West Systems Epoxy heating while curing?

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AlnessW

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Had a super weird experience mixing West Systems 105/205 epoxy today. I was doing my usual nosecone anchor "layups" with Kevlar as seen in numerous of my build threads.

2 pumps of 105 resin, 2 pumps of 205 fast hardener, mix thoroughly in cup. Apply layups to first nosecone...no problems so far.

Move on to second nosecone, add one section of Kevlar as the epoxy starts to quickly heat up. After I got that in place, maybe 20 seconds later as I'm soaking the next section of Kevlar, the mix continues heating up until it's nearly scalding, practically burning my fingers and starting to melt the inside of the plastic cup I was mixing in. As this point the epoxy is curing super quickly (within seconds it's suddenly very firm) and giving off small amounts of smoke. I was so worried about it spontaneously combusting that I moved the cup and mixing stick outside, but thankfully it didn't.

I went back to check on my first nosecone and the epoxy there (from that same batch!) showed no signs of heating or smoking, and in fact was still runny as it should have been.

Anyone seen this kind of thing happen with West Systems before? I'm baffled because I've mixed over a dozen batches of this stuff in the exact same fashion and never had a problem - same cups, same sticks, etc... Could there have been some sort of contaminant inside the cup from before that reacted with the epoxy?

Any theories are welcome...
 
What you are describing is known as an exotherm. The reaction that cures to epoxy has gone out of control and is feeding heat back into it self to causing the reaction to go faster and produce more heat and the cycle repeats. The smoke you saw is really bad to breath in and can be absorbed through the skin. My guess is you got a couple of bad pumps of resin and a couple of full pumps of hardener. Or you had it mixed in a very tall skinny mixing container or it was to warm where you were working, or some combination of all three.

I would use a scale to weigh components or actually measure out the volumes don't rely on pumps.

A shallow container will allow heat to escape easier. If it gets really out of hand mix in sand to absorb the heat and pour it out onto a flat surface.
 
larger batches run into this. exothermic reaction.... more epoxy, more heat, faster reaction.... When you pulled the first bit out, you lowered the heat so it stayed the same. the bulk of it feed itself.
 
This happened to me once, but under slightly different circumstances. I was using Rocketpoxy to beef up an Aerotech kit that I had just recently CA'd together. Where the epoxy touched the wet CA, it smoked and got super hot. I haven't mixed the two since then! Anyone know what causes this?

Nate
 
Had a super weird experience mixing West Systems 105/205 epoxy today. I was doing my usual nosecone anchor "layups" with Kevlar as seen in numerous of my build threads.

2 pumps of 105 resin, 2 pumps of 205 fast hardener, mix thoroughly in cup. Apply layups to first nosecone...no problems so far.

Move on to second nosecone, add one section of Kevlar as the epoxy starts to quickly heat up. After I got that in place, maybe 20 seconds later as I'm soaking the next section of Kevlar, the mix continues heating up until it's nearly scalding, practically burning my fingers and starting to melt the inside of the plastic cup I was mixing in. As this point the epoxy is curing super quickly (within seconds it's suddenly very firm) and giving off small amounts of smoke. I was so worried about it spontaneously combusting that I moved the cup and mixing stick outside, but thankfully it didn't.

I went back to check on my first nosecone and the epoxy there (from that same batch!) showed no signs of heating or smoking, and in fact was still runny as it should have been.

Anyone seen this kind of thing happen with West Systems before? I'm baffled because I've mixed over a dozen batches of this stuff in the exact same fashion and never had a problem - same cups, same sticks, etc... Could there have been some sort of contaminant inside the cup from before that reacted with the epoxy?

Any theories are welcome...

How hot was the ambient air temp when you mixed the epoxy. I have had this same thing happen to me one summer day while fibreglassing some fins. Probably 3 pumps each of resin and catalyst in a solo cup and mixed it and set it down in the sun in 85 degree heat. Went to pick it up 2-3 minutes later and it was smoking and had melted the bottom out of the cup. Only ever happened the once but to be honest anything over a couple pumps gets put on a paper plate now so it spreads out and distributes the glue over a bigger area to help slow down the exothermic reaction.

