In situ SAXS/WAXS investigation of the structural evolution of poly(vinylidene fluoride) upon uniaxial stretching

The structural evolution of PVDF upon uniaxial stretching has been investigated by means of in situ SAXS/WAXS experiments. Special attention has been paid to the change in plastic deformation mechanisms as a function of draw temperature. Of prime importance with respect to electroactive properties, the present study confirms that the a to beta crystal phase transformation occurs in the whole temperature range between T-g and T-m. However two different plasticity mechanisms are evidenced. In fact, the alpha(c) crystalline relaxation, attributed to intracrystalline molecular motions, strongly impacts the deformation behavior. In the high temperature domain, where all mobilities related to the alpha(c) relaxation are unlocked, plasticity occurs by crystal block shearing and subsequent fibrillation, while within the alpha(c) transition range cavitational modes interfere with the fibrillation process, at the expense of global ductility. A morphological evolution scheme is proposed in the light of the in situ SAXS/WAXS data. (C) 2015 Elsevier Ltd. All rights reserved.