Prepolymeer

A prepolymer, or prepolymeer, is a polymeric oligomer that has not reached full polymerization and therefore retains reactive end groups. It is produced by partial polymerization, partial chain extension, or controlled reaction of monomers to give a material with a defined, lower molecular weight and functional end groups. Common end groups include isocyanate (NCO), epoxy, amino, hydroxyl, or mercapto functionalities. The reactive ends enable subsequent crosslinking or chain extension to form the final polymer network.

In polyurethane chemistry, an isocyanate-terminated prepolymer is created by reacting a polyisocyanate with a polyol. The resulting NCO-terminated prepolymer can be further reacted with diamines, diols, or other curing agents to produce rigid or flexible polymers with tailored properties. In epoxy systems, epoxy-terminated prepolymers act as reactive oligomers that cure with amines, acids, or anhydrides to form crosslinked thermosets. Prepolymers are also used in silicone, polyamide, and other resin systems, where controlled molecular weight and end-group functionality control pot life, viscosity, cure kinetics, and final performance.

Key advantages of prepolymers include easier processing due to lower viscosity, adjustable cure rates, and the ability to tune mechanical properties by selecting end groups and molecular weight. Limitations include sensitivity to storage conditions and moisture for certain end groups, potential migration of residual reactive species, and the need for compatible curing agents.

Overall, prepolymers serve as versatile intermediates that enable customized final materials across coatings, adhesives, sealants, and elastomeric applications.