Melting and crystallization of poly(vinylidene fluride) under high pressure

Abstract

Abstract Precise melting and crystallization temperatures of extended‐chain and folded‐chain crystals of form I and folded‐chain crystals of form II poly(vinylidene fluoride) under high pressure have been obtained by microdifferential thermal analysis (DTA). Upon heating at pressures above 4000 kg/cm 2 , the micro‐DTA thermogram of form II crystallized from the melt at atmospheric pressure shows melting of the form II structure and the melting of the folded‐chain and extended‐chain crystals of form I, formed through recrystallization processes. These features were clarified by supplemental methods. The bandwidth seen in electron micrographs of the extended‐chain crystal of form I obtained by crystallization under high pressure was in the range of 1500 to 2000 Å. At atmospheric pressure, the extended‐chain crystal of form I melted at 207°C, approximately 17°C higher than the folded‐chain crystal of form I and 31°C higher than the folded‐chain crystal of form II.