Evidence of silane coupling in torrefied agro‐industrial residue‐filled poly(styrene‐co‐butadiene) rubber compounds

Abstract

Heat-treated rice hull residues were evaluated as fillers in poly(styrene-cobutadiene) rubber (SBR) compounds. The currently used precipitated silica filler was replaced with torrefied filler in concentrations varying from 0 to 100 wt%, and the influence of coupler concentration varying from 0% to 3% (7 parts per hundred rubber or phr total) on the filler-rubber interaction was investigated. The curing process, dynamic properties, and mechanical properties of the SBR compounds were examined for silica-filled and torrefied rice hull (TRH)-filled materials with and without the coupling agent. Partial or full replacement of silica with TRH resulted in a systematic decrease in compound viscosity. Longer scorch (t s2 ) and shorter cure times (t 90 ) were also observed.Incorporation of TRH increased compound modulus (stress at 100% elongation or M100 and Young's modulus) but decreased tensile strength and elongation.The presence of coupler brought about improved dynamic and mechanical properties and 30% lower tan δ at 3 phr level. Results provided the first evidence that, when used as a filler in an SBR compound, torrefied rice hulls can be chemically coupled to the SBR polymer, resulting in increased polymerfiller interactions analogous to the conventional silica-coupler-polymer system.