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

Abstract 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 α to β 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 α c crystalline relaxation, attributed to intracrystalline molecular motions, strongly impacts the deformation behavior. In the high temperature domain, where all mobilities related to the α c relaxation are unlocked, plasticity occurs by crystal block shearing and subsequent fibrillation, while within the α 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.