Influence of UV radiation wavelength on conversion and temperature distribution profiles within dimethacrylate thick material during photopolymerization

Abstract

UV-light initiation is now commonly used to induce polymerization of multifunctional monomers. The highly crosslinked networks obtained have a wide variety of applications. The thermal effects which take place during polymerization can be the cause of non-homogeneity and defects in the final material. These defects greatly alter the physical properties of the final products, particularly the optical ones, which causes problems in the design of thick and optically perfect materials. To better control the homogeneity of photocured materials and to determine the influence of different experimental parameters on them, conversion and temperature distribution profiles within a material during photopolymerization were simulated numerically, using the general heat equation applied to one-dimensional system. To describe the true conditions of kinetic experiments, some necessary parameters were measured, like conversion, reaction rate, spectral irradiance of the Hg vapor lamp and dimethacrylate spectral absorbance. We focused our attention more particularly on the influence of the irradiation wavelength. Indeed, the high values of the spectral absorbance coefficient cause a great decrease in light intensity in the depth of the material and lead in turn to a sharp drop in conversion.