Structure Control of polymeric porous Membranes by Mechanical Operations

在高压下将聚四氟乙烯微粒拉伸成片状，即可形成多孔结构。这种多孔结构具有周期性循环的特点，这种周期性循环随机械操作的几个典型参数而变化。在相互垂直的两个方向上进行两步拉伸操作，大大提高了孔隙率。该多孔结构被提供为在与第一次拉伸操作平行地屈服的两个相邻纤维结构之间的狭缝状空隙。将拉伸操作的物理过程简化为流变学模型，并讨论了原丝结构的形成与起始聚四氟乙烯材料的分子结构密切相关。还尝试了对一种通用聚合物(PE)的拉伸操作，发现在拉伸操作中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.