UVuitharding

UVuitharding, also known as UV curing, is a photochemical process in which liquid coatings, inks, or adhesives polymerize and crosslink when exposed to ultraviolet light. In photoinitiated polymerization, photoinitiators absorb UV photons and generate reactive species that start chain reactions in monomers and oligomers, forming a solid film or adhesive layer.

There are two main mechanisms: free-radical and cationic curing. Free-radical systems, typically based on acrylates and methacrylates, cure rapidly but are sensitive to oxygen, which can create a tenuous surface layer known as an inhibition layer. Cationic systems, often epoxy- or vinyl ether-based, benefit from good depth of cure and moisture tolerance but may cure more slowly.

Formulations and systems use ultraviolet photoinitiators to trigger polymerization. Free-radical initiators include acetophenone and α-hydroxy ketones, while cationic systems rely on onium salts such as iodonium or sulfonium. UV LEDs (365–405 nm) and, historically, gas-discharge lamps provide the light energy. The choice of light source, photoinitiator, and monomer functionality determines cure speed, surface hardness, adhesion, and final mechanical properties.

Applications include coatings for wood, metal, and plastics; UV-curable inks for printing and digital imaging; adhesives; dental resins; and stereolithography resins for 3D printing. Advantages of UVuitharding include rapid curing at ambient temperature, solvent-free formulations, strong surface hardness, excellent chemical resistance, and reduced energy use. Limitations involve limited penetration in thick films, potential yellowing from certain photoinitiators, substrate opacity, and the need for post-curing to achieve full properties. Safety concerns include exposure to UV light and handling of photoinitiators, with appropriate shielding and PPE recommended.