Impact fracture behavior and damage mechanisms of PP/EVOH blends compatibilized with ionomer Zn2+

Abstract

In this work, the impact fracture behavior and the damage mechanisms of PP/EVOH blends compatibilized with ionomer Zn2+ were investigated, focusing on the effect of the compatibilizer and the EVOH content. Initiation energy release rate (GIC) values for the blends with EVOH content lower than 30 wt % were slightly lower or similar to that of neat PP, probably due to the premature failure induced by the presence of critical-size flaws derived from debonding of second phase particles. However, blends with 40 wt % EVOH exhibited higher GIC values than neat PP as a result of the increased number of EVOH particles able to induce energy-absorption mechanisms. An increase in the work of fracture values with EVOH content was also observed, especially for the blends with EVOH content above 30 wt %. Therefore, the incorporation of EVOH to PP led to blends more prone to ductile behavior than neat PP. Furthermore, Pukánszky and Maurer model was successfully applied to fit experimental data of GIC as a function of EVOH content and to confirm the lack of a significant effect of the ionomer Zn2+ on the impact fracture properties observed. Finally, from the study of the main deformation mechanisms it was established that the toughening effect of debonding of EVOH particles and subsequent ductile tearing of PP matrix around them which developed under quasi-static stresses were not able to develop under impact loading conditions.