esthetics, prepare a site for an implant or prosthetics, for ridge preservation procedures, and soft tissue contouring around [...] Read more.
Oral soft tissue thickening or grafting procedures are often necessary to cover tooth recession, re-establish an adequate width of keratinized tissue, correct mucogingival deformities improving esthetics, prepare a site for an implant or prosthetics, for ridge preservation procedures, and soft tissue contouring around dental implants. Gingival recession and root or implant exposure are commonly associated and have led to mucogingival deficiencies that have traditionally been treated with free gingival grafts and autogenous soft tissue grafts. The latter represents the gold standard in acquiring a functionally adequate zone of keratinized attached gingiva. However, soft tissue substitutes are more usually employed because they lessen morbidity and abbreviate surgical time. This review is aimed at assessing oral soft tissue augmentation techniques and biomaterials used from existing literature, principally concerning scaffolds from both human and animal-based tissue derivatives matrices. In order to avoid the use of human donor tissue, the xenogenic collagen matrices are proposed for soft tissue augmentation. In general, all of them have provided the remodeling processes and enhanced the formation of new connective tissue within the matrix body. Full article
(This article belongs to the Special Issue Polymeric Materials for Dental Applications)
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Article
Hydrolytic Degradation of Porous Crosslinked Poly(ε-Caprolactone) Synthesized by High Internal Phase Emulsion Templating
Polymers 2020, 12(8), 1849; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081849 - 18 Aug 2020
Cited by 3 | Viewed by 1133
Abstract
Porous poly(ε-caprolactone) (PCL) scaffolds were fabricated using the high internal polymerization emulsion (HIPE) technique. Bis(ε-caprolactone-4-yl) (BCY) was utilized as crosslinker. The crosslinking density and the volume fraction of the dispersed phase were varied in order to study the potential effect of these parameters [...] Read more.
Porous poly(ε-caprolactone) (PCL) scaffolds were fabricated using the high internal polymerization emulsion (HIPE) technique. Bis(ε-caprolactone-4-yl) (BCY) was utilized as crosslinker. The crosslinking density and the volume fraction of the dispersed phase were varied in order to study the potential effect of these parameters on the hydrolytic degradation at 37 °C and 60 °C. After different hydrolysis times the remaining solid samples were analyzed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), while the degradation products in the aqueous aging solutions were analyzed by laser desorption ionization-mass spectrometry (LDI-MS). The effect of temperature on the degradation process and release of degradation products was, as expected, significant. The temperature effect was also shown by FTIR analysis that displayed a pronounced increase in the intensity of the hydroxyl-group absorption band after 70 days of hydrolysis at 60 °C indicating significant cleavage of the polymer chains. LDI-MS analysis proved the release of oligomers ranging from dimers to hexamers. The product patterns were similar, but the relative m/z signal intensities increased with increasing time, temperature and crosslinking density, indicating larger amounts of released products. The latter is probably due to the decreasing degree of crystallinity as a function of amount of crosslinker. The porous structure and morphology of the scaffolds were lost during the aging. The higher the crosslinking density, the longer the scaffolds retained their original porous structure and morphology. Full article
(This article belongs to the Special Issue Biodegradable and Biobased Polymers Obtained via Step Polymerization)
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Editorial
Education and Research during Pandemics: Illustrated by the Example of Experimental Biocomposites Research
Polymers 2020, 12(8), 1848; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081848 - 18 Aug 2020
Cited by 1 | Viewed by 924
(This article belongs to the Special Issue Performance and Application of Novel Biocomposites)
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Article
Natural Formulations Provide Antioxidant Complement to Hyaluronic Acid-Based Topical Applications Used in Wound Healing
Polymers 2020, 12(8), 1847; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081847 - 18 Aug 2020
Cited by 4 | Viewed by 1052
Abstract
Hyaluronic acid (HA) promotes wound healing, and, accordingly, formulations based on HA have been widely used in regenerative medicine. In addition, naturally derived compounds, e.g., plant-based extracts and vitamin E, have exhibited antioxidant activity. In this study, a formulation containing hyaluronic acid, vitamin [...] Read more.
Hyaluronic acid (HA) promotes wound healing, and, accordingly, formulations based on HA have been widely used in regenerative medicine. In addition, naturally derived compounds, e.g., plant-based extracts and vitamin E, have exhibited antioxidant activity. In this study, a formulation containing hyaluronic acid, vitamin E, raspberry extract, and green tea was developed for potential topical applications, targeting wound healing. Rheological analysis was performed along with antioxidant and biological studies. The rheological characterization showed that the HA-based formulation is a thixotropic platform and possesses higher mechanical properties than the control formulation. To evaluate the wound healing potential of the formulation, an in vitro “wound healing” assay was carried out using human derived fibroblasts (HDF) with a cell-free gap on the tissue culture dish. The formulation showed better wound healing ability than the control formulation. Full article
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Article
Improvement of PLLA Ductility by Blending with PVDF: Localization of Compatibilizers at Interface and Its Glycidyl Methacrylate Content Dependency
Polymers 2020, 12(8), 1846; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081846 - 17 Aug 2020
Cited by 3 | Viewed by 826
Abstract
In this work, the localization of reactive compatibilizer (RC, containing poly(methyl methacrylate) (PMMA) backbone with randomly distributed glycidyl methacrylate (GMA) on it) at the polyvinylidene fluoride/poly(l-lactic acid) (PVDF/PLLA) interface has been manipulated by means of GMA contents. At the very beginning [...] Read more.
