A radical initiation ability of new initiating systems in photopolymerization of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol triacrylate has been investigated and presented. The evaluation of alkyltriphenyl-and tetraalkylborates, iodonium salts, N-alkoxypyridinium salts, maleimides, phthalimides, 1,3,5-triazine derivatives and others as a free radical source in combination with suitable photosensitizer for radical polymerization of triacrylate is described. It is assumed that the photochemical decomposition of a coinitiator molecule results in formation of free radicals, which further initiate polymerization. The order of activity of free radical sources on kinetic of photopolymerization was also presented. Different initiator activity can be explained by the difference in the decomposition rate constant and the reactivity of radicals formed toward the double bond of monomer. (C) 2017 Wiley Periodicals, Inc.