The Effects of Carbon Black-based Interactions on the Linear and Non-linear Viscoelasticity of Uncured and Cured SBR Compounds

The role of carbon black (CB) in the viscoelastic behaviour of rubber compounds was investigated to better understand the reinforcing mechanism. The influence of CB nanoparticles on the strain-dependency and relaxation phenomena of several styrene butadiene rubber (SBR) compounds was evaluated using rubberprocess- analyzer (RPA). Rheological results of uncured samples showed that reduced complex modulus with strain strongly depend on CB-rubber interactions. Filled master compounds showed greater modulus compared to raw SBR, which dropped rather abruptly; meaning more noticeable non-linear viscoelastic behaviour. The observed trend of damping factor recognized the linear viscoelastic behaviour for strain 15%, however, at higher strains a large positive deviation was noticed. In the strain region under 15%, CB-filled rubber showed more elastic behaviour than gum; more elastic as the CB loading increased while in the non-linear zone, the reverse trend was observed. Torsion relaxation modulus based on standard linear solid (SLS) model was plotted and found disputable changes regarding to varied factors. Both values of relaxed modulus and the relaxation slope increased as the functions of CB surface area and content, and also the relaxation time (τ) shifted to higher values. In addition, CB affected the cure characteristics and after cure relaxation. In the cured compounds, the slope of relaxed modulus was steeper at starting time (~0.01 s) and less steep at longer time than those of the master compound, reaching a considerable set at the end of relaxation which was dependent on CB level and size.