Definition Of Polyurethane Prepolymer

Polyurethane prepolymer is a high molecular polymer formed by the reaction of polyisocyanate and polyether or polyester polyol under certain conditions. Polyurethane prepolymer is simply a reactive semi-finished product obtained by controlling a certain ratio of polyisocyanate and polyol to react. Due to the wide variety of polyisocyanates and polyols, the reaction ratios are different.

According to the reaction characteristics of the terminal groups, polyurethane prepolymers can be divided into: isocyanate-terminated prepolymers, hydroxyl-terminated prepolymers, blocked group-containing prepolymers, and other groups such as terminal silyl groups and acrylate-terminated prepolymers. Polyurethane prepolymer of ester.

Prepolymers with NCO end groups are sometimes called modified polyisocyanates, which have high reaction characteristics, are easily affected by moisture, etc., and have a short storage period; prepolymers with OH end groups are called hydroxyl-terminated Prepolymers have general reactivity and a longer storage period. They are usually used as the main agent of adhesives. A blocking agent containing active hydrogen is used to react with the NCO group to protect the free NCO group in the polyurethane prepolymer to obtain a closed polyurethane prepolymer. The coating or adhesive prepared by this kind of prepolymer is heated and unsealed after construction, and the NCO group is regenerated, and the latter participates in the cross-linking reaction to make the system solidify.