In general, diene rubbers such as NR, SBR, CR, etc., wh […]
In general, diene rubbers such as NR, SBR, CR, etc., when the use temperature is not high and the solubility of the medium is small, through appropriate acid and alkali resistance, the vulcanizate has certain resistance to ordinary acids and alkalis. For those highly oxidizing and highly corrosive chemical media (such as concentrated sulfuric acid, nitric acid, chromic acid, etc.), fluorine-resistant rubber, butyl rubber, and other chemically stable rubbers should be used as the basis for corrosion-resistant formula design. . It is described below.
Except for silicone rubber, almost all rubbers have good resistance to sulfuric acid with a concentration of less than 60% at room temperature. But above 70 ℃, sulfuric acid with a concentration of about 70% is unstable except for natural rubber hard rubber, butyl rubber, chlorosulfonated polyethylene, ethylene-propylene rubber, and fluorine rubber. 98% concentrated sulfuric acid or 80% high temperature sulfuric acid has a very strong degree of oxidation and is unstable except fluoric sulfuric acid.
Nitric acid Even in a dilute nitric acid solution, the oxidation of rubber is very strong. When the concentration is higher than 5% at room temperature, only fluorine rubber, resin vulcanized butyl rubber, and chlorosulfonated polyethylene have good stability, but when the temperature is above 70 ° C and the concentration is 60%, only 23 type fluorine is available. Hur PTFE rubber can still be used, other rubbers are severely corroded and cannot be used.
Hydrochloric acid rubber reacts strongly under high temperature and high concentration of hydrochloric acid. Natural rubber reacts with hydrochloric acid to form a hard film on the surface, which can prevent the reaction from developing in depth. This film has excellent acid and alkali resistance, but has no elasticity. Chloroprene rubber, butyl rubber, and chlorosulfonated polyethylene have unique acid and alkali resistance. Among them, resin vulcanized butyl rubber is more prominent. Especially in the rubber conveyor belt industry is very important. Only fluororubber has better stability to high temperature and high concentration of hydrochloric acid.
Hydrofluoric acid Hydrofluoric acid is mostly mixed with nitric acid, hydrochloric acid and the like. It has a similar effect on rubber as hydrochloric acid, but has a much larger permeable acid and cannot form a hard film on the surface with natural rubber. At room temperature, when the concentration is about 50%, neoprene, butyl rubber, and polysulfide rubber are not used, but when the concentration exceeds 50%, only fluorine rubber has better resistance. In the mixed solution of hydrofluoric acid and nitric acid, the resistance of polyvinyl chloride is better.
Chromic acid is also a very strong oxidizing substance. Except for fluorine rubber, resin vulcanized butyl rubber, and chlorosulfonated polyethylene, other rubbers are not resistant to chromic acid. Chlorosulfonated polyethylene can only be used at normal temperature and below 5% concentration. Fluoro rubber and polyvinyl chloride resin have good resistance to high concentration of chromic acid.
Acetic acid In glacial acetic acid, even ordinary rubbers have a large swelling even at room temperature. Butyl rubber and silicone rubber also experience some swelling. However, almost no chemical action occurs, so even if the concentration is as high as 90% and the temperature is around 70 ° C, there is considerable resistance.