Field induced structure transition in poly (vinylidene fluoride)

Uniaxially stretched poly (vinylidene fluoride) (PVDF) films containing β-phase only or both α and β-phases as well as 12/um biaxially oriented commercial PVDF-films were investigated by means of modified x-ray and infrared techniques. The structural changes were examined in response to the applied poling field (≤ 450 MV/m) and the poling temperature at various levels. The changes in the orientation state determined by pole figure measurements, the various crystal phase transitions, the conformational conversion TGTS in TT, and the increase of ciystallinity in the β-phase were discussed in comparison with the piezoelectric strain and stress coefficients d31 and e31.