Polyisocyanaatprepolymers

Polyisocyanaatprepolymers, often referred to as prepolymers, are intermediate products in the synthesis of polyurethanes. They are formed by reacting an excess of a diisocyanate or polyisocyanate with a polyol, such as a polyester polyol or a polyether polyol. This reaction results in a molecule with terminal isocyanate groups (-NCO) and a polymeric backbone derived from the polyol. The length of the prepolymer chain and the type of isocyanate and polyol used can be tailored to achieve specific properties in the final polyurethane product.

These prepolymers are typically viscous liquids or solids at room temperature. Their primary advantage is that they reduce the volatility and handling hazards associated with free isocyanates, which are often highly reactive and can be irritating. The terminal isocyanate groups in the prepolymer are still highly reactive and readily undergo further reaction with compounds containing active hydrogen atoms, such as diols, diamines, or water. This subsequent reaction is what leads to the formation of the final polyurethane network.

Polyisocyanaatprepolymers are widely used in various applications, including coatings, adhesives, sealants, elastomers, and foams. The specific properties of the final polyurethane, such as its flexibility, hardness, chemical resistance, and thermal stability, are largely determined by the structure of the prepolymer and the curing agent used. By carefully selecting the components and reaction conditions during prepolymer formation, manufacturers can fine-tune the performance characteristics of the end product for a diverse range of industrial and consumer uses.