Photoinitiated Curing of Multifunctional Monomers

Abstract

Radiation curing is being increasingly used in advanced technology applications, owing to its distinct advantages, mainly its great speed, selective cure and 100% solid formulation. Under intense UV or laser irradiation, the polymerization of multiacrylate monomers was shown to proceed extensively in a fraction of a second. The kinetics of these ultrafast reactions was studied quantitatively by means of the newly developed real-time infrared (RTIR) photo-spectroscopy. From the conversion vs. time curves recorded, the efficiency of some novel photoinitiators and acrylic monomers has been evaluated in UV-curable resins. The crosslinking-polymerization was found to proceed with long kinetic chains, despite the high initiation rate provided by UV or laser irradiation. The actual rate at which polymer chains are growing has been first determined from the polymerization profile recorded upon pulsed laser exposure. The photocured polymers exhibit remarkable mechanical properties, as well as a great resistance to chemicals, heat and radiation. These characteristics, together with the process facility, account for the wide-spread applications of UV curable resins, in particular as protective coatings to improve the weatherability of polymer materials, such as poly(vinyl chloride). Other applications of laser-induced curing are to be found in stereolithography, optoelectronics, holography, and laser direct imaging.