Butyl rubber has good chemical stability and thermal stability, and the most outstanding are air tightness and water tightness. Its air permeability is only 1/7 of that of natural rubber and 1/5 of that of styrene-butadiene rubber, while its steam permeability is 1/200 of that of natural rubber and 1/140 of that of styrene-butadiene rubber. Therefore, it is mainly used for manufacturing various rubber products such as inner tubes, steam pipes, water tyres, dam bottom and gaskets.