Low-crosslinking multi-functionalization HVBR prepared in solvent free process by anionic grafted reaction

With sodium hydride (NaH) as activating agent and maleic anhydride (MAH) as modifier, a novel multi-functionalization high vinyl polybutadiene rubber (MFHVBR) was fabricated in the solvent-free process assisted with a internal mixer. The microstructures and reaction mechanisms of the resulting MFHVBR were characterized by FT-IR and 1H NMR spectra. The effects of NaH and MAH concentrations together with the influence of rotor speed, reaction temperature and time on the grafted MAH contents and gel fraction of MFHVBR were detailedly investigated, and the effects of different levels of grafting MAH on the freeze and heat resistance, vulcanization characteristics and physical mechanical properties were also explored. FT-IR and 1H NMR analyses indicated that the polar carboxyl groups and carbon-carbon double bonds were successfully introduced onto the MFHVBR molecular chains by two reaction mechanisms: substitution and addition mechanisms. It could be concluded that there existed the most appropriate reaction condition to achieve the highest grafted MAH contents of 3.25% and the corresponding gel fraction of 24.8% for the resulting MFHVBR. Moreover, as the grafted MAH contents increased, the glass transition temperature (Tg) of MFHVBR gradually decreased, and the curing rate, mechanical strength density and hardness were significantly enhanced with slightly decreasing abrasion resistance of MFHVBR, meanwhile, the increasing grafted MAH contents produced little effect on the heat resistance of MFHVBR.