Characterization of natural coating materials using Fourier transform infrared spectroscopy and pyrolysis-gas chromatography/mass spectrometry

Noriyasu Niimura, Hiroshi Terashima

Fourier transform infrared spectroscopy (FT-IR) with attenuated total reflectance (ATR) technique is one of the non-destructive analysis methods.  Using this method, a Japanese lacquer film and a cashew resin film were characterized.  Additionally, the results were compared with those obtained by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS).   Cashew resin has been used as a substitute of the Japanese lacquer, because it dries quickly and the cost is lower.  The absorption signals assigned to C-O stretching were detected at ca. 1260-1000 cm^-1 in the respective FT-IR spectra.  The signal at 1031 cm^-1 is prominent in the Japanese lacquer film, but that in the cashew resin film is not.  This prominent signal is attributed to plant gum.  The Japanese lacquer film is composed of plant gum of which main constituent is polysaccharide, but the cashew resin film is not. Using Py-GC/MS, the urushiol components were detected as the pyrolysis products from the Japanese lacquer film; however, cardanol components were detected from the cashew resin film.  The OH, CH, C=C and C-O stretching absorption signals detected by FT-IR are attributed to these compounds, though the prominent signal at 1031 cm^-1 in the Japanese lacquer film is done to the plant gum.