Mechanical and dielectric properties of MWCNT filled chemically modified SBS/PVDF blends

Abstract

The dielectric properties of styrene-butadiene-styrene block copolymer (SBS) were modified by two methods, covalently grafting polar methyl thioglycolate to the SBS main chains via thiol-ene click chemistry (MGSBS) and fabrication of nanocomposites by melt-blending with poly(vinylidene fluoride) (PVDF) and multi-walled carbon nanotubes (MWCNTs). The methyl thioglycolate pendant groups enhanced the dielectric permittivity of SBS from 4.4 to 11.8 at 1 kHz, ascribed to the increased dipole content of the SBS matrix under the applied electric field. The subsequent modification of MGSBS:PVDF:MWCNT composites at (69.5:29.5:1) wt% showed a maximum dielectric permittivity of 24.3 at 1 kHz along with a lower tensile strength and a higher elongation at break compared to their unmodified SBS counterpart composites. This can be ascribed to the enhanced compatibility between the MGSBS and PVDF as well as the increased electrical conductivity achieved by addition of MWCNTs. This work indicates that the increase of the SBS polarity by chemical modification is an effective way to enhance the dielectric and mechanical performance of the elastomeric nanocomposites.