Although soybean oil (SBO) has been used as a bio-based processing oil (PO) for rubber compounds, direct replacement of a conventional petroleum-based PO with SBO often results in a reduction of some important properties. As a result, it was of interest to investigate two higher molecular weight SBO-derived materials as POs, namely, sucrose octasoyate (SS) and poly(2-vinyloxyethyl)soyate (P2VOES). When these compounds were used in carbon black (CB)-filled SBR, mechanical properties were significantly improved. This result was mainly attributed to higher crosslink densities resulting from their higher degree of unsaturation per molecule as compared with SBO. Higher unsaturation per molecule increases the probability that the PO will be incorporated into the crosslinked network as elastically effective crosslinks as opposed to dangling chain ends. With regard to tire tread performance, both SS and P2VOES-based vulcanizates showed a lower predicted rolling resistance than the SBO-based control, and the P2VOES vulcanizate showed a better balance between rolling resistance and wet traction. Vulcanizates derived from SS and P2VOES showed a small tangent delta peak between −13 and 35 °C that might be associated with relatively highly crosslinked domains rich in SS or P2VOES.

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