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Differences between epoxy & polyurethane resin

Updated April 17, 2017

At a basic, chemical level, epoxy resin starts with the reaction of bisphenol A, which contains a benzene (carbon) ring and a hydroxyl (OH) functional group, and epichlorohydrin. Polyurethane resin, on the other hand, is based on the reaction of an organic (carbon) polyisocynate and an alcohol.

Expansion

Epoxy resin dries, or cures, to a very hard, unexpansive surface and is only suitable for indoor use. Polyurethane resin, on the other hand, is up to 50 times more expansive than epoxy resin, making it far more resistant to cracking and therefore suitable for indoor or outdoor use.

Curing

You can install polyurethane resin successfully at temperatures between -6.67 and 37.8 degrees Celsius, while epoxy resin requires temperatures above 10 degrees Celsius. If applied as a coating for concrete, polyurethane typically cures in two to four days, while epoxy can take up to eight days to cure.

Volatile Organic Compounds

All polyurethane resins contain moderate levels of volatile organic compounds (VOCs). Some industrial grade epoxies contain low levels of VOCs, but general-use epoxies sold in retail stores may have very high levels.

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About the Author

A full-time writer since 2006, David Dunning is a professional freelancer specializing in creative non-fiction. His work has appeared in "Golf Monthly," "Celtic Heritage," "Best of British" and numerous other magazines, as well as in the book "Defining Moments in History." Dunning has a Master of Science in computer science from the University of Kent.