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Polymers, Volume 11, Issue 8 (August 2019)

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Cover Story (view full-size image) Hydrogen bonding-generating events, including host–guest interactions at material surfaces, should [...] Read more.
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Open AccessArticle
Preparation and Properties of Rubber Blends for High-Damping-Isolation Bearings
Polymers 2019, 11(8), 1374; https://doi.org/10.3390/polym11081374 - 20 Aug 2019
Viewed by 474
Abstract
To improve the energy dissipation capacity of rubber isolation bearings, it is important to find a new rubber material with good applicability and high damping properties. Two types of blends were prepared using nitrile rubber (NBR), brominated butyl rubber (BIIR) and ethylene-vinyl acetate [...] Read more.
To improve the energy dissipation capacity of rubber isolation bearings, it is important to find a new rubber material with good applicability and high damping properties. Two types of blends were prepared using nitrile rubber (NBR), brominated butyl rubber (BIIR) and ethylene-vinyl acetate copolymer (EVA): NBR/BIIR and NBR/BIIR/EVA. The vulcanization, mechanical and damping properties of the blends were analyzed. The results show that both blends exhibit excellent vulcanization plateaus and mechanical properties. For NBR/BIIR, as the BIIR content increases, the complementary effects of NBR and BIIR afforded by blending are enhanced. Two damping peaks appeared in the tanδ-T curve and shifted toward lower and higher temperatures, respectively, which clearly widened the effective damping temperature range. However, the damping value in the valley of the tanδ-T curve was as low as 0.39. For NBR/BIIR/EVA, the addition of EVA greatly increased damping in the valley of the tanδ-T curve to approximately 0.54. EVA was observed to be the optimal polymer for improving the compatibility of the NBR/BIIR blend. Moreover, hot air thermal aging tests showed that both blends demonstrated good stability. Full article
(This article belongs to the Special Issue Reinforced Polymer Composites)
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Open AccessArticle
Development of a Simplified Radiation-Induced Emulsion Graft Polymerization Method and Its Application to the Fabrication of a Heavy Metal Adsorbent
Polymers 2019, 11(8), 1373; https://doi.org/10.3390/polym11081373 - 20 Aug 2019
Viewed by 487
Abstract
A simplified radiation-induced emulsion graft polymerization (SREG) method is proposed. This method involves a convenient and easy degassing process of a monomer solution using a commercially available sealed glass jar. A loaded weight on the lid of the jar was used to control [...] Read more.
A simplified radiation-induced emulsion graft polymerization (SREG) method is proposed. This method involves a convenient and easy degassing process of a monomer solution using a commercially available sealed glass jar. A loaded weight on the lid of the jar was used to control the jar’s internal pressure as the degassing of the monomer solution took place using a vacuum pump. The degassing method was highly reproducible, resulting from no bumping of the monomer solution. The initial grafting velocity was proportional to the absorbed doses of pre-irradiation between 5 and 20 kGy. This result indicates that dissolved oxygen was sufficiently eliminated from the monomer solution at such a level where the remaining oxygen had little effect on the grafting reaction at a dose of 5 kGy. The method was then applied to the fabrication of a heavy metal adsorbent that possessed a sufficient adsorption capacity of Co(II) ions. The SREG method is applicable to the fabrication of a wide variety of functional graft polymers because high-dose-rate gamma-ray radiation and expensive experimental equipment are not necessary. Full article
(This article belongs to the Special Issue Radiation Polymers)
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Open AccessArticle
Enhanced l-Lysine into 1,5-Diaminopentane Conversion via Statistical Optimization of Whole-Cell Decarboxylation System
Polymers 2019, 11(8), 1372; https://doi.org/10.3390/polym11081372 - 20 Aug 2019
Viewed by 460
Abstract
The global lysine companies in the feed industry have steadily built their production facilities due to the high demand for l-lysine in animal farms, and in recent years there have been excessive supply problems and the world market price of l-lysine [...] Read more.
The global lysine companies in the feed industry have steadily built their production facilities due to the high demand for l-lysine in animal farms, and in recent years there have been excessive supply problems and the world market price of l-lysine has fallen. In this study, the conversion of 1,5-diaminopentane (DAP) by decarboxylation of l-lysine was strategically chosen to enhance the value of lysine. The decarboxylation is enzymatically accessible, and Hafnia alvei, which is the producer of l-lysine decarboxylase, was applied as a whole-cell form. In the designed whole-cell biocatalytic system, the major four reaction factors were selected by fundamental investigation and then statistical optimization was performed to estimate the optimum condition. The predicted conversion was assessed at about 94.6% at the optimum conditions (125.1 mM l-lysine and 71.5 g/L acetone concentration at 35.2 °C for 8.4 h). Under the determined conditions, DAP conversions by using analytical, feed and industrial crude l-lysine were found to be 98.3%, 92.5% and 72.4%, respectively. These results could be suggested to solve the problem of excessive supplied lysine and also to provide guidance for improved enzymatic conversion by statistical optimization. Full article
(This article belongs to the Special Issue Microbial Production and Application of Biopolymers)
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Open AccessReview
Advances in Biodegradable Nano-Sized Polymer-Based Ocular Drug Delivery
Polymers 2019, 11(8), 1371; https://doi.org/10.3390/polym11081371 - 20 Aug 2019
Viewed by 517
Abstract
The effective delivery of drugs to the eye remains a challenge. The eye has a myriad of defense systems and physiological barriers that leaves ocular drug delivery systems with low bioavailability profiles. This is mainly due to poor permeability through the epithelia and [...] Read more.
The effective delivery of drugs to the eye remains a challenge. The eye has a myriad of defense systems and physiological barriers that leaves ocular drug delivery systems with low bioavailability profiles. This is mainly due to poor permeability through the epithelia and rapid clearance from the eye following administration. However, recent advances in both polymeric drug delivery and biomedical nanotechnology have allowed for improvements to be made in the treatment of ocular conditions. The employment of biodegradable polymers in ocular formulations has led to improved retention time, greater bioavailability and controlled release through mucoadhesion to the epithelia in the eye, amongst other beneficial properties. Nanotechnology has been largely investigated for uses in the medical field, ranging from diagnosis of disease to treatment. The nanoscale of these developing drug delivery systems has helped to improve the penetration of drugs through the various ocular barriers, thus improving bioavailability. This review will highlight the physiological barriers encountered in the eye, current conventional treatment methods as well as how polymeric drug delivery and nanotechnology can be employed to optimize drug penetration to both the anterior and posterior segment of the eye. Full article
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Open AccessArticle
Impact of CO2 on Pyrolysis Products of Bituminous Coal and Platanus Sawdust
Polymers 2019, 11(8), 1370; https://doi.org/10.3390/polym11081370 - 20 Aug 2019
Viewed by 443
Abstract
Abundant studies have been completed about factors on the pyrolysis of coal and biomass. However, few articles laid emphasis on using CO2 as a carrier gas to explore the compositional changes of pyrolysis products in coal and biomass pyrolysis for industrial application [...] Read more.
