Crystallization and thermal properties

Processing conditions and final properties of poly lactic acid (PLAs) are strongly influenced by the crystalline or amorphous structure of the polymer. Crystallization, crystallinity degree, and thermal properties of poly L-lactide (PLLA) depend on the polymer molecular weight, polymerization conditions, thermal history, purity, and so on. Multiple melting or crystallization peaks have been reported in calorimetric analysis after the isothermal crystallization of PLLA, with the melting of less perfect crystals, their reorganization in more perfect structures, and their final melting. Crystal morphology and amount depend on the preparation and crystallization conditions. PLA fibers can be produced by melt and solution spinning. The degradation-induced crystallization has a very important drawback for the biomedical use of PLLA as an implant material, which can last in the implant site for a very long time. Commercial PLA with or without fillers shows modification of thermal behavior during aging in hydrolytic or bacterial expositions, or in soil and compost.