Supercapacitive properties of electrodeposited polypyrrole on acrylonitrile–butadiene rubber as a flexible current collector

Flexible sheets consisting of acrylonitrile–butadiene rubber (NBR) and vapor-grown carbon fiber (VGCF) are newly prepared varying the composition (VGCF 10–30 wt%) for use as a current collector of supercapacitor electrodes. The electrical conductivity of as-prepared VGCF/NBR current collector can be enhanced as the content of VGCF increases. The VGCF/NBR current collector is then electrodeposited with pyrrole using a potentiodynamic cyclic voltammetry to yield a polypyrrole (PPy)/VGCF/NBR composite electrode. Cyclic voltammetry result for the PPy/VGCF/NBR composites shows that the sample with 30 wt% VGCF achieves a maximum specific capacitance (125.8 F g^?1) at 5?mV?s^?1 and reaches a lower specific capacitance at higher scan rates. In addition, the flexibility of supercapacitor electrode of PPy can also be established with a comparable capacitance value by using the NBR-based current collector.     

Impact of graphene oxide nanoparticles and carbon black on the gamma radiation sensitization of acrylonitrile–butadiene rubber seal materials

Seals prepared from acrylonitrile–butadiene rubber (NBR) are primarily used in nuclear services. Nevertheless, at relatively high ionizing radiation doses, NBR seal materials may undergo radiation-induced degradation processes, leading to adverse effects on the sealing ability life. Herein, to strengthen the functional characteristics of NBR seals against radiation, graphene oxide (GO) nanoparticles were prepared and characterized by transmission electron microscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR), and ultraviolet/visible spectroscopies. Various NBR/GO composites fabricated with different ratios of GO nanoparticles and in the presence or absence of carbon black (CB) were investigated via cross-linking density, scanning electron microscopy, XRD, FTIR, and mechanical and thermal stability analyses. The synergistic effect of the simultaneous presence of GO and CB on the NBR seal sensitization to gamma radiation up to a dose of 1 MGy was studied. The physicomechanical properties were enhanced by adding GO nanosheets up to 3 phr and by incorporating 35 phr of a CB with GO until 5 phr. Further, the application of γ-irradiation resulted in an overall enhancement in the mechanical, physical, and thermal stability of the prepared composites up to 0.5 and 1 MGy with GO nanosheets in the absence or presence of CB particles, respectively. The mechanical measurements indicated significant increments by loading with GO nanosheets in the absence and presence of CB as well as by irradiation. The tensile strength elevated up to about 121%, 336%, and 366% by adding 3 phr GO, 3 GO:35 CB phr, and 5 GO:35 CB phr, respectively.     

Impact of the aluminum sulfate 18-hydrate particle size on the coordination crosslinking behaviors of acrylonitrile–butadiene rubber–aluminum sulfate 18-hydrate composites

In this study, aluminum sulfate 18-hydrate [Al₂(SO₄)₃·18H₂O] particles of different sizes, which were obtained via high-energy ball-milling technology, were successfully compounded with acrylonitrile–butadiene rubber (NBR) to fabricate crosslinked rubber composites. The results suggest that high-energy ball milling had no significant change on the crystal structure of Al₂(SO₄)₃·18H₂O, but it significantly reduced the particle size. The effects of the particles size on the coordination crosslinking behaviors and mechanical properties of the NBR–Al₂(SO₄)₃·18H₂O composites were fully explored. The coordination crosslinking reaction was demonstrated to occur between the nitrile group (─CN) and Al(III). Moreover, with the decreasing particle size, the composites achieved a better interfacial adhesion and more crosslinking points, and this led to significant increases in the crosslinking density and the mechanical properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47717.     

