HOT Epoxy! Wowsers.

I mixed up some epoxy this evening using my cordless drill and a makeshift stirring dowl.  Normally, I have 30 minutes or so to work with the epoxy before it starts to get sticky.  But tonight it got wicked hot (like almost ready to melt the plastic mixing container) and started to get stringy really quick.  It hardened in about 15 minutes to the point where I couldn't even pour it out of the container.

Anyone know why this is?  I mixed it quite vigorously with the drill.  Also, it was pretty warm out this evening, say 80 degrees or so.  I believe my proportions were good, but its hard to tell with the pump system.

Thanks!

Jeremy


8 replies:

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RE: HOT Epoxy! Wowsers.

How much epoxy did you mix?  Huge batches are not recommended because of the reason that you encountered: they have an amazingly short pot-life.  When you mix epoxy, the reaction is exothermic, meaning that it throws off heat.  When you mix large batches, the heat produced cannot escape as easily, and tends to speed up the reaction... hence why it started curing so quickly that you couldn't work with it (especially combined with an ambient temp of 80 degrees).

Try mixing up batches no larger then 4 to 6 oz.  You'll have to mix quite a bit more, but you it should give you plenty of time to work with each batch.

~Chris 

 

RE: HOT Epoxy! Wowsers.

Winter is officially over, we have the first question about runaway epoxy reactions for the year. It's like the flowers blooming and the leaves budding, a sure sign of good paddling weather to come.

It was the temperature, Jeremy. The pumps and mixing had nothing to do with it.

The reaction between the resin and the hardener is controlled by temperature. The warmer the stuff, the faster it reacts. Also, the reaction gives off heat. The faster it reacts, the hotter it gets. Which just makes the reaction go that much faster, which makes it give off more heat...

There's 3 things you can do to keep this from happening. First, don't mix epoxy when it's that warm. Second, use a slower hardener if it's available. Third, mix a smaller batch. A smaller batch gives off less heat and  has relatively more surface area to radiate with.

Another possibility is to mix your batch and immediately pour it into a large flat tray. That also gives the epoxy more surface area to radiate the heat with.

Some builders in hot climates chill their epoxy when the weather's hot, but I've never needed to do that.

So it's time to adjust your mixing technique for the warmer seasons. Welcome to the club of builders who've made a smoking hockey puck (we all have at some point).

Laszlo

 

RE: HOT Epoxy! Wowsers.

Laszlo,

I've found that those smoking hockey pucks make nice coasters :-)

~Chris

RE: HOT Epoxy! Wowsers.

Thanks- it was quite a large batch.  Good to have all of you on my side with this project!

Cheers,

Jeremy

RE: HOT Epoxy! Wowsers.

I continue to be amazed by Laszlo.  All those boats and only one smoking hockey puck.  Sigh ...

RE: HOT Epoxy! Wowsers.

ootdb,

Who said only one? My favorite was the smoking ziploc bag of epoxy which melted all over my hand.That was HOT!

Chris,

I started my answer to Jeremy before yours posted, but you finished first. Guess the less long-winded win the race.

Laszlo

 

 

 

RE: HOT Epoxy! Wowsers.

Thank God winter is over and the first flowers are blooming - I wouldn't have been able to stand one more cold day. -.- I even was able to order one of my beloved serenata flower deliveries already and there are many more to come trust me - I am going to celebrate spring and summer like never before.^^

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