| abstract |
In a polytetrafluoroethylene oriented porous film provided by the present invention, the through-thickness air permeability, expressed as Frazier air permeability, is 4 cm3/(sec·cm2) or greater, and the total cohesive strength, as expressed by the product of the cohesive peel strength in an in-plane first direction and the cohesive peel strength in a second direction orthogonal in-plane to the first direction, is 1.9 (N/20 mm)2 or greater. The oriented porous film is highly air permeable, and yet, when incorporated into a filter member, for example, resists damage during handling or placement of said member in a housing or the like. |