Abundant studies have been completed about factors on the pyrolysis of coal and biomass. However, few articles laid emphasis on using CO2 as a carrier gas to explore the compositional changes of pyrolysis products in coal and biomass pyrolysis for industrial application and commercial value. The experiments on coal and biomass pyrolysis in N2 and CO2 using a horizontal tube furnace were conducted at 500 °C. The impact of introducing CO2 on the pyrolysis process of bituminous coal and Platanus sawdust was investigated. The nuclear magnetic resonance (NMR) spectra of tar and the characterizations of char including Brunner-Emmet-Teller (BET) measurements, scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectroscopy, and element analysis were studied. The findings in light of the experimental results show that introducing CO2 enhances the coal and biomass pyrolysis in a solid product by promoting the fracture of hydroxyl groups. It also promotes tar decomposition and the release of volatiles, which contribute to the occurrence of char with high porosity, pore volume, and specific surface. Furthermore, higher specific surface enhances the adsorption performance of char as active carbon. Simultaneously, CO2 promotes the increase of oxygen-containing aromatics especially the methoxy-containing aromatics, and the decrease of deoxygenated aromatic hydrocarbons in pyrolysis oils. In addition, the introduction of CO2 changes the amount of aliphatic compounds in various ways for the pyrolysis of coal and biomass. From a perspective of business, the changes in the composition of pyrolysis oil brought by CO2 may create new value for fuel utilization and industrial products. Full article
(This article belongs to the Special Issue Plant Polysaccharides Based Polymers)
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Open AccessArticle
Synthesis, Structural Characterization and Ligand-Enhanced Photo-Induced Color-Changing Behavior of Two Hydrogen-Bonded Ho(III)-Squarate Supramolecular Compounds
Polymers 2019, 11(8), 1369; https://doi.org/10.3390/polym11081369 - 19 Aug 2019
Viewed by 502
Abstract
Two coordination polymers (CPs) with chemical formulas, [Ho2(C4O4)2(C2O4)(H2O)8]·4H2O (1) and [Ho(C4O4)1.5(H2O)3] (2 [...] Read more.
Two coordination polymers (CPs) with chemical formulas, [Ho2(C4O4)2(C2O4)(H2O)8]·4H2O (1) and [Ho(C4O4)1.5(H2O)3] (2), (C4O42− = dianion of squaric acid, C2O42− = oxalate), have been synthesized and their structures were determined by single-crystal X-ray diffractometer (XRD). In compound 1, the coordination environment of Ho(III) ion is eight-coordinate bonded to eight oxygen atoms from two squarate, one oxalate ligands and four water molecules. The squarates and oxalates both act as bridging ligands with μ1,2-bis-monodentate and bis-chelating coordination modes, respectively, connecting the Ho(III) ions to form a one-dimensional (1D) ladder-like framework. Adjacent ladders are interlinked via O–H⋅⋅⋅O hydrogen bonding interaction to form a hydrogen-bonded two-dimensional (2D) layered framework and then arranged orderly in an AAA manner to construct its three-dimensional (3D) supramolecular architecture. In compound 2, the coordination geometry of Ho(III) is square-antiprismatic eight coordinate bonded to eight oxygen atoms from five squarate ligands and three water molecules. The squarates act as bridging ligands with two coordination modes, μ1,2,3-trismonodentate and μ1,2-bis-monodentate, connecting the Ho(III) ions to form a 2D bi-layered framework. Adjacent 2D frameworks are then parallel stacked in an AAA manner to construct its 3D supramolecular architecture. Hydrogen bonding interactions between the squarate ligands and coordinated water molecules in 1 and 2 both play important roles on the construction of their 3D supramolecular assembly. Compounds 1 and 2 both show remarkable ligand-enhanced photo-induced color-changing behavior, with their pink crystals immediately turning to yellow crystals under UV light illumination. Full article
(This article belongs to the Special Issue Metal-Organic Frameworks)
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Open AccessArticle
FeNxC Based Catalysts Prepared by the Calcination of [email protected] as the Cathode-Catalyst of Proton Exchange Membrane Fuel Cell
Polymers 2019, 11(8), 1368; https://doi.org/10.3390/polym11081368 - 19 Aug 2019
Viewed by 514
Abstract
Calcinated tris(ethylenediamine)iron(III) chloride was used as a non-precious metal catalyst (NPMCs) for a proton exchanged membrane fuel cell (PEMFC) under the protection of polyaniline (PANI), which behaves as both nitrogen source and carbon supporter. The optimal ratio of FeCl3/EDA was found [...] Read more.
Calcinated tris(ethylenediamine)iron(III) chloride was used as a non-precious metal catalyst (NPMCs) for a proton exchanged membrane fuel cell (PEMFC) under the protection of polyaniline (PANI), which behaves as both nitrogen source and carbon supporter. The optimal ratio of FeCl3/EDA was found to be close to 1/3 under the consideration of the electrocatalytic performance, such as better oxygen reduction reaction (ORR) and higher power density. Two-stage calcination, one at 900 °C in N2 and the other at 800 °C in mixed gases of N2 and NH3, result in an FeNxC catalyst (FeNC-900-800-A) with pretty high specific surface area of 1098 m2·g−1 covered with both micro- and mesopores. The ORR active sites focused mainly on Fe–Nx bonding made of various pyridinic, pyrrolic, and graphitic N-s after calcination. The max. power density reaches 140 mW·cm−2 for FeNC-900-800-A, which is superior to other FeNxC catalysts, experiencing only one-stage calcination in N2. The FeNxC demonstrates only 10 mV half-wave-voltage (HWV) loss at 1600 rpm after 1000 redox cycles, as compared to be 27 mV for commercial Pt/C catalyst in the durability test. Full article
(This article belongs to the Special Issue Polymerizations Promoted by Metal Complexes)
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Open AccessArticle
Fabrication of ZnO-Al2O3-PTFE Multilayer Nano-Structured Functional Film on Cellulose Insulation Polymer Surface and Its Effect on Moisture Inhibition and Dielectric Properties
Polymers 2019, 11(8), 1367; https://doi.org/10.3390/polym11081367 - 19 Aug 2019
Viewed by 478
Abstract
After a century of practice, cellulose insulating polymer (insulating paper/pressboard) has been shown to be one of the best and most widely used insulating materials in power transformers. However, with the increased voltage level of the transformer, research has focused on improving the [...] Read more.
