airless resin mixingq

[darryl]

This is a question, not a solution- I'm wondering if anybody has done anything like mixing resins in a vacuum. It would seem that it would be a good way to prevent mixing air in with it. Beyond that, perhaps a vacuum sealer would allow for the resins to be sealed away from air- you would have to knead the bag to mix it. Perhaps use a certain gas to purge the mixing container, and remain present during the mixing- would there possibly be a gas which would de-air very quickly, helium perhaps?

Vacuum seems best, as it would de-air the components plus prevent any kind of gas from getting mixed into the resin. Besides requiring a vacuum system, you would probably have to set up a mechanical mixing arrangement so you don't need to use your hands inside the chamber.

Then there's the issue of any additives you might be using- would they be drawn out of solution in any way because of the vacuum?

[Optics Curmudgeon]

You don't have to mix it in a vacuum, mix and then vacuum de-aerate. A refrigerator compressor will produce a good enough vacuum for this application. Some resins will foam a lot when first pumped on, so watch out for that when you first pump things down. A simple chamber with a thick clear plastic top works well, so you can watch how things are going. I've used this sort of thing for epoxies and two part silicone rubber, for high voltage potting.

[JoeLee]

I don't really understand the reason or the need to mix any type of resin in a vacuum.
There many kinds of resin are you referring to any one type in particular ?
If one were to do so you would have to mix it in a vacuum and then remove it to to apply it.
The closest thing I've ever seen to anything that mixes two components before they hit the atmosphere is this https://m.aliexpress.com/item/326748...W-Static-Mixer

JL....

[awemawson]

Potting resins for electronic items used to be supplied in a vacuum sealed two part bag, I've used the stuff years ago but I can't remember how the junction between the resin part and the catalyst was opened. Certainly the mixing was by kneeding then you cut a corner off the now joined bags and squeezed the mix into your potting box with no need to put in a vacuum chamber to pull the air out.

[Lew Hartswick]

Potting resins for electronic items used to be supplied in a vacuum sealed two part bag, I've used the stuff years ago but I can't remember how the junction between the resin part and the catalyst was opened. Certainly the mixing was by kneeding then you cut a corner off the now joined bags and squeezed the mix into your potting box with no need to put in a vacuum chamber to pull the air out.

It was a slit piece of tubing pinching a space between the two halves of the clear plastic envelope. I have used them probably 30 or more years ago .
...lew...

[BCRider]

A fellow I knew years ago was potting bugs, medals and such in the clear casting resin as well as making some of those resin covered wood slab tables. He used a water clear resin especially made for that stuff. It was a slow cure resin because of the de-airing in the vacuum chamber that was needed after mixing the resin. It was a 2:1 resin:hardener style as I recall. And it could be dyed with colorants. Both solid and transparent.

As I recall he was using a vacuum pump that looked a lot like an old fridge compressor on a plywood board.

The de-airing took some decent amount of time. Like 10 minutes or so. And the resin is in a mixing pot the whole time. So it has to be a very slow cure style of resin or the exothermic reaction of most resins of this sort would greatly reduce the working time as it heats up in the vacuum chamber initially. It really is a method suitable for slow cure options exclusively.

[RWO]

It was a slit piece of tubing pinching a space between the two halves of the clear plastic envelope. I have used them probably 30 or more years ago .
...lew...

3M was and is a maker. They are called Scotchcast kits. https://www.3m.com/3M/en_US/company-...94857497&rt=r3

RWO

[awemawson]

Yes Lew that was it !

Working backwards it must have been 1969 that I was working with that stuff - a younger and fitter me !

[darryl]

Some of my applications will require a 'water clear' resin (which usually would be a 2 to 1 mix and have a longer working and setting time) and others will be using the cheaper and more available epoxies (which usually are 1 to 1 mixes and can have a working time as short as about a half hour). Currently I use a vacuum de-airing setup and a centrifugal setup- I was just wondering if the 'airless' system was being used at all. It has its advantages, especially for short working time materials.

De-airing the separate components doesn't interfere with working time, but once mixed you're now on the clock. Warming the mixture helps with de-airing, but also shortens the working time. I was hoping to find a way to mix without introducing air into it- that would seem to be a progression of the state of the art.

[jcfx]

I work with resins and rubbers all day long, mixing resins in a vacuum is probably over kill, when you can mix and vacuum the resin.
Pot life is a consideration when vacuuming, the vac pump should have a CFM rating of 5 or higher, barometric pressure seems to
have an affect on degassing materials, this is just from observation, I'm sure there is proof of barometric pressures effect on vacuum some where.

Degassing the separate components to me is a waste of time since your introducing air when you combine the components, did that many eons ago
and found no advantage.

If your casting clear resins, pressure casting is another option, a paint pressure pot with 80lb of pressure does nicely, caveat on
pressure casting is that your resins shouldn't be mixed to a froth, I use a Jiffy mixer to introduce the least amount of air into the mixture.
And the big caveat with pressure casting is that the rubber mold material must be degassed, otherwise the trapped air in the cured rubber will
compress and cause bumps and warpage on the cast part, even leakage since the rubber is deforming.

What sort of additives ? I would guess that the TDS for the additive would have vapor pressure data, that might be of use to figure out
if you're losing anything, most additives I use ( dyes and pigments ) degassing has no effect.

[garyhlucas]

We use a fiberglass tank/building that is vacuum bagged in the mold and the resin comes in at the bottom corners and is pulled all the way to the top of a 11' tall tank by vacuum. Big tanks 12 feet wide, 50 feet long and 11 feet tall.

[jcfx]

That's quite a setup for vacuum infusion, just curious on how long it takes to set up the fabric, peel ply and channel layers ?

[boslab]

If you really want to stir under vacuum it’s fairly easy to stick the vacuum chamber on a magnetic stirrer if the chamber is small with acrylic top and bottom, seen it done in the lab I worked at a few times, what the chemists were making I dread to think, looked like coffee to me, glad I only had to repair things myself.
We did have a vacuum induction furnace that would melt about 4 or 5 tons max that had a stirrer made of graphite if needed the shaft went through a dublin (company name I think) swivel fitting that leaked so much we plugged the hole, we used to make steel and iron standards in the furnace so they had to homogenous, turned out stirring didn’t help much anyway the stirred standard and unstirred were about the same different in the middle to the outside as a result of solidification, just like iron or steel castings
Mark

[Dan Dubeau]

If your casting clear resins, pressure casting is another option, a paint pressure pot with 80lb of pressure does nicely, caveat on
pressure casting is that your resins shouldn't be mixed to a froth, I use a Jiffy mixer to introduce the least amount of air into the mixture.
And the big caveat with pressure casting is that the rubber mold material must be degassed, otherwise the trapped air in the cured rubber will
compress and cause bumps and warpage on the cast part, even leakage since the rubber is deforming.
.

I just picked up a pressure pot for that purpose. I have some gifts I want to make from resin and "waste wood" for some friends kids. I learned about that technique on you tube, and am anxious to try it out in a couple weeks. Any advice from a resin casting neophyte? I plan to vacuum stabilize the wood first before casting resin around it. That resin is not cheap up here and I don't want to spend any more money on the learning curve than I have to.

[MichaelP]

Dental labs and some offices use vacuum mixers for certain materials.
I'm not sure if the cost and cleanup efforts will be worth it for you if you use one for resin.