Strong increase of the dielectric response of carbon nanotube/poly(vinylidene fluoride) composites induced by carbon nanotube type and pre-treatment

The dielectric properties of multi walled carbon nanotube/poly(vinilidene fluoride) (CNT/PVDF) composites show large variations with carbon nanotube (CNT) type and fillers treatment during composite preparation. A preparation method involving toluene dispersion and corona discharge treatment has been developed allowing to obtain a maximum dielectric constant above 3000 and dielectric losses around 2.8 in a CNT/PVDF composite with 0.0419 CNT volume fraction. The electrical conductivity and dielectric response increase with CNT concentration within the composite with a strong variation around the percolation threshold. The main mechanism responsible for the large value of the dielectric constant is related to the preparation method, leading to an increase of the percolation threshold through the formation of a network of capacitors and resistors randomly connected in series and parallel. It is shown that the toluene and corona discharge methods decrease the electrical conductivity of the CNT/PVDF composite, increasing the dielectric response.This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PEST-C/FIS/UI0607/2014 PC thanks the FCT for the SFRH/BD/64267/2009 grant