Miscibility and cocrystallization behavior of two melt-processable random copolymers of tetrafluoroethylene and perfluoroalkylvinylether

Miscibility, crystallization behavior, and mechanical properties of blends made from melt-processsble perfluoropolymers of poly(tetra-fluoroethylene-c o-perfluoropropylvinylether) (PFA) and poly(tetrafluoroethylene-co-perfluor oethylvinylether) (EFA) have been examined by differential scanning calorim etry (DSC) and dynamic mechanical analysis (DMA). PFA and EFA (PEVE comonom er:5.7 wt%) blends cocrystallize regardless of crystallization speed and bl ending method. On the other hand, PFA/EFA blends that contain EFA with high PEVE comonomer content (PEVE: 13.3 wt%) formed segregated crystals. Howeve r, these blends [PFA/EFA (PEVE:13.3%)] showed a composition dependent singl e alpha -relaxation temperature which suggests that they are miscible in th e amorphous phase. Therefore, it is concluded that PFA/EFA blends are misci ble in the amorphous or molten state, they form segregated crystals during crystallization. In contrast, EFA containing low PEVE content form cocrysta ls with PFA from the melt. Measuring the hex life (folding endurance) of th e blends revealed that only 20% EFA (PEVE: 13.3%) is required to increase t he hex life of neat PFA by four times. (C) 2001 Elsevier Science Ltd. All r ights reserved.