IMPACT TOUGHENING OF POLYPROPYLENE BY ETHYLENE VINYL-ACETATE COPOLYMER

In this article we studied the potential of ethylene vinyl acetate copolymer (EVA) as an impact modifier for isotactic polYPropylene (PP). PP/EVA blend in the range 0-40 wt % EVA content is studied by using three grades of EVA containing 9, 12, and 19 wt % VA. Izod impact strength measurements were made at temperatures ranging from liquid nitrogen temperature to 60-degrees-C to explore the impact-toughening effect as a function of blending ratio both at low and above ambient temperatures. The results are compared with various reported blends of PP with other elastomers. Morphological studies through scanning electron microscopy on etched impact-fractured surfaces are carried out and a correlation of morphology and impact properties at various blending ratios is presented. Finally, a mathematical analysis of the data is performed in terms of second-degree polynomial to express impact strength as a simultaneous function of two variables, and an equation is proposed that shows the best fit with the experimental data. Relevant contour diagrams, based on the proposed equation, for optimization of properties are also presented.