Differential Scanning Calorimetric Studies of Non-isothermal Crystallization of HDPE and HDPE/CaCO3 Composites

Abstract

Crystallization of high density polyethylene (HDPE) and HDPE/CaCO₃ composites (10, 20 and 30% wt, CaCO₃) was investigated by differential scanning calorimetry (DSC) under non-isothermal conditions. The Avrami method modified by Jeziorny and a method developed by Liu et al. were employed to describe the non-isothermal crystallization process of the samples. The results showed that the Avrami exponent n decreased from 3.0 to 2.4 with an increase in the cooling rate from 5°C/min to 40°C/min, while the crystal growth constant Z_c was nearly constant (~1.1) at a 10°C /min   – 40°C/min cooling rate for all systems. The value of F(T) showed that the crystallization rate of the HDPE/10% CaCO₃ composite was the slowest at a given cooling rate. Moreover, the activation energy determined from the Kissinger method indicated little difference in the values of the activation energy for all systems, except the 30% CaCO₃ system which showed a slightly higher activation energy.