取向片晶簇温度-应变速率-应变三维空间结构演化规律与非线性力学行为的关系

The relationship between the nonlinear mechanical behaviors and microscopic structural evolutions during stretching is a key scientific problem for guiding post-stretching and service behavior of semi-crystalline polymeric materials. Due to the complex coupling of multi-scale characteristics of structure and relaxation dynamics in semi-crystalline polymers, the study on the intrinsic deformation mechanism to account for the nonlinear mechanical behaviors is still a great challenge for polymer industry and academia. In-situ techniques for the combination of high- and low-temperature ultra-fast stretching devices and the high time-resolved synchrotron radiation X-ray scattering will be developed in our project. This project intends to select polyolefin (PP or PE) precursor films composed of oriented lamellar stacks as the research object, which can decouple the complexity of multi-scale characteristics and simplify the three-dimensional microscopic stress analysis. Under a three-dimensional space with wide temperature, wide strain rate and large strain ranges, the structural evolution rules of multi-scale microscopic structures will be systematically studied, which will build a basic data foundation of oriented lamellar stacks for the study of the relationship between nonlinear mechanical behaviors and the coupling effects of structural transformation kinetics and relaxation dynamics in the future.

拉伸过程中半晶高分子材料非线性力学行为与微观结构演化的关系是指导后拉伸加工和预测服役行为的关键科学问题。鉴于半晶高分子空间结构多尺度与松弛时间多尺度的复杂耦合，至今该问题还是高分子科学和工业界的一大挑战。针对该挑战，本项目拟发展高、低温高速拉伸装置与高时间分辨同步辐射X射线联用的原位检测技术，选取含高取向片晶簇的聚烯烃（聚乙烯和聚丙烯）预制膜作为研究对象，实现多尺度结构的解耦和三维微观应力分析的简化，研究取向片晶簇中晶体与无定形组成的多相体系在温度-应变速率-应变三维外场空间拉伸过程中微观结构演化规律，探究结构转变动力学和松弛动力学的耦合效应，为构建半晶高分子材料非线性力学行为的微观机制和理论模型积累基础数据。

半晶高分子拉伸过程中的非线性力学行为对于理清高分子材料加工中的物理问题至关重要。本项目针对半晶高分子拉伸加工原理，主要研制与同步辐射X射线散射联用的原位高、低温高速拉伸装置，结合同步辐射X射线散射小角/宽角技术，在线跟踪取向聚丙烯、聚乙烯薄膜在不同温度和应变速率范围内的拉伸过程中的微观结构演化，探索其结构演化机制和规律，通过从小角散射信号强度、片晶取向、长周期和宽角上检测到的晶体取向、结晶度、晶胞参数等结构参数定量化分析，构建温度-应变耦合空间，应变速率-应变耦合空间的结构演化机制图，为精确调控半晶高分子材料加工、结构和性能提供一定的理论指导。