ROOM-TEMPERATURE TRANSITIONS AND MELTING OF TETRAFLUOROETHYLENE-HEXAFLUOROPROPYLENE COPOLYMERS WITH LOW COMONOMER CONTENTS

Differential scanning calorimetry has been used to study the room-temp erature transitions and melting of native and melt-crystallized tetraf luoroethylene-hexafluoropropylene (TFE-HFP) copolymers from aqueous di spersion polymerization, with low comonomer contents (between 0.15 and 0.8 mol% of HFP). At least three clear room-temperature transitions a re observed for the native polymers suggesting, according to previous evidence, the coexistence of two crystalline components. Also the beha viour after annealing at the melting temperature of the melt-crystalli zed samples has been investigated. Conclusions are drawn concerning th e morphology of the native and melt-crystallized polymers. An interpre tation of the melting peaks in the light of the suggestions given by t he room-temperature transitions is suggested.