Effects of modified silica on the co-vulcanization kinetics and mechanical performances of natural rubber/styrene–butadiene rubber blends

Rubber blends are widely used for combining the advantages of each rubber component. However, to date, how to determine and distinguish the vulcanization kinetics for each single rubber phase in rubber blends during the co-vulcanization process is still a challenge. Herein, high-resolution pyrolysis gas chromatography–mass spectrometry (HR PyGC-MS) was employed for the first time to investigate the vulcanization kinetics of natural rubber (NR) and styrene–butadiene rubber (SBR) in NR/SBR blends filled with modified silica (SiO₂). The reaction rates of crosslinking of each rubber phase in NR/SBR were calculated, which showed that the crosslinking rates of NR were much lower than those of SBR phase in the unfilled blends and blends filled with unmodified and silane modified silica. Interestingly, the vulcanization rates of NR and SBR phase were approximately same in the vulcanization accelerator modified silica filled blends, showing better co-vulcanization. In addition, the vulcanization accelerator modified silica was uniformly dispersed and endowed rubber blends with higher mechanical strength compared to the untreated silica. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48838.     

Development of porous nanocomposite membranes for gas separation by identifying the effective fabrication parameters with Plackett–Burman experimental design

In this research, Plackett–Burman experimental design was used as a screening method to investigate seven processing factors in the preparation of new polyethersulfone based porous nanocomposite membrane. Polymer concentration, nanoparticle type, nanoparticle concentration, solvent type, solution mixing time, evaporation time, and annealing temperature are variables that were evaluated to fabricate mixed matrix membranes using the evaporation phase inversion method for gas separation. According to obtained results, polymer concentration, nanoparticle concentration, solution mixing time, and evaporation time processing factors had significant effects on gas permeation. In addition, the nanoparticle type, nanoparticle concentration, and polymer concentration had substantial effects on membrane selectivity. From analysis of variance, it was found that the model used for membrane gas permeability and membrane selectivity as response values were more reliable within spaced levels. Scanning electron microscope, gas permeation experiments and statistical analysis showed that polymer concentration, nanoparticle type, nanoparticle loading and evaporation time significantly affected the final membrane morphologies and performances. According to this study, trade-off limitation between gas permeability and membrane selectivity could be eliminated by identifying the effective fabrication parameters.     

Application of hygrothermally decomposed polyurethane in rubber recipes Part 2–Influence of hygrothermally decomposed polyester–urethane on cure characteristics and viscoelastic behaviour of styrene/butadiene rubber

Abstract

Hygrothermally decomposed polyester–urethane (HD PUR) was mixed at concentrations up to 20 pphr with a styrene/butadiene rubber (SBR), using an efficient vulcanisation system. Changes in the cure behaviour were followed by vulcametry, plate–plate rheometry, and differential scanning calorimetry. It was found that the degree of crosslinking was increased by the incorporation of HD PUR, which acts as an accelerator in SBR stocks. Increasing crosslinking resulted in higher stiffness and strength and was accompanied by a reduction in elongation at break and swelling index.     

The effect of the heat treatment of spruce wood on the curing of melamine–urea–formaldehyde and polyurethane adhesives

The effect of the heat treatment of spruce wood on the curing of melamine–urea–formaldehyde (MUF) and polyurethane (PUR) adhesives was monitored by measuring their rheological properties by means of a rheometer. Instead of the standard aluminium discs, wooden discs, made from heat-treated wood with different degrees of thermal modification and conditioned in different climates, were used. The wooden discs provided more realistic curing of the adhesives compared to the real-life bonding of wood, because of solvent absorption. The results of the rheological measurements suggested that the modified wood inhibited the curing of MUF and PUR adhesives. The curing of the MUF adhesive was slower because of the reduced absorption of water from the adhesive. The curing of the one-component PUR adhesive was affected by the lower moisture content (MC) of the modified wood.     

Thermorheological studies of novel thermoplastic elastomeric blends of nitrile rubber (NBR) and scrap computer plastics (SCP) based on acrylonitrile–butadiene–styrene terpolymer (ABS)

Abstract

Thermorheological properties of thermoplastic elastomeric 60/40, 70/30 and 80/20 nitrile rubber (NBR)/scrap computer plastics (SCP) blends were studied by using parallel plate rheometer. The blends exhibit pseudoplasticity and obey power law model. The dynamically vulcanised blends have higher dynamic viscosities than their unvulcanised counterparts. Surface finish and die swell of the extrudates are improved upon dynamic vulcanisation. The thermoplastic elastomeric blends of NBR/SCP exhibit 'thermorheological complexity'.     