After a century of practice, cellulose insulating polymer (insulating paper/pressboard) has been shown to be one of the best and most widely used insulating materials in power transformers. However, with the increased voltage level of the transformer, research has focused on improving the insulation performance of the transformer’s cellulose insulation polymer. Considering the complex environment of the transformer, it is not enough to improve the single performance of the insulating polymer. In this study, a nano-structured ZnO-Al2O3-PTFE (polytetrafluoroethylene) multifunctional film was deposited on the surface of insulating pressboard by radio frequency (RF) magnetron sputtering. The effect of the multilayered ZnO-Al2O3-PTFE functional film on the dielectric and water contact angle of the cellulose insulating polymer was investigated. The scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) showed that the nano-structured ZnO-Al2O3-PTFE functional film was successfully deposited on the cellulose insulation pressboard surface. The functional film presented an obvious stratification phenomenon. By analyzing the result of the contact angle, it was found that the functional film shields the hydroxyl group of the inner cellulose and improves hydrophobicity. The AC breakdown field strength of the treated samples was obviously increased (by 12 to ~17%), which means that the modified samples had a better dielectric insulation performance. This study provides a surface modification method to comprehensively improve electrical properties and the ability to inhibit the moisture of the cellulose insulating polymer, used in a power transformer. Full article
(This article belongs to the Special Issue Polymeric Materials for Electrical Applications)
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Open AccessArticle
Pyrene-Functionalized Polyacetylenes: Synthesis and Photoluminescence Property
Polymers 2019, 11(8), 1366; https://doi.org/10.3390/polym11081366 - 19 Aug 2019
Viewed by 440
Abstract
Four pyrene-functionalized polyacetylenes were designed and prepared through a typical post-polymerization modification route, which is the highly efficient reaction between activated ester and primary anime groups. The chemical structures of the resultant polymers were characterized with multiple spectroscopic techniques and the data indicated [...] Read more.
Four pyrene-functionalized polyacetylenes were designed and prepared through a typical post-polymerization modification route, which is the highly efficient reaction between activated ester and primary anime groups. The chemical structures of the resultant polymers were characterized with multiple spectroscopic techniques and the data indicated the successful functionalization of the polyacetylenes. The introduction of the pyrene moieties into the polymer structure allowed us to investigate the interactions between the polymer backbone and side chains. For the mono-substituted polyacetylenes, both the monomer and excimer emission features of the pyrene groups could be recorded, while for the di-substituted polyacetylenes, the fluorescence from the pyrene excimer vanished and the fluorescence intensity from the pyrene monomer decreased, the fluorescence from the polymer chain predominated the emission features. The concomitant energy transfer from the pyrene monomer and excimer to poly(diphenylacetylene) backbone was associated with the underlying mechanism. In addition to the substitution modes, the linkage between the poly(diphenylacetylene) backbone and the pyrene moiety also played a significant role in the determination of the emission species. A long alkyl spacer was beneficial to the pyrene monomer emission while a short one may be helpful to the formation of the excimer and intramolecular energy transfer. Full article
(This article belongs to the Special Issue Surface Modification and Functionalization of Polymers)
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Open AccessArticle
Thermal and Mechanical Behavior of Wood Plastic Composites by Addition of Graphene Nanoplatelets
Polymers 2019, 11(8), 1365; https://doi.org/10.3390/polym11081365 - 19 Aug 2019
Viewed by 446
Abstract
Wood plastic composites (WPCs) incorporating graphene nano-platelets (GNPs) were fabricated using hot-pressed technology to enhance thermal and mechanical behavior. The influences of thermal filler content and temperature on the thermal performance of the modified WPCs were investigated. The results showed that the thermal [...] Read more.
Wood plastic composites (WPCs) incorporating graphene nano-platelets (GNPs) were fabricated using hot-pressed technology to enhance thermal and mechanical behavior. The influences of thermal filler content and temperature on the thermal performance of the modified WPCs were investigated. The results showed that the thermal conductivity of the composites increased significantly with the increase of GNPs fillers, but decreased with the increase of temperature. Moreover, thermogravimetric analysis demonstrated that coupling GNPs resulted in better thermal stability of the WPCs. The limiting oxygen index test also showed that addition of GNPs caused good fire retardancy in WPCs. Incorporation of GNPs also led to an improvement in mechanical properties as compared to neat WPCs. Through a series of mechanical performance tests, it could be concluded that the flexural and tensile moduli of WPCs were improved with the increase of the content of fillers. Full article
(This article belongs to the Special Issue Advances in Wood Composites)
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Open AccessArticle
Effect of Formation Route on the Mechanical Properties of the Polyethersulfone Composites Reinforced with Glass Fibers
Polymers 2019, 11(8), 1364; https://doi.org/10.3390/polym11081364 - 19 Aug 2019
Viewed by 506
Abstract
Interfacial interaction is one of the most important factors that affect the mechanical properties of the fiber reinforced composites. The effect of fabrics′ sizing removal from glass fibers’ surface by thermal treatment on the mechanical characteristics of polyethersulfone based composites at different fiber [...] Read more.
Interfacial interaction is one of the most important factors that affect the mechanical properties of the fiber reinforced composites. The effect of fabrics′ sizing removal from glass fibers’ surface by thermal treatment on the mechanical characteristics of polyethersulfone based composites at different fiber to polymer weight ratios was investigated. Three fiber to polymer weight ratios of 50/50, 60/40, and 70/30 were studied. Flexural and shear tests were carried out to illustrate the mechanical properties of the composites; the structure was studied using Fourier-transform infrared spectroscopy and scanning electron microscopy. It was shown that solution impregnation of glass fabrics with polyethersulfone before compression molding allows to achieve good mechanical properties of composites. The thermal treatment of glass fabrics before impregnation results in an increase in flexural and shear strength for all the composites due to the improvement of fiber–matrix interaction. Full article
(This article belongs to the Special Issue Reinforced Polymer Composites)
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Open AccessArticle
Plasticization of Polylactide with Myrcene and Limonene as Bio-Based Plasticizers: Conventional vs. Reactive Extrusion
Polymers 2019, 11(8), 1363; https://doi.org/10.3390/polym11081363 - 18 Aug 2019
Viewed by 515
Abstract
Polylactide (PLA) was blended by conventional and reactive extrusion with limonene (LM) or myrcene (My) as bio-based plasticizers. As-processed blends were carefully analyzed by a multiscale and multidisciplinary approach to tentatively determine their chemical structure, microstructure, thermal properties, tensile and impact behaviors, and [...] Read more.