In this work, the localization of reactive compatibilizer (RC, containing poly(methyl methacrylate) (PMMA) backbone with randomly distributed glycidyl methacrylate (GMA) on it) at the polyvinylidene fluoride/poly(l-lactic acid) (PVDF/PLLA) interface has been manipulated by means of GMA contents. At the very beginning of mixing, RC tends to stay in the PVDF phase due to the miscibility between PVDF and PMMA. Upon further shearing, more and more PLLA chains have been grafted on PMMA backbone, producing PLLA–g–PMMA copolymer. The balanced stress on two sides accounts for the localization of compatibilizers at the PVDF/PLLA interface. Finally, the stress of the PLLA side has been enhanced remarkably due to the higher graft density of PLLA, resulting in the enrichment of the copolymer in the PLLA matrix. The migration of RC from the PVDF phase to the immiscible interface and PLLA matrix can be accelerated by employing RC with higher GMA content. Furthermore, the compatibilizer localization produces a significant influence on the morphology and ductility of the PVDF/PLLA blend. Only when the compatibilizers precisely localize at the interface, the blend exhibits the smallest domain and highest elongation at break. Our results are of great significance for not only the fabrication of PLLA with high ductility, but also the precise localization of compatibilizers at the interface of the immiscible blend. Full article
(This article belongs to the Section Polymer Processing and Engineering)
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Review
State of the Art on Biomaterials for Soft Tissue Augmentation in the Oral Cavity. Part II: Synthetic Polymers-Based Biomaterials
Polymers 2020, 12(8), 1845; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081845 - 17 Aug 2020
Cited by 1 | Viewed by 1214
Abstract
Most of the polymers used as biomaterials for scaffolds are naturally occurring, synthetic biodegradable, and synthetic non-biodegradable polymers. Since synthetic polymers can be adapted for obtaining singular desired characteristics by applying various fabrication techniques, their use has increased in the biomedical field, in [...] Read more.
Most of the polymers used as biomaterials for scaffolds are naturally occurring, synthetic biodegradable, and synthetic non-biodegradable polymers. Since synthetic polymers can be adapted for obtaining singular desired characteristics by applying various fabrication techniques, their use has increased in the biomedical field, in dentistry in particular. The manufacturing methods of these new structures include many processes, such as electrospinning, 3D printing, or the use of computer-aided design/computer-aided manufacturing (CAD/CAM). Synthetic polymers show several drawbacks that can limit their use in clinical applications, such as the lack of cellular recognition, biodegradability, and biocompatibility. Moreover, concerning biodegradable polymers, the time for matrix resorption is not predictable, and non-resorbable matrices are preferred for soft tissue augmentation in the oral cavity. This review aimed to determine a new biomaterial to offset the present shortcomings in the oral environment. Researchers have recently proposed a novel non-resorbable composite membrane manufactured via electrospinning that has allowed obtaining remarkable in vivo outcomes concerning angiogenesis and immunomodulation throughout the polarization of macrophages. A prototype of the protocol for in vitro and in vivo experimentation with hydrogels is explained in order to encourage innovation into the development of promising biomaterials for soft tissue augmentation in the near future. Full article
(This article belongs to the Special Issue Polymeric Materials for Dental Applications)
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Article
Influence of the Architecture of Soft Polymer-Functionalized Polymer Nanoparticles on Their Dynamics in Suspension
Polymers 2020, 12(8), 1844; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081844 - 17 Aug 2020
Cited by 3 | Viewed by 922
Abstract
The behavior of nanogels in suspension can be dramatically affected by the grafting of a canopy of end-tethered polymer chains. The architecture of the interfacial layer, defined by the grafting density and length of the polymer chains, is a crucial parameter in defining [...] Read more.
The behavior of nanogels in suspension can be dramatically affected by the grafting of a canopy of end-tethered polymer chains. The architecture of the interfacial layer, defined by the grafting density and length of the polymer chains, is a crucial parameter in defining the conformation and influencing the dynamics of the grafted chains. However, the influence of this architecture when the core substrate is itself soft and mobile is complex; the dynamics of the core influences the dynamics of the tethered chains, and, conversely, the dynamics of the tethered chains can influence the dynamics of the core. Here, poly(styrene) (PS) particles were functionalized with poly(methyl acrylate) (PMA) chains and swollen in a common solvent. NMR relaxation reveals that the confinement influences the mobility of the grafted chain more prominently for densely grafted short chains. The correlation time associated with the relaxation of the PMA increased by more than 20% when the grafting density increased for short chains, but for less than 10% for long chains. This phenomenon is likely due to the steric hindrance created by the close proximity to the rigid core and of the neighboring chains. More interestingly, a thick layer of a densely grafted PMA canopy efficiently increases the local mobility of the PS cores, with a reduction of the correlation time of more than 30%. These results suggest an interplay between the dynamics of the core and the dynamics of the canopy. Full article
(This article belongs to the Special Issue Complex Fluids and Interfaces)
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Article
Influence Mechanism and Optimization Analysis of Technological Parameters for the Composite Prepreg Tape Winding Process
Polymers 2020, 12(8), 1843; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081843 - 17 Aug 2020
Cited by 2 | Viewed by 966
Abstract
Composite prepreg tape winding technology has proven to be an effective method for manufacturing revolving body composite structures in aerospace field. Process parameters including heating temperature, tape tension and roller pressure have an important impact on the winding products’ mechanical property such as [...] Read more.
