Photodegradation of Lacquer Tree Paint Films and Their External Appearance

Osamu WATANABE* and Katsutoshi NAGAI

Material Technology Department, Fukushima Technology Centre; 1-12, Machiikedai, Koriyama-shi
963-0215 Japan
Department of Materials Science and Engineering, Faculty of Engineering, Yamagata University;
4-3-16, Jonan, Yonezawa-shi 992-8510 Japan

Measurements of color difference, gloss, and surface structures on lacquer paint films were made to obtain an insight into their photodegradation and the results were discussed in terms of the internal structure and the photodegradation mechanism proposed in a preceding paper based on reversed micelle structure in lacquer tree paint. It was found that the degradation can be readily evaluated by correlating visual phenomenon with the variations of chemical structures.
Chemical degradation in particles of reversed micelle structure could be explored from the color change obtained from measurements of color difference. Definite tendencies of decrease in red-series, coloration of yellow-series and increase in whiteness were confirmed from the measurements on the cured lacquer tree paint films as a function of exposure time.
Furthermore, results obtained from mesurements on gloss and surface structure suggested that particles of reversed micelle structure dissociate from the cured lacquer tree paint films owing to weak interactions between reversed micelles. It was deduced that the variation in these results with exposure time could be ascribed to the difference in the size of dissociating particles.
The results obtained in the present study gave a further indication that the urushiol takes the reversed micelle structure in lacquer tree paint films.

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