可控增压条件下聚合物的成型及制品的结构-性能关系研究

The effect of controllable compressing process on the solidification behavior of the polymer melt is studied in this project, and the relationship between the structure evolution and mechanical properties of the products during uniaxial stretching is investigated with in situ measurements. Firstly, several polymers were chosen and solidified under rapid compression in order to obtain bulk amorphous products, and the critical condition for preparing amorphous materials will be discussed. Secondly, we also focus on the crystallizing behavior of the polymer melt during slow compression process, trying to explain quantitatively the way that the compressing temperature, compressing rate and compressing range affect the crystal structure. Finally, with in situ FTIR spectroscopy and X-ray diffraction measurements, the crystallization behavior of amorphous products during heating and stretching processes are investigated respectively, while the relationship between the crystalline skeleton force distribution and yielding behavior is also analyzed. This study focuses on the solidification behavior of the polymer melt induced by controllable compressing, not only providing theoretical support for the compressing method but also illustrating a new solution for the structure design of materials.

本项目关注可控增压过程对聚合物熔体固化行为的影响，并利用原位检测设备研究成型制品在拉伸过程中的结构演化与力学性能关系。首先，利用快速增压法固化聚合物熔体，期望制备出多种材料的大块非晶制品，并揭示压致非晶的临界条件。其次，研究慢速增压过程对聚合物熔体结晶行为的影响，定量化分析增压温度、增压速率和增压幅度对晶体结构的控制情况。最后，利用显微红外光谱和小角/广角X射线在线研究：1. 压致非晶制品的冷结晶行为和拉伸诱导结晶行为；2. 压制结晶制品在拉伸过程中的晶体受力情况与屈服行为关系。本研究不仅会对聚合物的压致固化成型工艺提供理论支持，更可能为材料的结构设计提供新方案。

与常规成型方法不同，本项目关注增压过程对聚合物熔体固化行为的影响，同时分析制品的结构演化与力学性能关系，研究对象包括纯高分子体系以及高分子纳米复合体系。从结晶机理上看，慢速增压过程中，分子链有充足的时间进行结构调整，能够形成热力学上较稳定的晶体结构；快速增压过程中，分子链来不及进行结构调整，会形成动力学上较稳定的亚稳态结构，这很可能是一个普适的规律。从工程应用的角度上看，人们可以对增压速率、设定压力和增压温度进行精确控制，该方法不仅能控制制品中亚稳相结构的含量，有目的地改善样品的某些性能，还可以改善产品中的结构不均匀和应力集中情况，有利于提高制品的机械性能和光学性能。此外，该方法可重复性好，能够获得普适的工艺参数，进而指导生产。