Composite prepreg tape winding technology has proven to be an effective method for manufacturing revolving body composite structures in aerospace field. Process parameters including heating temperature, tape tension and roller pressure have an important impact on the winding products’ mechanical property such as tensile strength. The aim of this study is to investigate the influence mechanism and optimization analysis of parameters for the composite prepreg tape winding process. Firstly, the sensitivity analysis for single parameter had be employed to reveal the influence mechanism of each winding parameter change on tensile strength. Secondly, iso-surfaces analysis for parameter range had be applied to describe the distribution law of parameter with continuous distribution characteristics. Then the coupling analysis for process parameters was carried out employing response surface methodology. The analysis results showed that tape tension has the most significant effect on the winding products’ tensile strength. And the outstanding parameter combination with the heating temperature of 72 °C, tape tension of 307 N and roller pressure of 1263 N was provided by response surface design software via desirability function method. The validation experiments showed that the optimal parameter combination has a positive guiding significance for improving the quality of winding products. Full article
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Article
Production of Biodegradable Palm Oil-Based Polyurethane as Potential Biomaterial for Biomedical Applications
Polymers 2020, 12(8), 1842; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081842 - 17 Aug 2020
Cited by 5 | Viewed by 1400
Abstract
Being biodegradable and biocompatible are crucial characteristics for biomaterial used for medical and biomedical applications. Vegetable oil-based polyols are known to contribute both the biodegradability and biocompatibility of polyurethanes; however, petrochemical-based polyols were often incorporated to improve the thermal and mechanical properties of [...] Read more.
Being biodegradable and biocompatible are crucial characteristics for biomaterial used for medical and biomedical applications. Vegetable oil-based polyols are known to contribute both the biodegradability and biocompatibility of polyurethanes; however, petrochemical-based polyols were often incorporated to improve the thermal and mechanical properties of polyurethane. In this work, palm oil-based polyester polyol (PPP) derived from epoxidized palm olein and glutaric acid was reacted with isophorone diisocyanate to produce an aliphatic polyurethane, without the incorporation of any commercial petrochemical-based polyol. The effects of water content and isocyanate index were investigated. The polyurethanes produced consisted of > 90% porosity with interconnected micropores and macropores (37–1700 µm) and PU 1.0 possessed tensile strength and compression stress of 111 kPa and 64 kPa. The polyurethanes with comparable thermal stability, yet susceptible to enzymatic degradation with 7–59% of mass loss after 4 weeks of treatment. The polyurethanes demonstrated superior water uptake (up to 450%) and did not induce significant changes in pH of the medium. The chemical changes of the polyurethanes after enzymatic degradation were evaluated by FTIR and TGA analyses. The polyurethanes showed cell viability of 53.43% and 80.37% after 1 and 10 day(s) of cytotoxicity test; and cell adhesion and proliferation in cell adhesion test. The polyurethanes produced demonstrated its potential as biomaterial for soft tissue engineering applications. Full article
(This article belongs to the Special Issue Advances in Sustainable Polyurethanes)
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Article
On the Synergistic Effect of Multi-Walled Carbon Nanotubes and Graphene Nanoplatelets to Enhance the Functional Properties of SLS 3D-Printed Elastomeric Structures
Polymers 2020, 12(8), 1841; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081841 - 17 Aug 2020
Cited by 7 | Viewed by 1584
Abstract
Elastomer-based porous structures realized by selective laser sintering (SLS) are emerging as a new class of attractive multifunctional materials. Herein, a thermoplastic polyurethane (TPU) powder for SLS was modified by 1 wt.% multi-walled carbon nanotube (MWCNTs) or a mixture of MWCNTs and graphene [...] Read more.
Elastomer-based porous structures realized by selective laser sintering (SLS) are emerging as a new class of attractive multifunctional materials. Herein, a thermoplastic polyurethane (TPU) powder for SLS was modified by 1 wt.% multi-walled carbon nanotube (MWCNTs) or a mixture of MWCNTs and graphene (GE) nanoparticles (70/30 wt/wt) in order to investigate on both the synergistic effect provided by the two conductive nanostructured carbonaceous fillers and the correlation between formulation, morphology, and final properties of SLS printed porous structures. In detail, porous structures with a porosity ranging from 20% to 60% were designed using Diamond (D) and Gyroid (G) unit cells. Results showed that the carbonaceous fillers improve the thermal stability of the elastomeric matrix. Furthermore, the TPU/1 wt.% MWCNTs-GE-based porous structures exhibit excellent electrical conductivity and mechanical strength. In particular, all porous structures exhibit a robust negative piezoresistive behavior, as demonstrated from the gauge factor (GF) values that reach values of about −13 at 8% strain. Furthermore, the G20 porous structures (20% of porosity) exhibit microwave absorption coefficients ranging from 0.70 to 0.91 in the 12–18 GHz region and close to 1 at THz frequencies (300 GHz–1 THz). Results show that the simultaneous presence of MWCNTs and GE brings a significant enhancement of specific functional properties of the porous structures, which are proposed as potential actuators with relevant electro-magnetic interference (EMI) shielding properties. Full article
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Article
Near-Infrared Radiation-Based Mild Photohyperthermia Therapy of Non-Melanoma Skin Cancer with PEGylated Reduced Nanographene Oxide
Polymers 2020, 12(8), 1840; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081840 - 17 Aug 2020
Cited by 8 | Viewed by 1327
Abstract
Using a one-step thermal reduction and non-covalent chemical functionalization process, PEGylated reduced nanographene oxide (rGOn-PEG) was produced from nanographene oxide (GOn) and characterized in terms of particle size, dispersion stability, chemistry, and photothermal properties, in view of its use for photothermal therapy (PTT) [...] Read more.
