Deformation-Induced Structural Changes of Carbon Black Fillers in Rubbers Investigated by Terahertz Polarization Spectroscopy

We investigated the polarization-dependent terahertz optical conductivity of rubber compounds with carbon black (CB) fillers under cyclic deformation to detect deformation-induced changes of the internal CB structure in a contactless manner. It is clearly observed that the conductivity during the unloading is reduced from that during the loading at the same draw ratios. To interpret this hysteresis of the conductivity, we perform theoretical calculation based on the effective medium theory. Comparing with the calculation, we attribute the hysteresis of the conductivity to the reduction of the anisotropy of the CB aggregates, which might result from the deformation-induced rupture of them.