Photoinitiator DETX (Diethylthioxanthone, Sensitizer)

Type I photoinitiators (PI-184, PI-907, PI-819) undergo direct alpha-cleavage upon UV exposure to generate two primary radicals. Type II photoinitiators (benzophenone, thioxanthones) absorb UV energy and reach an excited triplet state, then abstract hydrogen from a co-initiator (amine), generating secondary radicals. DETX is a Type II sensitizer: it does not directly initiate polymerization but transfers energy to amine co-initiators (MDEA, TEA) or other photoinitiators. Its advantage is strong absorption at 380–420 nm (useful for mercury lamp emission lines and violet LEDs) where Type I initiators often have weak absorption.