论文部分内容阅读
通过熔融共混法制备了一系列等比例聚左旋乳酸(PLLA)/聚右旋乳酸(PDLA)共混试样,采用差示扫描量热法(DSC)、核磁共振(13C-NMR)及广角X射线衍射(WAXD)等方法对共混产物进行了表征和研究分析.结果表明,等比例PLLA和PDLA熔融共混生成了立构复合物(stereocomplex,sc),同时部分均聚物发生酯交换反应,生成了立体嵌段物(stereoblock,sb),从而在DSC升温曲线上sc晶体处出现特殊的熔融双峰现象;随着熔融共混温度升高,sc晶体的生成率和结晶度逐渐下降;聚乳酸立构复合物的加工稳定性较好,二次加工后,sc晶体熔点基本不变,生成率和结晶度提高;由于sc晶体的存在,PLLA/PDLA共混物的耐热性能提高,退火热处理后耐热性能得到进一步提高.这对于开发高耐热聚乳酸及其加工应用具有重要的应用价值.
A series of PLLA / PDLA blends were prepared by melt blending method and characterized by differential scanning calorimetry (DSC), nuclear magnetic resonance (13C-NMR) and wide angle X-ray diffraction (WAXD) and other methods were used to characterize and analyze the blends.The results showed that stereocomplex (sc) was formed by the melt blending of equal proportion PLLA and PDLA, and partial homopolymer transesterification , A stereoblock (sb) was formed, and a special melting bimodal phenomenon appeared on the sc crystal of the DSC curve. With the increase of the melt blending temperature, the formation rate and degree of crystallinity of the sc crystal gradually decreased The polylactic acid stereocomplex has better processing stability. After the secondary processing, the melting point of sc crystal keeps unchanged and the formation rate and crystallinity increase. The heat resistance of PLLA / PDLA blend increases due to the existence of sc crystal , Heat resistance after annealing heat treatment to be further improved.This is an important application value for the development of high heat-resistant polylactic acid and its processing applications.