polyisotsyanaatin

Polyisocyanates are polymers that contain multiple isocyanate functional groups within their molecular structure. These groups, characterized by the N=C=O moiety, are highly reactive and readily participate in addition reactions, particularly with compounds containing active hydrogen atoms, such as hydroxyl (-OH), amine (-NH2), and carboxyl (-COOH) groups. This reactivity is the cornerstone of their widespread application.

The primary use of polyisocyanates is as a key component in the production of polyurethanes. When reacted with polyols (compounds containing multiple hydroxyl groups), polyisocyanates form urethane linkages, creating a vast array of polyurethane materials. The specific properties of the resulting polyurethane, such as flexibility, rigidity, and foam density, can be precisely controlled by selecting the appropriate type and molecular weight of both the polyisocyanate and the polyol.

Common types of polyisocyanates include toluene diisocyanate (TDI) and methylene diphenyl diisocyanate (MDI). TDI is often used in the manufacture of flexible polyurethane foams, commonly found in furniture and bedding. MDI is utilized in a wider range of applications, including rigid foams for insulation, coatings, adhesives, and elastomers. Other polyisocyanates, such as hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), are used to produce light-stable polyurethanes for coatings and other outdoor applications where UV resistance is important. The handling of polyisocyanates requires caution due to their reactivity and potential health hazards.