Polylactide (PLA) was blended by conventional and reactive extrusion with limonene (LM) or myrcene (My) as bio-based plasticizers. As-processed blends were carefully analyzed by a multiscale and multidisciplinary approach to tentatively determine their chemical structure, microstructure, thermal properties, tensile and impact behaviors, and hydrothermal stability. The main results indicated that LM and My were efficient plasticizers for PLA, since compared to neat PLA, the glass transition temperature was reduced, the ultimate tensile strain was increased, and the impact strength was increased, independently of the type of extrusion. The addition of a free radical initiator during the extrusion of PLA/LM was beneficial for the mechanical properties. Indeed, the probable formation of local branched/crosslinked regions in the PLA matrix enhanced the matrix crystallinity, the tensile yield stress, and the tensile ultimate stress compared to the non-reactive blend PLA/LM, while the other properties were retained. For PLA/My blends, reactive extrusion was detrimental for the mechanical properties since My polymerization was accelerated resulting in a drop of the tensile ultimate strain and impact strength, and an increase of the glass transition temperature. Indeed, large inclusions of polymerized My were formed, decreasing the available content of My for the plasticization and enhancing cavitation from inclusion-matrix debonding. Full article
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Open AccessArticle
Water-Dispersed Poly(p-Phenylene Terephthamide) Boosting Nano-Al2O3-Coated Polyethylene Separator with Enhanced Thermal Stability and Ion Diffusion for Lithium-Ion Batteries
Polymers 2019, 11(8), 1362; https://doi.org/10.3390/polym11081362 - 18 Aug 2019
Viewed by 589
Abstract
Polyethylene (PE) membranes coated with nano-Al2O3 have been improved with water-dispersed poly(p-phenylene terephthamide) (PPTA). From the scanning electron microscope (SEM) images, it can be seen that a layer with a honeycombed porous structure is formed on the membrane. The thus-formed [...] Read more.
Polyethylene (PE) membranes coated with nano-Al2O3 have been improved with water-dispersed poly(p-phenylene terephthamide) (PPTA). From the scanning electron microscope (SEM) images, it can be seen that a layer with a honeycombed porous structure is formed on the membrane. The thus-formed composite separator imbibed with the electrolyte solution has an ionic conductivity of 0.474 mS/cm with an electrolyte uptake of 335%. At 175 °C, the assembled battery from the synthesized composite separator explodes at 3200 s, which is five times longer than the battery assembled from an Al2O3-coated polyethylene (PE) membrane. The open circuit voltage of the assembled battery using a composite separator drops to zero at 600 s at an operating temperature of 185 °C, while the explosion of the battery with Al2O3-coated PE occurs at 250 s. More importantly, the interface resistance of the cell assembled from the composite separator decreases to 65 Ω. Hence, as the discharge rate increases from 0.2 to 1.0 C, the discharge capacity of the battery using composite separator retains 93.5%. Under 0.5 C, the discharge capacity retention remains 99.4% of its initial discharge capacity after 50 charge–discharge cycles. The results described here demonstrate that Al2O3/PPTA-coated polyethylene membranes have superior thermal stability and ion diffusion. Full article
(This article belongs to the Special Issue Polymeric Materials for Electrical Applications)
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Open AccessCommunication
Functionalized Cellulose Nanocrystals: A Potential Fire Retardant for Polymer Composites
Polymers 2019, 11(8), 1361; https://doi.org/10.3390/polym11081361 - 18 Aug 2019
Viewed by 535
Abstract
The flammability of synthetic thermoplastic polymers has been recognized as an increasingly important safety problem. The goal of this study was to evaluate a green and safe fire-retardant system comprising of cellulose nanocrystals (CNC) and zinc oxide nanoparticles (ZnO). CNCs coated with nano [...] Read more.
The flammability of synthetic thermoplastic polymers has been recognized as an increasingly important safety problem. The goal of this study was to evaluate a green and safe fire-retardant system comprising of cellulose nanocrystals (CNC) and zinc oxide nanoparticles (ZnO). CNCs coated with nano ZnO were incorporated in the high-density polyethylene polymer (HDPE) matrix at different concentrations. Fire testing results of different formulations of HDPE containing 0.4 to 1.0% zinc oxide coated CNC exhibited a substantial decrease in the average mass loss, peak heat release rate and total smoke release. The time to ignition exhibited a positive correlation with CNC-ZnO concentration. Modest improvement in the flexural strength and moduli of composites was noticed validating no adverse effects of CNC-ZnO complex. The transmission electron microscopy further confirmed dispersion of nanoparticles as well as the presence of some nanoparticle aggregates in the matrix. The uniform dispersion of CNC-ZnO complex is expected to further improve fire and mechanical properties of polymer. Full article
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Open AccessArticle
Hydrogen Bonding-Induced Assembled Structures and Photoresponsive Behavior of Azobenzene Molecule/Polyethylene Glycol Complexes
Polymers 2019, 11(8), 1360; https://doi.org/10.3390/polym11081360 - 16 Aug 2019
Viewed by 542
Abstract
We investigated the self-assembled structures and photoresponsive and crystallization behaviors of supramolecules composed of 4-methoxy-4′-hydroxyazobenzene (Azo) molecules and polyethylene glycol (PEG) that were formed through hydrogen-bonding interactions. The Azo/PEG complexes exhibited the characteristics of photoresponse and crystallization, which originated from Azo and PEG, [...] Read more.
