A STUDY OF THE FERROELECTRIC PHASE-TRANSITION OF VINYLIDENE FLUORIDE-TRIFLUOROETHYLENE COPOLYMERS BY AC CALORIMETRY

The ferroelectric phase transition in vinylidene fluoride-trifluoroethylene (VDF-TrFE) random copolymers was studied by ac calorimetry (ACC) and differential scanning calorimetry (DSC). By this combined approach, a higher-order component of the phase transition in the VDF 52% copolymer was separated successfully as a symmetric heat capacity peak with a response faster than 3.6 Hz. The ACC thermogram of the VDF 65% copolymer does not show any heat capacity peak. This disappearance of heat capacity peaks is interpreted in terms of the Martensitic transition. A method of obtaining the kinetic constant of the phase transition from the heating frequency dependence of sample heat capacity is also proposed. On the basis of this method, a value of the kinetic constant for the slower component of the phase transition in the VDF 52% copolymer was determined to be 2 s.