Preparation Of Bromobutyl Rubber And Characterization Of Its Structure And Property

Bromobutyl rubber (BIIR) is an elastomeric isobutylene-isoprene copolymer containing reactive bromine, which is necessary materials of making tubeless tires and pharmaceutical products. However, BUR has not been manufactured in China till now, and all BIIR products used in China are imported from other countries. Therefore, it is practical significant to study and develop the production process of BIIR.In this paper, BIIR was prepared using two different methods. The butyl rubber is bromized with liquid bromine Br2, or with in-situ produced bromine by virtue of the reaction of HBr and H2O2. The effects of some influencing factors on weight percent of bromine in BIIR were investigated, including reaction time, reaction temperature, concentration of butyl rubber, radical initiator, and light source. The structure and unsaturation degree of BIIR were analyzed by 1H-NMR and chemical titration. Molecular weight and its distribution were characterized by GPC, and Moony viscosity was measured by Mooney viscometer. The curing rates of IIR and BIIR were tested by sulfuration apparatus. The results showed that high content of bromine in bromobutyl rubber can be obtained by the present bromination process at 50℃,5min reaction, and 15% of rubber concentration. The importance of the influencing factors with respect to the bromine content of BIIR followed the order of reaction temperature, concentration of rubber, reaction time, and radical initiator. There are two different microstructures of bromobutyl rubber, viz. primary and secondary allylic configuration, and the later almost dominates. In comparison with butyl rubber, BIIR showed lower degree of unsaturation, higher molecular weight, lower Moony viscosity and wider distribution of molecular weight. Therefore, the reaction is primarily a substitution reaction rather than an addition reaction. Besides the scorch time and optimum cure time of BIIR were shortened considerably while its curing rate increased obviously. The properties of the BUR product prepared in this paper are comparable with the commercial one, Polysar2030.