Filler Network Recovery of Carbon Black Filled Rubber

Abstract

Change and restoration in carbon black filler network in SBR through reversing double-step large shear deformations were studied by the use of differential dynamic modulus. Unfilled rubber showed drop and complete recovery in G after elimination of step shear strain =0.5, showing drop in G is not due to chain scission but due to filler network rupture. Filled rubber also shows similar change and recovery in G , but rises over the initial value at long time region. This long time behavior may be due to physical aging. Elimination of the effect of physical aging allowed us to estimate relaxation time in restoration process. It was concluded that (a) differential dynamic modulus measured in recovery process is useful for the characterization of filler network, (b) carbon black filler network ruptured by strain recovers to the original structure by particle diffusion process, and (c) recovery rate of carbon black filler network is independent of amount of filler loading and deformation history.

Nonlinear Rheology of Rubber Materials

“…The relaxation time of CB aggregates merits further consideration [14]. The relaxation time t r signifies the time required for the centre of gravity of a body in motion to diffuse through space of the same order of size as itself, and can thus be written as in Equation 11 (11) where R aggregate and D aggregate are respectively the equivalent sphere diameter and diffusion constant of the CB aggregate.…”

“…z aggregate~6 ph local R aggregate (13) where h local is the local viscosity of the matrix polymer. Hence, t r is given by Equation 14: (14) h local and R aggregate would not be expected to depend on either CB concentration or strain. The relaxation time characteristic of the CB filler contact network should therefore show the following characteristics:…”