Electrical properties of poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) blended with carbon nanotubes

The composites of PVDF-HFP with various low concentrations (0-0.08 wt%) of single-walled carbon nanotubes (SWNTs) were prepared via solution casting and melt pressing, and were investigated for their enhanced dielectric and piezoelectric properties. It is found that the piezoelectric response increases by a factor of 1.5-3 over the pristine material for a 0.02 wt. % SWNT concentration in the polymer and decreases for higher concentrations. The principal reason for this optimal concentration is the solubility limit of SWNTs, as they are well dispersed up to 0.02 wt.% but become clustered for higher concentrations. Infrared spectroscopy and x-ray diffraction were used to reveal the interaction between the nanotube and polymeric phases. This analysis indicates that SWNTs content causes an increase in the piezoelectric β phase and a corresponding rise of the remanent polarization.