Using a one-step thermal reduction and non-covalent chemical functionalization process, PEGylated reduced nanographene oxide (rGOn-PEG) was produced from nanographene oxide (GOn) and characterized in terms of particle size, dispersion stability, chemistry, and photothermal properties, in view of its use for photothermal therapy (PTT) of non-melanoma skin cancer. GOn infrared spectrum presented more intense bands assigned to oxygen containing functional groups than observed for rGOn-PEG. GOn C/O ratio decreased more than 50% comparing with rGOn-PEG and nitrogen was present in the latter (N at % = 20.6) due to introduction of PEG-NH2. Thermogravimetric analysis allowed estimating the amount of PEG in rGOn-PEG to be of about 56.1%. Simultaneous reduction and PEGylation increased the lateral dimensions from 287 ± 139 nm to 521 ± 397 nm, as observed by transmission electron microscopy and dynamic light scattering. rGOn-PEG exhibited ≈13-fold higher absorbance in the near-infrared radiation (NIR) region, as compared to unmodified GOn. Low power (150 mW cm−2) NIR irradiation using LEDs resulted in rGOn-PEG heating up to 47 °C, which is within the mild PTT temperature range. PEGylation strongly enhanced the dispersibility of rGOn in physiological media (phosphate buffered saline, fetal bovine serum, and cell culture medium) and also improved the biocompatibility of rGOn-PEG, in comparison to GOn (25–250 μg mL−1). After a single NIR LED irradiation treatment of 30 min, a decrease of ≈38% in A-431 cells viability was observed for rGOn-PEG (250 μg mL−1). Together, our results demonstrate the potential of irradiating rGOn-PEG using lower energy, cheaper, smaller, and safer LEDs, as alternative to high power lasers, for NIR mild hyperthermia therapy of cancer, namely non-melanoma skin cancer. Full article
(This article belongs to the Special Issue Graphene-Polymer Composites II)
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Article
Plasticized Polystyrene by Addition of -Diene Based Molecules for Defect-Less CVD Graphene Transfer
Polymers 2020, 12(8), 1839; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081839 - 17 Aug 2020
Cited by 1 | Viewed by 1046
Abstract
Chemical vapor deposition of graphene on transition metals is the most favored method to get large scale homogenous graphene films to date. However, this method involves a very critical step of transferring as grown graphene to desired substrates. A sacrificial polymer film is [...] Read more.
Chemical vapor deposition of graphene on transition metals is the most favored method to get large scale homogenous graphene films to date. However, this method involves a very critical step of transferring as grown graphene to desired substrates. A sacrificial polymer film is used to provide mechanical and structural support to graphene, as it is detached from underlying metal substrate, but, the residue and cracks of the polymer film after the transfer process affects the properties of the graphene. Herein, a simple mixture of polystyrene and low weight plasticizing molecules is reported as a suitable candidate to be used as polymer support layer for transfer of graphene synthesized by chemical vapor deposition (CVD). This combination primarily improves the flexibility of the polystyrene to prevent cracking during the transfer process. In addition, the polymer removal solvent can easily penetrate between the softener molecules, so that the polymer film can be easily dissolved after transfer of graphene, thereby leaving no residue. This facile method can be used freely for the large-scale transfer of 2D materials. Full article
(This article belongs to the Section Polymer Applications)
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Article
Synthesis and Properties of Moisture-Cured Reactive Polyurethane Containing Castor Oil and Oxime Compounds
Polymers 2020, 12(8), 1838; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081838 - 17 Aug 2020
Cited by 3 | Viewed by 943
Abstract
Reactive polyurethane hot-melt resin (moisture-cured reactive polyurethane, PUR) could successfully be prepared from poly(tetramethylene ether) glycol (PTMG), castor oil and dimethylglyoxime (DMG) by one or two-stage synthesis. Fourier-transform infrared spectroscopy (FTIR) analysis showed that the synthesis resins belonged to NCO-capped castor oil-based polyurethane. [...] Read more.
Reactive polyurethane hot-melt resin (moisture-cured reactive polyurethane, PUR) could successfully be prepared from poly(tetramethylene ether) glycol (PTMG), castor oil and dimethylglyoxime (DMG) by one or two-stage synthesis. Fourier-transform infrared spectroscopy (FTIR) analysis showed that the synthesis resins belonged to NCO-capped castor oil-based polyurethane. The thermal behaviors of the cured PUR were analyzed by differential scanning calorimeter (DSC) and dynamic mechanical analyzer (DMA) instruments. The results showed that the cured resin provided remeltable properties under the dosages of 3 wt% DMG. Furthermore, the phenomenon could be proved by FTIR analysis according to the characteristic absorption peak of NCO groups after the cured resin was heated. Comparing different syntheses, the resin prepared by one-stage synthesis showed random distribution of DMG with PUR structure and that prepared by two-stage synthesis had distribution of DMG with branching structure in the prepolymer. The former obtained lower remeltable temperatures from 90 to 130 °C than the latter temperatures, which had temperatures above 125 °C. The tensile test showed that all of the PUR films exhibited typical tough behavior. Thus, the cured resin with DMG dosages of 3 wt% provided remeltable and mechanical properties at the same time. Overall, the crosslinking density and numbers of dynamic bonds should be kept in balance for preparation of remeltable PUR. Full article
(This article belongs to the Special Issue Dynamic Networks for Sustainable and Self-Healing Polymers)
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Review
The Application of Polysaccharides and Their Derivatives in Pigment, Barrier, and Functional Paper Coatings
Polymers 2020, 12(8), 1837; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081837 - 16 Aug 2020
Cited by 7 | Viewed by 1380
Abstract
As one of the most abundant natural polymers in nature, polysaccharides have the potential to replace petroleum-based polymers that are difficult to degrade in paper coatings. Polysaccharide molecules have a large number of hydroxyl groups that can bind strongly with paper fibers through [...] Read more.
