Wednesday, June 04, 2014

Water Everywhere

This has been one of the most frustrating weeks in my career. It's not that 5+ inches of rain fell Sunday morning, but that the relative humidity in the lab crept up to 70% over the weekend. And all that water was absorbed by components going into a polyurethane formulation.

Water and polyurethanes, and even more specifically isocyanates, do not get along.
The water reacts with the isocyanate to form a carbamic acid which is unstable and gives off CO2. And that means your urethane is going to get foamy. It's great if you want to make a polyurethane foam, but I don't. At least not for this project.

Worse yet, the isocyanate has now been reduced to an amine which then reacts with the isocyanate to make a polyurea. And since we know from Newton's Third Law of Isocyanate Chemistry that "For every urethane reaction, there is an equal but faster urea reaction", the isocyanate is now foamy and partially polymerized.

Our isocyanate and polyols were in sealed bottles and were fine, but the additives to the coating seem to have absorbed far more moisture than we ever thought possible. So we're firing up the vacuum oven to dry everything out. But just like how your clothing can get wet in a downpour in just a few seconds but need the better part of an hour to dry out in a dryer, so it is with drying our materials. There is no indicator that they are dry enough. We go for a while and run a test sample. Go for a while longer and run another test sample. Go for a while longer...

Previous Years
June 4, 2013 - Heads are starting to roll in Kuwait

June 4, 2012 - PPE for the Fashionable Industrial Polymer Chemist

June 4, 2010 - Plastic People of the Universe

June 4, 2010 - Clients and Secrecy

June 4, 2009 - The Queen is Dead. Long Live the Queen

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