Rheological and Mechanical Characterization of Styrene‐Butadiene Rubber Reinforced With Recovered Carbon Versus Carbon Black

ABSTRACT We studied the rheological and mechanical property effects of replacing N650 carbon black (CB) with recovered carbon (rC) filler in styrene‐butadiene rubber (SBR) compounds, using a type of rC produced from end‐of‐life tires by a chloramine devulcanization process. When compared at the same filler loading, rC gave a smaller Payne effect than CB in the uncured and cured states; this is consistent with the larger particle size for rC (lower surface area) and associated less tendency for filler networking. In Fourier transform rheology (FT‐rheology), the strain amplitude ( γ 0 ) dependence of the ratio of the third harmonic to the first harmonic for the dynamic torque ( I 3/1 ) showed clear differences for compounds with rC versus CB. We proposed and utilized a new empirical Double Sigmoidal Nonlinearity Model (DSNM) to fit the γ 0 ‐dependent I 3/1 . This modeling approach captured well the data for all compounds and allowed the nonlinear rheological differences between rC and CB fillers to be effectively quantified. The cure curves, along with temperature‐dependent viscoelastic measurements of the cured materials, indicated a reduction in crosslink density from substituting rC for CB. This under‐cure effect, in addition to less filler reinforcement, resulted in deterioration of tensile mechanical properties from substituting rC for CB.