Structures, electrical, and dielectric properties of PVDF-based nanocomposite films reinforced with neat multi-walled carbon nanotube

Abstract

We report, herein, on the structures, melting/crystallization, electrical, and dielectric properties of poly (vinylidene fluoride) (PVDF) nanocomposites reinforced with a neat multiwalled carbon nanotube (MWCNT). For our purposes, PVDF/MWCNT nanocomposite films with a wide range of MWCNT contents (0.0–20.0 wt%) are prepared via ultrasonicated solution-mixing and melt-compression methods. It is found that MWCNTs become well dispersed in nanocomposites by wrapping them with PVDF chains. The relative content of β-phase to α-phase crystals of a PVDF matrix is higher for the nanocomposite films with higher MWCNT content; although, the overall crystallinity of the nanocomposites is almost identical, irrespective of the MWCNT content. The electrical conductivity and dielectric permittivity of the nanocomposites as a function of frequency are strongly dependent on the MWCNT content. The electrical percolation threshold of PVDF/MWCNT nanocomposites is formed between 2.0 and 5.0 wt% MWCNT. The neat PVDF and nanocomposites with low MWCNT contents of 0.2 and 1.0 wt% are electrically insulating materials (∼10⁻⁹ S/cm at 10² Hz) with low dielectric permittivity of 9–28; while the nanocomposites with high MWCNT contents of 5.0–20.0 wt% have relatively high electrical conductivity values (10⁻⁴∼10⁻² S/cm at 10² Hz). In contrast, the nanocomposite with 2.0 wt% MWCNT has a huge dielectric permittivity of ∼6520 at 10² Hz, although it has relatively low electrical conductivity of ∼10⁻⁸ S/cm at 10² Hz. The huge dielectric permittivity of the nanocomposite with 2.0 wt% MWCNT could be caused by charge accumulation at the interfacial layers between PVDF chains and MWCNTs in the vicinity of the electrical percolation threshold.