Non-isothermal cold crystallization behavior and kinetics of poly(l-lactide): effect of l-lactide dimer

Abstract

The effects of l-lactide dimer as additives on the crystallization behavior of poly(l-lactide) (PLLA) films were studied. Hence, neat PLLA films and PLLA containing l-lactide (5 % w/w) (PLLA/La) were prepared in dichloromethane at room temperature via solution casting. The non-isothermal cold crystallization of PLLA films were studied using differential scanning calorimetry at various heating rates including 2.5, 5, 7.5, 10 and 15 °C/min. However, the X C% was increased for PLLA/La films in comparison with neat PLLA films. The crystallization kinetics was then analyzed by the Avrami, Jeziorny, Ozawa and Mo kinetic models. It is found that all the kinetic models were established to describe the experimental data fairly well except the Ozawa model. The values of t 1/2, Z C and F(T) indicated that the crystallization rate increased with increase in heating rates for PLLA and PLLA/La films. However, l-lactide dimer incorporated in PLLA films accelerates the crystallization process of PLLA at the high heating rate. The nucleation constant (K g) and the surface free energy (σ e) based on Lauritzen–Hoffman theory indicated that these parameters for PLLA/La films is lower than neat PLLA.