Crystallization Behavior of PP in Composites with EPDM and a Surface Modified Nano-Calcium Carbonate

A modified nano-CaCO ₃ (RCCR) was prepared by mixing the stearic acid treated nano-CaCO ₃ (CCR) with organic agent containing —OH, —COOH, and C=C groups and it was then melt compounded with polypropylene PP and Ethylene-propylene-diene mischpolymer (EPDM) to prepare PP/EPDM/nano-CaCO ₃ composites. The effects of RCCR on the crystallization behavior of PP in the composites were studied by DSC. The crystal type structure of PP in the composites was studied by X-ray diffraction and polarized optical microscope (POM). It was found that RCCR acts as a nucleating agent. It initiates PP crystallizing at higher temperature, and lowers degree of crystallinity and crystal size, and induces the formation of β crystallite. RCCR in collaboration with EPDM can obviously increase the content of β crystallite. Isothermal crystallization studies reveal that the activation energy of PP in PP/EPDM/RCCR is lower than that of PP/EPDM/CCR.