We investigated the self-assembled structures and photoresponsive and crystallization behaviors of supramolecules composed of 4-methoxy-4′-hydroxyazobenzene (Azo) molecules and polyethylene glycol (PEG) that were formed through hydrogen-bonding interactions. The Azo/PEG complexes exhibited the characteristics of photoresponse and crystallization, which originated from Azo and PEG, respectively. When Azo/PEG complexes were dissolved in solvents, hydrogen-bonding interaction hindered the rotation and inversion of mesogens, causing a reduction in the photoisomerization rate compared with the photoisomerization rate of the neat Azo. The confinement of Azo/PEG complexes in thin films further resulted in a substantial decrease in the photoisomerization rate but an increase in the amounts of H-aggregated and J-aggregated mesogens. Regarding PEG crystallization, ultraviolet irradiation of Azo/PEG complexes increased the quantity of high-polarity cis isomers, which improved the compatibility between mesogens and PEG, subsequently increasing the crystallization temperature of PEG. Moreover, the complexation of Azo and PEG induced microphase separation, forming a lamellar morphology. Within the Azo-rich microphases, mesogens aggregated to form tilted monosmectic layers. By contrast, PEG crystallization within the PEG-rich microphases was hard confined, indicating that the domain size of the lamellar morphology was unchanged during PEG crystallization. Full article
(This article belongs to the Special Issue Photoresponsive Polymeric Materials)
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Open AccessArticle
Dielectric and Thermal Conductivity of Epoxy Resin Impregnated Nano-h-BN Modified Insulating Paper
Polymers 2019, 11(8), 1359; https://doi.org/10.3390/polym11081359 - 16 Aug 2019
Viewed by 505
Abstract
Epoxy resin-impregnated insulation paper (RIP) composites are used as the inner insulation of dry condenser bushing in the ultra-high voltage direct current (UHVDC) power transmission system. To improve the dielectric properties and heat conductivity of RIP, hexagonal boron nitride (h-BN) nano-flakes are added [...] Read more.
Epoxy resin-impregnated insulation paper (RIP) composites are used as the inner insulation of dry condenser bushing in the ultra-high voltage direct current (UHVDC) power transmission system. To improve the dielectric properties and heat conductivity of RIP, hexagonal boron nitride (h-BN) nano-flakes are added to the insulation paper at concentrations of 0–50 wt % before impregnation with pure epoxy resin. X-ray diffraction (XRD), scanning electron microscopy (SEM) observations, thermal conductivity as well as the typical dielectric properties of direct current (DC) volume conductivity. DC breakdown strength and space charge characteristics were obtained. The maximum of nano-h-BN modified heat conductivity reach 0.478 W/(m·K), increased by 139% compared with unmodified RIP. The DC breakdown electric field strength of the nano-h-BN modified RIP does not reduce much. The conductivity of nano-h-BN modified is less sensitive to temperature. As well, the space charge is suppressed when the content is 50 wt %. Therefore, the nano-h-BN modified RIP is potentially useful in practical dry DC bushing application. Full article
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Open AccessArticle
Theoretical Prediction of Mechanical Strength and Desalination Performance of One-Atom-Thick Hydrocarbon Polymer in Pressure-Driven Separation
Polymers 2019, 11(8), 1358; https://doi.org/10.3390/polym11081358 - 16 Aug 2019
Viewed by 506
Abstract
One-atom-thick materials hold promise for the future of membrane-based gas purification and water filtration applications. However, there are a few investigations on the mechanical properties of these materials under pressure-driven condition. Here, by employing molecular simulation techniques and continuum mechanics simulation, we investigate [...] Read more.
One-atom-thick materials hold promise for the future of membrane-based gas purification and water filtration applications. However, there are a few investigations on the mechanical properties of these materials under pressure-driven condition. Here, by employing molecular simulation techniques and continuum mechanics simulation, we investigate the mechanical strength of two-dimensional hydrocarbon polymers containing sub-nanometer pores with various topologies. We demonstrate that the mechanical strengths of the membranes are correlated with their pore sizes and geometries. In addition, when the pore size of substrates is controlled within a reasonable range, all of the membrane candidates can withstand the practical hydraulic pressure of few megapascal. The studied materials also exhibit better seawater desalination performance as compared to the traditional polymeric reverse osmosis membrane. This work presents a new route to design new separation membrane, and also propose a simulation method to evaluate the mechanical strength and desalination performance. Full article
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Open AccessArticle
Redox-Active Gel Electrolyte Combined with Branched Polyaniline Nanofibers Doped with Ferrous Ions for Ultra-High-Performance Flexible Supercapacitors
Polymers 2019, 11(8), 1357; https://doi.org/10.3390/polym11081357 - 16 Aug 2019
Viewed by 567
Abstract
In this work, the effects of utilizing an Fe2+/Fe3+ redox-active electrolyte and Fe2+-doped polyaniline (PANI) electrode material on the performance of an assembled supercapacitor (SC) were studied. The concentration of the redox couple additive in the electrolyte of [...] Read more.
In this work, the effects of utilizing an Fe2+/Fe3+ redox-active electrolyte and Fe2+-doped polyaniline (PANI) electrode material on the performance of an assembled supercapacitor (SC) were studied. The concentration of the redox couple additive in the electrolyte of the SC was optimized to be 0.5 M. With the optimized concentration of 0.4 M Fe2+, the doped PANI branched nanofibers electropolymerized onto titanium mesh were much thinner, cleaner, and more branched than normal PANI. A specific capacitance (Cs) of 8468 F g−1 for the 0.4 M Fe2+/PANI electrode in the 1 M H2SO4 + 0.5 M Fe2+/Fe3+ gel electrolyte and an energy density of 218.1 Wh kg−1 at a power density of 1854.4 W kg−1 for the resultant SC were achieved, which were much higher than those of the conventional PANI electrode tested in a normal H2SO4 electrolyte (404 F g−1 and 24.9 Wh kg−1). These results are among the highest reported for PANI-based SCs in the literature so far and demonstrate the potential effectiveness of this strategy to improve the electrochemical performance of flexible SCs by modifying both the electrode and electrolyte. Full article
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Open AccessArticle
Effect of Graphene Oxide Coating on Natural Fiber Composite for Multilayered Ballistic Armor
Polymers 2019, 11(8), 1356; https://doi.org/10.3390/polym11081356 - 16 Aug 2019
Viewed by 589
Abstract
Composites with sustainable natural fibers are currently experiencing remarkably diversified applications, including in engineering industries, owing to their lower cost and density as well as ease in processing. Among the natural fibers, the fiber extracted from the leaves of the Amazonian curaua plant [...] Read more.
