Polymethylene polyphenylisocyanates, Polymeric MDI
Diphenylmethane diisocyanate (MDI), see D-023, is the generic name of a product used in industrial settings. Polymeric MDI (PMDI), the primary technical/commercial form of MDI, is actually a mixture that contains 25-80% monomeric 4,4'-MDI as well as oligomers containing 3-6 rings and other minor isomers, such as the 2,2'-isomer. The exact composition of PMDI varies with the manufacturer. PMDI is used to make rigid and flexible foam, foundry resin sand binders, and heat insulating material.