Radiation Cure Coatings

Radiation cure coatings are organic monomer or polymer resin binders of low viscosity that polymerize to a cured film when subjected to radiation. Two main types of radiation curing are used: electron beam (EB) and ultraviolet (UV). In both processes, the materials used are solvent free and 100% reactive, giving off little vapor, creating no pollution problems. Curing time ranges from a fraction of a second to minutes depending on the source of radiation. Curing is achieved at or slightly above room temperature, which allows heat sensitive materials, such as plastics, wood, and electronic components to be coated without harm. Because no baking ovens are needed, less floor space is required for finishing. The differences between EB and UV curing systems must be considered:

• Electron-beam radiation is much stronger than UV. Ultraviolet coatings usually require activators to initiate curing, potentially shortening storage life.

• Electron-beam coatings cure almost instantaneously, whereas UV coatings may require several seconds to several minutes.

• Ultraviolet coatings are generally limited to thin clear films (up to 75 pm, or 3 mils); EB can be clear or pigmented (up to 255 pm, or 10 mils).

• Ultraviolet lamps generate heat from 38 to 49 °C (100 to 120 °F); EB does not. Thermally sensitive substrates may cause problems if UV cured.

• Electron-beam curing has higher equipment cost than UV.

• Ultraviolet coatings are more readily available than EB coatings.

0 0

Post a comment