Polytetrafluoroethylene porous film and preparation and use thereof.

摘要

A porous polytetrafluoroethylene film which is obtainable by biaxially stretching a semisintered polytetrafluoroethylene (PTFE) material having a sintering degree ( DELTA H1- DELTA H3)/( DELTA H1- DELTA H2) of 0.30 to 0.80 (wherein DELTA H1 is the heat of fusion of the unsintered PTFE material, DELTA H2 is the heat of fusion of the sintered PTFE material and DELTA H3 is the heat of fusion of the semisintered PTFE material), at an area draw ratio of at least 50 and heat setting the stretched film at a temperature higher than the melting point of sintered polytetrafluoroethylene.