Wanted: Adhesive that Won't Out-Gas in Ultra-High Vacuum

Smooth-On makes a great set of products. Their web site is helpful. I have a contact there if you need. Also, Dri-Tac makes a very good 1 part eco friendly poly adhesive called Dri-Tac 7500. They have others too. I recommend both companies highly and have a long lasting professional relationship with both.

I guess I should have asked how much you need?

Is it not possible to position the mirror without a bond only by mechanical means? If correctly designed they are not sensitve to temperature variations.

NASA has a lab in Greenbelt MD that tests materials for outgassing for spacecraft applications.

There's also a MIL Spec for this, but the # escapes me.

Google "outgassing for spacecraft applications" and see what you get.

LL

Hi Laughing Jaguar

For a small quantity try a Bostik product called "Titan Bond plus"

product code: 267872

Available in larger quantities is a product called Armstrong Adhesive A-12

made by Armstrong Epoxy Adhesives, resin technology group at easton, MA 02375

(508) 230-8070

We normally use the second product in our ultra high vac/cryo units with no apparent

outgassing.

hope this helps.

Hello Laughing Jaguar:

This may sound like a silly question, .........Do you think anyone in a Cryogenic thing would worry about their hair?...........That is not the question, but I could not resist.

What size is the mirror, and does it fill one face or wall of the cryo? And what size and shape is the inside of the chamber? If you can give me a ref' like the name and or number I can look the details up.

Take care and am looking but need the size.

Does the mirror have to fit one side on the chamber or can it be suspended.

And one more thing. Do you need to use the chamber while the glue or other attachment is still 'wet', is this part of the testing you do?

Good luck and please tell me a few of the answers I asked. Thank you.

Hello Laughing Jaguar:

are you using this for Gas Chromatography? And why do you need the mirror. would not a chromed surface or highly polished stainless do the same job And perhaps be fixed using the cryogenic liqid fixture already in the chamber?or fixed by a similar screw base to a gauge that is in there?

You have to realise I have not looked in a cryogenic chamber.

The cryogenic bit is the biggest problem - could mean embrittlement - otherwise 2pack epoxy but probably you need to find one that is polyamide cured rather than amine cured - by keeping the polyamide high and the epoxy low you could retain a higher plasticity. These types are usually found in paints rather than adhesives must be 100% solid. If you can get your hands on the base resins - Epoxy (eg Epicote 828 eqivalent) and polyamide you could make your own - it is a simple mix.

Hi ,

what is "extremely" high cryogenic vacuum? Which pressure, which temperature?

In any vacuum below 10^-3 mbar, not only material volume but also surfaces are reservoirs of volatile whatever.

This will get much word below 10-6mbar and really ugly below 10-9 mbar.

I once measured outgassing and the worst part was a magnet which was a significant gas-source for more than 3 months!

Best epoxi is from the high temperature curing ones. But those may be too brittle.

Best I used was CIBA AT1 and the high temperature strain-gage glues.

Cryo: I don't know, but if you search the last 4 months of NASA technical notes there was an article on an epoxi suited for cryo use.

From Polytec I often had excellent (but expensive) glues of many different types, I am sure they can serve your needs.

http://www.polytec-pt.com/eur/default_787.

I would not search and try but I would rather follow the suggestion made above by Nick Name: only clamp or screw the metallic mirror.

RHABE

If you insist on using a bonding agent or adhessive, I suggest that you contact Master Bond. They have an extensive selection of epoxies and adhesives that work at cryogenic temperatures. Flexibility will be the problem. The low temperatures will cause any epoxy or urethane to harden. I suggest that you design your mirror mount using something other than epoxy, silicone, urethane etc. Use instead, clips or mechanical brackets to hold the mirror. Epoxy will induce stresses in your mirror and may cause it to distort. To me 10-8 torr and lower is considered UHV. All epoxies will outgas in that level of vacuum. Contact the Advanced Photon Source at Argonne National Laboratory, they routinely mount mirrors and silicone crystals in UHV Chambers. I don't think they use epoxy. NASA has done extensive outgassing studies of epoxies. They searching their data base could help you.

Embrittlement I see as a problem. Out gassing of a high molecular weight polymer with no solvent should not be a problem. As Boeing can glue their planes together with epoxy and have them stay together at sub-zero temperatures under stress you stand a good chance. Of course they do use belt & braces and rivet as well as glue!.

The mechanical fixer lobby probably has a good point -as a glue man I must defend the stickers.

google Sika one of the biggest adhesive manufacurers out there

To all who reponded so generously. Thank you!

Just to clarify something. The operating temps are quite high. Cryogenic pumps are used only for obtaining the interim vacuum levels, not to reduce the temps. After that turbo molecular pumps reduce it further to the vacuum level required by the process. Typically about 10 to the -8 or -9.

One of you suggested that we use a machined metal substrate, polished to the surface finish needed. As it turns out that is what I am designing now so the adhesive fixturing issue is no longer a factor, unless someone changes their mind again and I find myself back to a glass substrate.

Thanks. . . . . everyone!

L.J.

Take care..........

I logged on remotely and was not aware I was not logged in when I wrote the previous post, thank you all, for your support.

Laughing Jaguar

Hello Guest,

Is your work so secret you cannot answer any questions? Damn! I wanted to get some idea how this cryogenic thingy was going to look inside? B, B, Blast! I nearly said bugger but think I got away without saying it.?

Take care and good luck..........

"Is your work so secret you cannot answer any questions?"

