Cure and photodegradation of two-package acrylic/urethane coatings

Abstract

Ind. Eng. Chem. Prod. Res. Dev. 1986, 25, 289-296 289 of composites fabricated with resin-treated coir fiber mat showed an posites based on untreated coir fiber mat a significant reduction in ILSS was observed ( Figure 11).It may be concluded from these studies that a coating of USP resin on coir fibers improves the compatibility of Kulkarnl, A. G.; Cheriyan, K. A.; Satyanarayana, K. G.; Rohatgi, P. K. J. Appl. folym. Scl. 1983, 28, 625. Mukherjee, R. N.; Pal, S. K.; Sanyal, S. K.; Sanyal, S. K. J. Appl. po/ym. Scl. 1983, 28, 3029. Prasad, S. V.; Pavithran, C.; Rohatgl, P. K. J. Mater. Sci. 1983, 18, 1443. SrMhar, M. K.; BasawaraJappa, G.; Kasturl. S. G.; Balasubramanlum I n d h J. Texf. Res. 1982, 7 , 87. Varma, D. S.; Varma, M.; Varma, I. K. Text. Res. J. 1984, 54, 827. Varma, D. s.; Varma. M.; Varma, I. K.. "Coir Fibers I1 Evaluation as a reinforcement in unsaturated polyester resin", J . Reinf. flast. Compos. 1985. 4 . 419. at humidities, for 'Omfibers with matrix resin and improves the aging characteristics of composites. Varma, 'D. 'S.; Varma, M.; Varma, I. K., "Composite Materials from Coir Fibers", submitted for publication to folym. Mater. Scl. Eng , Registry No. Acrolite 404, 101374-98-5. L i t e r a t u r e Cited Belmares, H.; Barrera, A.; Castilio, E.; Verheugen, E. V.; Monjaras. M.; Patfoort, G. A.; Bucquoye, M. E. N. Ind. Eng. Chem. Prod. Res. Dev. 1981, 20, 555.The chemistry and kinetics of cure and hotodegradation of two-package acrylic/urethane coatings have been band in the infrared has been found to obey simple second-order kinetics. The activation energy of the cross-linking reaction is 8.2 kcal/mol. Second-order kinetics and the relatively low activation energy lead to coatings with greater cure latitude (substantially wider cure windows) than typical acrylic/melamine coatings of similar composition. The urethane cross-links formed on cure are found to degrade on exposure to ultraviolet light. Loss of urethane cross-links has been found to be photochemical rather than hydrolytic in nature. The chemistry of cross-link degradation is a function of the composition of the acrylic copolymer and can be greatly inhibited by the addition of hindered-amine light stabilizers. measured by infrared and magic-angle ' t: C NMR spectroscopies. The rate of disappearance of the Isocyanate

Photo-oxidation of acrylic-urethane thermoset networks. Relating materials properties to changes of chemical structure

“…1 shows the IR spectrum of the acrylic-urethane from before ageing to 2700 h of photo-oxidation in artificial accelerated ageing. The initial spectrum and the main band assignments have already been discussed in previous papers [17,18]. Fig.…”

Photodegradation and photostabilization of urethane crosslinked coatings

“…In previous studies of acrylic urethane photodegradation under harsh exposure conditions, it was found that the addition of TIN 770 reduced the rate of both cross-link scission and carbonyl growth (Bauer et al, 1986(Bauer et al, , 1988. The photooxidation rate remained constant over the exposure time.…”

Formaldehyde release from acrylic/melamine coatings during photolysis and the mechanism of photoenhanced cross-link hydrolysis

“…Support for the participation of peracid species in coating oxidation is found in model compound studies by Felder et al (1980). IR and NMR studies of coating degradation chemistry reveal substantial differences between urethane and melamine cross-linked coatings containing Tinuvin 770 (Bauer et al, 1986). This additive is both more effective and more persistent in urethane coatings than in melamine coatings.…”