MELT-RHEOLOGICAL PROPERTIES OF PP/EVA BLEND

This paper describes a study of melt-rheological properties of the binary blend of isotactic polypropylene (PP) and ethylene-vinyl acetate copolymer (EVA) at varying blending ratios (from 0 to 40 wt % EVA content) and using three samples of EVA containing different vinyl acetate contents (VA %), viz. 9, 12, and 19%. Measurements made on a capillary rheometer at three different temperatures (210, 220, and 230-degrees-C) in a shear stress range of 10(4)-10(6) Pa (shear rate 10(1)-10(4) s-1 ) are presented and discussed for the effects of blend composition and shear stress on the flow curves, melt viscosity and melt elasticity. Morphology of the blend studied through scanning electron microscopy revealed distinct differences in size and number density of dispersed EVA droplets, which are discussed in terms of the variation of average size and number density of the dispersed EVA droplets as a function of blend composition and shear stress. Melt-rheological properties and morphology of dispersion are correlated and found quite consistent.