Dielectric constant of rolled polyvinylidene fluoride

Abstract

The contribution of dipole orientation to dielectric constant is markedly affected by rolling. The intensity of the γ peak is increased and the maximum shifted slightly to higher temperatures and frequencies. The shift is much larger with the β peak. Its intensity, however, is reduced by rolling. Long before the maximum of the β peak is reached, annealing effects irreversibly change the sample. With annealing, the values of the dielectric constant gradually approach those of the unrolled material. The observed effects can be explained by a substantial orientation of chains in the roll plane, which is perpendicular to the applied electric field. Such an orientation increases the average contribution of dipoles in crystal defects to polarisation as observed in the γ peak. Stronger interaction between partially aligned chains in the amorphous matrix hampers the rotation of chain segments in the electric field, and hence reduces the β peak and shifts it to higher temperatures.