Feasibility of oxidized soybean oil for rubber devulcanization

Abstract

This study investigates the feasibility of using oxidized soybean oil (Ox-SO) for mechano-chemical devulcanization of sulfur-cured natural rubber. A 22 full factorial design of experiment was used to determine the effect of devulcanization time (20, 40 min) and amount of Ox-SO (6, 10 phr) in the crosslink density and sol-gel content of devulcanized VR (DVR). After conductive heating and stirring of soybean oil for 60 h, a peroxide value of 316.3 meq O2 kg−1 oil was achieved which corresponds to approximately 2500 ppm of lipid hydroperoxides. Decreasing the devulcanization time (from 40 to 20 min) and amount of Ox-SO (from 10 to 6 phr) decreased the crosslink density by 71.1% and increased the sol content by 228.2%. The optimum conditions are 20 min of devulcanization time and 6 phr of Ox-SO where the crosslink density of VR is reduced to 6.2×10−5 mol cm−3 and the sol content is 10.2% (control VR crosslink density: 2.1×10−4 mol cm−3, sol content: 3.1% ). In summary, Ox-SO was found to be a feasible agent for rubber devulcanization. DVR blends with virgin rubber are required to assess Ox-SO’s commercial readiness.