二氧化碳混入式辅助成型聚乳酸的结晶和服役性能研究

新版“限塑令”的颁布标志着可降解塑料产业的发展迎来重大机遇。聚乳酸来源广，稳定性高，是最常见的可降解塑料，但因结晶度低而导致的产品服役性能差的问题依然是聚乳酸推广应用面临的瓶颈问题。为解决该问题，本项目提出一种二氧化碳混入式辅助注塑成型工艺，通过二氧化碳调控聚乳酸晶体结构，提升聚乳酸构件的力学性能和服役寿命。利用自建的原位高压多光学观测系统和自建的二氧化碳混入式辅助注塑成型系统，本项目拟研究二氧化碳对聚乳酸结晶形核和晶型的影响规律，揭示聚乳酸在二氧化碳中的结晶形核机理与晶型转变机制，探明聚乳酸晶体结构对于产品力学性能、降解速率的影响规律，建立聚乳酸成型工艺-微观结构-服役性能的内在关系模型，实现聚乳酸产品的强度韧性和降解速率的有效调控，解决阻碍聚乳酸推广应用面临的瓶颈问题。该研究不仅对可降解塑料的成型加工具有实际指导意义，而且对揭示聚合物在浓溶液中的结晶机理具有重要理论价值。

The promulgation of new ‘plastic bag’ marks an important opportunity for the development of degradable plastic industry. Poly (lactic acid) (PLA) is the most common degradable plastic with a wide source and high stability. However, the problem of poor service performance of product caused by low crystallinity remains to be the bottleneck problem faced by the popularization and application of PLA. To solve this problem, this project proposed a forming technology assisted by mixing with carbon dioxide. This technology can improve the mechanical properties and service life of PLA product though regulating the crystal structure by carbon dioxide. This project will use a self-built in-situ high-pressure multi-optical observation system and a self-built injection molding system assisted by mixing with carbon dioxide to further study the influence of carbon dioxide on the nucleation and form of PLA crystal. The mechanism of nucleation and transformation of PLA crystal in carbon dioxide will be revealed. The influence of the PLA crystal structure on the mechanical properties and degradation rate of products will be studied. The intrinsic relationships model of process-microstructure-performance of PLA will be established. The strength toughness improvement and degradation rate regulation of PLA product will be achieved. Finally, this project targets solving the bottleneck problem that hinders the popularization and application of PLA. This study has not only practical guiding significance to the implement of the forming process of degradable plastic, but also important theoretical value to reveal the crystallization mechanism of polymer in concentrated solution.