COMBINED DIELECTRIC AND MECHANICAL INVESTIGATION OF FILLER NETWORK PERCOLATION BEHAVIOR, FILLER–FILLER CONTACT, AND FILLER–POLYMER INTERACTION ON CARBON BLACK–FILLED HYDROGENATED ACRYLONITRILE–BUTADIENE RUBBER

Abstract

ABSTRACTThe filler network percolation behavior, filler–filler contact, and filler–polymer interaction of carbon black (CB)–filled hydrogenated acrylonitrile–butadiene rubber were investigated with the combination of dielectric and mechanical properties, by means of changing CB concentration, CB-specific surface area, cycling deformation for vulcanizates, and rotation speed of rotors in the internal mixer during the mixing process. A dielectric relaxation spectrometer was used to determine the percolation threshold of the CB network, which was made up of filler–filler contact, combined with the percolation theory. Dynamic mechanical analysis and a universal testing machine were employed to observe the filler–filler contact and filler–polymer interaction. The filler–filler bonds were determined by analysis of the Arrhenius plot on the basis of temperature sweep. The filler–polymer interaction and filler–filler contact were determined by hysteresis loss dependence and analysis of the reinforcement factor on the basis of strain sweep and quasi-static stress–strain behavior. The model of variable network density proposed by Maier and Goritz was applied to explain the contribution of stable and unstable bonds, which constituted the filler–polymer interaction, to storage modulus. The results showed that the percolation threshold of the filler network increased with an increase in rotation speed and a decrease in CB-specific surface area, which indicated that the filler–filler contact was affected by increasing rotation speed to some degree. Cycling deformation did not obviously affect the percolation threshold. This means that the filler–filler contact was not obviously affected by cycling deformation. However, the filler–polymer interaction was weakened by this procedure, according to careful investigation for the variation of some mechanical properties. We found new interesting correlations between the macroscopic mechanical properties and CB concentration. The molecular nature of these findings was discussed, combined with the overlap model and traditional molecular slip theory.