Greg
 
I stopped using cups for epoxy layups and instead use small plastic or paper plates. Since switching to plates I have never had an issue with surprise exothermic reaction. This has nothing to do with West epoxy all epoxy's are capable of the same thing. A thin layer of epoxy is significantly less likely to have an exothermic reaction unless you get the ratios wrong and it has to be way off spec to cause a exothermic reaction in a plate.
 
Thanks all for the feedback! I posted this same question to one of our local email lists and the consensus was exactly the same = exothermic reaction turned into a "thermal runaway." I would attribute that to 2 things - a) mixing a large batch, and b) mixing on a warm day.

I would use a scale to weigh components or actually measure out the volumes don't rely on pumps.
Again, I've always measured this stuff using pumps and have never had any issue with correct ratios.

This happened to me once, but under slightly different circumstances. I was using Rocketpoxy to beef up an Aerotech kit that I had just recently CA'd together. Where the epoxy touched the wet CA, it smoked and got super hot. I haven't mixed the two since then! Anyone know what causes this?

Nate
Yikes! Not sure what may have happened, but maybe try waiting for the CA to cure first?

How hot was the ambient air temp when you mixed the epoxy.
Pretty warm. In fact, earlier today after it cooled down a bit outside, I mixed another (SMALL) batch with no issues.

This has nothing to do with West epoxy all epoxy's are capable of the same thing.
After today, I believe it!
 
Very common with West Epoxy. In ambient temps above 85 degrees or in large batches move to their mid temp catalyst.
 
I've had it happen multiple times. With the heat down here in Texas during the summer it's hard to escape. I actually had to get a helper to help me layup a tube once because I I knew from the last tube I had that I would not have time to finish the layup.

Like most others said, smaller batches, or work faster. :p another thing I've heard is putting the cup in a bowl of ice cold water. It'll pull the heat away from the epoxy and give you a little more time.
 
I use a double bowl system on larger epoxy batches. I use a small yogurt container for the epoxy, and that sits in a container of ice.

On really hot days my epoxy goes in the refrigerator before I mix it.

Also, I'll simply mix it on my workbench. My epoxy workbench is a waxed piece of countertop, so cured epoxy pops right off. :)
 
Very common with West Epoxy. In ambient temps above 85 degrees or in large batches move to their mid temp catalyst.
Wouldn't be surprised if it was 85 degrees or warmer where I was mixing...

I've had it happen multiple times. With the heat down here in Texas during the summer it's hard to escape. I actually had to get a helper to help me layup a tube once because I I knew from the last tube I had that I would not have time to finish the layup.

Like most others said, smaller batches, or work faster. :p another thing I've heard is putting the cup in a bowl of ice cold water. It'll pull the heat away from the epoxy and give you a little more time.
I use a double bowl system on larger epoxy batches. I use a small yogurt container for the epoxy, and that sits in a container of ice.

On really hot days my epoxy goes in the refrigerator before I mix it.

Also, I'll simply mix it on my workbench. My epoxy workbench is a waxed piece of countertop, so cured epoxy pops right off. :)
All good ideas, thanks guys. Per my post above, my solution was to mix a smaller batch and not leave it in the cup for as long.
 
West Systems pumps are very accurate and a great way to easily dispense the stuff. If you pump and measure, it won't be off much at all.

All the other info is pretty accurate. Too deep a container of mixed epoxy will "kick" much quicker than if it is in a shallow container, especially if the air temp is high.

--Lance.
 
Switch to at least a 2 qt plastic paint mixing pail.
The thinner the depth of the epoxy is; the longer you will have, with less heat build up.
Epoxy of this sort does not like confined spaces.


JD
 
Yeah. If you have a deep pot of epoxy then this will happen, and it's not just west systems. Mix in something larger so it's thin in the bottom of the container - helps keep it cool. Also you can change to the 206 hardener instead of 205 for a slower cure. I use 206 or sometimes 207 when wrapping tubes.
 
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