Laser interferometric technique for measuring polymer cure kinetics

An optical interference apparatus for the analysis of polymer curing kineti cs is described. The device employs a helium-neon laser and a home-built Mi chelson interferometer to measure refractive index variations and film thic kness variations during film polymerization. The refractive index variation provides a phenomenological measure of the extent of cure. The technique i s demonstrated by collecting interferometric curing profiles for a UV photo curable acrylate resin formulation. Systematic comparisons of curing profil es are made as a function of UV illumination intensity and photoinitiator c oncentration. Several aspects of the curing process are characterized by th ese interferometric measurements, such as film shrinkage, gel. point format ion, and the kinetics of photopolymerization inhibition. (C) 1999 John Wile y & Sons, Inc.