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 compoundswas investigated to better understand the reinforcing mechanism. The influenceof CB nanoparticles on the strain-dependency and relaxation phenomena ofseveral styrene butadiene rubber (SBR) compounds was evaluated using rubberprocess-analyzer (RPA). Rheological results of uncured samples showed that reducedcomplex modulus with strain strongly depend on CB-rubber interactions. Filled mastercompounds showed greater modulus compared to raw SBR, which dropped ratherabruptly; meaning more noticeable non-linear viscoelastic behaviour. The observedtrend of damping factor recognized the linear viscoelastic behaviour for strain <15%,however, at higher strains a large positive deviation was noticed. In the strain regionunder 15%, CB-filled rubber showed more elastic behaviour than gum; more elastic asthe 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 andfound disputable changes regarding to varied factors. Both values of relaxed modulusand 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 thecure characteristics and after cure relaxation. In the cured compounds, the slope ofrelaxed modulus was steeper at starting time (~0.01 s) and less steep at longer timethan those of the master compound, reaching a considerable set at the end of relaxationwhich was dependent on CB level and size