Electrical properties of melt-mixed polypropylene and as-grown carbon nanofiber composites: Analysis of their interphase via the AC conductivity modeling

The morphology, crystallinity, and electrical conductivity (sigma ' and sigma '') as a function of frequency of polypropylene (PP) melt-extruded with different amounts of as-grown carbon nanofibers (CNFs) from 0 to 1.4 vol. % are examined. The PP/CNF composites present CNF aggregates randomly distributed within the PP and an insulator-conductor transition at CNF contents near 0.9 vol. %. The degree of crystallinity of PP/CNF composites with loadings of 1.4 vol. % increases similar to 15% with respect to the neat PP (similar to 34%), with sigma ' similar to 8.6 x 10(-5) S m(-1) (sigma '' similar to 8.3 x 10(-4) S m(-1)) at 2 MHz. In addition, the values of the electrical conductivity sigma(int)' similar to 2.9 x 10(-6) S m(-1) (sigma(int)''similar to 3.7 x 10(-4) S m(-1)) at 2 MHz, as a result of the interphase (phi(int) similar to 0.05 vol. %) of the 1.4 vol. % PP/CNF composites, are estimated by the use of a modified generalized effective medium model (GEM). The analysis gathered in here indicates that the interphase between the polymer and the conducting particle may have a quantifiable effect on the electrical properties of carbon-based polymer composites, and this fact should not be neglected in the production of conducting polymer composites (CPCs) with enhanced electrical properties.