Epoxy Resin and the Red Gas Cloud

Epoxy Resin and the Red Gas Cloud
A chemist mixed epoxy and a catalyst that caused an overheated reaction producing a reddish gas cloud. What caused this reaction?
Mysteries of Science


One cold winter day in Northfield, Minnesota a reddish cloud of gas drifted over the highway. Few know where it came from or the real story that is about to be revealed.

A chemist at a manufacturer of flexible printed circuits and specialty products was cleaning out the laboratory stock room. He came across a 5-gallon pail of epoxy resin. The chemist wanted to harden the resin so that it could be classified as a solid waste and be disposed of in the dumpster. So he mixed up some epoxy and catalyst and put it into the pail while he continued his work in the lab.

Some time later he discovered the bucket was hot. Realizing the epoxy should not be getting hot the chemist carried it outside and tossed it into a snow bank. The bucket was soon steaming and was melting the snow. Worried, the chemist grabbed a shovel and buried the bucket with snow.  Soon there was billowing smoke coming from the snow bank where the pail was buried. The smoke turned reddish and the fire department was called in. 

What caused this reaction with the epoxy resin that could eventually be seen throughout the entire city?

Here's the rest of the story.

Epoxies give off heat when they polymerize, or harden, and this is why a 5-minute epoxy gets warm when you mix it. As you scale up the volume, the surface area where heat is lost does not increase at the same rate. So the larger the volume, the more heat and the higher the final temperature.

There will be some point in scaling up, where critical mass is reached and an epoxy mix will become a runaway reaction. If the mass is large enough it will get so hot that it will decompose and may catch fire. There was too much heat, even when the bucket was in the snow.

What about the red cloud? The epoxy contained a bromine compound as a flame retardant and the bromine produced the reddish gas.     

Is there a lesson? Maybe it's to be aware that things can happen when working in scale factors that are not expected.


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