A comparison study of alkyd resin used in art works by Py-GC/MS and GC/MS: The influence of aging

• Py-GC/MS with double-shot technique, THM-GC/MS as well as GC/MS methods were applied for the characterization of drying and degradation of alkyd paints.
• Oxidization products such as aldehyds were detected.
• The formation of free phthalic anhydride during aging was found.
• The possibility for the identification of alkyd components by those techniques was discussed.

In order to study the drying process and the degradation processes of alkyd resins, different types of alkyds for art works were investigated by pyrolysis-gas chromatography and mass spectrometry (Py-GC/MS) with double-shot technique, thermally assisted hydrolysis and methylation (THM-GC/MS) as well as GC/MS after derivatized with the reagent of m-trifluoromethylphenyl trimethylammonium (Meth-Prep II) methods. By using Py-GC/MS with double-shot technique, the oxidization products of alkyds including 2-octenal, 2-decenal, 2,4-decadienal, nonanal and 2-undecenal could be detected during drying, while the main component of alkyd – phthalic anhydride was found in higher amount in aged samples than unaged ones, indicating the formation of free phthalic anhydride during aging. The characterization of the main components of alkyds such as dibasic acid, polyol and drying oil can be achieved by using the techniques (THM-GC/MS) and GC/MS with the derivatization reagent Meth-Prep II. The decrease of unsaturated fatty acids and increase of phthalic anhydride were observed in the aged alkyd samples by those two techniques. The complementation of different analytical techniques provided several and different results, which are useful for a better understanding of the drying and degradation properties of alkyd resins.