Effect of organoclay content on mechanical and rheological properties of dynamically cross-linked acrylonitrile-butadiene rubber/poly(ethylene-co-vinyl acetate)/organoclay nanocomposites

Blends of poly(ethylene-co-vinyl acetate) (EVA) and acrylonitrile-butadiene rubber (NBR) with NBR content of 50 wt% and organoclay (OC) contents of 1, 3, 5 and 7 wt% have been prepared and cross-linked with 0.3 wt% dicumyl peroxide (DCP) in an internal mixer. The results obtained from x-ray diffraction and transmission electron microscopy for the uncross-linked nanocomposites containing 7 wt% OC show that although a part of the nanofiller layers are exfoliated, the rest of the particles remained almost intercalated. However, it is found that cross-linking with DCP markedly increased the amount of exfoliated platelets. The results also reveal that gel content and cross-linking rate slightly increased in the presence of the OC. The analysis of data obtained from the tensile experiments indicates that the tensile modulus and yield stress of the nanocomposites are superior to those of the unfilled blend and the values improve with the increase in the OC content. Apart from the value of strain at break, all other mechanical properties studied are found to be higher for the cross-linked nanocomposites than those of their uncross-linked counterparts. Moreover, the relaxation ratio and relaxation rate index are decreased with an increase in the OC content for the uncross-linked and cross-linked materials.