Effects of compatibility on foaming behavior of polypropylene/polyolefin elastomer blends prepared using a chemical blowing agent

Polypropylene (PP) exhibits poor foaming property because of its low melt strength arising from its linear chains and relatively narrow molecular weight distribution. To fabricate a PP foam without crosslinking, PP should be blended with polyolefin elastomers (POEs) using chemical blowing agents. In this study, the effects of POE types and contents in a PP matrix were studied by analyzing the melt flow index, morphology, and thermal and dynamic viscoelastic properties. Furthermore, the POE type/content and foaming conditions (i.e., foaming temperature and oven residence time) were optimized by investigating the volume expansion ratio (VER), cross-sectional morphology, and hardness of the PP/POE foams. We focused on how the foaming behavior and foaming conditions were affected by the compatibility and POE content in the PP/POE blend. The results demonstrated that the optimal VER of ∼9 was obtained at 30 wt % POE and foaming conditions of 220 °C for 9 min.