聚氨酯-聚乳酸共混物的制备及性能

通过熔融共混挤出法制备不同质量比的热塑性聚氨酯-聚乳酸(TPU-PLA)共混物,采用SEM、DSC、TG、微卡软化点温度测定仪和熔融流动速率仪对共混物的表面形态结构、热学、高温加工等性能进行研究。结果表明:TPU-PLA共混物表面光滑且呈现出脆性断裂形貌特征,共混体系两种高聚物呈"海岛"分布;TPU-PLA共混体系中PLA与单独PLA相比,玻璃化转变温度Tg由69.60℃(Original PLA)变为57.58℃(PLA70)、53.29℃(PLA50)和55.64℃(PLA30),TPU均匀分散于PLA基体中且相界面分明,这都说明TPU-PLA共混体系为部分相容体系;TPU-PLA共混物的热失重起始分解温度范围为180~200℃,最快分解温度范围为310~350℃,热稳定性良好;TPU含量占共混物10%~30%时,共混物高温的临界变形温度相对单一体系有所提高;随TPU含量的继续增加,共混物熔融指数呈现先增大后减小的变化趋势,其中PLA与TPU质量比为4∶6的TPU-PLA共混物熔融指数达到最大,为1 406g·(10min)-1。

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.