Structure Control of polymeric porous Membranes by Mechanical Operations

多孔结构被证明是通过在高压下对组装的PTFE微粒进行拉伸操作而形成的。多孔结构的特征在于周期性循环，其沿着几个典型的机械操作参数变化。通过在两个相互垂直的方向上进行的两步拉伸操作，孔隙率大大提高。多孔结构作为与第一拉伸操作平行产生的两个相邻原纤维结构之间的狭缝状空隙提供。拉伸操作的物理过程被简化为一个流变学模型，并讨论了原纤结构的形成与起始PTFE材料的分子结构的密切关系。拉伸操作也尝试了通用聚合物（PE）和拉伸操作中的精确的温度控制是必不可少的。

A porous structure was shown to be formed by a stretching operation on the assembled PTFE microparticles into a sheet at a high pressure. The porous structure was well characterized by a periodical cycle, which was varied along several typical parameters of the mechanical operations. The porosity was greatly enhanced by the two-step stretching operation done in two directions perpendicular to each other. The porous structure was provided as a slit-like void between two adjoining fibril structures yielded in parallel with the first stretching operation. The physical process of the stretching operation was simplified into a rheological model and the formation of the fibril structure was discussed in a close relation with the molecular structure of the starting PTFE material. The stretching operation was also attempted to a general-purpose polymer (PE) and an accurate temperature control in the stretching operation was revealed to be indispensable.