POLYTETRAFLUOROETHYLENE POROUS FILM AND PREPARATION AND USE THEREOF

摘要

A polytetrafluoroethylene porous film, which is prepared by stretching a semisintered polytetrafluoroethylene material and heating the stretched material at a temperature higher than the melting point of sintered polytetrafluoroethylene, has an area ratio of fibrils to nodes of from 99:1 to 75:25, an average fibril diameter of from 0.05 to 0.2 .mu.m, a largest node area of not larger than 2 .mu.m2 and an average pore size of from 0.2 to 0.5 .mu.m and achieves low pressure loss.