One-step regulating the microstructure in physical foaming process of polypropylene

Abstract

ABSTRACT In this work, the innovative bimodal insulating polypropylene (PP) foam was produced through a straightforward one-step mechanism with only one blowing agent, supercritical CO2. Based on differential scanning calorimetry (DSC) data, as well as scanning electron microscopy (SEM) images, it was deduced that the induced-crystallinity of PP at the start of the foaming process could determine the final foam structure predominantly. In the amorphous region, the rigid amorphous phase, which is profoundly affected by the temperature of the foaming process and also the polymer chain configurations, can accommodate nano-sized cavities, while more extensive cells can grow throughout the flexible amorphous region having higher mobility.The bimodal foam morphology is developed in a certain proportion of the rigid amorphous and flexible amorphous phase.