4,4′-Methylenebis(phenyl isocyanate)

4,4′-Methylenebis(phenyl isocyanate) (MDI) is an aromatic diisocyanates class of monomer that is widely used in the production of polyurethane plastics, foam insulation, coatings, adhesives, and sealants. It is highly reactive due to the presence of two isocyanate functional groups. MDI is known for its excellent strength, durability, and resistance to chemical and environmental damage, which makes it useful in resin composition, lithographic printing plates, coating films, optical films, image display devices, semiconductor devices, and polyurethane foam production.

4,4′-Methylenebis(phenyl isocyanate) can be used as a starting material to synthesize:

• Polyurethane cationomers, that are applicable in medical implants.
• A prepolymer for preparing self-healable polyurethane elastomers.

It can also be used as a cross-linking agent to synthesize PEBA (polyether-block-amide) copolymer with improved mechanical properties, which are mainly used in soles, medical tubes, aerospace parts, and chemical separation. Additionally, MDI is also used as a crosslinker to covalently modify graphene oxide (GO) and enhance the corrosion resistance of polystyrene coatings. The resultant polystyrene/GO-MDI composite coatings showed superior corrosion resistance to unmodified polystyrene coatings. This approach can potentially be used to improve the durability of materials in various industrial and biomedical applications.