Utilization of Maleic Anhydride Modified Ground EVA Waste in NBR Vulcanizates

Abstract

Abstract The influence of poly(ethylene-co-vinyl acetate) (EVA) waste (EVAW) on the rheological and mechanical properties of NBR vulcanizates compounds was studied. The optimum concentration of EVAW, which has presented higher ultimate tensile strength, was found to be 70 phr. In addition, the influence of EVAW modified with maleic anhydride as adhesion promoter was studied. Two distinct routes of modification with maleic anhydride were selected, originating a carboxylated EVA waste (EVAWCOOH) and an anhydride EVA waste (EVAWMA). An improvement of tensile strength and aging resistance was observed with the substitution of EVAW by EVAWCOOH or EVAWMA. A very good resistance to compression set has been achieved with the addition of EVAWCOOH. The improvement of mechanical performance was attributed to a better dispersion of EVAW along NBR matrix, promoted by the enhanced modified-waste polarity, which allowed a good interaction with polar NBR. The presence of anhydride group in functionalized EVAW resulted in the highest values of tensile strength but lower elongation at break and also lower values of tan delta obtained from dynamic testing. These behaviors have been attributed to an increase of crosslink density due to the reaction between zinc oxide and succinic pendant groups of EVAWMA.