FLUORESCENCE PROBE TECHNIQUES (FPT) FOR MEASURING THE RELATIVE EFFICIENCIES OF FREE-RADICAL PHOTOINITIATORS

A new method for determining the relative efficiencies of free-radical photoinitiators is reported. Called the fluorescence probe technique (FPT), the method has been used to determine the relative initiation e fficiencies of several commercial photoinitiators and new phenyl glyox ylate derivatives in the photopolymerization of a model monomer, triet hylene glycol diacrylate. The reactivity of each initiator was measure d in reference to that of a standard commercial initiator, 2,2-dimetho xy-2-phenylacetophenone, Irgacure 651. Efficiencies differ widely amon g the acetophenone derivatives studied, and the phenylglyoxylate initi ators are somewhat less reactive than the standard.