Importance

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Abstract

A method for preparing thin fluoropolymer (PTFE) films, said method generally having the steps of: a) providing an unsintered fluoropolymer film; b) pre-sintering expansion of the film; c) sintering the expanded film with dimensional restraint to prevent shrinkage; and d) post-sintering stretching of the film to a final thickness preferably less than 0.002 inches. The post-sintering stretching of the film in step d may be accomplished in a single step, or may include a series of post-sintering stretching steps. Steps b and c of the method may be carried out bypassing the calendared film through a machine direction orienter device and, thereafter, step d of the method may be accomplished by subsequently repassing the sintered film through the machine direction orienter device, one or more additional times.

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First Claim