The surface properties and the surface-treatment of the sillicon nitride exposed to the atmosphere with alcohols (n-octanol, n-cetanol) and octadecyl trichlorosilane were investigated through Xray photoelectron spectroscopy, Xray diffraction method, scanning electron microscopy, dispersive properties, infrared absorption spectra and pyrolysis, respectively. The followings were ascertained from these results : (1) The surface properties of silicon nitride were converted from hydrophilic to hydrophobic through the surface-treatment, but the composition and the structure of the substrate were invariable. (2) The characteristic absorption of surface group of surface-treated silicon nitrides was not detected by means of the infrared absorption spectra because of the small number of surface group per unit weight due to small surface area of the nitrides. (3) The pyrolysis curves and pyrolysis products of the surface-treated silicon nitrides showed the same as those of the surface-treated silica gel with the same reagents used for the surface-treatment. (4) Since the O1s peak was observed in the Xray phtoelectron spectrum of silicon nitride, the surface of silicon nitride was perceived to be covered by the silicon dioxide. (5) Thus, the surface of silicon nitride exposed to the atmosphere was composed of the silicon dioxide layers formed by the reaction with the atmospheric oxygen or water and its surface was covered by the surface hydroxide (surface silanol), therefore, the methods for the surface-treatment of silica gels were acertained to be effective also for that of silicon nitride.
In order to elucidate the photodegradation process of methacrylate resin/butylated melamine resin paint films, four kinds of methacrylate resins have been synthesized from methyl methacrylate (MMA), hydroxyethyl methacrylate (HEMA), and styrene (ST) (ST conts. : 0, 20, 40, 60% by wt. in the resin). Their photodegradation processes have investigated by using ESR and FT-IR spectroscopies. It has been found from these measurements that in the photodegradation process of methacrylate paint films, hydrogen, methacrylate, and methyl radicals are generated, followed by the formations of dimer acid and benzyl compounds. The use of an anthrapyridine pigment to the resins resulted in the formation of a stable anthraquinone radical (g=2.0042), when the resins were irradiated by ultra-low pressure and ultra-high pressure mercury arc lamps at room temperature. The concentration of the radical increased as the styrene content increased. The relationships between the concentration of the anthraquinone radical and gloss retention and color difference of the painted panels exposed under ultra-low pressure mercury arc lamp and sunshine weather meter were also examined, which leads to the useful application of the ESR measurements to determine the degree of degradation of resins. Finally the degradation mechanism of the resins are discussed based on the results.