|MadSci Network: Engineering|
Hi Brett, Good question! I haven't been able to find any commercially available waterproofings that thin, so if you've got one, you can probably make a lot of money... First off, I'm assuming you mean "completely waterproof" as being totally protected against ingress of water while continuously immersed. The British Standards Institution (BSI) has a specification BS EN 60529:1992 that is used to rate the... um... waterproofedness of an object. The highest rating, IPX8, means that it can withstand a 30 minute immersion under 33 feet (~2 ATM) of water without leaking. There were no films that were as thin as sub-micron that were waterproof. The smallest I found was GORE-TEX which was only available at 1.5 mil (38 microns). Films of rubbers or plastics were thicker than that. Bear in mind that most films run on the order of 50 micron or larger, just to have enough structural strength to hold together. An alternative to a separate layer would be a coating on the bag that would provide waterproofing qualities. There has been progress in plasma deposited layers of Teflon, but this has been primarily for Friction Resistance and Dielectric Properties. They can grow layers as thin as you want them, but the real trick would be to get one thin enough to be sub-micron, but thick enough to be waterproof. Then you've got to deal with the thickness of the substrate layer you were depositing the teflon onto, so it's a tough objective. So while there's nothing out there right now that's waterproof and sub- micron, that certainly doesn't mean it can't be done. Hope this helps! Jeff Yap Mad Scientist Waterproof bags: GPS International Aquapac International
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