系带分子在聚己内酯及其相容共混物的拉伸形变和断裂行为中的作用机理研究

Tie molecules, to a large extent, determine the yield and fracture behavior of crystalline polymers, and hence the study of their mechanism is of great value in practical application. The purpose of the present project is to study the microstructural evolution behavior of polycaprolactone and its miscible blends under tensile deformation by means of in-situ synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. The number of tie molecules can be effectively manipulated by controlling the constituent ratio of mixtures and preparation procedures. Afterwards, a two-dimensional phase diagram concerning plastic flow and crack growth is to be established via in-situ optical microscopy, and then the dependence of tensile deformation and crack growth on the microstructural parameters is to be elucidated on the mesoscopic and microscopic scale utilizing SAXS and WAXD, respectively. Therefore,the role of tie molecules in the plastic deformation and fracture behavior can be identified ,thus setting the theoretical basis for the enhancement of mechanical performance and service lifetime in polymeric materials.

系带分子在很大程度上决定了结晶高分子材料的屈服和断裂行为，因此其作用机理的研究具有重要的实际应用价值。本项目拟采用同步辐射小角X射线散射和广角X射线衍射技术在线研究聚己内酯及其相容共混物在拉伸作用下的微观结构演化规律。通过控制共混物样品的组成比例和制备条件实现系带分子数量的有效调控，然后利用在线光学显微镜方法构建一个关于塑性流动和裂纹扩展的二维相图，进而分别从介观和微观尺度上阐明拉伸形变和裂纹扩展的微观结构参数依赖性，从而揭示塑性形变和断裂过程中的系带分子作用机制，为提高材料的力学性能和服役时间奠定理论基础。

高分子材料的力学性能在很大程度上依赖于连接相邻片晶的系带分子，因此研究系带分子在结晶高分子材料的屈服和空洞化行为中的作用机理具有重要的理论意义和实际价值。本项目通过控制加工成型条件、结晶温度以及非晶高分子的性质等实现不同微观结构和形态的聚己内酯及其相容共混物的制备，然后采用广角、小角和超小角X射线散射方法原位研究了分子链、片晶、微孔等微观结构在拉伸作用下的演化规律，发现了塑性形变和空洞化的之间的竞争取决于片晶的力学稳定性，证实了球晶-微纤转变的熔融-重结晶机理以及大应变时的微纤滑移机理，阐明了系带分子的数量决定球晶-微纤转变的临界应变大小和微纤之间滑移的程度，提出了空洞化起源于晶相并贯穿于相邻的片晶和非晶区，揭示了微孔引发和发展的系带分子依赖性，为理解高分子材料的失效机理和延长其服役时间提供理论基础。