Pure methyl diphenyl diisocyanate (MDI) occurs as white to pale yellow crystals or flakes with a slightly musty odour. It is soluble in acetone, benzene, kerosene and nitrobenzene. It reacts readily with water to form insoluble polyureas and may polymerise under the influence of temperatures above 204oC.
MDI is made available both in pure form and as a mixture of MDI, the dimer and trimer.
Mixed MDIs is referred to as polymeric isocyanates or PMDI.
MDI is used mainly in polyurethane (PU) foams. Rigid foams are mostly used in construction, refrigeration, packaging and insulation.
Flexible foams are used in furniture, bedding and transportation.
MDI is also used to make binders, elastomers, adhesives, sealants and coatings.