The electrical properties of polypropylene (PP), grafted polypropylene (PP-g-PVP), and modified-grafted PVP with alpha-cyano-beta-(2-thienyl) crotononitrile were investigated. Also, the electrical characteristic of the modified-grafted PVP subjected to gamma-irradiation (60 kGy) was studied. The results show that the sigma of trunk polymer undergoing different degree of grafting generally increases as function of the grafting yield. The grafting yield between 64.1 and 149% resulted in a progressive decrease in Delta E sigma value. Inclusion of sulfur-containing substrate in different films, having various grafting yields, leads to both increase and decrease in sigma values. A significant increase in a values is observed upon inclusion of sulfur-containing substrate having maximum grafting yield (149%). These changes are accompanied by fluctuation in sigma values. The exposure of sulfur-containing substrate in grafting film to a dose of 60 kGy results in a significant decrease in Delta E sigma values for the films undergoing a grafting yield between 64.1 and 149%. The observed changes in Delta E-sigma of different films investigated could be attributed mainly to corresponding changes in (sigma'(0) values. The observed improvement in electrical properties is mainly because of possible increase in concentration of charge carrier and/or their mobilities. The scanning electron micrographs of some selected films show significant changes in the morphology of the films investigated due to changing the grafting yield, inclusion of sulfur-containing substrate, and exposure to gamma-irradiation. (c) 2007 Wiley Periodicals, Inc.