Enhanced electroactive β phase in three phase PVDF/CaCO₃/nanoclay composites: Effect of micro‐CaCO₃ and uniaxial stretching

Abstract

ABSTRACT In this study, electroactive polar phase transformation and crystallinity of poly(vinylidene fluoride) (PVDF)‐based composites, such as PVDF/CaCO 3 /nanoclay, is explored as a function of micro‐CaCO 3 fraction and draw ratio ( R ) of uniaxial stretching. Composites including PVDF/clay, PVDF/CaCO 3 and most importantly PVDF/CaCO 3 /clay with varying fraction of micro‐CaCO 3 were extruded into homogenous and flexible cast films. Characterization via Fourier transform infrared spectroscopy, X‐ray diffraction, and differential scanning calorimetry (DSC) confirmed the presence of β phase in all the composites incorporated with micro‐CaCO 3 and nanoclay either individually (i.e., PVDF/CaCO 3 and PVDF/clay films, respectively) or together (i.e., PVDF/CaCO 3 /nanoclay composites). Interestingly, a gradual but significant improvement in this electroactive phase (β phase) was obtained with successive increment in CaCO 3 content into a fixed composition of PVDF and nanoclay (PVDF/CaCO 3 /clay composites). Further increment in β phase content was obtained via uniaxial stretching to different draw ratios and at a temperature of 90 °C, where for PVDF/CaCO 3 /clay (especially, 100–35‐3 and 100–40‐3) samples almost no α phase was observed irrespective of R . Conversely, the crystallinity of melt extruded samples decreased gradually all the way with CaCO 3 concentration in PVDF/CaCO 3 /clay composites compared to the neat PVDF while increased gradually with increasing draw ratio. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44940.