Composites with sustainable natural fibers are currently experiencing remarkably diversified applications, including in engineering industries, owing to their lower cost and density as well as ease in processing. Among the natural fibers, the fiber extracted from the leaves of the Amazonian curaua plant (Ananas erectifolius) is a promising strong candidate to replace synthetic fibers, such as aramid (Kevlar™), in multilayered armor system (MAS) intended for ballistic protection against level III high velocity ammunition. Another remarkable material, the graphene oxide is attracting considerable attention for its properties, especially as coating to improve the interfacial adhesion in polymer composites. Thus, the present work investigates the performance of graphene oxide coated curaua fiber (GOCF) reinforced epoxy composite, as a front ceramic MAS second layer in ballistic test against level III 7.62 mm ammunition. Not only GOCF composite with 30 vol% fibers attended the standard ballistic requirement with 27.4 ± 0.3 mm of indentation comparable performance to Kevlar™ 24 ± 7 mm with same thickness, but also remained intact, which was not the case of non-coated curaua fiber similar composite. Mechanisms of ceramic fragments capture, curaua fibrils separation, curaua fiber pullout, composite delamination, curaua fiber braking, and epoxy matrix rupture were for the first time discussed as a favorable combination in a MAS second layer to effectively dissipate the projectile impact energy. Full article
(This article belongs to the Special Issue Natural Fibres and their Composites)
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Open AccessArticle
Graphene/Carbon Paper Combined with Redox Active Electrolyte for Supercapacitors with High Performance
Polymers 2019, 11(8), 1355; https://doi.org/10.3390/polym11081355 - 16 Aug 2019
Viewed by 545
Abstract
Graphene/carbon paper is prepared by pyrolyzing graphene modified cellulose filter paper and directly used as a binder-free electrode to assemble a supercapacitor (SC) with a redox active electrolyte, containing a Fe3+/Fe2+ additive. By the graphene incorporation and the carbonization of [...] Read more.
Graphene/carbon paper is prepared by pyrolyzing graphene modified cellulose filter paper and directly used as a binder-free electrode to assemble a supercapacitor (SC) with a redox active electrolyte, containing a Fe3+/Fe2+ additive. By the graphene incorporation and the carbonization of the cellulose fibers, both the microstructure and the electrical conductivity of the carbon paper are promoted greatly. The filter paper derived carbon (FPC) electrode exhibits a specific capacitance (Cs) of 2832 F·g−1 in a 1 M H2SO4 + 0.5 M Fe3+/Fe2+ electrolyte at 1 A·g−1, which is about 81 times that in a normal H2SO4 electrolyte. With the modification of graphene, the capacitive performance of the SC is enhanced further and a remarkable Cs of 3396 F·g−1 at 1 A·g−1 is achieved for a graphene modified filter paper carbon (GFPC) electrode, which remains at ~632 F·g−1 at 10 A·g−1. The free standing GFPC electrode also exhibits good cycling stability (93.8% of capacitance retention after 2000 cycles) and an energy density of 118 Wh·kg−1 at a power density of 500.35 W·kg−1, all of which are much higher than those of FPC. These encouraging results suggest that the graphene modification of electrode materials combined with a Fe3+/Fe2+ redox active electrolyte is a prospective measure to fabricate SC with an ultrahigh performance. Full article
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Open AccessArticle
Optimization of the Curing and Post-Curing Conditions for the Manufacturing of Partially Bio-Based Epoxy Resins with Improved Toughness
Polymers 2019, 11(8), 1354; https://doi.org/10.3390/polym11081354 - 15 Aug 2019
Viewed by 493
Abstract
This research deals with the influence of different curing and post-curing temperatures on the mechanical and thermomechanical properties as well as the gel time of an epoxy resin prepared by the reaction of diglycidyl ether of bisphenol A (DGEBA) with an amine hardener [...] Read more.
This research deals with the influence of different curing and post-curing temperatures on the mechanical and thermomechanical properties as well as the gel time of an epoxy resin prepared by the reaction of diglycidyl ether of bisphenol A (DGEBA) with an amine hardener and a reactive diluent derived from plants at 31 wt %. The highest performance was obtained for the resins cured at moderate-to-high temperatures, that is, 80 ° C and 90 ° C , which additionally showed a significant reduction in the gel time. This effect was ascribed to the formation of a stronger polymer network by an extended cross-linking process of the polymer chains during the resin manufacturing. Furthermore, post-curing at either 125 ° C   or 150 ° C yielded thermosets with higher mechanical strength and, more interestingly, improved toughness, particularly for the samples previously cured at moderate temperatures. In particular, the partially bio-based epoxy resin cured at 80 ° C and post-cured at 150 ° C for 1 h and 30 min, respectively, showed the most balanced performance due to the formation of a more homogeneous cross-linked structure. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Open AccessArticle
Ultrasonic Thermal-Assisted Extraction of Phosvitin from Egg Yolk and Evaluation of Its Properties
Polymers 2019, 11(8), 1353; https://doi.org/10.3390/polym11081353 - 15 Aug 2019
Cited by 1 | Viewed by 469
Abstract
Phosvitin (Pv) is the principal phosphoprotein in chicken egg yolk and the most highly phosphorylated protein in nature. Pv is a good natural food antioxidant and emulsifier. However, the current extraction methods present disadvantages of complicated operation and are time-consuming. In this paper, [...] Read more.
Phosvitin (Pv) is the principal phosphoprotein in chicken egg yolk and the most highly phosphorylated protein in nature. Pv is a good natural food antioxidant and emulsifier. However, the current extraction methods present disadvantages of complicated operation and are time-consuming. In this paper, Pv was extracted from the egg yolk by ultrasonic thermal-assisted extraction (UTAE). The effects of heating time, ultrasonic power and ultrasonic time on the extraction of Pv were investigated by a single factor. The purity of Pv, ratio of nitrogen to phosphorus (N/P), and activity were used as evaluation indexes. An efficient extraction of Pv was achieved when the sample was heated for 15 min at 80 °C and then processed for 10 min of ultrasonic treatment with an ultrasonic power of 600 W. Under optimal conditions, the purity and activity of Pv were 80% and 98%, respectively, whereas the ratio of N/P was 3.1. The obtained Pv was identified by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE), Fluorescence analyses, fourier-transform infrared (FT-IR), and liquid chromatography-nanoelectrospray ionization mass spectrometry (Nano LC-ESI-MS/MS) analysis. The results showed there is no significant difference in the properties of Pv obtained by UTAE and Pv standard. The developed extraction approach is a simple, industrial compatible method without the use of any organic solvents. Full article
(This article belongs to the Special Issue Protein Biopolymer II)
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Open AccessArticle
A Tough, Water-Resistant, High Bond Strength Adhesive Derived from Soybean Meal and Flexible Hyper-Branched Aminated Starch
Polymers 2019, 11(8), 1352; https://doi.org/10.3390/polym11081352 - 14 Aug 2019
Viewed by 499
Abstract
Soybean meal (SM)-based adhesive exhibited a great potential to replace petroleum-derived ones to alleviate the energy crisis and eliminate carcinogenic formaldehyde. However, the bad water resistance (caused by low crosslinking density) and inherent brittleness of SM adhesive severely hindered its application. However, improving [...] Read more.
