Diphenylmethane diisocyanate

Diphenylmethane diisocyanate (CAS 101-68-8), commonly known as MDI, is a core isocyanate monomer used to produce polyurethane polymers.

Where is Diphenylmethane diisocyanate used?

• Building and construction: primary reactant in rigid polyurethane and polyisocyanurate insulation panels for high thermal resistance in thin cross-sections
• Automotive: structural foam components, seating, headliners and interior trim parts
• Adhesives and sealants: crosslinker bonding wood, metal and composites
• Coatings and elastomers: abrasion-resistant surfaces for industrial flooring, rollers and protective linings
• It reacts with polyols to build polymer chains, enabling engineered foam density, hardness and durability.
• Used as a binder in particleboard and in the production of sand-based foundry molds.
• Used to produce low-density foam for packaging.
• MDI-based polyurethane products are also used as adhesives, plastics, paints, sealants and coatings.

Good to know: Polymeric MDI is the dominant commercial form for foam applications; pure MDI grades serve elastomer formulators requiring tighter isomer control.

Typical specification

• Commercial pure MDI monomer contains about 98% 4,4'-MDI, with the 2,4'-MDI and 2,2'-MDI isomers typically present at variable concentrations of about 2% and 0.5% respectively.
• Commercial MDI bases can contain monomer concentrations varying between 25 and 75%.
• Polymeric MDI (PMDI) is a liquid mixture of oligoisocyanates generally containing between 45 and 55% unpolymerized MDI.
• White to light-yellow, odorless solid in flake form.

Regulatory status

• Subject to restrictions on manufacture, placing on the market or use under EU REACH Regulation (EC) No 1907/2006.
• If placed on the market as a specific isomer or a mixture of isomers, the supplier must specify the commercialised form (Note C).

Technical content is compiled and updated by the SoleChem product team from public technical sources; the certificate of analysis (COA) governs product-specific specifications.