PHOTOPOLYMERIZATION OF MULTIFUNCTIONAL POLYMERS .5. POLYURETHANE-ACYLATE RESINS

A kinetic study of the light-induced copolymerization of a polyurethane-diacrylate with various acrylic monomers has shown the great reactivity of monomers containing a carbamate or oxazolidone function. A few milliseconds of irradiation is enough to polymerize nearly all the acrylate functions, each photon absorbed inducing the polymerization of over 10,000 double bonds. Atmospheric oxygen has a strong inhibitory effect on these radical-induced polymerizations carried out in thin films. The photo-initiator was found to have great influence on both the rate and the quantum yield of the polymerization. u.v. cured polyurethane-acrylate coatings exhibit high flexibility, excellent impact resistance and a fair hardness which can be substantially enhanced by the addition of a diacrylate monomer.