The effect of heat treatment on water sorption in polylactide and polylactide composites via changes in glass-transition temperature and crystallization kinetics

Abstract

Water sorption into polylactide (PLA) and polylactide-montmorillonite (PLLA-MONT) composites containing 5 wt % of montmorillonite (MONT) under different heat treatment conditions was studied using the quartz crystal microbalance/heat conduction calorimetry (QCM/HCC) technique. Results showed that water sorption in neat polymer films and composite films increased with heat treatment temperature up to 120 °C. Differential scanning calorimetry was used to measure the glass-transition temperature and isothermal crystallization kinetics of all samples. The mobility of the amorphous domain in all samples increased with heat treatment temperature, indicated by the decrease in glass-transition temperature. PLA composites crystallized at a much faster rate than neat PLA did because MONT acted as a nucleating agent. Under the same heat treatment condition, water sorption in PLLA-MONT composites was always higher than that in neat PLA due to the presence of the hydrophilic hydroxyl groups on the surface of MONT particles. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 Water sorption and glass-transition temperature of neat polylactide and polylactide-montmorillonite composites vary with heat treatment conditions. Although the crystallinity of all samples is similar, high heat treatment temperatures produce samples with lower glass-transition temperatures (higher mobility) and higher sorption (lower Henry's Law constant). Both neat polylactide and composite samples show very similar trends, but composites samples exhibit higher mobility and higher sorption. © 2011 Wiley Periodicals, Inc.