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Aluminum foil hermetic sealing 3

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UMgooch

Chemical
Aug 25, 2009
3
Our application requires a hermetically sealed, heat conducting pouch for a chemical heating reaction to conduct heat to a surrounding water environment. The byproducts of the heating reaction are hazardous and must be kept separate from the water environment. We have been attempting to make hermetically sealed aluminum foil pouches, and sealing aluminum to various polymers to no avail. The aluminum foil pouches leak regardless of the bonding method. We have attempted tapes, adhesives, epoxies, failed heat seals, etc.

Can aluminum foil be welded to itself, either heat welded or ultrasonically welded?

Also, are there any solutions available to seal aluminum foil to polymer films such as polyethylene, PET, or polypropylene?
 
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Yes, Al foil can be welded to itself using an ultrasonic apparatus. In fact, a company called Solidica developed a rapid prototyping system based on this principle. I have absolutely no expertise in this area, so I can't comment on its suitability for sealing in your environment.
 
I'm gonna have to be contrary, and I will probably have my nose rubbed in it, as TVP is a pretty smart guy.

But, ultrasonic welding of aluminum as a seal weld is a non-starter in my book. The weld will be unreliable unless you can ensure that the surface oxides on the foil are removed and/or well mixed/broken up into the weld so as not to create a leak path. That's a pretty tall order in thin material. Whatever process used should include an inert cover gas (e.g. helium, argon) to control said oxides from forming (in addition to what's already on the part surface).
 
There are aluminum foil/Mylar film laminate films that are readily available that are designed to be heat sealable and have very good barrier properties. Just search for the right packaging film supplies.
 
Mylar is a good material, but all I've found have very thin Aluminum layers compared to polyethylene or polystyrene layers. This eliminates the good heat transfer capabilities of the material.

If parts of the polyethylene or polystyrene layers of Mylar could be removed leaving only foil, that could be useful. Or rather, a foil piece with PE or PS-coated edges would be very useful.
 
Mylyar is PET polymer. Why would you remove it? Thin films do allow heat flow and they increase the durability, corrosion resistance and puncture resistance by orders of magnitude.
 
It sounds like you want a potato chip bag.
 
HDS, our Wellness folks give you a star! (Have a good weekend!)
 
Upon lab testing, Mylar isn't nearly as conductive as we need. We're looking into adhesives and other bonding methods for aluminum. Also, if there are Mylar composites with thick layers of aluminum compared to the polymer layers, those could be useful as well.
 
Increasing aluminum thickness will not increase through-thickness thermal conductivity. While it is a good conductor it still represents a thermal resistance. It would help to spread the heat across the surface.
 
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