Piezoelectric properties of the oriented porous poly(vynilidene) fluoride films

The piezoactive porous poly(vynilidene) fluoride films are prepared in the process based on melt extrusion. It is shown that the orientation efforts at the uniaxial extension stages initiate polymorphous transition and the pore formation, both. It was observed that β-phase percentage increases with enhancement of uniaxial extension degree but a growth of melt draw ratio at the extrusion stage reduces the effectiveness of polymorphous transition at uniaxial extension. The samples were polarized by high voltage contact method and also by corona discharge. The influence of polarization conditions on piezomodulus d31 of the films was investigated. It is demonstrated that polarization by corona discharge is more effective than by high voltage polarization.