When epoxy cures it releases heat in an exothermic reaction. I was adding some glass-fibre reinforcement to the telescope tube and mixed 140 g of L285 epoxy into an ordinary plastic cup. I got about half-way through the job when I noticed the cup heating up. I tried putting it in a cold water-bath, but it was too late by then... It quickly got very hot and all of it cured instantly! At room temperature this resin should have a 60 min pot-life, but now it cured in about 5 minutes. Not much harm done, but I understand these things can cause fires and all kinds of trouble when people deal with kg or tens of kg amounts.
Note to self: 100 g or more of L285 needs to be mixed in a shallow container with lots of surface-area which provides cooling. RTFM.
Does anyone else have pictures or stories about exothermic melt-downs?
1. Comment by Peter Harrison
7/Dec/2009 at 01:56
Doh! I did exactly this in the weekend. My first batches were mixed in a container that was wider. This time around I mixed in a plastic "beer" cup similar to the one pictured above. I noticed a slight amount of steam coming off after fives minutes, and it all set rock hard in minutes. No great loss, but was instructive in the mixing of epoxy.
2. Comment by Administrator
10/Jan/2010 at 22:07
The RTFM link seems to be broken, it should link to a nice pdf-book called "SP guide to composites" which google will find for you, or you might check this link:
http://www.bolton.ac.uk/CODATE/SPGuidetoComposites.pdf