Physical,Mechanical and Thermal Degradation Properties of Ethylene Vinyl Acetate and Hydrogenated Nitrile Rubber Blends

Abstract

The physical properties, aging, oil, fuel, saline water resistance and abrasion resistance of miscible blends of ethylene vinyl acetate (EVA) copolymer and hydrogenated nitrile rubber (HNBR) are reported. The thermogravimetric analysis (TGA) and microscopic studies of the fracture surface have also been included in this study. At ambient temperatures the tensile and tear strength increase with EVA content in the blend, but above 50°C an opposite trend is observed due to softening of crystalline segments in EVA. Aging, oil, fuel and saline water resistance increase with HNBR content in the blend. The abrasion loss increases steeply with increasing proportions of EVA. Ridges perpendicular to the direction of abrasion are observed in the worn surface of the blends containing more than 30 parts of EVA and the ridge spacing increases with EVA content. The abraded surface of HNBR does not show any ridges except scores in the direction of abrasion. The mechanism of wear changes from fictional to abrasive wear for HNBR rich blends. The TGA studies reveal the improvement in thermal stability of EVA on blending it with HNBR. Scanning electron microscopic observations of the tensile fracture surface show a ductile type of failure for blends having up to 50 wt.% of EVA whereas for HNBR rich blends, the failure is more similar to a brittle type.