拉伸流场下超高分子量聚乙烯Shish-Kebab晶体的形成与演变研究

This project, based on UHMWPE fiber as example, in-situ studies the formation and evolution of Shish-Kebab crystals of polymer material, with varying degrees of chain entanglement, in elongation flow field. The aim of this project is develop and perfect the formation and evolution mechanism of Shish-Kebab crystals and the nature of effect of structural evolution on material properties. Resins for the project using UHMWPE resin with low molecular weight than the existing industrial production, through changing the concentration of resin to adjust the degree of entanglement of primary fibers, and through the use of the resin with different branching degree to fine-tune the chain entanglement, form a series of primary fibers with different degree of entanglement. Using SAXS/WAXD technology of small angle light station in Shanghai Synchrotron Radiation Facility, offline and online research the formation and evolution mechanism of Shish-Kebab crystals of UHMWPE primary fiber, with different entangle degree, in elongation flow field, and the effect of crystals formation and evolution on fiber mechanical performance is also studied, to reveal the natural mechanism of the formation and evolution of Shish-Kebab crystals on the material mechanical performance, and establish the relationship of chain structure-chain tangle-technology parameter-crystal evolution-fiber performance, settle theory and experimental foundation of the exploration of low cost, new, high concentration gel-spinning technology.

本项目以UHMWPE纤维为示例，原位研究不同链缠结程度的高分子材料在拉伸流场下Shish-Kebab晶体结构的形成与演化，以发展和完善Shish-Kebab晶体形成演化的机理及影响材料性能的本质认识。本项目采用比现有工业生产所用树脂分子量低的UHMWPE树脂，通过改变纺丝液浓度来调节原纤维的缠结程度，并通过选用具有不同分子链支化度的树脂来微调链缠结，形成系列不同缠结程度的原纤维，利用上海光源小角线站的SAXS/WAXD联用技术，离线及在线研究不同缠结程度的UHMWPE原纤维在拉伸流场下Shish-Kebab晶体的形成与演化,认识上述结构变化对纤维力学性能的影响，从而揭示Shish-Kebab晶体的形成演化及其对材料性能影响的内在机理，建立链结构-链缠结-工艺参数-晶体演化-纤维性能之间的关系，为探索低成本化的新型高浓度冻胶纺丝工艺奠定理论和实验基础。

本项目对超高分子量聚乙烯（UHMWPE）纤维中试生产线不同工序的样品进行离线结构研究，分析了温度和拉伸比等工艺条件对Shish-Kebab晶体形成和演化的影响，确定了Shish-Kebab结构与纤维力学性能的关系；通过改变UHMWPE树脂的纺丝液浓度来调节纤维的缠结程度，形成系列不同缠结程度的各工序阶段纤维，利用上海光源的小角X射线散射和广角X射线衍射技术，原位研究了不同缠结程度的UHMWPE原纤维在拉伸流场下Shish-Kebab晶体的形成与演化，形成了低缠结和高缠结两种条件下Shish-Kebab晶体的形成与演化机理；通过研究UHMWPE/甲壳素纳米晶复合纤维中Shish-Kebab晶体的演化，发现纤维中的Shish-Kebab晶体的同步演化对提高原纤维可拉伸性和成品纤维力学性能有很大帮助；通过上述研究，基本建立了链结构-链缠结-工艺参数-晶体演化-纤维性能之间的关系，在此基础上探索了低成本化的高浓度冻胶纺丝工艺，通过工艺优化可以得到制备成本大幅度降低而且纤维力学性能下降不多的高浓度纺丝工艺。以上结果既能发展和完善Shish-Kebab晶体形成与演化的机理及影响材料性能的本质认识，也对探索低成本化的新型UHMWPE冻胶纺丝工艺提供了理论和实验基础。