A study of the mechanical anisotropy in shear of high‐draw, low‐draw, and voided poly(vinylidene fluoride)

Abstract

The mechanical anisotropy in shear of oriented from I poly(vinylidene fluoride) sheet has been studied, completing the measurement of all nine independent compliances for this material. The morphology is parallel‐crystallite; however, the crystalline regions are not lamellar in shape, but take the form of blocks with a bricklike shape oriented along the draw direction. The results have been analyzed in terms of a three‐dimensional generalization of the Takayanagi model. First, modelling of the three principal extensional compliances based on previous measurements indicates that the gaps between the crystalline units are smaller in the transverse directions than in the draw direction. A voided sample shows a marked increase in the transverse compliances of the amorphous regions and considerable anisotropy owing to the voids. Secondly, a novel development of the Takayanagi model has been made to analyze the shear behavior. This has enabled the calculation of the shear compliances of the amorphous regions and indicates that the larger magnitude of the shear compliance in the plane normal to the draw direction is due to the large magnitude of the corresponding amorphous shear compliance, and that this is not affected by increased draw ratio or by the voids.

Frequency dependence of hysteresis associated with the electromechanical performance of PVDF film

“…The randomly oriented crystallites exist predominantly in the polar ferroelectric Form I (or β) form as indicated by a strong reflection at 2 θ = 21.2° in the wide angle X‐ray diffraction spectrum. The morphology of drawn PVDF film has been described as parallel–crystallite where crystallites take the form of blocks with a bricklike shape oriented along the draw direction 27…”

The structure and properties of block poly(vinylidene fluoride) and systems based on it

“…154 Certain details of the formation of the voids in the cold drawing (T d = 80 °C) of PVDF have been investigated by Kochervinskii et al 47 Attention was drawn to the fact that the probability of the formation of voids under identical cold drawing conditions may depend significantly on the nature of the initial supermolecular structure. Two PVDF films, obtained by quenching from the melt and by slow crystallisation, were investigated.…”

Polarization Build-Up and Relaxation Phenomena in Corona Poled Ferroelectric Polymers

“…Рассчитаем плотность компенсирующих зарядов, предполагая, что их захват наиболее вероятен на границах поляризованных кристаллитов [15,19]. Учитывая, что ПВДФ имеет кирпичеподобную структуру [23], получаем для плотности зарядов…”