Properties of the Blends of Ethylene-Vinyl Acetate and Ethylene-alpha-Olefins Copolymers

摘要

The effect of the vinyl acetate(VA)content on the thermal,viscoelastic,rheological,morphological and mechanical behaviors in various blends of ethylene-vinyl acetate(EVA)/ethylene-alpha-olefm copolymers was investigated using 28,22 and 15 mol% of VA in EVA.In the DSC melting and crystallization thermograms of all of the EVA systems blended with ethylene-alpha-olefin copolymers,discrete peaks were observed which were related to the constituents.In the dynamic mechanical thermal analysis,the storage modulus increased with increasing content of ethylene-alpha-olefm copolymers.In addition,the transition regions relating to the tan delta peaks varied with the VA content.The crossover point between G' and G" varied depending on the VA contents,and shear-thinning was more prominent in the EVA/EtBC system.In the SEM investigation,a discrete phase morphology was observed in both the EVA/EtBC and EVA/EtOC blends,but the contrast improved with decreasing VA content.However,the tensile strength and modulus improved,but the elongation at break reduced with decreasing VA content,implying that the ethylene-alpha-olefin copolymers play the role of reinforcing materials.Thus,the EVA and ethylene-alpha-olefm components in the copolymers are immiscible in the molten and solid states,but are nevertheless mechanically compatible.