Characterisation of novel polymeric antioxidant and its thermo-oxidative aging resistance for natural rubber vulcanizates

Hydroxyl terminated polybutadiene bound 2,2-methylenebis (4-methyl-6-tert-butylphenol) (HTPB-IPDI-MPH) was prepared by binding 2,2-methylenebis (4-methyl-6-tert-butylphenol) (MPH) onto hydroxyl terminated polybutadiene (HTPB) using isophorone diisocyanate (IPDI) as bridging agent. The structure of HTPB-IPDI-MPH was characterised by Fourier transform infrared spectroscopy, H-1 nuclear magnetic resonance (NMR) spectroscopy, C-13 NMR spectroscopy and gel permeation chromatography. The thermal stability ofHTPB-IPDI-MPHwas studied by thermal gravity analysis (TGA). The thermo-oxidative aging resistance of HTPB-IPDI-MPH for natural rubber (NR) vulcanizates was investigated by mechanical properties, cross-link density assessment and TGA, and then, possible mechanism of thermo-oxidative aging resistance of HTPB-IPDI-MPH for NR was proposed. The results showed that HTPB-IPDI-MPH had better thermal stability than the corresponding low molecular antioxidant MPH. The thermo-oxidative aging resistance and thermo-oxidative degradation of NR vulcanizates containing HTPB-IPDI-MPH were better than that of NR vulcanizates containing MPH obviously, indicating that the synergetic effect of phenolic -OH and -NHCOO- groups existed in HTPB-IPDI-MPH, which could enhance ability to scavenge free radical.