Comment by Composite Analytica on 31 Aug 2009 at 22:34:24
Probably Polytetrafluoroethylene (PTFE) based flexible is suitable. The permeability of 100% Acetone vapour in PTFE in ambient condtions is in the order of 1E-8 gram/m x s. Divide this figure by the wall thickness and multiply this figure with the total wall square to obtain the total mass flux per second.
Polyethylenes (PE's) could also be used but they have short life time expectation due to potential for stress cracks (the grades with higher crystallinity). Moreover, their permeation is a factor 10 - 20 higher than the PTFE based polymers. Fluoro treated PE's have a slight better performance, but the same drawback on the long term (although permeation appoaches the virgin PTFE performance).
Concluding: for long term service life the PTFE based solution with a crystallinity in the order of 50 to 60 percent should be really appropriate.