Effect of PANI Content in MWCNTS/PANI/EP Semiconducting Coatings on Sample Resistance

The development of ultra-high voltage direct current transmission project puts forward higher requirements for the accuracy of the standard device, and the standard device outside the insulating sleeve with the voltage level will occur with the increase of the equivalent resistance of the nonlinear decrease, which seriously affects the accuracy of the standard device, this problem can be managed by the standard device outside the insulating sleeve coated with semiconducting paint. However, the coating of semiconductive paint itself will reduce the resistance of the insulating sleeve, so it is necessary to control the resistance of the paint. In this paper, semiconductive coatings were prepared by adding both MWCNTs and PANI fillers to the epoxy resin matrix, and coated on the outer wall of the epoxy insulating sleeve. The effect of PANI content on the sample resistance is analyzed by adjusting the content of PANI and testing the resistance values of the samples with different PANI contents. It was found that, at the same voltage, the resistance of the samples with PANI was two orders of magnitude larger than that of the samples with only MWCNTs. This is because the particle size of PANI is relatively large and the conductivity is weaker than that of MWCNTs, and the addition of PANI destroys the conductive pathway formed between the fillers of MWCNTs. With the increase of PANI content, the resistance value of the samples showed a tendency of decreasing and then increasing, and the resistance value of the samples was the smallest when the PANI content was <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.5 \text{wt} \%$</tex>. During the process of increasing the content of PANI from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.5 \text{wt} \%$</tex> to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.5 \text{wt} \%$</tex>, the number of PANIs between MWCNTs in the composites increased, and the carriers transported between the MWCNTs and the PANIs became more, so the sample resistance value decreased. When the content of PANI is greater than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{1. 5}$</tex> <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$w t \%$</tex>, as the content of PANI increases, not only the number of PANI between MWCNTs becomes larger, but also the distance between MWCNTs is larger, and the difficulty of carrier transmission rises, so the sample resistance gradually increases.