Influence of MWNTs on electrical and hydrophobic properties of poly(vinylidene fluoride) composites

In the present study, poly(vinylidene fluoride) (PVDF)/multi-walled carbon nanotube (MWNT) composites with weight fractions between 0.25 and 4wt% were prepared by simple solution-cast method. The electrical properties were measured by impedance analyzer. The electrical conductivity showed a significant increase, which are similar to 7 orders of magnitude higher for 1wt% MWNT composites as compared to pure PVDF. This suggests formation of a conducting network of MWNTs at 1wt% in the insulating polymer matrix. The dielectric constant increased significantly -- from a value of similar to 3 for pure PVDF to similar to 46 for 0.5wt% MWNT composites at 1 Hz -- with lower weight fractions of MWNT (up to 0.5wt%). However, at higher weight fractions of MWNT (1wt% and above) the dielectric constant values were obtained till 0.5 Hz and above this frequency, the dielectric constant showed a sudden drop, which is apparently due to electrical breakdown. Further it was found that the water contact angle of PVDF increased significantly with MWNT incorporation, transforming the hydrophilic PVDF (contact angle similar to 68 degrees) to a hydrophobic composite (contact angle >90 degrees) with an invariable increase in contact angle with MWNT weight fraction. These results demonstrate the potential of these composites as materials for hydrophobic conducting coatings. (C) 2015 Elsevier Ltd. All rights reserved.