Soybean meal (SM)-based adhesive exhibited a great potential to replace petroleum-derived ones to alleviate the energy crisis and eliminate carcinogenic formaldehyde. However, the bad water resistance (caused by low crosslinking density) and inherent brittleness of SM adhesive severely hindered its application. However, improving crosslinking density is generally accompanied by a toughness reduction of the adhesive. Herein, we developed a flexible long-chain starch with a hyper-branched structure (HD), and incorporated it with SM and a crosslinking agent to prepare a novel SM adhesive. Results showed that this adhesive exhibited both excellent water resistance and enhanced toughness. The wet bond strength of plywood fabricated using this adhesive was 354.5% higher than that of SM adhesive. These achievements are because introducing HD with hyper-branched groups enhanced crosslinking density, while HD’s flexible long-chain structure improved toughness of the adhesive. This HD can promote the development of tough and hydrophobic bio-based composites. Full article
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Open AccessReview
A Personal Journey across Fluorescent Sensing and Logic Associated with Polymers of Various Kinds
Polymers 2019, 11(8), 1351; https://doi.org/10.3390/polym11081351 - 14 Aug 2019
Viewed by 546
Abstract
Our experiences concerning fluorescent molecular sensing and logic devices and their intersections with polymer science are the foci of this brief review. Proton-, metal ion- and polarity-responsive cases of these devices are placed in polymeric micro- or nano-environments, some of which involve phase [...] Read more.
Our experiences concerning fluorescent molecular sensing and logic devices and their intersections with polymer science are the foci of this brief review. Proton-, metal ion- and polarity-responsive cases of these devices are placed in polymeric micro- or nano-environments, some of which involve phase separation. This leads to mapping of chemical species on the nanoscale. These devices also take advantage of thermal properties of some polymers in water in order to reincarnate themselves as thermometers. When the phase separation leads to particles, the latter can be labelled with identification tags based on molecular logic. Such particles also give rise to reusable sensors, although molecular-scale resolution is sacrificed in the process. Polymeric nano-environments also help to organize rather complex molecular logic systems from their simple components. Overall, our little experiences suggest that researchers in sensing and logic would benefit if they assimilate polymer concepts. Full article
(This article belongs to the Special Issue Fluorescent polymers for sensing and imaging)
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Open AccessArticle
Raspberry-Like Polysilsesquioxane Particles with Hollow-Spheres-on-Sphere Structure: Rational Design, Controllable Synthesis, and Catalytic Application
Polymers 2019, 11(8), 1350; https://doi.org/10.3390/polym11081350 - 14 Aug 2019
Viewed by 532
Abstract
Raspberry-like hollow-spheres-on-sphere (HSOS) particles with reactive surfaces, uniform sizes and monodisperse properties were rational designed and fabricated to immobilize gold nanoparticles for the catalytic reduction of 4-nitrophenol. HSOS polysilsesquioxane (PSQ) particles were constructed by an organic alkali catalyzed sol-gel process from trialkoxysilane precursors [...] Read more.
Raspberry-like hollow-spheres-on-sphere (HSOS) particles with reactive surfaces, uniform sizes and monodisperse properties were rational designed and fabricated to immobilize gold nanoparticles for the catalytic reduction of 4-nitrophenol. HSOS polysilsesquioxane (PSQ) particles were constructed by an organic alkali catalyzed sol-gel process from trialkoxysilane precursors with stabilized polystyrene (PS) nanoparticles as both a sacrifice template and a Pickering emulsifier. The PSQ particles were fabricated in an ice bath with methyltrimethoxysilane and mercaptopropyltrimethoxysiane as a co-precursor, tetramethylammonium hydroxide (TMAH) as a catalyst, polyvinylpyrrolidone (PVP) and sodium lignosulfonat as co-stabilizers and PS latex as a hard template. The formation mechanism of the hierarchical particles was investigated in detail by the time study through imaging the particles at regular time intervals during the reaction process. Various effect factors on the morphology were studied systematically which showed that the precursor composition, the content of PS, TMAH and PVP are the most important factors. The hierarchical structure combined with the mercaptopropyl groups on both the surface and the skeleton to make it possible to adsorb guest molecules. Au nanoparticles were immobilized on the particles for the catalytic reduction of 4-nitrophenol to 4-aminophenol. The unique PSQ colloids with hollow-spheres-on-sphere extended the family of the hierarchical structures and has shown the potential applications in separations, drug delivery and heterogeneous catalysts. Full article
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Open AccessArticle
Factorial Design and Optimization of Landfill Leachate Treatment Using Tannin-Based Natural Coagulant
Polymers 2019, 11(8), 1349; https://doi.org/10.3390/polym11081349 - 14 Aug 2019
Viewed by 605
Abstract
In this study, tannin-based natural coagulant was used to treat stabilized landfill leachate. Tannin modified with amino group was utilized for the treatment process. Central composite design (CCD) was used to investigate and optimize the effect of tannin dosage and pH on four [...] Read more.
In this study, tannin-based natural coagulant was used to treat stabilized landfill leachate. Tannin modified with amino group was utilized for the treatment process. Central composite design (CCD) was used to investigate and optimize the effect of tannin dosage and pH on four responses. The treatment efficiency was evaluated based on the removal of four selected (responses) parameters; namely, chemical oxygen demand (COD), color, NH3–N and total suspended solids (TSS). The optimum removal efficiency for COD, TSS, NH3–N and color was obtained using a tannin dosage of 0.73 g at a pH of 6. Moreover, the removal efficiency for selected heavy metals from leachate; namely, iron (Fe2+), zinc (Zn2+), copper (Cu2+), chromium (Cr2+), cadmium (Cd2+), lead (Pb2+), arsenic (As3+), and cobalt (Co2+) was also investigated. The results for removal efficiency for COD, TSS, NH3–N, and color were 53.50%, 60.26%, and 91.39%, respectively. The removal of selected heavy metals from leachate for Fe2+, Zn2+, Cu2+, Cr2+, Cd2+, Pb2+, As3+ and cobalt Co2+ were 89.76%, 94.61%, 94.15%, 89.94%, 17.26%, 93.78%, 86.43% and 84.19%, respectively. The results demonstrate that tannin-based natural coagulant could effectively remove organic compounds and heavy metals from stabilized landfill leachate. Full article
(This article belongs to the Special Issue Environmentally Sustainable Polymers)
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Open AccessArticle
In-mold and Machine Sensing and Feature Extraction for Optimized IC-tray Manufacturing
Polymers 2019, 11(8), 1348; https://doi.org/10.3390/polym11081348 - 14 Aug 2019
Viewed by 588
Abstract
Injection molding is a mature technology that has been used for decades; factors including processed raw materials, molds and machines, and the processing parameters can cause significant changes in product quality. Traditionally, researchers have attempted to improve injection molding quality by controlling screw [...] Read more.
