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ABSTRACT:An organic-inorganic hybrid condensate formed by the reaction of lacquer sap and organic functional silane was examined to develop a naturally drying lacquer. The hydroxyl group of urushiol contained in the lacquer sap underwent alcoholysis reaction with the organic functional silane and generated a high molecular weight polymer of polysiloxane. The natural drying process of the hybrid lacquer film is a hydrolysis reaction. In addition, the activities of the alkoxy groups in the organic functional silane showed that the methoxy activity was higher than ethoxy, and trimethoxy activity was higher than dimethoxy. The amino residues in organic functional silane react with the cathechol ring of urushiol, and then the hybrid oxidizes to a dark color. However, there is a tendency for the ring-opening reduction of an epoxy group to produce a light color due to the coexistence of epoxy silane.

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Examination of thermal degradation of natural and synthetic lacquer films by pyrolysis-gas chromatography with mass spectrometry (Py-GC/MS) is reviewed. Due to the instantaneous heating decomposition, side reactions of internal or intermediate samples hardly occur, and the pyrolysis products can be retrieved without any change. Py-GC/MS has been used to analyze the composition of insoluble polymers and investigate degradation of resin materials. Lacquer film is a cross-linked polymer that is insoluble in any solvent. The aim of this review is to describe the application of Py-GC/MS to the analysis of lacquer, including natural lacquer saps, synthetic lacquer derivatives, and their films. After analyzing the chemical structures of the specific pyrolysis products by mass spectrometry, the lacquer tree species and growing region can be determined. These results have great significance for the protection and restoration of lacquer-coated cultural treasures.

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