Photodiscoloration inhibition of wood coated with UV-curable acrylic clear coatings and its elucidation

Wood coated with urethane-modified acrylic coatings was susceptible to yellowing induced by light. To find out the mechanism for inhibiting its photodiscoloration, wood specimens covered with separate acrylic clear free films containing stabilizers were used to simulate coated wood. Ultraviolet light absorbers tested in this: study reduced not only the discoloration of coating films but also those of the underlying wood. HALS was not helpful in reducing the photodiscoloration of wood coated with aromatic urethane-modified acrylate containing light absorbers, but it showed a significant synergistic effect on the inhibition of photodiscoloration of wood coated with aliphatic urethane-modified acrylate containing light absorbers. Comparisons of the UV transmission spectra of coating films revealed that HALS preserved the absorption capability of the light absorber in aliphatic urethane-modified acrylate after the lightfastness test, therefore elongating the service life of light absorber and, consequently, that of the coating. (C) 2000 Elsevier Science Ltd. All rights reserved.