Yes and no. If I told you the application, it would generate more questions than I have the ability or permission to answer.

Thanks for you understanding and support.

Laughing Jaguar

Hello Guest,

Thanks for you understanding and support.

BTW, you do not have my 'understanding' support. I just do not know what the world is coming to when we cannot discuss 'SECRETS' with each other!

Shouted that loud enough, ................everyone should hear!

Take care, no probs.........

LJ, I realize you've moved past this at the moment, but just in case this comes back around to needing glue, this may be useful to you. (it landed in my in-box just a few minutes ago...)

http://masterbond.com/tds/ep29lpsp.html

Hi,

Cryogenically-Serviceable Epoxy Meets NASA Low-Outgassing Specifications

A truly remarkable, innovative epoxy adhesive, sealant, and protective
coating has gained widespread acceptance for service at cryogenic temperatures.
Master Bond EP29LPSP not only functions at temperatures as low as 4
degrees K,
but also withstands cryogenic shocks (i.e., from room temperature down to liquid helium temperatures in a 5-10 minute time period). Additionally, it meets NASA low-outgassing requirements.

http://masterbond.com/tds/ep29lpsp.html

This information was distributed by:

nasatechbriefs@LISTSERV.ABPI.NET

RHABE

I have used a product called Torr Seal distributed by Varian Vacuum Products. There are many others. It works well depending on the vacuum regime you are working in. Mechanical fastening is another option, but you need to assure that you minimize the opportunity for vitual leaks. They can be as disruptive as outgassing.

Laughing Jaguar

Could you not use mechanically attached magnets? You would have no glue but a, from the out side controllable Attachment. Like in the way an aquarium cleaner/scubber is moved inside the tank. No problems with gasses there. Just a thought Mate, Ky.

"Could you not use mechanically attached magnets?"

There is an extremely high energy microwave in the area. Any material that can be magnetic is outllawed. Most all components are stainless.

L.J.

Laws are Laws! Was just a thought. Thanks for letting me know, Ky.

Hi L.J.

you should refrain from SS in high microwave environment, loss is considerable and distortion may be not wanted.

If you are forced to use metallic elements than titanium (lower electric conductivity) will be better.

Why not "bad elastic properties" but nevertheless used as a spring? Would require some unusual design but no big problems!

I designed elastic systems from many unusual materials (including aluminum alloys) so why not these? Our plasma coating has high temperature, high ion- and electron- density but no microwaves and makes use of flexible elements.

If temperature is above absolute zero and below 2000°C than metallic flexures are possible. Above 1000°C I would think ceramic.

Do you shield your magnets to prevent microwave heating and destroying of the magnets?

RHABE

Sorry to inform you that I have a problem understanding:

If temperature is above absolute zero and below 2000°C than metallic flexures are possible. Above 1000°C I would think ceramic.

Or am I missing something here? Thanks, Ky

High temp plastics or ceramics?

High temp plastics or ceramics?

If temperature is above absolute zero and below 2000°C than metallic flexures are possible. Above 1000°C I would think ceramic.

Hi Charley

No, I seem to have problem with with absolute zero and bellow 2000°C Both do not exist to my knowledge. And what are flexures? and 1000C is below 2000C which makes it inclusive on my side of the Ranch.

High temperature plastics are not even mentioned in this sentence. I am now more confused but will not worry about it too much.

I am not splitting hairs here I hope, Ky.

If you need very strong bonding you could use an electromagnet. Magnets work in a

vacuum, don't they?

Life is a Tank

Glass is not magnetic. You'd STILL need an adhesive to stick a metal backing plate to the mirror.

Rorschach

Well, it is not new to me that glass is not magnetic, although I live on this Magnetic Island.That does not stop one to attach metal to the glass with out using glue. I have in my workshop heaps of small clamps,vices, and other bits and pieces that could be used to do that job. Nice try to make me look a bit stupid though!

The problem with mechanical clamps is that if it is tight when the assembly is cold, it will shatter when it heats up. If it is tight when it is hot, it will be loose when it is cold. Even controlled expansion alloys and ceramics move a little, and they'll probably move at different rates. you'd have to use some kind of spring in the system which adds positional uncertainty to what would appear from the description to be a high accuracy optical assembly.

As you noticed I mentioned that a "correct design" will solve the problem. to avoid what you mention there are several ways to center and support the mirror and maintain it in the position with one or more springs which will compensate for the differential dillatation. A good mechanical designer will be able to do it. Since I have the feeling that the participant who asked the question corresponds to the profile I dared suggest such a solution.

I am limited to certain types of stainless steel in an environment densely populated by microwaves. LOTS! And it can get hot. Any springs will be external to the region.

Laughing Jaguar

Hello,

I operate a thin film coating chamber with 2 electron beam guns.Standard operating tempeture is around 150c. Occasionally up to 250c. Mbase vacuum prior to depositon is usually mid 10-7. Deposition pressure from outgassing usually around 10-4. We foil the unit to protect it from the coating and use a couple feet of KAPTON TAPE. Great stuff. there are a couple different grades be sure you purchase the one right for your application.

DaveG

P.S. I USE DIFFUSION PUMP AND THE UNIT IS 44" SQ.

The high vacuum 2 component, solvent free epoxy called Torr Seal is designed for this purpose. Manufactured by Varian. Look up Torr Seal in google

It will adhere to metals, ceramics, and glass, will seal any sort of vacuum system or component to 10-9 torr 45-120degrees C

Master Bond EP29LPSP