Preparation and properties of thermoplastic polyurethane-polylactic acid blends

Various mass ratio thermoplastic polyurethane-polylactic acid (TPU-PLA) blends were prepared by melting blends. The morphology, thermal characteristics, and high-temperature processing performance of TPU-PLA blends were studied with SEM, DSC, TG, Vicat Softening Temperature (VST) and Melt Flow Rate (MFR), respectively. The results show that the morphologies of TPU and PLA in blends present as a "sea-island" distribution. Glass transition temperature T_g of the PLA in the blends changes from 69.60℃(Original PLA) to 57.58℃(PLA70), 53.29℃(PLA50) and 55.64℃(PLA30), and TPU distributes in PLA evenly as dispersing phases. There are clear interfaces between the dispersing phases and continuous phases. It indicates that TPU-PLA blends are an incompatible system. The crystallinity of original PLA is lower than that in TPU-PLA blends, due to overlapping of crystallization and melting. The initial decomposition temperature of TPU-PLA blends are around 180-200℃ and the fastest decomposition temperature of TPU-PLA are about 310-350℃. The thermal properties of TPU-PLA blends are favorable. When the mass ratio of TPU is 10%-30%, the material critical deformation temperature of blends is enhanced relatively to original PLA and TPU. The melt index of blends is increased firstly and then decreased as the mass ratio of TPU increased. As the mass ratio of TPU is 40%, the melting index of blends is highest which is 1406 g · (10 min)^-1.