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Q&A About Polyurethanes

Q: Our company recently began making custom prepolymers based on 4,4’-MDI (diphenylmethane diisocyanate). We are working on a drum scale during this startup phase and have noticed that our products have a hazy appearance. What is causing this problem?

A: Hazy prepolymers are most often caused by one of two reasons: the presence of MDI dimer in the starting isocyanate or the reaction of the isocyanate with moisture. For a smaller-scale operation, MDI is delivered in drums at ambient temperature. It is a solid with a melting point of 39

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Dr. Jeffrey Dormish's e-mail

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Jeffrey F. Dormish, Ph.D., holds the position of Research Fellow and is responsible for the development of new polyurethane adhesive applications, with a focus on waterborne raw materials.

Dr. Dormish joined Covestro LLC (then known as Bayer) in 1980. Since that time, he has held various research and application development positions of increasing responsibility, and worked in polyurethane research at Bayer AG in Germany for two years. He has a bachelor’s degree in chemistry from the University of Dayton and a doctorate in chemistry from the Pennsylvania State University. For additional information on the topics addressed or to ask another question, email jeff.dormish@covestro.com with the subject line “Polyurethanes Q&A.”