Study on the Influence Law of Dispersant on the Resistance Value of MWCNTs/PANI Epoxy Semiconducting Coatings

Under the action of strong DC electric field, the resistance of the insulating cylinder of high-voltage DC voltage divider shows a nonlinear decrease with the increase in electric field strength, which leads to the decrease in measurement accuracy. It is shown that the effect can be suppressed to a certain extent by applying a semi-conductive coating on the surface of the insulating outer barrel. However, due to the inherent properties of the conductive nano-fillers, it is difficult to achieve uniform dispersion in the polymer matrix, which limits the electric field modulation ability of the coating and makes it difficult to fundamentally solve the nonlinear effect of the insulating outer barrel resistance. In this study, based on the multi-walled carbon nanotubes/polyaniline (MWCNTs/PANI) epoxy semiconducting coating system, the effects of dispersant type and dosage on the variation in the coating equivalent resistance with voltage were investigated. The semiconducting coatings with different dispersion states of conductive fillers were prepared by regulating the types and amounts of alkyl ammonium salt dispersants, polymer urethane dispersants, and low molecular weight unsaturated polycarboxylic acid polymer dispersants, and analyzed in combination with the equivalent resistance test, SEM microscopic morphology characterization, and coating adhesion test. The results show that the dispersion of the conductive filler has a significant effect on the suppression of the resistance nonlinear effect, and the polymer polyurethane dispersant can make the filler uniformly dispersed by virtue of the strong spatial site resistance, and the equivalent resistance change rate is lower than 28% under the additive amount of 0.5-1.5%, which has an excellent suppression of the nonlinear effect of the insulation resistance, and the adhesion of the coating is significantly improved to grade 0. The study provides theoretical basis and experimental support for the optimization of the preparation process of high-performance MWCNTs/PANI semiconducting coatings, which can help to improve the measurement accuracy and operational stability of high-voltage DC voltage dividers.