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

Abstract

ABSTRACTIn this study, electroactive polar phase transformation and crystallinity of poly(vinylidene fluoride) (PVDF)‐based composites, such as PVDF/CaCO3/nanoclay, is explored as a function of micro‐CaCO3 fraction and draw ratio (R) of uniaxial stretching. Composites including PVDF/clay, PVDF/CaCO3 and most importantly PVDF/CaCO3/clay with varying fraction of micro‐CaCO3 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‐CaCO3 and nanoclay either individually (i.e., PVDF/CaCO3 and PVDF/clay films, respectively) or together (i.e., PVDF/CaCO3/nanoclay composites). Interestingly, a gradual but significant improvement in this electroactive phase (β phase) was obtained with successive increment in CaCO3 content into a fixed composition of PVDF and nanoclay (PVDF/CaCO3/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/CaCO3/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 CaCO3 concentration in PVDF/CaCO3/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.