Flex life of tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer (PFA)
View Patent ↗A process is provided for improving the MIT flex life of tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer, said perfluoroalkyl containing from 1 to 5 carbon atoms, comprising incorporating melt flowable polytetrafluoroethylene into said copolymer and thereafter heat treating the resultant composition at a temperature of at least 280° C., the amount of said polytetrafluoroethylene and said heat treatment being effective to increase the flex life of said composition by at least 2× the flex life of both said copolymer and said composition prior to said heat treatment and to thermally transform the composition in the solid state, which is epitaxial co-crystallization of the polymer components of the composition.
1. Process for improving the MIT flex life of tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer, said perfluoroalkyl containing from 1 to 5 carbon atoms, comprising incorporating at least 15 wt % melt flowable polytetrafluoroethylene into said copolymer and thereafter heat treating the resultant composition in the solid state at a temperature of at least 280° C. to increase the flex life of said composition by at least 2× the flex life of said copolymer prior to said heat treatment.
2. Process of claim 1 wherein the amount of said melt flowable polytetrafluoroethylene is 15 to 35 wt % based on the total weight of said composition.
3. Process of claim 1 wherein said heat treatment is carried out at for at least 24 hr.
4. Process of claim 1 wherein said heat treatment is carried out at a temperature of at least 300° C. for at least 2 days.
5. Process of claim 1 wherein the effect of the incorporation of said polytetrafluoroethylene into said copolymer on said flex life prior to said heat treatment is to decrease said flex life of said composition.
6. Process of claim 1 wherein said resultant composition is melt fabricated into an article and it is said article that is subjected to said heat treatment.
7. Process of claim 1 wherein the melt flow rate of said copolymer is at least 5 g/10 min.
8. Process of claim 1 wherein the melt flow rate of said copolymer is at least 6 g/10 min.
9. Process of claim 8 wherein the melt flow rate of said copolymer is no greater than 50 g/10 min.
10. Process of claim 2 wherein said heat treatment is carried out for at least 24 hours.
11. Process of claim 1 wherein said heat treatment is carried out at a temperature of at least 310° C.
12. Process of claim 1 wherein the amount of said melt flowable polytetrafluoroethylene is at least 18 wt % based on the total weight of said composition.
13. Process of claim 12 wherein the amount of said melt flowable polytetrafluoroethylene is at least 20 wt % based on the total weight of said composition.
14. Process of claim 1 wherein the amount of said melt flowable polytetrafluoroethylene is no more than 50 wt % based on the total weight of said composition.