Preparation of dispersible nanosilica surface-capped by hexamethyl disilazane via an in situ surface-modification method and investigation of its effects on the mechanical properties of styrene–butadiene/butadiene rubber

Silica has been established as one of the most promising materials in green tires. The filler–rubber interactions can increase the comprehensive performance of rubber composites. In this study, sodium silicate was used as the silicon source and hexamethyl disilazane (HMDS; molecular formula: C₆H₁₉NSi₂) was used as a modifier to synthesize dispersible silica (DNS) via an in situ surface-modification method. The effects of the HMDS-capped silica on the properties of rubber–matrix composites made of styrene–butadiene rubber (SBR) and high-cis-polybutadiene rubber (BR9000 or BR) were investigated with Zeosil 1165MP (Z1165-MP; a commercial highly dispersible silica produced by Rhodia for the production of green tires in the rubber industry) as a reference. The results show that the SBR–BR–DNS composite was before the SBR–BR–Z1165-MP composite in increasing the tear strength and elongation at break and reducing the compression heat buildup. On the basis of the resulting properties, the reinforcing behaviors in the rubber–matrix composites were analyzed. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47763.     

The effect of rippled graphene sheet roughness on the adhesive characteristics of a collagen–graphene system

A great amount of effort has been made in order to reach a more precise understanding of the adhesion phenomenon that happens as a vital component of several biological systems. Therefore, a firm understanding of the important factors that influence this phenomenon is of special importance in triggering the adhesive characteristics of different biological, bio-inspired and synthetic materials in fields such as tissue engineering.In this study the adhesive characteristics of a multi-material system consisting of the frequently used synthetic material, graphene, in the form of armchair-configuration sheets, and an important biological filament which is type 1 Collagen consisting of 3 alpha helices, has been studied in detail. The main emphasis of this study is placed on understanding the effects of the roughness characteristics of the inorganic elements which are the graphene sheets on the overall adhesive features of the system which are quantified within the framework of two main criteria: adhesion energy and peeling force. At first, the methodology used in order to obtain graphene sheets with various roughness values is described in detail. The abovementioned criteria are then evaluated through Molecular Dynamics (MD) modeling of the system in the NAMD simulation software environment and various simulation scenarios are studied.     

The effect of TiO2 particle size on the characteristics of Au–Pd/TiO2 catalysts

The nanocrystalline TiO₂ materials with average crystallite sizes of 9 and 15 nm were synthesized by the solvothermal method and employed as the supports for preparation of bimetallic Au/Pd/TiO₂ catalysts. The average size of Au–Pd alloy particles increased slightly from sub-nano (< 1 nm) to 2–3 nm with increasing TiO₂ crystallite size from 9 to 15 nm. The catalyst performances were evaluated in the liquid-phase selective hydrogenation of 1-heptyne under mild reaction conditions (H₂ 1 bar, 30 °C). The exertion of electronic modification of Pd by Au–Pd alloy formation depended on the TiO₂ crystallite size in which it was more pronounced for Au/Pd on the larger TiO₂ (15 nm) than on the smaller one (9 nm), resulting in higher hydrogenation activity and lower selectivity to 1-heptene on the former catalyst.     

