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Radiation curing is a welt established and highly efficient method for crosslinking of coatings, printing inks 1 The photoinitiator , the key component in such systems is responsible for light
absorption and generation of reactive species like radicals and/or cations. The photochemical
generation of radicals can be divided in four major groups:
1. Photodissociation: a- cleavage (Norrish Type I process) or t3- cleavage
2. Intramolecular 'y hydrogen abstraction (Norrish Type II process)
3. Intermolecular hydrogen abstraction
4. Electron transfer followed by proton transfer
The generated radicals could be monitored by various spectrometric methods like Laser Flash
Photolysis (LFP), electron spin resonance (ESR) or chemically induced dynamic nuclear polarization (CIDNP) spectrometry. Alternatively, the formed radicals could be quenched with stable radicals non-polymerizable double bond to create stable products, which could be analyzed with analytical routine methods like NMR, IR or MS. In literature different quenchers such as ,6 and 7 (Figure 1) have been described.