Morphology, mechanical and viscoelastic behaviour of blends of nitrile rubber and ethylene-vinyl acetate copolymer

Abstract

Nitrile rubber/ethylene-vinyl acetate copolymer (NBR/EVA) blends with different ratios were prepared by using a two roll mixing mill. The morphology of the blends was studied using optical and electron microscopies. The morphology of the blends indicated a two phase structure in which the minor phase is dispersed as domains in the major continuous phase. However, between 40 and 50 wt% of NBR content both NBR and EVA exist as continuous phases and generate a co-continuous morphology. The viscoelastic properties have been determined using a Rheovibron Viscoelastometer at 35 Hz over a wide range of temperatures. The effect of blend ratio on the mechanical properties such as tensile strength, elongation at break, stress-strain behaviour and hardness has been investigated. The mechanical properties increase with the increase of EVA content in the blend. Attempts have been made to correlate the variation of properties with morphology of the blend. Various composite models have been used to fit experimental mechanical and viscoelastic data.