Effect of spatial confinement on the development of β phase of polypropylene

The focus of this study was the effect of spatial confinement on the development of nucleating agent-induced β phase polypropylene (PP) in the dynamically vulcanized thermoplastic elastomers (TPVs) based on dynamically vulcanized PP/ethylene-propylene-diene rubber (EPDM) blend. The melting behaviors, crystalline structures and the morphologies of the blends were studied by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM). The results indicate that the EPDM phase undergoes a series of changes from the dispersed phase to a continuous one, and again to the dispersed phase with increased content of curing agent, and the PP component always shows itself in a continuous phase. In this process, with the content of the nucleating agent unchanged, the content of β phase PP in the blends initially increases a little and then decreases with increasing PF (Phenolic resin) content. We believe spatial confinement provides a good explanation for the development of β phase PP.