Hysol 1C "I don't get no respect"

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
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George Schmermund
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Hysol 1C "I don't get no respect"

Post by George Schmermund » Sun Mar 18, 2007 11:38 pm

There seem to be some rumors that Hysol 1C is over rated and maybe should even be shunned for use in high vacuum work. This reputation is really undeserved and most probably the result of the products misapplication. If your system leaks, find and remove the source of the leak. Using any sort of patching material as a sealer is far removed from any good vacuum practice.

If, on the other hand, you want to join two parts together to form a reliable and tight seal that has to work in a high vacuum environment, this epoxy is hard to beat. Of course there's always welding or brazing, but if you're trying to join dissimilar materials your going to run into problems with these methods. 1C to the rescue! When properly mixed and applied, (to an absolutely clean surface) it will withstand a 150 deg.C bake for hours. (maybe indefinitely, but my own tests can confirm the several hours claim.)

Now, some might say "yeah, if your pump is big enough you can make a booger look like a good high vacuum material!" Well, maybe, but the acid test is to have a significant amount of 1C exposed to the inside of a high vacuum experiment and then hard seal the experiment. How long can a useful vacuum be maintained under those conditions, especially if some of the sealed-in parts are elevated to incandescent temperatures? Few folks have actually done the test.

There are tables and graphs and manufacturers claims that can be referred to. All well and good. I sometimes fall prey to them myself. But, at the end of the day, I'm still a pudding taster.

The posted photos show some of the results of using 1C to seal homemade vacuum triodes. I built these back in 1994 (Steve H. can probably verify the era of that lunacy). Anyhow, they've been sitting on a shelf quietly composting for 13 years now. I decided to test there serviceability today and fired several of them up. They still work!

As can be seen along the base seal, I was most generous with the 1C on both sides of the joint. The test today was to run the filaments for 15 minutes each and check for any sign of resistance change in the heater. If there is any loss of filament material due to air or contamination, this very small diameter tungsten does a self-destruct and turns into a cloud of white powder in a couple of seconds.

The power input didn't budge.
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Anything obvious in high vacuum is probably wrong.

tligon
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Can't hold a candle to JB Weld ;)

Post by tligon » Mon Mar 19, 2007 12:07 am

Take it from a guy who has used epoxies in a materials testing lab, on Universal Testing Machines, Hysol is very good, but JB Weld is phenomenal.

We strength-tested epoxies and also used them to adhere things like foams or plasma-sprayed coatings to test fixtures. Hysol is a lab standard, and there is nothing wrong with it. But one day I ran out and had to get something from the hardware store. I decided to give JB Industro-Weld a try.

It held up fine for the test, then it came time to remove it from the test fixture. With Hysol, just hit it with a little LN2, and it pops loose. I hit the JB with LN2 and it just sat there. So I immersed the part until the LN2 stopped boiling, and wailed on it with a hammer. It just laughed. I finally machined it off.

And the hot end of the spectrum is pretty phenomenal, too ... the stuff was developed to repair cast iron engine blocks.

The only catch with JB is it is heavily filled with powdered iron, so if you need something non-magnetic, use the Hysol.

With either one, you want the slow-setting formulations, which develop a much stronger bond.

We once put some strong magnets inside stainless steel cans, and the welding company said the welder did that job and then quit. Controlling the arc in a strong magnetic field was nearly impossible. If I had to make a similar gadget today, I would epoxy the can closed instead.

George Schmermund
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Re: Can't hold a candle to JB Weld ;)

Post by George Schmermund » Mon Mar 19, 2007 12:34 am

Sorry, Tom, but I think I've missed something here. What do jackhammers and engine blocks have to do with the vapor pressure of a material when it's in a sealed high vacuum environment?
Anything obvious in high vacuum is probably wrong.

tligon
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Re: Can't hold a candle to JB Weld ;)

Post by tligon » Mon Mar 19, 2007 1:11 am

Sorry, JB Weld is kind of an in-joke every where I've worked, because I'm notorious for using it. That, and my Swiss Army Knife.

JB works pretty well in a vacuum, too. Both products are 100% solids epoxies, and fully cured don't outgas enough to tell. I repaired a couple of busted feedthrus with it once, on a system with an RGA, and it didn't make any detectable peaks.

The thing I found most remarkable was its adhesion at cryogenic temperatures. It is the only epoxy I know of that will stand that.

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Re: Can't hold a candle to JB Weld ;)

Post by DaveC » Mon Mar 19, 2007 10:04 pm

I think Tom's last comments identified the key points.... the outgassing of the (unfilled) epoxies is a large burden at even modest vacuum levels. The filler as long as it is inorganic probably doesn't matter, too much, as long as there is a maximum fill.

You can make a reasonably good approximation to Torr Seal or
HySol by taking the slow cure epoxy and adding silica "flour" to fill it. You can't get 100% fill (obviously), but when it's as stiff as you can manage it, it's ready.

Thanks for the alert on JB-Weld, Tom, I haven't tried it in vacuum yet... but will soon.

A good bake out for whichever you use (to 90 C if the parts will take it) will outgas most everything, before you put it under vacuum.

Dave Cooper

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Doug Coulter
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Re: Hysol 1C "I don't get no respect"

Post by Doug Coulter » Tue Jun 05, 2007 9:19 pm

Gorgeous work on those vacuum tubes! I putz with them here, but lack the glassblowing skills/materials to do good glass/metal seals and such, so far. It never occurred to me to even try expoxy in a sealed off unit, I'd heard there was far too much outgassing. Maybe this is why some not so scrupulous vendors try to get $100 a packet for "true vacuum epoxy"?

I'm going to try the JB weld real soon. Would they Hysol 1C be the same as the "hysol !C-LV" sold at McMaster-Car, tan with a 2::1 mix ratio?

I have been cutting the tops from old metal vacuum tubes to get cheapie glass-metal seals for low voltages, and this works fine -- you can then weld or solder the tube into the system. Or, interestingly, they are close enough to precisely 1" od to work with the tubulation adapters sold at Lesker. Easy on and off that way.

I have also found that one can rejuvenate oxide filaments and cathodes from tubes that have been opened, even if open for quite awhile. I "rescued" parts from a very old 4 pin "5U4" sort of tube, and got the filament to emit electrons quite nicely and at the normal temperature for this. All it takes is repeating the original process (though you're not starting with carbonates like they are, but hey, this works). You heat the filament to 150 to 200% of the original volts, while pulling out some emission, and do this for a couple hours, then just let it sit there hot for another hour or two with no emission. Bring it back down to normal heater volts, and it's good as new, or so it seems. I'm sure if the result would stand being bombarded by ions in an ion source, however, but I plan to test this -- always try the easy stuff first!
Why guess when you can know? Measure!

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