Nonisothermal crystallization of poly(l-lactide) in poly(l-lactide)/olive stone flour composites

Abstract

Nonisothermal crystallization of poly(l-lactide) in poly(l-lactide)/olive stone flour (PLLA/OSF) composites was studied applying differential scanning calorimetry (DSC). The analysis was carried out during cooling of the melt at different and constant rates. The kinetic parameters of the crystallization were determined by the Avrami, Ozawa and Mo methods. The Avrami analysis revealed the existence of two mechanisms of nonisothermal crystallization in all samples. The Ozawa and Mo methods failed to successfully describe the crystallization behaviour of PLLA with or without OSF. The effective activation energy of nonisothermal crystallization was estimated with the Friedman method. The kinetic analysis using the Friedman method showed the complexity of the crystallization process. The results of structural investigation shown that OSF has a low influence on the interplanetary distance of PLLA crystal phase. The crystallite size of PLLA decreases with increasing cooling rates and the conditions for the growth of the lamellar structure is more suitable at the lower cooling rate.