Methylene diphenyl diisocyanate, most often abbreviated as MDI, is an aromatic diisocyanate. The 4,4' MDI isomer is the most widely used isomer, and is also known as 4,4'-diphenylmethane Diisocyanate (also known as Pure MDI). MDI is a chemical that reacts with polyols used in the production of polyurethanes.
MDI is primarily used in the production of rigid polyurethane foams for insulation purposes for houses or refrigerator, to save heating and cooling costs. MDI is also used to produce many types of footwear, sports and leisure products. MDI can also be used as a binder for wood and to produce mould cores for the casting industry.