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

Abstract

A modified nano-CaCO₃ (RCCR) was prepared by mixing the stearic acid treated nano-CaCO₃ (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-CaCO₃ 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.

Keywords

polypropylene EPDM nano-calcium carbonate nucleation crystallization.

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