PP/EVA blends: Mechanical properties and morphology. Effect of compatibilizers on the impact behavior

Abstract

ABSTRACT:The mechanical properties of blends of isotactic polypropylene (PP) and poly[ethylene-co-(vinyl acetate)] (EVA) are studied under tension at several temperatures (from -30• C to room temperature). The morphology and thermal properties are given attention at every stage of the stretching process. To improve the impact resistance of the blends, poly[propylene-graft-(maleic anhydride)] (PPMA) and hydroxylated EVA (EVAOH) are used as compatibilizers. The domain size of the dispersed phase decreases with compatibilizer content, improving the impact resistance of the blends. This is accompanied with changes in the morphology of such systems. C

Effect of heterophasic or random PP copolymer on the compatibility mechanism between EVA and PP copolymers

“…This better dispersed morphology could be attributed to the interfacial interactions and to the effectiveness of the shear mixing exerted by the screw configuration used. Similar results were obtained by Maciel et al,13 who found a reduction in particle size of the dispersed EVA phase when a compatibilizer was incorporated to the blend. These smaller an better dispersed domains confirms the higher interaction of the PP‐ r ‐EP, even at lower EVA content of the blends, previously demonstrated by a single and unique T g (E“) and by the melting temperature depression observed by DSC.…”

“…6). This mechanical property behavior was also observed by Ramirez‐Vargas et al12 and Gupta et al7 Maciel et al13 has reported an increase on the impact strength in PP/EVA blends when using PPMA and EVAOH as compatibilizers.…”

“…These results corroborate the partial miscibility or compatibility of these types of blends. Other authors have13 reported an enhancement on strain in PP/EVA blends when the EVA content was increased. Elongation at break results is shown in Figure 9 where it can be seen that the PP‐ r ‐EP showed higher values than the PP‐EP for the entire range of compositions studied.…”

“…Gupta et al,7 have studied the morphology, rheology and mechanical properties of PP/EVA blends, finding that the impact strength was enhanced with higher than 30% EVA content, and that the impact strength was also a function of the VA (9, 12, and 19%) content of EVA which was related to the reported morphologies. An increase on the mechanical properties of blends of iPP and EVA, when polypropylene grafted maleic anhydride (PPgMA) and hydroxylated EVA (EVAOH), were used as compatibilizers, has been reported 13. The impact properties of EVA/iPP systems was improved when calcium carbonate was included as a reinforcement 14.…”

Optimization of fall height setting for drop weight tested polypropylene

“…In content of 40 % of EVA in the blend, the impact resistance increased of more than 270 % with the addition of 6.2 phr of compatibilizers at ambient temperature. Moreover, with increasing the compatibilizer content to 10 phr, an additional rise in the impact resistance was obtained [3].…”