Effect of extrusion process and various elongation ratios on the structural and dielectric properties of PVDF-based copolymer containing micro and nano-sized crystallites

Abstract

In this contribution, the effect of the extrusion process of the poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) with the subsequent elongation/poling on its structural and dielectric properties is presented. The extrusion can be understood as continuous processing of polymer melts in the large scale (in comparison to solvent casting), when the thickness of the final product can be varied depending on the final operation conditions. Herein, the PVDF-co-HFP sheets of 5 cm in width were extruded using a single screw extruder. The fabricated sheets were cooled down and then, they were cut to the stripes and subsequently stretched to various elongations (100, 200 and 500 %) using a universal tensile testing machine. Such samples were investigated using FTIR in order to determine the effect of the elongation process on the transformation of the alpha-phase to the beta-crystalline phase. The extend of the electro-active beta-phase was quantified and its impact on the dielectric properties was investigated. The results clearly demonstrated that the elongation has a crucial effect on the final dielectric properties of the PVDF-co-HFP.