As one of the most abundant natural polymers in nature, polysaccharides have the potential to replace petroleum-based polymers that are difficult to degrade in paper coatings. Polysaccharide molecules have a large number of hydroxyl groups that can bind strongly with paper fibers through hydrogen bonds. Chemical modification can also effectively improve the mechanical, barrier, and hydrophobic properties of polysaccharide-based coating layers and thus can further improve the related properties of coated paper. Polysaccharides can also give paper additional functional properties by dispersing and adhering functional fillers, e.g., conductive particles, catalytic particles or antimicrobial chemicals, onto paper surface. Based on these, this paper reviews the application of natural polysaccharides, such as cellulose, hemicellulose, starch, chitosan, and sodium alginate, and their derivatives in paper coatings. This paper analyzes the improvements and influences of chemical structures and properties of polysaccharides on the mechanical, barrier, and hydrophobic properties of coated paper. This paper also summarizes the researches where polysaccharides are used as the adhesives to adhere inorganic or functional fillers onto paper surface to endow paper with great surface properties or special functions such as conductivity, catalytic, antibiotic, and fluorescence. Full article
(This article belongs to the Special Issue Polysaccharides II)
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Article
Stress Distributions for Hybrid Composite Endodontic Post Designs with and without a Ferrule: FEA Study
Polymers 2020, 12(8), 1836; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081836 - 16 Aug 2020
Cited by 5 | Viewed by 1015
Abstract
The aim of the current work was to analyze the influence of the ferrule effect for hybrid composite endodontic post designs consisting of carbon (C) and glass (G) fiber-reinforced polyetherimide (PEI), in upper canine teeth. Starting from theoretical designs of C-G/PEI hybrid composite [...] Read more.
The aim of the current work was to analyze the influence of the ferrule effect for hybrid composite endodontic post designs consisting of carbon (C) and glass (G) fiber-reinforced polyetherimide (PEI), in upper canine teeth. Starting from theoretical designs of C-G/PEI hybrid composite posts with different Young’s moduli (Post A—57.7 GPa, Post B—31.6 GPa, Post C—graduated from 57.7 to 9.0 GPa in the coronal–apical direction) in endodontically treated anterior teeth, the influence of the ferrule effect was determined through finite element analysis (FEA). On the surface of the crown, a load of 50 N was applied at 45° to the longitudinal axis of the tooth. Maximum principal stresses were evaluated along the C-G/PEI post as well as at the interface between the surrounding tooth structure and the post. Maximum stress values were lower than those obtained for the corresponding models without a ferrule. The presence of a ferrule led to a marked decrease of stress and gradients especially for posts A and B. A less marked effect was globally found for Post C, except in a cervical margin section along a specific direction, where a significant decrease of the stress was probably due to local geometric features, compared to the model without a ferrule. The presence of a ferrule did not generally provide a marked benefit in the case of the graduated Post C, in comparison to other C-G/PEI posts. The outcomes suggest how such a hybrid composite post alone should be sufficient to optimize the stress distribution, dissipating stress from the coronal to the apical end. Full article
(This article belongs to the Special Issue Polymers for Biomedical Modeling)
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Review
Composites and Copolymers Containing Redox-Active Molecules and Intrinsically Conducting Polymers as Active Masses for Supercapacitor Electrodes—An Introduction
Polymers 2020, 12(8), 1835; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081835 - 16 Aug 2020
Cited by 3 | Viewed by 1084
Abstract
In this introductory report, composites and copolymers combining intrinsically conducting polymers and redox-active organic molecules, suggested as active masses without additional binder and conducting agents for supercapacitor electrodes, possibly using the advantageous properties of both constituents, are presented. A brief overview of the [...] Read more.
In this introductory report, composites and copolymers combining intrinsically conducting polymers and redox-active organic molecules, suggested as active masses without additional binder and conducting agents for supercapacitor electrodes, possibly using the advantageous properties of both constituents, are presented. A brief overview of the few reported examples of the use of such copolymers, composites, and comparable combinations of organic molecules and carbon supports is given. For comparison a few related reports on similar materials without intrinsically conducting polymers are included. Full article
(This article belongs to the Special Issue Polymers for Energy, Electronics and Sensing)
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Article
In-Situ Deposition of Metal Oxides Nanoparticles in Cellulose Derivative and Its Utilization for Wastewater Disinfection
Polymers 2020, 12(8), 1834; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081834 - 16 Aug 2020
Cited by 1 | Viewed by 758
Abstract
The target of this work is to investigate and assess the utilization of the synthesized in-situ deposition of metal oxide nanoparticles such as nano-nickel oxide (nNiO), nanocopper oxides (nCuO) and nanoiron oxides (nFe3O4) in aminated cellulose (Acell), as a [...] Read more.
The target of this work is to investigate and assess the utilization of the synthesized in-situ deposition of metal oxide nanoparticles such as nano-nickel oxide (nNiO), nanocopper oxides (nCuO) and nanoiron oxides (nFe3O4) in aminated cellulose (Acell), as a protected and compelling antibacterial channel of contamination from domestic wastewater. The prepared Acell and nNiO/Acell, nCuO/Acell and nFe3O4/Acell nanocomposites were characterized by field emission-scanning electron microscopy (FE-SEM), Fourier transform-infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), selected area diffraction pattern (SAED) and X-ray diffraction techniques (XRD). TEM declared the synthesis of nNiO, nCuO and nFe3O4 with regular size of 10, 23 and 43 nm, correspondingly. The antibacterial impact of both nNiO/Acell, nCuO/Acell and nFe3O4/Acell nanocomposites was inspected against Gram-positive microorganisms (Enterococcus faecalis, Staphylococcus aureus) and Gram-negative microbes (Escherichia coli, Salmonella typhi) utilizing agar disk diffusion routes. Furthermore, the ability of the synthesized nanocomposites as sterilizers for optional domestic wastewater was studied. The data for the disk diffusion obtained revealed that nFe3O4/Acell had a greater antibacterial impact than nCuO/Acell and nNiO/Acell. In addition, the purification of domestic wastewater utilizing 1.0 mg of nFe3O4, nCuO and nNiO in 1 gm of Acell was accomplished by killing 99.6%, 94.5% and 92.0% of total and fecal coliforms inside 10 mins, respectively. Full article
(This article belongs to the Section Biomacromolecules, Biobased and Biodegradable Polymers)
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Article
Mechanical Strength, Thermal Conductivity and Electrical Breakdown of Kenaf Core Fiber/Lignin/Polypropylene Biocomposite
Polymers 2020, 12(8), 1833; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081833 - 15 Aug 2020
Cited by 3 | Viewed by 1040
Abstract
Mechanical strength, thermal conductivity and electrical breakdown of polypropylene/lignin/kenaf core fiber (PP/L/KCF) composite were studied. PP/L, PP/KCF and PP/L/KCF composites with different fiber and lignin loading was prepared using a compounding process. Pure PP was served as control. The results revealed that tensile [...] Read more.
