Photocuring Activity of Several Commercial, Near UV Activated Photoinitiators in Clear and Pigmented Systems

By Juan Segurola, Norman S. Allen, Michele Edge, Aitor Parrondo, Ian Roberts

Some of the most important commercial near UV photoinitiators have been analyzed by UV spectroscopy to evaluate the type of electronic transitions occurring upon absorption of light. Photocuring studies have been undertaken by real time infrared spectroscopy (RTIR) in clear and pigmented (black, magenta, cyan, and yellow) systems with UV and visible light at different photoinitiator concentrations in the presence of air.

Generally, the Type I photofragmenting photoinitiators appear to operate more effectively under UV excitation when compared with the Type II thioxanthones, especially in pigmented systems. There is a reasonable correlation between the UV and visible absorption properties of the respective initiators and their overlap with the excitation source.