Modified Soybean Oil-Extended SBR Compounds and Vulcanizates Filled with Carbon Black

Soybean oil (SO) was modified through the reaction with dicyclopentadiene (DCPD) at a pressure of 0.14-0.21 MPa and a temperature of 240°C. Carbon double bonds in the soybean oil molecules were converted into norbornyl groups of different ratios. SBR compounds with 60 phr of carbon black (CB), 30 phr of different extender oils including SO, modified SO (MSO) and naphthenic oil (NO) were prepared. The gel fraction, crosslink density, bound rubber fraction, curing behavior, thermal, mechanical and dynamic properties and reactions between the SO, MSO and curatives were investigated. It was found that with an increase of the modification level, the gel fraction of the SBR/MSO vulcanizates slightly increased while the crosslink density and bound rubber fraction decreased. The SBR/MSO compounds and vulcanizates showed a lower glass transition temperature (T_g) and better thermal stability than those of the SBR/NO compounds and vulcanizate. The SBR/MSO compounds exhibited faster curing. Their vulcanizates showed lower modulus and higher elongation at break and tensile strength in comparison with the SBR/NO vulcanizates. The tire performance predictors based on the dynamic mechanical analysis indicated that the use of SBR/MSO compounds in tire tread expected to improve traction but increase rolling resistance compared to the SBR/NO compounds. After adjusting the curative recipe, the tensile properties and abrasion resistance of the SBR/MSO vulcanizates were tremendously improved. Use of this recipe is expected to achieve similar traction and lower rolling resistance compared to the SBR/NO recipe. The addition of MSO to SBR showed improved thermal and mechanical properties and had a promising possibility to replace petroleum oils in the rubber improving safety in tire production.