MECHANISMS OF ANTIOXIDANT ACTION - ANTIOXIDANT-ACTIVE PRODUCTS FORMED FROM THE DIALKYL THIODIPROPIONATE ESTERS

Some products of the decomposition of dimethylsulphinyldipropionate (DMSD) have been identified and have been found effective as antioxidants. The only products able to destroy hydroperoxides as rapidly as DMSD are sulphur dioxide and methyl-β-sulphinopropionate (MSP). The latter undergoes pyrolysis to give sulphur dioxide at the elevated temperatures during processing of polymers; at lower temperatures, it appears to give rise to an equally effective acid catalyst (probably SO2 or H2SO4) by disproportionation and further oxidation by hydroperoxides. MSP and its further oxidation product, methyl-β-sulphopropionate (MSOP), are auto-synergistic, showing both chain-breaking and peroxide decomposing activity. There is no evidence that MSOP is involved in the inhibition processes. © 1979.