Injection molding is a mature technology that has been used for decades; factors including processed raw materials, molds and machines, and the processing parameters can cause significant changes in product quality. Traditionally, researchers have attempted to improve injection molding quality by controlling screw position, injection and packing pressures, and mold and barrel temperatures. However, even when high precision control is applied, the geometry of the molded part tends to vary between different shots. Therefore, further research is needed to properly understand the factors affecting the melt in each cycle so that more effective control strategies can be implemented. In the past, injection molding was a “black box”, so when based on statistical experimental methods, computer-aided simulations or operator experience, the setting of ideal process parameters was often time consuming and limited. Using advanced sensing technology, the understanding of the injection molding process is transformed into a “grey box” that reveals the physical information about the flow behavior of the molten resin in the cavity. Using the process parameter setting data provided by the machine, this study developed a scientific method for optimal parameter adjustment, analyzing and interpreting the injection speed, injection pressure, cavity pressure, and the profile of the injection screw position. In addition, the main parameters for each phase are determined separately, including injection speed/pressure during the mold filling phase, velocity-to-pressure switching point, packing pressure and time. In this study, the IC tray was taken as an example. The experimental results show that the method can effectively reduce the warpage of the IC-tray from 0.67 mm to 0.20 mm. In addition, the parameters profiles obtained by parameter optimization can be applied for continuous mass production and process monitoring. Full article
(This article belongs to the Special Issue Processing and Molding of Polymers)
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Open AccessArticle
Thermal Conductivity Enhancement Derived from Poly(Methyl Methacrylate)-Grafted Carbon Nanotubes in Poly(Methyl Methacrylate)/Polystyrene Blends
Polymers 2019, 11(8), 1347; https://doi.org/10.3390/polym11081347 - 13 Aug 2019
Viewed by 605
Abstract
This paper presents a method to enhance thermal conductivity using poly(methyl methacrylate)(PMMA), polystyrene(PS) blends, and incorporation of multiwalled carbon nanotubes (MWCNTs). MWCNTs are selectively localized in PMMA phase to improve conductive properties. In addition, Surface of MWCNTs was treated with PMMA to enhance [...] Read more.
This paper presents a method to enhance thermal conductivity using poly(methyl methacrylate)(PMMA), polystyrene(PS) blends, and incorporation of multiwalled carbon nanotubes (MWCNTs). MWCNTs are selectively localized in PMMA phase to improve conductive properties. In addition, Surface of MWCNTs was treated with PMMA to enhance affinity between matrix and filler. PMMA grafting helps filler localization on matrix phase. Composites using two polymers enhanced thermal conductivity by ~11% compared with composites using only PS or PMMA. Also, PMMA grafting on the surface of MWCNTs enhanced thermal conductivity by ~13% compared with samples without PMMA grafting. Full article
(This article belongs to the Special Issue Polymer Hybrid Composites)
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Open AccessArticle
Highly Selective and Reproducible Electrochemical Sensing of Ascorbic Acid Through a Conductive Polymer Coated Electrode
Polymers 2019, 11(8), 1346; https://doi.org/10.3390/polym11081346 - 13 Aug 2019
Viewed by 655
Abstract
The surface of an Au-disc electrode was modified through electro polymerization of aniline, in the presence of dodecyl benzene sulphonic acid (DBSA) and sulphuric acid (H2SO4) solution. The polymerization conditions were pre-optimized so that micelle formation and solution coagulation [...] Read more.
The surface of an Au-disc electrode was modified through electro polymerization of aniline, in the presence of dodecyl benzene sulphonic acid (DBSA) and sulphuric acid (H2SO4) solution. The polymerization conditions were pre-optimized so that micelle formation and solution coagulation could be minimized and surfactant doped polyaniline film could be obtained through a quick, simple and one step polymerization route. The synthesized material was characterized via Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and cyclic voltammetry (CV). The effective surface area of the Au-disc, calculated through cyclic voltammetry, was immensely increased through a polyaniline (PANI) coating (0.04 and 0.11 cm2 for bare and PANI coated gold respectively). The modified electrode was utilized for ascorbic acid (AA) sensing. The changing pH of electrolyte and scan rate influenced the PANI electrode response towards AA. The modified electrode was highly selective towards AA oxidation and showed a very low limit of detection i.e. 0.0267 μmol·L–1. Moreover, the PANI coating greatly reduced the sensing potential for AA by a value of around 140 mV when compared to that on a bare gold electrode. Full article
(This article belongs to the Special Issue Polymer Based Bio-Sensors)
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Open AccessArticle
Piezoelectric Films Based on Polyethylene Modified by Aluminosilicate Filler
Polymers 2019, 11(8), 1345; https://doi.org/10.3390/polym11081345 - 13 Aug 2019
Viewed by 536
Abstract
The development, universality and miniaturization of electronic devices leads to the search for new piezoelectric materials, among which recently, polymers play an increasingly important role. In this work, composites based on two types of polyethylene—high density polyethylene (HDPE), and medium density polyethylene (MDPE)—and [...] Read more.
The development, universality and miniaturization of electronic devices leads to the search for new piezoelectric materials, among which recently, polymers play an increasingly important role. In this work, composites based on two types of polyethylene—high density polyethylene (HDPE), and medium density polyethylene (MDPE)—and aluminosilicate fillers were obtained by extrusion process. This method allowed obtaining flexible electrets in the form of a thin film after polarization under a constant electric field of 100 V/μm. The morphology of the composites was characterized by scanning electron microscopy, whereas the crystallinity was determined by X-ray diffraction. The mechanical properties and thermal stability of the composites were examined by means of tensile tests and thermogravimetry, respectively. The piezoelectric characteristics were appointed by measuring the electric charge and the voltage in the polarized samples. Piezoelectric coefficients, and the stability of electrets over time were also determined. Moreover, the effect of film orientation on piezoelectric properties was investigated. Composites with appropriate morphology (i.e., well dispersed filler particles in the polymer matrix and formed holes) were obtained which ensured permanent electrical polarization. It was found that the best piezoelectric, mechanical properties and thermal stability exhibits HDPE composite with 5% of aluminosilicate filler. Full article
(This article belongs to the Special Issue Multiphase Structure of Polymeric Materials and Physical Properties)
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