polüuretaanprepolümeerid

Polyurethane prepolymers are intermediate compounds in the synthesis of polyurethanes. They are formed by reacting an excess of an isocyanate with a polyol. This reaction creates a molecule with terminal isocyanate groups and a higher molecular weight than the starting polyol. The choice of isocyanate and polyol, along with their molecular weights and functionalities, determines the properties of the resulting prepolymer. Common isocyanates used include toluene diisocyanate (TDI) and methylene diphenyl diisocyanate (MDI), while polyols can be polyethers or polyesters.

These prepolymers are typically viscous liquids or solids and are not usually used directly as end products. Instead, they serve as reactive components in a subsequent polymerization step. In this second stage, the prepolymer reacts with a chain extender, which is a compound with active hydrogen atoms, such as diols, diamines, or water. This reaction extends the polymer chains, leading to the formation of a high molecular weight polyurethane. The properties of the final polyurethane, such as hardness, flexibility, and chemical resistance, can be tailored by selecting specific prepolymers and chain extenders. Polyurethane prepolymers find applications in the production of coatings, adhesives, sealants, elastomers, and foams.