Electrical properties of polypropylene and polyaniline compounds

Electrical measurements were conducted on different polymer compounds consisting of polypropylene (PP) and polyaniline. Both undoped polyaniline (PANI emeraldine base) and doped PANI blended with PP were studied. Electrical permittivity, loss factor and breakdown voltages with dc, ac and lightning impulse (LI) voltages of the test films were measured at the laboratory of the Technical Research Centre of Finland (VTT) and at the high voltage laboratory of Tampere University of Technology. The real part of the permittivity (ε´) of the compounds consisting of PP with 1 wt-% and 2.5 wt-% of doped PANI was approx. 13 % and 21 % higher than ε´ of pure PP (at 298 K and 50 Hz) respectively. The loss factor (tan δ) increased only slightly by adding 1 wt-% of doped PANI to pure PP. With other compounds studied tan δ was at least 5 times higher than with pure PP. The AC breakdown voltages of the compounds consisting of PP with 1 wt-% or 2.5 wt-% of doped PANI were at the same level as the breakdown voltages of pure PP. The lightning impulse breakdown voltages of the same compounds were even higher than the value of pure PP. Stearic acid additive (wt-% 0.25-1.0) decreased the ac and LI breakdown voltages by approx. 20%.