Influence of Extender Oil on Properties of Solution Styrene-Butadiene Rubber Composites

Crosslink density of a rubber vulcanizate determines the chemical and physical properties, while bound rubberis an important factor to estimate reinforcement of a filled rubber compound. Extender oil is added to a raw rubber withvery high molecular weight for improving processability of a rubber composite. Influence of extender oil on crosslink den-sity, bound rubber formation, and physical properties of solution styrene-butadiene rubber (SSBR) composites with differingmicrostructures was investigated. Crosslink densities of non-oil-extended SSBR (NO-SSBR) vulcanizates were higher thanthose of oil-extended SSBR (OE-SSBR) ones. Bound rubber contents of NO-SSBR compounds were also greater than thoseof OE-SSBR ones. The experimental results could be explained by interfering of extender oil. The OE-SSBR vulcanizateshad low modulus but long elongation at break, whereas the NO-SSBR ones had high modulus but short elongation at break.It was found that the crosslink densities affected the physical properties more than the bound rubber contents. The moduliincreased with increase in the crosslink density irrespective of extender oil, while the elongation at break decreased. Eachvariation of the tensile strengths of NO-SSBR and OE-SSBR vulcanizates with the crosslink density showed a decreasingtrend. Tear strength of the OE-SSBR vulcanizate increased with increase in the crosslink density, whereas variation of thetear strength of NO-SSBR vulcanizate with the crosslink density showed a weak decreasing trend.Keywords: solution SBR, extender oil, crosslink density, bound rubber, physical property