高压“喷射流”法制备超高分子量聚乙烯微孔材料的机理研究

There are some defects in the traditional UHMWPE microporous materials processing methods including powder sintering, such as a long process, low efficiency, high energy consumption. In this project the High Pressure “Jet Flow” Method is first proposed，that is, by use of unique “jet flow” die flow characteristic of UHMWPE, the secondary particles generated under high injection pressure act as the basic elements, and the porous structure is quickly formed in mold cavity by non-compact compressure and accumulation of these particles. Aided by observation and quantitative characterization, from the view of viscoelastic rheology, the forming mechanism of “Jet Flow” and control of the morphology of the particles will be discovered; on basis of visualized observation on morphology transformation of “Jet Flow” particles during compressing, the physics and mathematics model for dynamic accumulation of “Jet Flow” particles will be established by Discrete Element Method of mechanics of granular media, and with combination to condensed matter physics, the special pore-forming mechanism will be revealed. Then the relationship between the material, technology parameters, devices and micropore structure and properties will be explored in detail, and therefore the control theory for preparation of UHMWPE microporous materials by High Pressure “Jet Flow” method will be founded. Due to the success of this project, a novel method with high efficiency, energy saving and environmentally friendly will be invented in the field of preparation of UHMWPE microporous material, which could promote the development of polymer microporous material processing industry.

传统的粉末烧结法等UHMWPE微孔材料制备方法存在流程长、效率低、能耗高等不足。本项目首次提出高压“喷射流”法，利用UHMWPE独特的“喷射流”口模流动特性，以高压注射下生成的“喷射流”二次粒子为单元，通过模内非致密压缩堆积而快速形成孔隙结构。拟借助观测和定量表征，从粘弹流变特性出发，探明UHMWPE“喷射流”形成机理及颗粒形态结构的调控机制；在对“喷射流”颗粒压缩运动过程中形态结构演化的可视化观测基础上，采用散体动力学的离散元法对“喷射流”颗粒的动态堆积成孔行为建立物理数学模型，结合凝聚态结构分析，揭示其独特动态成孔机制；深入探讨物料体系、工艺参数、关键机械结构参数与微孔结构、性能的关联，从而建立高压“喷射流”法制备UHMWPE微孔材料的孔隙结构、性能调控理论。本项目成功后，将在UHMWPE微孔材料制备领域开创一种高效、节能、环保的新方法，有望推动聚合物微孔材料加工工业的进步。

传统的间歇式粉末烧结法制备超高分子量聚乙烯（UHMWPE）微孔材料，存在流程复杂、周期长、效率低、劳动强度大、能耗高、环保性差等缺陷。本项目巧妙地对UHMWPE独特的“喷射流”口模流动特性加以利用，以高压“喷射流”注射压缩法工艺，使注塑机喷嘴射出的“喷射流”颗粒在模具型腔内通过压缩粘结堆积而形成孔隙结构。.通过UHMWPE熔体在可视化喷嘴流道内流动的在线观察，结合粘弹流变性分析，提出了高压“喷射流”演变过程的六阶段模型和三种条件下的熔体破裂及“喷射流”形成机理，从而揭示了UHMWPE“喷射流”现象产生的内在机理；通过研究工艺参数、流道参数、原料体系分子量对“喷射流”粒子微观形态和粒径分布的影响，得到了形成理想“喷射流”二次粒子的较佳参数；通过“喷射流”颗粒在可视化注射压缩模具型腔内运动的在线观察，建立了“喷射流”颗粒充模与压缩堆积成孔的七阶段动态演化模型和“喷射流”颗粒堆积行为的软球碰撞物理数学模型；结合流变特性、凝聚态结构分析及对粉末烧结法成孔过程的可视化观察和比较，建立了不同于粉末烧结法静态成孔的动态成孔机制；深入研究了物料体系（分子量、交联）、工艺参数、模具结构（注射方向）与试样微孔结构、性能的内在关联，从而建立起高压“喷射流”法制备UHMWPE微孔材料的孔隙结构、性能调控理论，最终成功地制得了孔隙结构和性能优于现有商业化粉末烧结法UHMWPE滤芯的注塑微孔试样（平均孔径为12.66μm、孔隙率为42.03%），由此开创了一种替代传统粉末烧结法的全新而独特的微孔材料先进制备方法，为开辟自动化程度高、高效、节能、环保的新型微孔材料制备技术在过滤领域的工业化应用奠定了坚实的理论基础，具有极为重要的科学意义和广阔的应用前景。.