Nonlinear piezoelectricity in oriented films of PVDF and its copolymers

The nonlinear Piezoelectric constant for the stretched and poled films of polyvinylidene fluoride (PVDF) and (75/25) copolymer of vinylidene fluoride and trifluoroethylene has been determined by measuring the second harmonic component of polarization under sinusoidal stress. The constant increased above the glass transition temperature. A simple interpretation for the mechanism of nonlinear piezoelectricity is presented assuming the residual polarization is decreased by applying the tension perpendicular to the molecular chain axis.<
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