Patent ID: 7276287

Claim:
Method for producing an article from a PTFE composition via melt processing comprising the steps of: i) heating the PTFE composition to above its crystalline melting temperature, said crystalline melting temperature being in the range of about 320° C. to about 335° C.; ii) shaping the melt into the desired form under processing conditions involving extensional or shear flow, said shaping the melt including injection molding, iii) cooling the composition below the crystalline melting temperature, to obtain an article which displays orientation of the polymer molecules such that upon heating to a temperature that is 10° C. above its melting temperature, after melting the article displays a change in size of at least 5% in at least one dimension wherein the PTFE composition comprises a melt-processable tetrafluoroethylene polymer or a blend of two tetrafluoroethylene polymers, said polymer or polymer blend having a strain at break of greater than 10% or a stress at break of greater than 15 MPa (at room temperature and a strain rate of 100% min) an amount of co-monomer less than 1 mol %, said co-monomer being selected from hexafluoropropylene, perfluoro(alkyl vinyl ether), and perfluoro-(2,2-dimethyl-1,3-dioxole); a melt-flow index (according to ASTM D 1238-88 at 380° C. under a 21.6 kg load) of greater than 0.25 g/10 min, and less than 75 g/10 min.