Heat exchange and damage of carbon black-filled styrene-butadiene rubber under uniaxial cyclic loading

In this paper, we present an original experimental approach combining infrared thermography, analysis of voiding, and swelling tests to investigate damage mechanisms in carbon black (CB)-filled styrene-butadiene rubber (SBR). Heat exchange and voiding under uniaxial cyclic loading have been observed. A mechanical and electrical percolating filler network was identified by atomic force microscopy and electrical conductivity for the SBR with highest content of fillers (60 phr). SBR materials with a non percolating filler network show a reversible thermal energy dissipation during a series of cyclic loading, concomitant with reversible voiding mechanisms, through the successive formation and closing of voids. The SBR with the percolating network undergoes, during the series of cyclic loading, a high dissipation of energy under the form of heat, concomitantly with irreversible voiding mechanisms. Such mechanisms are shown to be due primarily to (i) the alteration of the filler network and/or filler/rubber interface and to a lower extent to (ii) the rubber matrix alteration (chains scission and/or crosslink breakage) as demonstrated by ex-situ swelling. Deformation mechanisms in carbon black (CB) filled Styrene Butadiene Rubber (SBR). At a CB content above the percolation threshold, the damage induced by the deformation is irreversible and associated with a high heat exchange during the first cycle, consistent with Mullins effect. image