Sudden Epoxy Heating?

General Composites Discussions Composites Talk
#1

I had mixed a batch of Proline 4100 and was doing a carbon fiber layup. I mixed the correct amount of resin and hardener (a 5-1) into a paper cup and started mixing. The carbon fiber layup went as planned, no problems or heating. Suddenly at about 15minutes into the pot life, the epoxy in the cup heated up and hardened in about 2 minutes. The paper cup was smoking hot and when I grabbed it, i got a good size burn on my fingers. The epoxy on the layup was warm but not hot and the epoxy that dripped off of the layups was still at room temperature.
What Happened? :confused::confused::confused:

I know that you guys might not be familiar with the Proline 4100 system. I have only found it at high power rocket vendors. Such as this one:
http://rocketrywarehouse.com/product_info.php?products_id=194

To find the info sheet, just google “Proline 4100” and click on the first PDF.

I might be changing back to US composites resin after this experience… :suspicious:

Thanks,
Alex

#2

Your resin exothermed aka thermal runaway. Causes could be:

It was a hot day - most pot lifes are stated with a room temp, eg: 2hrs at 22C, hotter will be faster, colder slower.

You mixed it too hard - you add kinetic energy when you mix it. The more energy put in, the faster it will cure.

You had a lot in a cup with small surface area - as the resin cures it generated heat, if this heat can’t be dissipated it will speed up the curing which will create more heat and so on. Having the resin in a large shallow container with lots of surface area will allow excess heat to escape. If you have it in a tall narrow cup the heat can’t escape and will build up.

Most likely it is a mixture of all three. But some resins are more prone to runaway than others.

#3

http://en.wikipedia.org/wiki/Exothermic

#4

Over here we call it “tsjernobilysing”. Guess why.

I guess all epoxies can be forced to do that. Just mix enough. Reminds me of the guy mixing 30 kgs of epoxy, pouring it into his wooden boat, and start rolling it upwards to saturate the bare wood. Did someone tell him the stuff had a 15 minute potlife? I guess not… :slight_smile:

Or the 130 kgs (280 lbs) of mixed (slow) epoxy that was pulled out of an infusion project, and into a barrel. That one caught fire.

#5

Thanks for the info guys! Is there anything I can do to prevent this from happening again?

#6

Mix less, keep cool, use wide tray instead of mixing cup. Or use slower stuff.