流动场与可自组装成核剂协同调控聚乳酸复合材料结晶行为的研究

Tailoring the crystallization rate of polylactide (PLA) and evolution of its structure and morphology during crystallization is the key of cystallization study for heat-resistant PLA and has great significance for broadening the application fields and the industrialization development of PLA. In this project, (1) a small melt-drawing device will be developed and (2) the isothermal extension-induced crystallization of high-molecular-weight poly(L-lactide) (PLLA) /poly(D-lactide) (PDLA) blend (HMPPB) with self-assembled nucleating agent will be investigated through the combination of in-situ synchrotron X-ray study and ex-situ characterization. (3) The results will be compared to that of shear-induced crystallization of this HMPPB for analyzing the influence of different temperature and flow fields on the nucleation and competitive growth of different crystals, lamellar stacking and orientation, etc. in HMPPB/nucleating agent composite. (4) The study will reveal the interplay among nucleating agent and its self-assembly, the HMPPB melt, flow and flow-induced crystallization, and clarify the flow-induced crystallization mechanism of HMPPB under different processing conditions. In addition, through the synergistic effect among flow field and self-assembled nucleating agent, the behavior of crystallization kinetics and the formation of supermolecular structure of HMPPB will be controlled. This study will provide the theoretical guidance and experimental basis for the design and preparation of high-performance heat-resistant PLA.

调控聚乳酸的结晶速率及其在结晶过程中的形态结构演变是研究耐热型聚乳酸结晶的关键，对拓宽聚乳酸的应用领域和产业化发展意义重大。本项目拟（1）研制一台小型熔体拉伸装置；（2）通过同步辐射X射线在线跟踪和离线检测相结合的方式，研究含可自组装成核剂的高分子量左旋聚乳酸（PLLA）/右旋聚乳酸（PDLA）共混物（HMPPB）的等温拉伸诱导结晶；（3）并将其与HMPPB的剪切诱导结晶对比，分析不同流动场和温度场对HMPPB/成核剂复合材料多种晶体的成核、竞争生长、片晶堆栈和取向等方面的影响；（4）揭示成核剂及其自组装、HMPPB熔体、不同流动场及流动诱导结晶之间的相互作用规律，阐明不同加工条件下的流动诱导结晶机理，并通过可自组装成核剂和流动场的协同作用，调控HMPPB的结晶动力学行为以及超分子结构的形成。最终为高性能耐热聚乳酸的设计和制备提供理论指导和实验依据。

调控聚乳酸的结晶速率及其在结晶过程中的形态结构演变是研究耐热型聚乳酸结晶的关键，对拓宽聚乳酸的应用领域和产业化发展意义重大。本项目1) 自行成功研制了一台高精度可控温小型熔体拉伸实验机，与同步辐射X-射线联用，可用于在线分析聚乳酸熔体等温拉伸诱导结晶过程中的结构演变；2).制备一系列包含不同浓度成核剂TMB-5的高分子量PLLA/PDLA共混物（HMPPB），运用剪切热台、自制小型熔体拉伸装置、偏光显微镜（POM）、流变仪、差示扫描量热仪（DSC）、热重分析仪（TG）、广角X射线衍射（WAXD）、扫描电镜（SEM）等分析测试方法研究成核剂在不同流动场和温度场下的自组装进程及其对HMPPB的结晶形态、结晶动力学和热性能的影响；3) 以聚乳酸为基材研制可降解辐射致冷薄膜，并提升该薄膜的耐热性能。同时，设计研制新型的辐射致冷性能测试装置，以提高测试的准确性、降低测试成本及实现快速测试。