polüisotsüanadi

Polyisocyanates are a class of chemical compounds characterized by the presence of multiple isocyanate functional groups (–N=C=O) within a single molecule. These compounds are crucial intermediates in the production of polyurethanes, a versatile class of polymers found in a wide array of applications.

The reactivity of the isocyanate group with compounds containing active hydrogen atoms, such as alcohols and amines, forms the basis of polyurethane chemistry. When a polyisocyanate reacts with a polyol (a molecule with multiple hydroxyl groups), it forms a urethane linkage, creating a polymer chain. The properties of the resulting polyurethane can be tailored by selecting different polyisocyanates and polyols, varying their molecular weights, and incorporating other additives.

Common examples of polyisocyanates include toluene diisocyanate (TDI) and methylene diphenyl diisocyanate (MDI). TDI is often used in the production of flexible foams for furniture and automotive seating, while MDI finds applications in rigid foams for insulation, coatings, adhesives, and elastomers. The choice between TDI and MDI, and their specific isomeric forms, depends on the desired flexibility, rigidity, and other performance characteristics of the final polyurethane product.

Polyisocyanates themselves can be synthesized through various routes, typically involving the phosgenation of diamines or the dimerization/trimerization of monoisocyanates. Due to the reactive nature of isocyanate groups, handling polyisocyanates requires specific safety precautions to avoid exposure, as they can be respiratory irritants and sensitizers.