Mechanical strength, thermal conductivity and electrical breakdown of polypropylene/lignin/kenaf core fiber (PP/L/KCF) composite were studied. PP/L, PP/KCF and PP/L/KCF composites with different fiber and lignin loading was prepared using a compounding process. Pure PP was served as control. The results revealed that tensile and flexural properties of the PP/L/KCF was retained after addition of lignin and kenaf core fibers. Thermal stability of the PP composites improved compared to pure PP polymer. As for thermal conductivity, no significant difference was observed between PP composites and pure PP. However, PP/L/KCF composite has higher thermal diffusivity. All the PP composites produced are good insulating materials that are suitable for building. All PP composites passed withstand voltage test in air and oil state as stipulated in IEC 60641-3 except PP/L in oil state. SEM micrograph showed that better interaction and adhesion between polymer matrix, lignin and kenaf core fibers was observed and reflected on the better tensile strength recorded in PP/L/KCF composite. This study has successfully filled the gap of knowledge on using lignin and kenaf fibers as PP insulator composite materials. Therefore, it can be concluded that PP/Lignin/KCF has high potential as an insulating material. Full article
(This article belongs to the Special Issue Natural Fibre Composites and Their Mechanical Behavior)
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Article
Nanoformulation Design Including MamC-Mediated Biomimetic Nanoparticles Allows the Simultaneous Application of Targeted Drug Delivery and Magnetic Hyperthermia
Polymers 2020, 12(8), 1832; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081832 - 15 Aug 2020
Cited by 5 | Viewed by 1436
Abstract
The design of novel nanomaterials that can be used as multifunctional platforms allowing the combination of therapies is gaining increased interest. Moreover, if this nanomaterial is intended for a targeted drug delivery, the use of several guidance methods to increase guidance efficiency is [...] Read more.
The design of novel nanomaterials that can be used as multifunctional platforms allowing the combination of therapies is gaining increased interest. Moreover, if this nanomaterial is intended for a targeted drug delivery, the use of several guidance methods to increase guidance efficiency is also crucial. Magnetic nanoparticles (MNPs) allow this combination of therapies and guidance strategies. In fact, MNPs can be used simultaneously as drug nanocarriers and magnetic hyperthermia agents and, moreover, they can be guided toward the target by an external magnetic field and by their functionalization with a specific probe. However, it is difficult to find a system based on MNPs that exhibits optimal conditions as a drug nanocarrier and as a magnetic hyperthermia agent. In this work, a novel nanoformulation is proposed to be used as a multifunctional platform that also allows dual complementary guidance. This nanoformulation is based on mixtures of inorganic magnetic nanoparticles (M) that have been shown to be optimal hyperthermia agents, and biomimetic magnetic nanoparticles (BM), that have been shown to be highly efficient drug nanocarriers. The presence of the magnetosome protein MamC at the surface of BM confers novel surface properties that allow for the efficient and stable functionalization of these nanoparticles without the need of further coating, with the release of the relevant molecule being pH-dependent, improved by magnetic hyperthermia. The BM are functionalized with Doxorubicin (DOXO) as a model drug and with an antibody that allows for dual guidance based on a magnetic field and on an antibody. The present study represents a proof of concept to optimize the nanoformulation composition in order to provide the best performance in terms of the magnetic hyperthermia agent and drug nanocarrier. Full article
(This article belongs to the Special Issue Nanoparticle Functionalization by Polymers: Methods and Applications)
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Article
Association between Nonionic Amphiphilic Polymer and Ionic Surfactant in Aqueous Solutions: Effect of Polymer Hydrophobicity and Micellization
Polymers 2020, 12(8), 1831; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081831 - 15 Aug 2020
Cited by 13 | Viewed by 1354
Abstract
The interaction in aqueous solutions of surfactants with amphiphilic polymers can be more complex than the surfactant interactions with homopolymers. Interactions between the common ionic surfactant sodium dodecyl sulfate (SDS) and nonionic amphiphilic polymers of the poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO-PPO-PEO) type have [...] Read more.
The interaction in aqueous solutions of surfactants with amphiphilic polymers can be more complex than the surfactant interactions with homopolymers. Interactions between the common ionic surfactant sodium dodecyl sulfate (SDS) and nonionic amphiphilic polymers of the poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO-PPO-PEO) type have been probed utilizing a variety of experimental techniques. The polymer amphiphiles studied here are Pluronic F127 (EO100PO65EO100) and Pluronic P123 (EO19PO69EO19), having the same length PPO block but different length PEO blocks and, accordingly, very different critical micellization concentrations (CMC). With increasing surfactant concentration in aqueous solutions of fixed polymer content, SDS interacts with unassociated PEO-PPO-PEO molecules to first form SDS-rich SDS/Pluronic assemblies and then free SDS micelles. SDS interacts with micellized PEO-PPO-PEO to form Pluronic-rich SDS/Pluronic assemblies, which upon further increase in surfactant concentration, break down and transition into SDS-rich SDS/Pluronic assemblies, followed by free SDS micelle formation. The SDS-rich SDS/Pluronic assemblies exhibit polyelectrolyte characteristics. The interactions and mode of association between nonionic macromolecular amphiphiles and short-chain ionic amphiphiles are affected by the polymer hydrophobicity and its concentration in the aqueous solution. For example, SDS binds to Pluronic F127 micelles at much lower concentrations (~0.01 mM) when compared to Pluronic P123 micelles (~1 mM). The critical association concentration (CAC) values of SDS in aqueous PEO-PPO-PEO solutions are much lower than CAC in aqueous PEO homopolymer solutions. Full article
(This article belongs to the Special Issue Polymer Micelles II)
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Article
A Kinetic Analysis of the Thermal Degradation Behaviours of Some Bio-Based Substrates
Polymers 2020, 12(8), 1830; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081830 - 15 Aug 2020
Cited by 2 | Viewed by 938
Abstract
In the present paper, we report on a detailed study regarding the thermal degradation behaviours of some bio-sourced substrates. These were previously identified as the base materials in the formulations for fireproofing wood plaques through our investigations. The substrates included: β-cyclodextrin, dextran, potato [...] Read more.
