Patent ID: 8236898

Claim:
A method for forming a melt-mixed composition, comprising melt mixing: (i) submicrometer-size particles comprising non-melt flowable polytetrafluoroethylene and particles comprising melt-fabricable perfluoropolymer, or (ii) submicrometer-size core/shell particles having a non-melt flowable polytetrafluoroethylene core and a melt-fabricable perfluoropolymer shell, at a shear rate of at least about 75 s −1 , wherein said melt-fabricable perfluoropolymer has a melt flow rate of from about 0.1 to 500 g/10 min as measured in accordance with Table 2 of ASTM D-1238-94a, wherein said non-melt flowable polytetrafluoroethylene has a melt creep viscosity of at least 1×10 6 Pa·s at 380° C. and constitutes at least about 4 wt % of the combined weight of said non-melt flowable polytetrafluoroethylene and said melt-fabricable perfluoropolymer, wherein said melt-mixed composition comprises a dispersion of said submicrometer-size particles comprising non-melt flowable polytetrafluoroethylene in a continuous phase comprising said melt-fabricable perfluoropolymer, and wherein said melt-mixed composition exhibits thixotropy when being subjected to increasing shear in the molten state.