Photoinitiator free radicals, photogeneration

Cationic cure mechanisms are an alternative approach to uv curing. This involves the photogeneration of ions, which initiate ionic polymerization. This process is not subject to oxygen inhibition, as are some of the free radical mechanisms. Cationic cure mechanisms generally also provide less shrinkage and improved adhesion. The disadvantages are that the photoinitiators are sensitive to moisture and other basic materials. The acidic species can also promote corrosion. As a result, the vast majority of uv formulations are acrylate-based and cure by a free radical mechanism. 

UV photografting of poly(methacrylic acid) (PMAA) on the surface of PHBHV fibers, and complexation of in-situ photogenerated silver nanoparticles (Ag NPs) (Fig. 6.10). The photografting process is conducted through a photoinduced free-radical process employing a ketone-based photoinitiator in aqueous medium [39]. 

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