Coating and/or Material to minimize CO2 permeation

[MMcCawley]

Hi,

I'm working on a medical design project that will utilize a high pressure gas (likely CO2) stored at the vapor pressure (~850 psi) over a long period of time (2-4 years). My concern is gas permeation of the CO2 over time. The "pressure vessel" will likely be injection molded out of ABS, Polycarbonate or similar and the design will likely have an O-ring or seal (material TBD) interface. I realize that I'm certainly not the first person to run across this problem- The automotive strut industry must have solved this problem years ago since struts store Nitrogen at 200+ ATM's for 10+ years without significant leakage rates. Beverage bottle manufactures also coat PET 2L soda bottles with Silicon Oxide to reduce CO2 permeation. I was hoping to find someone with expertise in this area that could help guide me towards the best materials and/or coatings to reduce CO2 permeation. Is there any information that you could provide with me to help in my research of seal materials and coatings? Any assistance that you could provide me is greatly appreciated.

Thanks for your time,
Matt McCawley

 

[IRstuff]

some use DLC:

http://dbnst.nii.ac.jp/english/detail/1823

TTFN
faq731-376

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[btrueblood]

Butyl rubber is still the standard against which other polymers are compared for gas permeability. Amusing anecdote: I have been brewing beer lately, but was disappointed in the carbonation in my Grolsh-style flip top bottles, even after adjusting the priming sugar upwards. I bought some butyl rubber sheet and made gaskets to seal the cheap bottle caps. Next batch brewed was a bit...foamy, and the caps made a nice "pop" (like a champagne cork) when first cracking the bottles...and one bottle exploded just sitting on the shelf (in its plastic tub).