Permeability gases through elastomers

Permeation (naturally permeability) of gas through materials such as rubber hoses, elastomer seals, etc. (unless these parts have become brittle and thus leaky ). 

Among hydrocarbon elastomers, butyl rubbers are outstanding in their low permeability to gases. The process of permeation of a gas through a polymeric film involves solution of gas in the polymer at the high pressure side, diffusion through the thickness of the film, and evaporation at the low... 

Diffusion of a gas or liquid through a semi-permeable material. The permeability of elastomers to gases varies with the elastomer type and with the gas. Butyl rubber is much less permeable to air than is natural rubber hence its use in tyre inner tubes and similar apphcations. The rate of permeation is generally related to the size of gas molecule, i.e., the smaller the molecule the higher the rate. The exception is C02 which has a rate 10 to 100 times greater than that of nitrogen. 

Permeability is a process in which liquid or gas molecules dissolve in the elastomer, on one side of the membrane and diffuse through the other side and there escape out. The solubility of a gas or liquid in a given elastomer is closely related to its tendency to condense and is also related to the interaction between the gas/Iiquids molecules and the elastomer molecules. 

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