In the present paper, we report on a detailed study regarding the thermal degradation behaviours of some bio-sourced substrates. These were previously identified as the base materials in the formulations for fireproofing wood plaques through our investigations. The substrates included: β-cyclodextrin, dextran, potato starch, agar-agar, tamarind kernel powder and chitosan. For deducing the Arrhenius parameters from thermograms obtained through routine thermogravimetric analyses (TGA), we used the standard Flynn–Wall–Ozawa (FWO) method and employed an in-house developed proprietary software. In the former case, five different heating rates were used, whereas in the latter case, the data from one dynamic heating regime were utilized. Given that the FWO method is essentially based on a model-free approach that also makes use of multiple heating rates, it can be considered in the present context as superior to the one that is dependent on a single heating rate. It is also relevant to note here that the values of energy of activation (Ea) obtained in each case should only be considered as apparent values at best. Furthermore, some useful, but limited, correlations were identified between the Ea values and the relevant parameters obtained earlier by us from pyrolysis combustion flow calorimetry (PCFC). Full article
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Article
Development of Biocomposite Polymeric Systems Loaded with Antibacterial Nanoparticles for the Coating of Polypropylene Biomaterials
Polymers 2020, 12(8), 1829; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081829 - 15 Aug 2020
Cited by 2 | Viewed by 1194
Abstract
The development of a biocomposite polymeric system for the antibacterial coating of polypropylene mesh materials for hernia repair is reported. Coatings were constituted by a film of chitosan containing randomly dispersed poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles loaded with chlorhexidine [...] Read more.
The development of a biocomposite polymeric system for the antibacterial coating of polypropylene mesh materials for hernia repair is reported. Coatings were constituted by a film of chitosan containing randomly dispersed poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles loaded with chlorhexidine or rifampicin. The chlorhexidine-loaded system exhibited a burst release during the first day reaching the release of the loaded drug in three or four days, whereas rifampicin was gradually released for at least 11 days. Both antibacterial coated meshes were highly active against Staphylococcus aureus and Staphylococcus epidermidis (106 CFU/mL), displaying zones of inhibition that lasted for 7 days (chlorhexidine) or 14 days (rifampicin). Apparently, both systems inhibited bacterial growth in the surrounding environment, as well as avoided bacterial adhesion to the mesh surface. These polymeric coatings loaded with biodegradable nanoparticles containing antimicrobials effectively precluded bacterial colonization of the biomaterial. Both biocomposites showed adequate performance and thus could have potential application in the design of antimicrobial coatings for the prophylactic coating of polypropylene materials for hernia repair. Full article
(This article belongs to the Special Issue Advanced Polymers for Biomedical Applications)
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Article
Control the System and Environment of Post-Production Wind Turbine Blade Waste Using Life Cycle Models. Part 1. Environmental Transformation Models
Polymers 2020, 12(8), 1828; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081828 - 14 Aug 2020
Cited by 7 | Viewed by 1068
Abstract
Controlling the system—the environment of power plants is called such a transformation—their material, energy and information inputs in time, which will ensure that the purpose of the operation of this system or the state of the environment, is achieved. The transformations of systems [...] Read more.
Controlling the system—the environment of power plants is called such a transformation—their material, energy and information inputs in time, which will ensure that the purpose of the operation of this system or the state of the environment, is achieved. The transformations of systems and environmental inputs and their goals describe the different models, e.g., LCA model groups and methods. When converting wind kinetic energy into electricity, wind power plants emit literally no harmful substances into the environment. However, the production and postuse management stages of their components require large amounts of energy and materials. The biggest controlling problem during postuse management is wind power plant blades, followed by waste generated during their production. Therefore, this publication is aimed at carrying out an ecological, technical and energetical transformation analysis of selected postproduction waste of wind power plant blades based on the LCA models and methods. The research object of control was eight different types of postproduction waste (fiberglass mat, roving fabric, resin discs, distribution hoses, spiral hoses with resin, vacuum bag film, infusion materials residues, surplus mater), mainly made of polymer materials, making it difficult for postuse management and dangerous for the environment. Three groups of models and methods were used: Eco-indicator 99, IPCC and CED. The impact of analysis objects on human health, ecosystem quality and resources was controlled and assessed. Of all the tested waste, the life cycle of resin discs made of epoxy resin was characterized by the highest level of harmful technology impact on the environment and the highest energy consumption. Postuse control and management in the form of recycling would reduce the negative impact on the environment of the tested waste (in the perspective of their entire life cycle). Based on the results obtained, guidelines and models for the proecological postuse control of postproduction polymer waste of wind power plants blades were proposed. Full article
(This article belongs to the Special Issue Eco-Innovative Engineering of the Polymer Material’s Life Cycle)
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Article
Preparation of Antimicrobial Fibres from the EVOH/EPC Blend Containing Silver Nanoparticles
Polymers 2020, 12(8), 1827; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081827 - 14 Aug 2020
Cited by 3 | Viewed by 792
Abstract
The article presents a new fabrication method for bioactive fibres with a microporous structure of ethylene–vinyl alcohol copolymers (EVOH)/ethylene−propylene copolymer (EPC) blends. The experimental work carried out resulted in obtaining EVOH/EPC polymer blends fibres with the addition of glycerol and sodium stearate. Different [...] Read more.
