Published March 1982
Ultraviolet (UV) and electron beam (EB) are two types of radiation curing for coatings, printing inks, and adhesives. Infrared, which is sometimes included also, is for our purpose more appropriately regarded as a form of thermal curing. PEP Report No. 116, issued in 1977, concerned EB curing; the present report concentrates on UV.
The use of UV curing was first commercialized during the 1960s in West Germany for furniture. At present a total of several thousand UV curing lines operate in the United States, Western Europe, and Japan.
In radiation curing, the diluent and the polymeric resin used in thermally cured coatings are replaced by a reactive liquid vehicle (monomers and unsaturated oligomers) in which a pigment may be dispersed. When the wet coating is irradiated by UV or EB, it polymerizes. The weight and thickness laid down are essentially unchanged during curing. UV curing requires the use of a photoinitiator; EB does not.
This report includes a description of the major markets for UV curing in the United States, Western Europe, and Japan, along with market sizes and projections. Market participants for chemicals and UV curing equipment are identified.
Chemistry is covered for the four commercially available types of UV curable: acrylate, unsaturated polyester/styrene, thiolene, and epoxy. Formulation components--0ligomers, photoinitiators (and photo- sensitizers), and reactive diluents (multifunctional and monofunctional monomers) are discussed.
A separate section discusses commercial curing lamps and equipment. Patents pertaining to UV curable coatings are summarized in Section 5.
Section 7 of the current report compares the economics of UV, thermal, and EB curing.