Chemical Resistance of Fluorocarbon Elastomers
Fluorocarbon elastomers, in general, are resistant to automotive oils and fuels, aircraft jet fuels and lubricants, chlorinated solvents, aromatic solvents, water and salt solutions, aqueous acids and some hydraulic fluids. They are attacked to varying degrees by strong caustics; polar solvents such as acetone and MEK; ammonia; hydrogen sulfide; high ph amine corrosion inhibitors and red fuming nitric acid. As previously discussed, some properties such as acid resistance can be enhanced by the choice of polymer type and compounding ingredients. We have run comparative tests on several of our sheet gasket compounds in various fluid media and those properties are shown on the following pages.
Some applications require that the fluoroelastomer not only resist the swelling effect of the fluid medium, but it must not contaminate it due to the extraction of various chemicals from the polymer seal. One such application is deionized water used in nuclear powered, electric utility facilities. The compounding ingredients used in manufacturing fluoroelastomer sheeting or other types of rubber sheeting, can contain impurities that could leach into the fluid stream. The elastomers themselves, although generally of a high molecular weight and very stable in nature, can lose ions or salt compounds upon extended fluid immersion. Usually this loss is measured in parts per million (ppm) and is insignificant in overall seal integrity. In order to address this industry with an appropriate seal, Mosites Rubber Company has tested several of our sheet materials for leachable chloride. The extraction was performed with deionized water for 24 hours at reflux (212° F); followed by 16 hours at room temperature (75° F). Chloride analysis was by ion chromatography. The results are listed below.
|Mosites #10125||0.5 x 10-6 Micrograms / gram|
|Mosites #10138||0.9 x 10-6 Micrograms / gram|
|Mosites #10228||0.9 x 10-6 Micrograms / gram|
Fluoroelastomer compounds also withstand the cumulative effects of radiation exposure. The mode of failure is embrittlement due to hardness increase as exposure time increases. They will typically remain usable until exposure to 1 x 108 rads of Gamma radiation.