4,4'-MDI

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Methylene diphenyl 4,4'-diisocyanate (4,4'-MDI), also known as Pure MDI, is the isocyanate used as the monomer feedstock for polyurethane production. It is a large commodity chemical compound,

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Other MDI isomers include 2,2'-MDI and 2,4'-MDI, but these have no commodity size. Mixtures of all MDI monomers (often mainly 4,4'-MDI with minor amounts of 2,4-MDI) are known as Polymeric MDI.

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• Hazards of TDI, MDI, and HDI
• Isofact American Chemistry Council Diisocyanates Panel

Isocyanate: Isocyanate is the chemical group of atoms -N=C=O (1 nitrogen, 1 carbon, 1 oxygen), as opposed to cyanate, -O-C≡N, which is formed from cyanogen in the normal -ate manner. An isocyanate is a compound containing the isocyanate group. These compounds are reactive and therefore toxic and are known...

Monomer: In chemistry, a monomer (from Greek mono "one" and meros "part") is a small molecule that may become chemically bonded to other monomers to form a polymer....

Feedstock: A feedstock is a petrochemical used as a raw material to be fed into a machine or processing plant. Examples of feedstock petrochemicals are ethylene, propylene, butadiene, benzene, toluene, xylene, and naphthalene....