COCRYSTALLIZATION AND MISCIBILITY IN BLENDS OF VINYLIDENE FLUORIDE-TETRAFLUOROETHYLENE AND VINYLIDENE FLUORIDE-HEXAFLUOROACETONE COPOLYMERS

Differential scanning calorimetric and dynamic mechanical analyses were carried out to investigate the melting behavior and miscibility of blends of vinylidene fluoride-tetrafluoroethylene and vinylidene fluoride-hexafluoroacetone copolymers, both polymers being crystalline. Blends showed a different melting behavior with the annealing temperature; single or double melting peaks were observed on annealing over an entire blend composition. They were ascribed to the cocrystallization or separate crystallization of blends, respectively. On the other hand, annealing of quenched samples affected the glass transition behavior of blends; single or double glass transition temperatures were observed depending on the annealing condition in the dynamic mechanical measurements. It was well explained with the miscibility of amorphous phases of blends at annealing temperature. Consequently it was found that the cocrystallization in the blends could be occurred in the miscible amorphous phases. Particularly this blend system showed the upper critical solution temperature (UCST) behavior in both the crystalline and amorphous phases; it was almost rare phenomenon that the polymer blends showed UCST behavior.