Abstract: Polypropylene/sepiolite (PP/SEP) composites were investigated using differential scanning calorimeter (DSC) and polarized light microscope. Avrami equation was used to analyze isothermal crystallization. It showed that with increasing crystallization temperatuer（Tc）,The crystallization rate reduced, The parameter values of n and K become lower, and the half-time(t1/2) for become higher. At a given Tc, the presence of sepiolite resulted in high crystallization rate and small crystallite size due to its significant heterogeneous nucleating effect.

Key words: sepiolite, polypropylene, composites, isothermal crystallization, kinetics