Mixed too much epoxy

Between lams we have a refrigerator in the shop that we put the unused portion in. It just slows down the inevitable. The chemical process has started. And down to 10deg, I don't know. My frige is at like 55deg +or-.

We mostly use that technique for gelcoat. It allows the boat that we're working on to cure a bit between coats so we don't get sags.

Suggest you don't let it freeze. Some pre-pregs store at 40f (4.4C) for up to 6 months but are very susceptible to moisture which effects bonding properties. However, bulk epoxy ?????

Cheshirecatman

I put several pumps worth of mixed epoxy in my wife's freezer compartment under a tight polyethylene cover. It was excellent for 3 days til used up later for fill etc.. No problems- except with the wife.....
Chemical reactions slow by 50% for each 10 degree C drop in temperature.

signed Dave Carlson PhD Physical-Organic Chemist.

So when it it heats up again, the chemical process starts up again? No problem?
Taking it a bit further, if I work in a cold room laminating parts and heat the part later, the process will still kick in at 100% (or as well as if I worked at a constant 20degC)?

Rolf, thats quite a good technique for doing epoxy work overhead to stops mess and drips. Put it on cold and then warm it up once its in place to wet it out.

I have used this technique with catalyzed products many times.

Usually with paints such as Imron, Awlgrip, DP40, and misc. epoxies. I found that by putting the unused portions in the refer I could keep them for a week or two and then use them with good results.

However, I am not sure the chemical properties are as good as with a normal cure. I never saw problems but nothing I did was structural in nature.

I wonder if structural expoxies might be compromised somewhat by doing this.

Re: Epoxy for CF cloth, glass repair or polyester gel coat repair. When West System or any epoxy is mixed- it does not care how fast it polymerizes. As long as this chemical reaction has correct amounts of each reagent, it should go to completion. Just at different speeds depending on temperature.

Thus if you heat it, for each 10 degrees C ABOVE room temperature its reaction speed will also double. So, I mix well and then immediately separate off the likely excess in a quite shallow dish so it does not cook off.

Keep cool in the fridge, then freeze asap covered, thus DRY: use a Zip-lok polyethylene bag. Newspaper-sleeve thin polyethylene tubes are very useful for a cup of epoxy because they WON'T TIP OVER.

Be sure to emphasize ahead of time to your female crew/wife that this is non-stinky epoxy. It is NOT catalyzed polyester resin and WILL NOT STINK UP HER FRIDGE. Now- does she really trust you?

Note- If you over-mix warm epoxy, mix in fumed silica gel or colored dye, then hold a compact storage cup- it may self destruct in 10 minutes. Quick and cool is best.

Prepreg carbon comes with the epoxy already added and is kept in referigeration until use. this is how some high tech big boats are done so it must be structuraly sound.

Have you been watching the Vendee lately? <img src="<>/eek.gif" alt="eek" title="eek" height="15" width="15" />

Dave,

I've had a little different experience with mixing epoxy when it was cold in that it wouldn't cure. Once mixed and the reaction started, I've never had a problem with low temperatures. I have, on a couple of occasions, mixed West System (fast hardner) when the resin and hardner were below 40 degrees and I had real problems with it curing. I make sure it's warm now before I start to mix.

I went back to my 6oz of mixed epoxy/resin in a plastic container in about 30 mins at about 20deg and it had hardened and melted the plastic cup. It hardened faster than the part that I was making in the warm shop. So, I guess the mass of liquid had already started the chemical reaction and had enough internal heat that it wouldnt slow down.

Interesting.

I bet if you use the slow hardener, the exothermic heat generated wouldn't be extreme enough to overcome the ambient temperature.

In other words the pero-fluvial cryobenarium would not exceed the polar molecular matriculum dicrundi.There by not having a gelatinous mound of defecation in the sub 32 degree insulated box.
(If youda used the slow hardenerer your sh!t wouldn't of kicked in da freezer)
Tawd

So, I mix well and then immediately separate off the likely excess in a quite shallow dish so it does not cook off.

D. Carlson.

Fellas, I'd reread the good Doctor on this one. <img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />

Uhh...yeah - that too! <img src="<>/blush.gif" alt="blush" title="blush" height="15" width="15" />

Well.. With the cost of west System ,I would never mix more than I needed, therefore taking off the excess is not an option. Once I know I have excess(usually scraped off of the project), it's too late. I've tried saving it by cooling it and it has never worked for me . Slowed it down, but still gelled within 20 minutes. I would think if there was a way to save extra, some of the boatshops I worked for would have used the technique.
Todd

Whut it is, is them thar boy molecules want to get all jiggy with the girl molecules REAL BAD, and never let go. If'n they's too cold, not much happens, even if they is an equal number of them all mixed up close together. But if y'all lets thesehere boys and girls get too hot, its like the clothes all get flung off and they start to seriously party down. Cooling them off don't help much then- its too dang late, Bubba. Hope this helps.... The ol' Doc.

So it's all about proper parenting.

Since I'll be starting a project for myself soon, I'm thinking of working out of a wide shallow pan rather than a cup.

Whachya'll think?

Mix it thoroughly in a smaller container, use what you need and then move it to shallow pan if you need more time.

What is your project? Perhaps a new thread in the builders section?

Small cups, and dont mix more than you need. Have some extra parts lying stand-by for gluing and very little epoxy is thrown away.

It always pays to have the guy that is paying for the epoxy to do the batching.That way he will never mix too much!

Failing that, I try to have a filling job in the background so that any excess can be mixed with filler and used on that.

I have just come to the end of my 50 gallon drum of West. Like the death of a friend it is.