Investigation of morphology, crystallinity, thermal stability, piezoelectricity and conductivity of PVDF nanocomposites reinforced with epoxy functionalized MWCNTs

Abstract

In order to improve the dispersion state of multi-walled carbon nanotubes (MWCNTs) and to get a synergistic effect when incorporated in polyvinylidene flouride (PVDF) matrix, multi-walled carbon nanotubes (MWCNTs) were oxidized and then grafted with di-glycidyl ether of bisphenol-A (DGEBA) by a linker moiety, hexamethylene diamine (HMD). Modified MWCNTs (HD-MWCNTs) with various concentrations of 1.0 wt% to 10 wt% were incorporated in polyvinylidene fluoride (PVDF) matrix for the fabrication of polymeric nanocomposites (PVDF/HD-MWCNTs). Compared to pristine MWCNTs (P-MWCNTs), the structural and thermal analysis of both modified MWCNTs showed a well crystalline structure with a uniform tubular morphology as well as uniform and improved dispersion was achieved in their nanocomposites with PVDF. Enhanced dispersion is attributed to a strong interfacial interaction of the modified MWCNTs with polymer chains of PVDF. Therefore, by thermal analysis of PVDF/HD-MWCNTs nanocomposites both melting temperature (Tm) and temperature of crystallization (Tc) have revealed the uniform distribution of nanotubes and enhancement of heterogeneous nucleating effect leading to formation of β-phase which is in complete agreement with SEM, FTIR, XRD, TGA and d33 value. Piezoelectric and electrical conductivity values measured for PVDF/HD-MWCNTs nanocomposites were observed to rise with increase in concentration of HD-MWCNTs up to 5 wt% where the percolation threshold (fc) is attained. PVDF/HD-MWCNTs nanocomposite with highest electrical conductivity of 1.13 x 10−3 Scm−1 at filler loading of 5 wt% was successfully achieved. These simultaneous improvement in properties anticipate that PVDF/HD-MWCNTs nanocomposites can be useful for variety of energy applications.