Dielectric relaxation of near-percolated carbon nanofiber polypropylene composites

Abstract

In this work, the morphological, structural and dielectric analysis of near-percolated polypropylene (PP) com- posites containing carbon nano bers (CNF) processing by melt-mixing are investigated. Whereas the morpholog- ical analysis shows that CNF exhibit some tendency to agglomerate within the PP matrix, the structural analysis showed rst a general decrease in the intensity of the IR bands as a consequence of the interaction between carbon nano bers and PP matrix and second an increase of the crystallinity degree of the PP/CNF composites when compared to the pure PP. The dielectric analysis demonstrates enhanced dielectric constants (from 2.97 for neat polymer to 9.7 for 1.9 vol% loaded composites at 200 Hz) and low dielectric losses. Furthermore, the dielectric relaxation for composites with concentrations in the vicinity of percolation is evidenced and well de- scribed by the generalized polydispersive Cole-Cole model from which the values of static dielectric constant , high frequency dielectric constant , distribution of relaxation time (α) and mean relaxation time (τo ), are determined, suggesting that this latter analysis constitutes a strong tool for understanding the relationships between microstructure and dielectric properties in this type of polymer composites.