Journal of Elastomers & Plastics

Electromagnetic interference (EMI) shielding characteristics of ethylene vinyl acetate (EVA) and ethylene propylene diene (EPDM) and their 50: 50 blend filled with conductive carbon black and short carbon fibre (SCF) have been studied. The measurements of shielding effectiveness (SE) were carried out in two different frequency ranges 100-2000 MHz and 8-12 GHz (X-band range). The return loss and the loss due to absorption were also measured as a function of frequency in the X-band range and microwave region. It is observed that the SE of the composites is frequency dependent, especially at higher frequency range, and it increases with increasing frequency. The SE also increases with the increase in filler loading. It was found that electromagnetic waves interact with the material via the impurities, inclusions and voids existing in the bulk composites. The SCF-filled composites show higher SE compared to that of conductive carbon black. The correlation between SE and conductivity of the various composites is also discussed. The results suggest that the fibre-filled (20 phr) composites can be used for the EMI shielding, as well as for some microwave applications.

A new homogeneous bimetallic catalyst, based on Rh-Ru compounds, for the hydrogenation of acrylonitrile-butadiene copolymer(NBR) has been prepared. This paper described a study of the catalyst preparation and its hydrogenation process of NBR. The hydrogenation catalytic activity and selectivity of this bimetallic catalyst system (BMSC)was compared to two catalysts, RhCl(PPh₃)₃ and RuCl₂(PPh₃)₃. NBR and hydrogenated NBR(HNBR) have also been characterized by infrared spectrum. The results showed that this new bimetallic complex catalyst offers good catalyst activity and excellent selectivity in NBR hydrogenation process to produce a highly saturated (98%) HNBR without gel formation. In addition, properties of the vulcanized HNBR have high tensile strength, elongation, tear strength and low permanent set. Its hot air ageing performance and oil swell test indicate that this HNBR is as good as those of current commercial products. Moreover, this new bimetallic complex catalyst, in conjunction with metal recovery system developed in this laboratory offers potential economic advantage in industrial applications.

The large deformation of elastomeric (rubber-like) materials has been commonly analyzed within the context of hyper elasticity. Although there is ample experimental evidence suggesting the nonhomogeneity of these materials, the majority of the hyperelastic models assume the material homogeneity. In the present study, a Gent material model is generalized in light of recent experimental studies to be able to simulate the shearing deformation of a non-homogeneous isotropic incompressible elastomeric slab. The numerical solution of the static equilibrium equations shows that the shearing response of non-homogeneous slabs is substantially different from that of homogeneous slabs. The finite chain extensibility, which is a characteristic of most rubber-like materials, is shown to have a self-homogenizing effect on the strain field in addition to its well-known stiffening effect on the stress field.

Effects of perpendicular tensile loads on the mechanical behavior and biaxial tensile load ratios on stress-strain behaviors of single ply of nylon cord-rubber composite are studied respectively under biaxial tensile conditions employing a cruciform specimen. Experimental results indicate that transverse mechanical properties of nylon cord-rubber composite with longitudinal constant tensile loads are distinct from its uniaxial transverse tensile mechanical properties. This can be attributed to the action of longitudinal tension that makes the material rigidify in the direction perpendicular to the fiber. The mode of failure is representative of matrix-dominated failure. However, effects of transverse constant tensile load on longitudinal tensile mechanical properties are indistinctive compared with corresponding uniaxial longitudinal tensile mechanical properties. This could be due to a larger difference between longitudinal and transverse mechanical properties. Its dominating failure mode is typical fiber-dominated mode. Effects on biaxial tensile load ratios on its transverse stress-strain behaviors are obvious; whereas, longitudinal stress-strain behaviors under different biaxial tensile load ratios are almost identical. Large differences between longitudinal and transverse tensile properties can be direct reasons resulting in dissimilarities between longitudinal and transverse tensile mechanical behaviors of cord-rubber composite under biaxial tensile loading.