取向非晶聚乳酸等温冷结晶过程中微结构演化

项目名称： 取向非晶聚乳酸等温冷结晶过程中微结构演化

项目编号： No.50873094

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 金属学与金属工艺

项目作者： 王亚明

作者单位： 郑州大学

项目金额： 34万元

中文摘要： 本课题系统研究了不同取向程度的非晶聚乳酸在等温冷结晶过程中的微结构演化。取得的主要结果如下：（1）聚乳酸在较低温度冷结晶时会形成α8242;晶，α8242;晶在较高温度退火时能转化成α26230;，并且，在转化的过程中伴有熔融发生；（2）对于以不同牵引速率得到的挤出流延聚乳酸薄膜，用偏振FTIR和二维广角X射线衍射（2D-WAXD）均未检测到结晶和取向的存在，然而，将薄膜两端固定后退火，得到的是有明显取向的结晶试样，我们认为，挤出流延薄膜可能存在FTIR及2D-WAXD检测不到的大尺度链取向，在退火过程中，这些取向的大尺度链会倾向于收缩，但由于两端固定，因此，有应力诱导的结晶发生，最终得到取向的结晶态；（3）将聚乳酸在橡胶态拉伸可在一定条件下得到取向的中间相，在随后的退火过程中，一个反常的实验发现是高拉伸应变试样退火后得到的结晶形态却没有低拉伸应变试样的完善。本研究可为预测和控制取向聚乳酸制品的微结构和性能提供依据，对丰富和发展高分子材料凝聚态物理学科理论是有意义的。

中文关键词： 生物降解高分子材料；聚乳酸；取向；结晶；微结构

英文摘要： In this project, the microstrucutre evolution of amorphous poly(lactic acid) (PLA) with various orientation content upon isothermal cold-crystallization was investigated systematically. The main results are as follows: (1)The disorder (α8242;) phase of PLA was found in PLA cold-crystallized at lower temperatures, and a disorder-to-order (α8242;-to-αphase transition occurred during the annealing process of the α8242;-crystal at elevated temperatures,meanwhile, a melting process was involved during the phase transition; (2) The extrusion cast PLA films were found to be amorphous and unoriented regardless of the take-up speeds applied, using two-dimensional wide angle X-ray diffraction (2D-WAXD), polarized Fourier transform infrared (FTIR) techniques, however, upon constrained annealing, oriented crystalline structures developed. The findings could be explained by the presence of global orientation during film casting and stress-induced crystallization upon constrained annealing; (3) PLA can develop an unique structure called the mesomorphic phase (mesophase) under tensile deformation at certain conditions from the amorphous state of PLA, and upon subsequent annealing, we observed an unusual cold-crystallization behavior that the crystal structure of the sample with higher extension strain formed after annealing was less perfect than that of the one with lower extension strain. The study can provide suggestions for predicting and controlling the microstrucutre and properties of oriented PLA products, and is meaningful for enriching and developing the theory of the subject of solid state polymer physics.

英文关键词： Biodegradable polymer; Poly(lactic acid); Orientation; Crystallization; Microstructure