PE/PC原位微纤共混物二次流动过程中的复杂结晶结构的演变与控制

In-depth understanding of structural change and morphological development in polymer subjected to thermo-mechanical fields is always the main emphasis in the research of polymer engineering and high performance modification. The current research mainly focuses on the formation mechanisms of polymer materials' morphology under the low shear，low strain and single flow field. However, little research focuses on morphology development and structure control of polyolefin/fiber blending system under complex flow field and interaction between melts in practical processing. As reported in our previous work, complex crystalline structure (transcrystallinty, hybrid shish-kebab and shish-kebab) of PE/PC in situ microfibril blends subjected to the secondary flow was found, but the formation mechanisms of complex crystalline structure in the secondary flow are still unclear. Therefore, in this project, based on the previous research, we will investigate the complex crystalline morphological development of PE/PC in situ microfibril blends subjected to secondary flow and command the fundamental rules of the relationship between the flow fields, PC microfibril and macromolecule chains of PE subjected to secondary flow. And combined with numerical simulation, response mechanism of PE/PC in situ microfibril blends subjected to secondary flow will be discussed for building models which are suitable for description of PE/PC in situ microfibril blends'motion and morphological evolution in PE/PC in situ microfibril blends melt subjected to secondary flow. At the same time, the relationship between complex crystalline structures and properties will be also studied to illustrate the processing parameters/morphology/property relationship of PE/PC in situ microfibril blends melt subjected to secondary flow, and to provide the theoretical and experimental basis for controlling the composite' properties and solving the fundamental scientific issues of morphological development during processing.

聚合物在外场条件下的结构演变及其控制一直是高分子材料及高性能化的研究重点。目前的研究主要集中在一些小剪切、低应变下单一聚合物在一次流动过程下高分子材料形态结构的形成机制及控制。然而，关于实际加工过程中，聚烯烃/纤维共混体系在复杂外场及熔体多次相互作用中结晶结构演变及控制的研究尚不多见。在我们初步研究中，PE/PC原位微纤共混物在二次流动中出现了复杂结晶结构（横晶、杂化串晶和普通串晶），但是具体的形成机制尚不清楚。因此，本项目拟在前期研究工作的基础上，探究PE/PC原位微纤共混物熔体在二次流动中，外场、PC微纤与大分子响应之间的关系，建立PE/PC原位微纤在二次流动中的运动模型，深入理解二次流动中PE/PC原位微纤共混物复杂结晶结构的演变规律；阐明二次流动中外场控制-形态结构-力学性能之间相互关系，从而对PE/PC原位微纤共混物二次流动中的基本科学问题及性能调控提供理论依据。

该项目探寻了聚合物体系在熔体二次流动过程中形态结构的演变规律与控制方法，通过创新性地在聚合物基体中引入不同性质的纤维，形成了稳定、不松弛的“shish”，从而诱导基体聚合物分子链形成杂化串晶结构（Hybrid shish-kebab），并且通过控制纤维的直径以及拓扑结构，对hybrid shish-kebab的结构进行优化，首次在制品中构筑了三维空间互锁的hybrid shish-kebab结构，使制品从多层次的结晶结构转变为高取向、均一的精细结构，并且可以较大幅度地提高材料的强度和模量。同时，探索了聚烯烃/纤维共混物在熔体二次流动过程中结晶结构的演变规律，建立了外场-形态结构-性能的关系。基于此理论和控制方法，在材料内部成功地构筑了预期的结构-外刚内韧的结晶结构。