The article presents a new fabrication method for bioactive fibres with a microporous structure of ethylene–vinyl alcohol copolymers (EVOH)/ethylene−propylene copolymer (EPC) blends. The experimental work carried out resulted in obtaining EVOH/EPC polymer blends fibres with the addition of glycerol and sodium stearate. Different concentrations of glycerol (38%, 32%) and sodium stearate (2%, 8%) were used to prepare the fibres. The purpose of using different concentrations of stearate and glycerol was to evaluate the effect of additives on the structure and properties of the fibres. A significant influence of the additives used on the morphological structure of the fibres was found. The resulting fibres were modified with an AgNO3 solution and reduced to silver nanoparticles (AgNPs), to give the fibres bioactive properties. The fibres obtained with the addition of 8% stearate have a more developed surface, which may influence the amount of adsorbed silver particles inside the fibre. However, the durability of depositing silver particles after multiple washes has not been tested. Three types of microorganisms were selected to assess the microbiological activity of the obtained fibres, i.e., Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa and Escherichia coli. The fibres have antibacterial activity against gram positive and negative bacteria. The largest inhibition zones were obtained for gram-positive bacteria Staphylococcus aureus, ranging from 3 to 10 mm depending on the concentration of AgNPs. The morphology of the blends fibres was characterized by scanning electron microscopy (SEM) and optical microscopy (OM). The occurrence of elemental silver was analysed by energy dispersive spectroscopy (EDS) analysis. The changes of the polymer structure chemistry are studied by Fourier transform infrared spectroscopy (FTIR). Full article
(This article belongs to the Special Issue Metal- and Metal Hybrid-Filled Polymer Nanocomposites)
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Communication
Micro/Nanostructured Coating for Cotton Textiles That Repel Oil, Water, and Chemical Warfare Agents
Polymers 2020, 12(8), 1826; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081826 - 14 Aug 2020
Cited by 6 | Viewed by 1217
Abstract
Using a lotus leaf as our model, we fabricated an extremely low surface energy micro/nanostructured coating for textiles that repel oil, water, and chemical warfare agents (CWAs) using a simple process that is suitable for large scale production. This coating, called “OmniBlock”, consisted [...] Read more.
Using a lotus leaf as our model, we fabricated an extremely low surface energy micro/nanostructured coating for textiles that repel oil, water, and chemical warfare agents (CWAs) using a simple process that is suitable for large scale production. This coating, called “OmniBlock”, consisted of approximately 200-nm silica nanoparticles, tetraethylorthosilicate, 3-glycidoxypropyl trimethoxysilane, and a perfluorooctanoic acid-free fluoropolymer (Fluorolink S10) that was cross-linked between Si-O-Si groups via a sol-gel process. The perfluorooctanoic acid-free fluoropolymer-coated silica nanoparticles were simply applied to the surface of a cotton fabric by a dip–dry–cure process, forming dense, continuous, and uniform layers of OmniBlock coating. OmniBlock modified the surface of the cotton fibers, creating a rough, high surface area uniform coating with many micro-crevasses. As a result, n-dodecane, water, and CWAs beaded up without wetting the surface, exhibiting large contact angles of 154° for water and 121° for n-dodecane, with a small shedding angle of 5° and contact angle hysteresis of 3.2° for water. The designed coating showed excellent liquid repellence properties against three types of CWAs: 129°, 72°, and 87° for sulfur mustard (HD), soman (GD), and VX nerve agents, respectively. Furthermore, OmniBlock coating shows good mechanical properties under tensile strength and wash tests. This remarkable ability to repel CWAs is likely to have potential military applications in personal protective equipment systems requiring self-cleaning functions. Full article
(This article belongs to the Section Polymer Applications)
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Article
Improving the Reactivity of Sugarcane Bagasse Kraft Lignin by a Combination of Fractionation and Phenolation for Phenol–Formaldehyde Adhesive Applications
Polymers 2020, 12(8), 1825; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12081825 - 14 Aug 2020
Cited by 5 | Viewed by 1033
Abstract
The low reactivity of lignin hinders its application as a phenol substitute in phenol–formaldehyde (PF) resin. Therefore, the combination of fractionation and phenolation was adopted to enhance the reactivity of lignin for preparing a phenol–formaldehyde resin adhesive. Sugarcane bagasse kraft lignin and its [...] Read more.
The low reactivity of lignin hinders its application as a phenol substitute in phenol–formaldehyde (PF) resin. Therefore, the combination of fractionation and phenolation was adopted to enhance the reactivity of lignin for preparing a phenol–formaldehyde resin adhesive. Sugarcane bagasse kraft lignin and its fractions were employed to replace 40 wt% of phenol to prepare a PF adhesive. The fractionation increased the reactivity of lignin, however the as-prepared lignin-based PF (LPF) hardly met its application requirements as an adhesive. Therefore, the phenolation of lignin under an acidic condition was adopted to further improve its reactivity. The phenolated lignin was characterized by FTIR, gel permeation chromatography, and NMR, indicating its active sites increased while its molecular weight decreased. The phenolated lignin was used to replace 40 wt% of phenol to prepare a PF adhesive (PLPF) which was further employed to prepare plywood. The results indicated that the combination of fractionation and phenolation effectively enhanced the reactivity of lignin, and eventually improved the properties of the PLPF and its corresponding plywood. The free formaldehyde content of PLPF decreased to 0.16%. The wet bonding strength of the as-prepared plywood increased to 1.36 MPa, while the emission of formaldehyde decreased to 0.31 mL/L. Full article
(This article belongs to the Section Polymer Applications)
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