Fotocuring

Fotocuring, also known as photopolymerization, is the rapid hardening of a resin or coating initiated by exposure to light. The resin contains photoinitiators that absorb light and generate reactive species (radicals or cations) that start polymerization or crosslinking, allowing solidification at ambient temperature.

The process can proceed via radical polymerization, common for acrylates and methacrylates, or via cationic polymerization, typical for epoxies and vinyl ethers. In radical systems, light-activated initiators produce radicals that propagate chain growth; in cationic systems, photoinitiators generate acids that catalyze opening reactions. Light sources include ultraviolet (UV) and visible wavelengths, often delivered by LEDs or mercury lamps. Photoinitiators are chosen to match the light source, with camphorquinone and related compounds used for visible-light curing, and others like TPO or Ivocerin used for UV/visible systems. Depth of cure depends on light penetration, resin opacity, initiator concentration, and oxygen inhibition, which can suppress surface polymerization in radical systems.

Materials and applications for photocuring span coatings, adhesives, dental resins and composites, 3D printing (stereolithography and digital light processing), and electronics encapsulation. Common photocurable formulations include acrylates, methacrylates, epoxies, and certain silicone resins.

Advantages of fotocuring include rapid cure at room temperature, reduced volatile organic compounds, and energy efficiency. Limitations involve restricted penetration depth in thicker layers, shrinkage and internal stresses, surface inhibition by oxygen, potential yellowing or aging of the material, and safety considerations related to UV exposure and residual photoinitiators. Process control often requires optimization of irradiance, exposure time, and post-curing to achieve desired mechanical properties.