Irradiation effects and beam strength in polyurethane materials for laser elements

Effects of irradiation on structure peculiarities and viscoelastic properties of the polyurethanes, synthesized by a polycondensation method with a use of different diisocyanate and glycol components have been investigated. Photooxydation processes are shown to change elasticity of the materials, glass transition temperature and average molecular mass for the chain segments between polymer cross-linked points, and also induce accumulation of hydroxyls in the system due to the formation of alcohol and hydroperoxide groups. Beam strength of the polyurethanes is found out to be dependent on the polymer chemical structure, in particular, on a length of the aliphatic block and density of the cross-linking network. Good agreement between the results obtained by the dynamic mechanical analysis, IR-spectroscopy, EPR methods and the data for the single-pulse laser destruction thresholds allows to predict photooxidation susceptibility for the further developed polyurethane materials.