Experimental design to enhance the surface appearance,the internal structure,and the shear stresses of injected and metallized polycarbonate/acrylonitrile–butadiene-styrene parts

Polycarbonate (PC) and acrylonitrile–butadiene–styrene (ABS) possess thermal and mechanical properties, which make them materials of choice for automotive components. These properties have presented PC/ABS as an eligible replacement for metals in automotive industry. The aim of this study was to explore a new approach to determine the optimum conditions for obtaining quality and shear stresses of the injected and metalized PC/ABS parts. For this purpose, the following six injection-molding parameters such as material temperature (137 _ma ), injection pressure (P _inj ), holding pressure (P _h ), mold temperature (T _mo ), holding time (t _h ), and cooling time (t _c ) were considered at four different values. The effect of the injection parameters studied has been analyzed through the quality and the shear stresses values of the injected and metallized PC/ABS specimens. Optical microscopic and confocal laser scanning microscope (CLSM) results demonstrate that the occurrence of some defects such as weld line, blister, poor adhesion, metal residue, sand scratch. Moreover, scanning electron microscope (SEM) findings show the presence of core defects and solidified pellets. Shear stresses vary between 3.78 and 5.8 MPa for the injected specimens and 4.5 and 6.4 MPa for the metallized specimens. The optimum injection parameter combinations were conditioned by producing flawless injected and metallized PC/ABS parts having a significant shear stress value. Thus, the optimum combinations consists of: a T_ma of 260 °C, a P_inj ranging between 30 and 50 bar, a P_h ranging between 20 and 25 bar, a T_mo of 40 °C, a t_h ranging between 8 and 14 sec. and a t_c of 25 sec. These findings may have interesting applications in automotive part industry. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48384.     

Impact of carboxylated styrene–butadiene copolymer on the hydration kinetics of OPC and OPC/CAC/AH: The effect of Ca2 + sequestration from pore solution

It was found that carboxylated styrene–butadiene latex copolymer retards OPC and accelerates a ternary binder system based on OPC/CAC/anhydrite. The reason behind both effects is the sequestration of Ca^2 + ions from the pore solution. In the case of OPC, the depletion of Ca^2 + hinders the formation of cement hydrates and thus retards hydration of OPC, whereas for the ternary binder system, the depletion of Ca^2 + shifts the solubility equilibrium of CaSO₄ in favor of sulfate. As a result, the dissolution of anhydrite is accelerated and ettringite formation is enhanced. The consequence of these processes is earlier strength development, which is highly desirable in drymix mortar applications. The results explain why anionic SB latex performs particularly well in ternary binder systems.     

The physical–chemical behaviour of amino cross-linkers and the effect of their chemistry on selected epoxy can coatings’ hydrolysis to melamine and to formaldehyde into aqueous food simulants

In this study, the suitability of four chemically different melamino cross-linkers for use in formulating epoxy coatings was investigated on the basis of the composition and of the tendency of cured coatings to hydrolyse to melamine and to formaldehyde when they were retorted in aqueous food simulants. The four cross-linkers were characterised for their composition identity, flow behaviour, thermal stability and for the presence of residual species. The different cross-linkers were used individually to cross-link selected epoxy coatings. The effects of the cross-linker chemistry, the curing conditions and the kinetics of the hydrolysis and subsequent migration processes, leading to melamine and formaldehyde were investigated following thermal treatments that were designed to represent the conditions of food sterilisation. The results show that each cross-linker type is different in its rheological characteristics, its solids content, its thermal behaviour and its physical properties. The chemistry of each cross-linker plays a major role in the manner in which the epoxy coatings undergo hydrolysis to release melamine and formaldehyde. The greatest migration of melamine (from an unpigmented epoxy anhydride coating, cured with the hexamethoxymethyl melamine cross-linker) into the 10% (v/v) aqueous ethanol food stimulant, after retorting at 131 °C, for 1 h was 525 μg/6 dm². The greatest migration of formaldehyde into the simulant was also from this coating at 11 μg/6 dm², when retorted at 131 °C for 1 h. The curing conditions affected the extent of the cross-linker hydrolysis. The influence of varying the curing time and the curing temperature was used to control the hydrolysis of the cross-linked, epoxy-based coatings. A decrease in the extent of cross-linker hydrolysis by 50–80% was achieved in all cases as the temperature of the curing was increased, in stages, from 160 °C to 200 °C.