Radiation curing refers to polymerization induced by radiation such as ultraviolet (UV) light, electron beam (EB), or visible light. Like thermal polymerization methods, radiation curing transforms a low viscosity liquid into a crosslinked solid. Unlike thermal polymerization, radiation results in low energy consumption and very fast cure times. Radiation curing of adhesives is finding great application in the electronics industry and in advancing pressure sensitive adhesives on tapes and labels.
In terms of chemistry, two basic types of UV radiation curing adhesive systems exist: free radical and cationic. Intense UV illumination can be used to generate reactive species such as free radicals or cations from a photoinitiator. These reactive species then promote the polymerization of multifunctional monomers. The majority of commercial UV curing systems is the free radical type, and these adhesives use acrylic or acrylate components. Although less commonly used, radiation initiated cationic polymerization offers several advantages over free radical polymerization.