Comparison of Modified Soybean Oil and Petroleum Oil in Carbon Black Filled SBR Compounds and Vulcanizates

Carbon black (CB) filled SBR compounds and vulcanizates containing soybean oil (SO), modified soybean oil (MSO) and naphthenic oil (NO) were prepared. The MSO is norbornylized SO prepared through the reaction of SO and dicyclopentadiene of different ratios. The processing characteristics, curing behavior, thermal properties, gel fraction, crosslink density, bound rubber fraction, mechanical properties, dynamic properties and the reaction between the SO, MSO and the curatives were evaluated. It was found that SBR/MSO compounds and vulcanizates showed a lower T_g and better thermal stability than those of SBR/NO. SBR/MSO compounds also indicated a shorter curing time and a lower maximum torque compared to those of the SBR/NO compounds. With an increase of the modification level, the bound rubber fraction of the CB-filled SBR/MSO compounds decreased, the gel fraction of the SBR/MSO vulcanizates slightly increased and the crosslink density decreased. The CB-filled SBR/MSO vulcanizates exhibited lower modulus and higher tensile strength and elongation at break in comparison with CB-filled SBR/NO and SBR/SO vulcanizates. The performance predictors from the dynamic analysis of CB-filled SBR/MSO vulcanizates indicated better traction but higher rolling resistance compared to the CB-filled SBR/NO and SBR/SO vulcanizate. After adjusting the curative recipe, the CB-filled SBR/MSO vulcanizates indicated an increased strength and elongation at break, slightly lower modulus, lower rolling resistance and similar abrasion resistance, traction compared to the CB-filled SBR/NO vulcanizate. The addition of MSO to SBR has a promising possibility to replace petroleum oils in the rubber.