Isothermal Crystallization Kinetics of Polypropylene/CaCO3 Blends

Abstract

Crystallization of polypropylene (PP) and PP blended with 10, 15, and 20 wt% CaCO₃ was investigated using Differential Scanning Calorimetry (DSC) under isothermal conditions at four different crystallization temperatures of 110, 115, 120 and 125°C. The kinetic parameters were analyzed using
the Avrami equation. The results show that the Avrami exponent, n, decreased with increasing crystallization temperature, except for a crystallization temperature TC of 125°C where the opposite effect was observed. At the same crystallization temperature, the values of n for PP/CaCO₃ blends were slightly lower than for PP, which suggests that the addition of CaCO₃ to PP caused a slight decrease in heterogeneous nucleation. Both PP and PP/CaCO₃ blends followed three-dimensional crystallization growth. The value of the crystallization rate constant, k, strongly depended on the crystallization temperature, which decreasing with increasing crystallization temperature and CaCO3 content. The rate
of the three-dimensional crystallization growth was reduced by increasing the crystallization temperature and CaCO₃ content.