Synthesis and Characterization of Epoxidized Butyl Rubber

The epoxidation of rubber is an effective way to improve the oil resistance, gas permeability and other properties of the modified product. Although extensive research has been carried out on the epoxidation of natural rubber and other unsaturated rubber, few studies focused on the epoxidation of butyl rubber (IIR) and the possible side reaction of the epoxy group in the epoxidized IIR (EIIR). In this study, the epoxidation of IIR was invesitigated in detail for the first time, and the basic properties of the obtained epoxidized IIR were characterized. The epoxidation of IIR was carried out in n-hexane employing m-chloroperoxybenzoic acid (mCPBA) as the epoxidation reagent. The effects of the ratio of raw materials, reaction temperature, and the concentration of IIR solution, on the epoxidation reaction were investigated systematically. The structure of EIIR was characterized and the degree of epoxidation was calculated quantitatively by H-1-NMR spectra. The optimal conditions for the synthesis of EIIR with complete epoxidation and without side-reaction were determined: 15% IIR solution with 1.1 times of mCPBA relative to double bond reacted at 40-45 degrees C for 45 min, and then the solution was washed with NaOH aqueous solution to remove the formed acid. Furthermore, the side reaction that occurred during the epoxidation reaction and post-treament procedure was affirmed through the comparison with model compound reaction and the side reaction in the epoxidation of IIR by hydrogen peroxide/formic acid. The ring-opening reaction of the epoxy group via hydrolysis is the main form in EIIR, which is different from those in ENR. The epoxidation of IIR lead to slight increase of T-g and thermal decomposition temperature, as evaluated by the results of DSC and TGA. Finally, the solubility and epoxy-group content analysis showed that EIIR possesses excellent strorage stability. [GRAPHICS] .