UV-curable coatings have been widely used in many industries and represent a class of coatings with no or low volatile organic compounds (VOC). The main components of UV-curable coating systems are oligomers, which have functions similar to resins and can be used as binders or film-forming agents. Oligomers have a great influence on the reactivity and mechanical properties of coatings, which is why they are generally the main consideration when designing formulations.

UV oligomers can be defined as complex of molecules composed of monomer units, which are one of the main components of the UV solution. Depending on the raw materials and the polymerization reaction mechanism, there are urethane acrylate, polyester acrylate, acrylic acrylate, amino acrylate and epoxy acrylate.  Many of these oligomers are functionalized with one or more functional groups to promote crosslinking, flexibility or adhesion.

In addition to oligomer types, there are many other oligomers mainly used to reduce viscosity and VOC in coatings. The UV oligomers used to reduce the viscosity of the formulation are often referred to as reactive diluents. Reactive diluents have two functions, one is to reduce the viscosity similar to that of the solvent, and the other is to react with the other oligomers and crosslinking agent in the coating to become part of the cured coating film, thereby improving flexibility, adhesion, weather resistance and substrate wettability.