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Polyvinylidene fluoride was dissolved together with solid sodium hydroxide as catalyst in a dimethylsulfoxide/ acetone mixture and moderately dehydrofluorinated. The dehydrofluorination leads to a partial degradation of the fluorohydrocarbons, and in particular to main-chain scission and to formation of carbon double or triple bonds. This enhances the absorption at UV-vis frequencies. The degradation process also generates a large amount of excess charges in the polymer, which influence the electrical polarization behavior of the dehydrofluorinated polymer. Uniaxial stretching of moderately dehydrofluorinated polyvinylidene fluoride leads to films in a polar phase. Dipole polarization in the degraded and stretched films is demonstrated by means of switching experiments
Piezo-, pyro- and ferroelectricity in poly (vinylidene fluoride-hexafluoropropylene) copolymer films
(2004)
Thin films of poly(vinylidene fluoride-hexafluoropropylene) P(VDF-HFP) show significant electroactive properties, such as piezoelectricity, pyroelectricity and electrostriction. Suitable polar P(VDF-HFP) copolymer films can be prepared by melt-pressing or solution-casting. Dipolar orientation causes the macroscopic polarization and thus also the symmetry breaking necessary for electroactive properties. We discuss the polarization build-up in thin, stretched and non-stretched, films of P(VDF-HFP) copolymer with a HFP content of 15%. Poling currents measured in-situ during electric poling are analyzed and the polarization is calculated. Suitable electric poling leads to hysteresis phenomena of the polarization as a function of the electric field as well as to significant polarization during switching experiments. Our results indicate dipolar orientation also in non-stretched P(VDF-HFP) films