Patent ID: 6984697

Claim:
A method of improving stress crack resistance comprising the steps of: a) providing a fluorothermoplastic composition comprising interpolymerized units derived from: about 94 to about 97.5 mole percent (mol %) tetrafluoroethylene (TFE); about 2 to about 3 mol % perfluoro (propyl vinyl ether) (PPVE); and about 0.5 to about 3 mol % hexafluoropropylene (HFP); wherein the fluorothermoplastic lacks a significant melt peak above 300° C. as measured via differential scanning calorimetry (DSC), and/or a number of double flexure cycles to failure that fits the equation: log(flex life cycles)≧0.71+4.0*(MFI (−0.294) ); b) shaping an article from the composition; and c) exposing the article to a stress cracking agent.