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Poly(vinylidenefluoride-trifluoroethylene)-based (P(VDF-TrFE)-based) terpolymers represent a new class of electroactive polymer materials that are relaxor-ferroelectric (RF) polymers and that offer unique and attractive property combinations in comparison with conventional ferroelectric polymers. The RF state is achieved by introducing a fluorine-containing termonomer as a “defect” into the ferroelectric P(VDF-TrFE) copolymer, which reduces the interaction between the VDF/TrFE dipoles. The resulting terpolymer exhibits a low Curie transition temperature and small remanent and coercive fields yielding a slim hysteresis loop that is typical for RF materials. Though the macroscopic behavior is similar to RF ceramics, the mechanisms of relaxor ferroelectricity in semi-crystalline polymers are different and not fully understood yet. Structure-property relationships play an important role in RF terpolymers, as they govern the final RF properties. Hence, a review of important characteristics, previous studies and relevant developments of P(VDF-TrFE)-based terfluoropolymers with either chlorofluoroethylene (CFE) or chlorotrifluoroethylene (CTFE) as the termonomer is deemed useful. The role of the termonomer and of its composition, as well as the effects of the processing conditions on the semi-crystalline structure which in turn affects the final RF properties are discussed in detail. In addition, the presence of noteworthy transition(s) in the mid-temperature range and the influence of preparation conditions on those transitions are reviewed. A better understanding of the fundamental aspects affecting the semi-crystalline structures will help to elucidate the nature of RF activity in VDF-based terpolymers and also help to further improve their applications-relevant electroactive properties. ispartof: FERROELECTRICS vol:586 issue:1 pages:60-81 status: published

This paper presents a step-wise poling method of a Vinylidene Fluoride TriFluoroEthylene (VDF/TrFE) copolymer film. A 1 μm VDF/TrFE copolymer layer is deposited on a silicon substrate using a spin-coating technique. After a poling treatment the unstretched copolymer will be pyroelectric. The step-wise poling that allows fractional poling is compatible with semiconductor technology and performed at room temperature.

The inverse photopyroelectric technique (IPPE) was adapted for the measurement of the thermal effusivity of resins during isothermal curing. The pyroelectric sensor consisted of a 9 μm PVDF film heated by a modulated laser beam and coated with a thick layer of uncured epoxy. From the high frequency part of the pyroelectric spectra of this bilayer the sensitivity of the pyroelectric detector was determined, while from the low frequency part the sample's effusivity (cρk)1/2 was found. The isothermal crosslinking of an DGEBA-based epoxy with DDM was studied at cure temperatures between 38 and 60°C. The thermal effusivity shows a marked increase until it drops when the rubber to glass transition is passed, i.e. when the network formed vitrifies to its glassy state. Concurrent results from modulated differential scanning calorimetry (MDSC) showed that the increase in the effusivity by up to 30% is mainly caused by the increase in thermal conductivity due to the crosslinking, while the stepwise decrease should ...

The built-up of the spatial polarization distribution in thin poly(vinylidene fluoride) film samples was investigated for different poling field strength using the Laser Intensity Modulation Method (LIMM).1