Influence of processing on the nonlinear conductive properties of PAni/XLPE and PAni/EPDM composites

Materials with nonlinear conductivity is sometimes used as field grading materials in high voltage applications. With respect to this, the electrical conductive properties of composites containing polyaniline (PAni) and carbon black (CB) as electroactive fillers have been studied with respect to the filler/matrix ratio, type of matrix material and how the composites were processed. Flat pads were made pressed from EPDM-PAni-composites, XLPE-PAni-granulates and from extruded XLPE-PAni-tapes, with eight different PAni-CB/matrix ratios in order to represent molded and vulcanized tape applications. It was found that the choice of matrix indicate an influence on the non-linearity of the conductivity while the low field conductivity was in the same range. The amount of polyaniline and carbon black had also an influence on the conductive properties of the composites; most notably the amount of carbon black filler had a significant impact on the low field conductivity levels. The changing of sample preparation procedure affected conductivity by several decades and it is concluded that the processing parameters at preparation of field grading layers has a significant impact on the conductive properties.