Originally Posted by
prathmann
CO2 passes through rubber inner tubes much more readily than either N2 or O2, but the effect is due to chemical effects, not the size of the molecules. As stated by the OP, the CO2 molecules are largest of these three but still diffuse through more readily. CO2 consists of carbon with two double bonds to oxygen atoms. When this comes in contact with the carbon compounds of the rubber tube it can readily form a temporary bond to them - in effect sticking to the rubber molecule. That makes it more likely that it will eventually migrate through the rubber and escape to the outside air. OTOH, N2 molecules just bounce off the inner surface of the inner tube and are much less likely to find their way through.
Yes it did not make sense to me until I dug a bit into google and the way it was explained was that the CO2 is more or less "soluble" in the butyl that most inner tubes are made out of.
Molecule size wise it makes no sense, but looking at the interaction between the gas and the butyl it makes sense.
There is another product that comes in a "CO2" type container that is not supposed to leak out like CO2.......I tripped over it while looking up stuff about this, and I am not finding it easily right now :-).
Bill