The crystalline phase transformation of poly(vinylidene fluoride)/poly(vinyl fluoride) blend films

Abstract

AbstractPoly(vinylidene fluoride) (PVDF), poly(vinyl fluoride) (PVF), and their blends were prepared by solution casting, followed by quenching in ice water after melting to obtain an α‐crystalline phase. The films were drawn by solid state extrusion at two different drawing temperatures, 50°C and 110°C. The crystalline phases were analyzed by DSC and FTIR. In the undrawn films, the content of β‐crystalline phase in the blend of PVDF/PVF 88.5/11.5 was higher than in the PVDF homopolymer, but it was lower than in the PVDF film with a draw ratio higher than 4. The α‐crystalline phase in PVDF/PVF blends was mostly transformed into the β‐crystalline phase beyond a draw ratio of 4, regardless of the draw temperature and PVF content. The α‐crystalline phase of PVDF systematically transformed into the β‐crystalline phase with increasing draw ratio. The crystallinity of PVDF/PVF blend films drawn at 110°C was higher than those drawn at 50°C. In the drawn blend films, characteristic IR bands of the α form were shifted to those of the β form and completely changed into those of β form at draw ratio of 4, regardless of the draw temperature and PVF content.