Synthesis and antioxidative properties in natural rubber of novel macromolecular hindered phenol antioxidants containing thioether and urethane groups

Two novel macromolecular hindered phenol antioxidants containing thioether and urethane groups were synthesized by the combination of thiol-acrylate Michael addition and nucleophilic addition. First, a hindered phenol with hydroxyl (GM-ME) was synthesized by Michael addition between 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylphenyl) methyl-4-methylp-henyl acrylate (GM) and 2-mercaptoethanol (ME). Then macromolecular antioxidants GM-ME-IPDI and GM-ME-TDI were obtained after GM-ME reacted with isophorone diisocyanate (IPDI) and toluene diisocynate (TDI), respectively. The structures of the macromolecular antioxidants were confirmed by FT-IR, 1H NMR and MALDI-TOF-MS. TG analysis showed that the thermal stability of the GM-ME-IPDI and GM-ME-TDI were higher than that of the GM. The oxidation induction time (OIT) and accelerated thermal aging tests of natural rubber vulcanizates showed that the thioether and urethane groups of GM-ME-IPDI and GM-ME-TDI played an important role in improving antioxidative efficiency. In addition, it was found that the urethane group connected with benzene ring had better antioxidative ability than that connected with alicyclic ring.