Carbon black (N‐330), organically modified nanoclay (NC) based ternary, particulate nanocomposites comprising of epoxidized natural rubber matrix having 25 mol% of epoxy group (ENR‐25) were prepared in an open two‐roll mill. Investigations of cure characteristics, dynamic mechanical, tensile, thermal, and morphological characteristics were conducted using Rheometric analysis, Dynamic Mechanical Analysis (DMA), mechanical property evaluation, Thermo‐gravimetric analysis (TGA), High Resolution Transmission Electron Microscopy (HR‐TEM), respectively, to derive the interrelation among the developed nanostructures inside the composite, crosslinking density, performance properties obtained there from. A satisfactory level of correlation was obtained among various results, which indicated the formation of “nanounit” comprising of N‐330 and NC inside ENR‐25 matrix. To optimize the nanostructures, ENR based compounds containing various combinations of NC and N‐330 was prepared. Thorough and systematic structure‐property analyses were performed on those composites. Optimum stoichiometric combination of N‐330 and NC inside the ENR‐25 matrix was derived (ratio of N‐330 and nanoclay in wt% = 20:15), which showed synergistic effect of one filler upon another that was ultimately reflected in their dynamic mechanical and tensile properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Electrical and electromagnetic interference shielding effectiveness (EMI SE) properties of the ethylene methyl acrylate (EMA)/multiwalled carbon nanotube (MWNT) nanocomposites have been studied. High resolution transmission electron microscope (HRTEM) was used to validate the MWNTs dispersion state and network connections of its microstructure. The electrical resistance of the nanocomposites decreases significantly with MWNTs content. DC resistivity and AC conductivity measurement on the nanocomposite samples showed that the insulator to conductor transition took place within 10 wt% MWNTs concentration. It has been found that as MWNT concentration increased network connections improved. The EMI SE of the nanocomposites has also been investigated. The highest SE (∼20 dB) of these nanocomposites is realistic for an industrial application. EMA/MWNT nanocomposites provide sufficient intrinsic EMI shielding capability which may be hopeful for electrical and electronic applications. The morphology correlates well with the electrical and electromagnetic behavior of these nanocomposites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

The ethylene methyl acrylate copolymer (EMA) and multiwalled carbon nanotube (MWNT) based composites were prepared by solution mixing as well as by melt processing of the films obtained after solution mixing. Field emission scanning electron microscopy, transmission electron microscopy, and XRD were used to characterize morphologies of various composites. MWNTs were found to be more dispersed in the composites prepared by melt process after solution process. There was no obvious agglomeration of MWNTs at lower % loading (up to 2.5%) in the polymer matrices especially the composites are prepared solution plus melt mixing and consequently better interaction between MWNTs and EMA matrix was anticipated. XRD and differential scanning calorimetry studied showed that the nanotubes affect the crystallization process and subsequently their role as a nucleating agent was established. These are reflected in the mechanical properties of the composites. Dynamic mechanical analysis showed that the storage modulus of the composites drop very sharply beyond 2.5 wt% of MWNT content with increasing % strain and it reflects the Payne effect (a substantial decrease in the storage modulus of a particle-reinforced polymer with an increase in the amplitude of dynamic oscillations). The influence of concentration of filler was also realized by frequency sweep experiment. The incorporation of MWNTs in EMA offered a stabilizing effect since onset of degradation occurs at higher temperatures for composites.

Thermoplastic vulcanizates (TPVs) are a special class of thermoplastic elastomers that are generally produced by the simultaneous mixing and crosslinking of a rubber with a thermoplastic polymer at an elevated temperature. Novel peroxide-cured TPVs based on blends of silicone rubber and the thermoplastic Engage (an ethyleneoctene copolymer) have been developed. These TPVs exhibit very good overall mechanical and electrical properties. With an increasing concentration of dicumyl peroxide, the tensile strength, modulus, and hardness of the TPVs increase, whereas the elongation at break decreases. Significant correlations have been obtained from oscillating disc rheometer torque values with various physical properties, such as the modulus and tension set of the TPVs. The aging characteristics and recyclability of the silicone-based TPVs are also excellent. Scanning electron microscopy photomicrographs of the TPVs have confirmed a dispersed phase morphology.

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Abstract. Thermoplastic vulcanizates (TPVs) are a special class of thermoplastic elastomers, which are produced by simultaneously mixing and crosslinking a rubber with a thermoplastic polymer at an elevated temperature. Peroxide-cured TPVs based on blends of silicone rubber and thermoplastic Engage of two different types, mainly ethylene-octene and ethylenebutene copolymers at different blend ratios have been developed. A detailed comparative study of ethylene-octene vs. ethylene-butene based TPVs are mainly focused in this paper. These TPVs exhibit very good overall mechanical and electrical properties. With increasing amount of Engage in the blends at a fixed concentration of peroxide and coagent, tensile strength, modulus and hardness of the TPVs were found to increase considerably. Ageing characteristics and recyclability of silicone rubber based TPVs are also found excellent. Rheological studies confirm the pseudoplastic nature of these TPVs.

The rheological behavior of nanocomposites based on multiwalled carbon nanotube (MWNT) with three commercial grades of ethylene methyl acrylate (EMA) copolymers containing 9, 24, and 30 wt% methyl acrylate (MA) was investigated under dynamic and steady shear flow (in a capillary) conditions. Storage modulus (in dynamic shear) value increases especially at higher frequency levels due to increased polymer‐filler interactions. Both the unfilled and filled composites exhibit rheological behavior of non‐Newtonian fluids. In both steady shear and capillary flow, the nanocomposites register a slightly higher viscosity than neat EMAs, with dependence on the MWNTs content. All systems with various loading of MWNTs represent an increase in elastic response with increasing frequency. The die swell decreases with the MWNTs loading. Dynamic and steady shear rheological properties register a good correlation in regard to the viscous versus elastic response of such systems inline with the Cox–Merz concept. Increased MA content leads to inferior dispersion of MWNTs in EMA matrix. Morphological studies exhibit that MWNTs become more aligned along longitudinal direction after extrusion leading to improved dispersion. Copyright © 2010 John Wiley & Sons, Ltd.

Proton exchange membrane (PEM) fuel cell stack requires gaskets and seals in each cell to keep the reactant gases within their respective regions. Gasket performance is integral to the successful long-term operation of a fuel cell stack. This review focuses on properties, performance and degradation mechanisms of the different polymer gasket materials used in PEM fuel cell under normal operating conditions. The different degradation mechanisms and their corresponding representative mitigation strategies are also presented here. Summary of various properties of elastomers and their advantages and disadvantages in fuel cell'environment are presented. By considering the level of chemical degradation, mechanical properties and cost effectiveness, it can be proposed that EPDM is one of the best choices for gasket material in PEM fuel cell. Finally, the challenges that remain in using rubber component as in PEM fuel cell, as well as the prospects for exploiting them in the future are discussed.