Title
Ultraviolet light absorber mobility in crosslinked coatings: Experiments and modeling
Document Type
Article
Date of Original Version
3-1-2007
Abstract
The diffusion of an ultraviolet absorber (UVA) across a concentration step change in an acrylic melamine clearcoat was measured via micro-ultraviolet spectroscopy. Concentration profiles were obtained after diffusion times of 4-200 h at steady temperatures of 70, 80, and 90 °C. The glass transition temperature of the coating was measured via dynamic mechanical analysis for each time-temperature pair, and Tg was observed to increase with thermal aging, with a faster rate of increase at higher aging temperatures. The change in Tg was modeled using a first-order dependence on the deviation from a long-time Tg asymptote. The diffusion coefficient was then represented by a free volume expression, and the combination provided an accurate model of the measured concentration profiles. The time-dependent increases in glass transition temperature helped to explain why UVA diffusion does not alleviate concentration gradients created by photooxidation under natural weathering conditions. © 2006 Elsevier B.V. All rights reserved.
Publication Title, e.g., Journal
Progress in Organic Coatings
Volume
58
Issue
4
Citation/Publisher Attribution
Peters, C. A., K. R. Ellwood, Y. Srivastava, M. E. Nichols, and M. L. Greenfield. "Ultraviolet light absorber mobility in crosslinked coatings: Experiments and modeling." Progress in Organic Coatings 58, 4 (2007): 272-281. doi: 10.1016/j.porgcoat.2006.12.004.