In order to elucidate the degradation process of epoxy resin paint film, bisphenol A/epichlorohydrin type epoxy clear films were coated on the sample tube of ESR (X-Band) and they were exposed under ultra-low pressure mercury arc lamp (Main wave length : 254 nm) so as to detect radical by ESR equipment.
A stable radical was detected and was identified as phenoxyl radical of g=2.0042.
The change of FT-IR spectra of clear film exposed for 24 hours under the lamp was measured.
In the photo-degradation process of resin film, phenoxyl radical was induced. Then, quinonoid and aldehyde compounds appeared gradually while various low molecules were evaporated.
White paints using four kinds of surface treated titanium dioxides were prepared in the same epoxy/butylated urea system.
Relative quantity of phenoxyl radical and gloss retention for four kinds of painted film were measured after exposing under the lamp.
As the results, it was pointed out that the more the relative quantity of phenoxyl radical, the lower the gloss retention.
View full abstract