The Relationship between Specific Structure and Gas Permeability of Bromobutyl Rubber: A Combination of Experiments and Molecular Simulations

The relationship between the specific structure and gas permeability of brominated poly(isobutylene-co-isoprene) rubber (BIIR) is investigated by a combination method of both experiments and molecular simulation. It is found that the various content of secondary allyl bromide isoprene (SABI) units exert an effect on transport behavior, including both diffusion and solution behavior of small molecule in BIIR, glass transition temperature, and vulcanization characteristics. The results show that a minimum value of permeability coefficient exists with the increase of SABI content. Moreover, more SABI in BIIR will lead to a rise in glass transition temperature and curing rate. It means that the gas permeability of BIIR can be further improved by adjusting composition of the copolymer BIIR. Meanwhile, this research may also provide useful information for understanding the penetration mechanism of oxygen in the BIIR matrix and supply a theoretical tool for designing high air tightness rubber materials.