How to "freeze" the Epoxy cure process...

[dmitry100]

I know lots of guys (probably) do this but I guess this could prove helpful to some people who find themselves waste pots of (not so cheap) epoxy at times because you couldn't use it up in time before it starts to cure-- especially after mixing fillers like silica making that window that much more smaller.

What I found was keeping the mixed pot as cold as possible made the epoxy stop from curing for as long as it stays cold.

So now when I'm epoxying parts-- I use 2 similar sized cups which are to be stacked on top of each other: 1 for the epoxy mixture, the other for putting a few ice cubes from your ice machine so that the 2 cups can be stacked on each other to keep the epoxy cold. Now I'm able to use the mixture up until the ice melts... Which is a while.

My question is... Can remaining epoxy be kept in the refrigator or the freezer to be used days or weeks later without compromising strength in any way?

[Fluid]

It is the heat generated from an exothermic reaction which "cures" epoxy, so it may be possible to substantially slow the reaction in the freezer. Using 30 or 60 minute expoxy should solve the problem of curing too fast.

But really, is it worth saving at most a buck or two while compromising a future glue joint? It isn't to me.



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[longballlumber]

Am I missing something... Only mix up what you need????

[dmitry100]

Does nobody use west systems 105/207 ? If that's the case then the pumps always give you a minimum amount and it's typically way too much for small work. Their pumps can't give you half a pump otherwise the 2 part mixtures won't be accurate. Unless someone suggests any other way?

[kfxguy]

Does nobody use west systems 105/207 ? If that's the case then the pumps always give you a minimum amount and it's typically way too much for small work. Their pumps can't give you half a pump otherwise the 2 part mixtures won't be accurate. Unless someone suggests any other way?

I have estimated the mixture with the pumps so I could mix up much less and it cured just fine. Do a little experimenting with it. You'll find that the not getting the mixture exactly to the gram doesn't make much of a difference. I first started out by measuring the weight of a full pump of the eopxy and the hardener. I wrote that on the can. Say (for simplicity) that it dispensed 20 grams of epoxy with one pump and 4 grams of hardener for one pump. If I needed less I'd do 10g epoxy and 2g hardener as measured on my gram scale.

[longballlumber]

You can mix West Systems by weight in addition to volume using the same 5:1 ratio. I don't even use the pumps. I transfer resin and hardener into appropriately sized "squirt" bottles. This allows me to dispense directly into the mixing cup while sitting on the scale.

http://www.westsystem.com/ss/dispensing-mixing/

West even sells a "small batch" kit with bottles and a scale....

http://www.jamestowndistributors.com/userportal/show_product.do?pid=6558&familyName=WEST+System+320+Scale

[dmitry100]

Hmm... Using a scale is a good idea.

Any Postal scale that can read grams would suffice... or does it need to be more specific than that?

[kfxguy]

Man I just use a $10 scale from harbor freight. I keep two on hand. It will eventually fail if you get epoxy in it. Lol

[dmitry100]

lol thats what i feel when i buy/use cheap stuff like this: http://www.amazon.com/Stainless-Electronic-Digital-Micrometer-Carrying/dp/B00LUDV9ZG/ref=sr_1_6?ie=UTF8&qid=1464275754&sr=8-6&keywords=Digital+Caliper

but... it works and functions like any $30 - $40 one. China seems to make okay stuff these days (half the time)... I'm gonna assume they used to be notoriously worse 15-20 years ago.

[srislash]

Dmitry, just a suggestion but I have been going this route

http://i1128.photobucket.com/albums/m488/SRIslash/Mobile%20Uploads/image_zpsb6dcc120.jpg (http://s1128.photobucket.com/user/SRIslash/media/Mobile%20Uploads/image_zpsb6dcc120.jpg.html)

I have recently started using the digital scale the woman got for me two years ago.

[longballlumber]

Yep, I have used the syringe method in the past as well. I still find weighing it out works better for me. The link to the "small batch" kit from west was to simply show all the parts needed for the suggested technique. I too use a scale and bottles from harbor freight.

[Shooter]

Yep, I have used the syringe method in the past as well. I still find weighing it out works better for me. The link to the "small batch" kit from west was to simply show all the parts needed for the suggested technique. I too use a scale and bottles from harbor freight.

I second the 'by weight' method. You need a very accurate jewelers scale (~$30), but it's the way to go! I set the tare, then pump the required amount of resin in the cup, then the hardener. For a very small amount: 5 grams resin, 1 gram hardener (5:1 by weight).

[dmitry100]

Btw guys, I have 105/207 west systems... and 406 silica additive. Would you guys recommend glueing mounts with that combination? Should hold just as good as the 205 stuff right?

[longballlumber]

If you using 207 it's a different ratio (3:1)... While it states it can be used as a structural adhesive, it takes longer to "cure to maxim strength". I've always had the understanding the 205 or 206 was better/stronger for "gluing" stuff vs. the 207 being a finishing resin. Since the 207 was much more viscous, it was ideal for laminating composites. However, if your adding filler to get a different consistency you need to add more than if your using the 205/206.

http://www.westsystem.com/ss/207-special-clear-hardener/

Let us know how it works for you.

[dmitry100]

Darn it, so it's gonna be that much more weaker for structural (mounts, etc) even with a bunch of silica ? :(

[bzubee]

Silica doesn't add strength chopped fiber adds strength silca just aids sanding like micro balloons =plastic

[dmitry100]

Thats all it does though? It says it increases strength on their product page though. But yea, might be a good idea to throw in some CF fibers.

406 Colloidal Silica is a thickening additive used to control the viscosity of the epoxy and prevent epoxy runoff in vertical and overhead joints. 406 is a very strong filler that creates a smooth mixture, ideal for general bonding and filleting. It is also our most versatile filler. Often used in combination with other fillers, it can be used to improve strength, abrasion resistance, and consistency of fairing compounds, resulting in a tougher, smoother surface.

[bzubee]

chopped fibers I'm reffering to are "chopped cotton fibers" not carbon fiber but that will work also for some instances. Chopped cotton fibers work best when laminating two pieces together such as servo mounts to hull.

[dmitry100]

I'm gonna assume you're not actually talking about regular balls of cotton that can be found at any convenience store?

[Fluid]

http://www.finitefiber.com/cotton.html


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[dmitry100]

Ah ok, fluid -- would cotton then be stronger than chopped CF cloth in the mix ?

[bzubee]

Yes it would for certain applications. Such as described in previous posts. layering chopped fiber when laminating anything it will be stronger.