PHYSICAL, MECHANICAL AND THERMAL-DEGRADATION PROPERTIES OF ETHYLENE-VINYL ACETATE AND HYDROGENATED NITRILE RUBBER BLENDS

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 t hermogravimetric analysis (TGA) and microscopic studies of the fractur e surface have also been included in this study. At ambient temperatur es the tensile and tear strength increase with EVA content in the blen d, but above 50 degrees C an opposite trend is observed due to softeni ng of crystalline segments in EVA. Aging, oil, fuel and saline water r esistance increase with HNBR content in the blend. The abrasion loss i ncreases steeply with increasing proportions of EVA. Ridges perpendicu lar to the direction of abrasion are observed in the worn surface of t he blends containing more than 30 parts of EVA and the ridge spacing i ncreases with EVA content. The abraded surface of HNBR does not show a ny ridges except scores in the direction of abrasion. The mechanism of wear changes from frictional to abrasive wear far HNBR rich blends. T he TGA studies reveal the improvement in thermal stability of EVA on b lending it with HNBR. Scanning electron microscopic observations of th e tensile fracture surface show a ductile type of failure for blends h aving up to 50 wt.% of EVA whereas for HNBR rich blends, the failure i s more similar to a brittle type.