Diisocyanates

Diisocyanates are organic compounds that contain two isocyanate groups (-N=C=O) per molecule. They are key reagents in the production of polyurethane polymers and related materials, serving as crosslinking and chain-extending agents. Diisocyanates can be aromatic, such as methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI), or aliphatic, such as hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI).

Chemically, the two NCO groups enable polymerization with polyols and other nucleophiles to form urethane linkages, producing materials with a wide range of properties from flexible foams to rigid boards and coatings. The choice of diisocyanate affects reactivity, durability, color, and odor of the final product.

Common applications include polyurethane foams (both rigid and flexible), coatings, adhesives, elastomers, and sealants. The molecular structure and substitution pattern influence isomer distribution, reactivity, and processing behavior, enabling tailored materials for automotive, construction, furniture, and packaging sectors.

Health and safety considerations are central to diisocyanate use. Exposure can irritate the eyes, skin, and respiratory tract and may cause sensitization, including occupational asthma. Control measures focus on closed processing, adequate ventilation, exposure monitoring, and appropriate personal protective equipment. Diisocyanates are reactive with water, and moisture can cause foaming and pressure buildup in containers, so they are stored in sealed, dry conditions and handled with care to minimize inhalation and dermal contact.