Thermal Degradation of the Lacquer Film by Pyrolysis-Gas Chromatography-Mass Spectrometry

Abstract

Sap of the lacquer tree dries into a brilliant and tough film. It is a latex composed of urushiol, water, plant gum, water-insoluble glycoprotein, and laccase. Thermal degradation of the lacquer film was studied by pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS) using two and single-stage pyrolysis techniques. Urushiol, plant gum and waterinsoluble glycoprotein which were isolated from the lacquer sap was used to study the pyrolytic behavior of lacquer film by single-stage pyrolysis under best optimum pyrolysis condition. The characteristic peak appearing on the pyrograms were identified using a mass spectrometer which was directly attached to the gas chromatography. On the basis of the observed pyrograms, the degradation and polymerization mechanisms of the lacquer film were discussed. Consequently, it was evidenced that the format ion of lacquer film proceeds through the side chain-side chain C-C coupling and nucleus-side chain C-O coupling besides phenol coupling and nucleus-side chain C-C coupling.