Ultra Low Vacuum Adhesive

[gwolf2]

I am trying to find a sealing material or an adhesive which has a permeability about 10x lower than butyl rubber. I am trying to hold a vacuum of 10-4 mbar/torre for 1-5 years and I know from my geometry that butyl rubber won't do the trick. 10-4 torre is about as good as you will get without installing additional absorbers for the lighter gases which pass through metal.

I made an extensive product search 2 years ago and came up with nothing. I thought that I would try again now as new products appear quite often. Here are my requirements.

Either:

A pre-formable seal material with strength and stiffness similar to rubber which will fit between a well-prepared steel or aluminium frame and toughened glass plate.

Or:

1) An adhesive which will bond aluminium or steel to glass.
2) Has a strength similar to common epoxy ie around 10MPa
3) Can be outgassed at a temperature less than 50C, and/or by storage under vacuum prior to final charging.

I realise that this material probably doesn't exist yet but it's worth asking from time to time. I know of one newish polymer which will go to 2-3x better than butyl rubber but that still isn't enough, I need 10-20x better.

Regards,

gwolf

 

[gwolf2]

unclesyd - I had a close look at Vacseal II. It needs a bakeout at 250C or higher for about an hour. The thermal expansion of the two parts will break the seal. :-(

 

[unclesyd]

As the curing of Vacseal is a problem another approach could be to use a high vacuum grease, Apiezom, Dow, Varian, or Krytox on the O-ring. I think the life of these greases are long enough to cover your time frame.
You might want to contact Apiezom for their recommendation

http://www.pchemlabs.com/product.asp?pid=2599

 

[gwolf2]

Thanks a lot, I'll look into it. I have also been looking into redesigning the joint to minimise differential expansion stresses during a bakeout but this is naturally a bit more involved. I have FE to take a close look at the joints.