Acrylic and Vinyl Resins Identification by Pyrolysis-Gas Chromatography/Mass Spectrometry: A Study of Cases in Modern Art Conservation

Abstract

This paper describes the identification of acrylic and vinyl resins applied in the art and conservation fields by pyrolysis gas chromatography-mass spectrometry. Initially, commercial samples of painting varnishes, binding media, coatings, adhesives, and consolidants were analyzed for method development and preparation of a reference database for the individual polymer materials. The analysis conditions (pyrolytic and chromatographic) were optimized in order to obtain the best resolution for a fragment mixture, using low amounts of sample (microgram range) without previous treatment. The pyrolysis temperature influenced the fragmentation and, consequently, the resolution of the obtained pyrogram. The characterization of the resins was carried out through the identification of the monomers units or thermal degradation products based on their mass spectra, and then linking them to the structure of the possible polymer. As practical examples, the methodology was applied with success to the binding medium identification of the main brands of acrylic artists' paints present in the American and European markets. Additionally, analyses of art and conservation materials of two paintings from the Collection Amigas da Cultura at the Universidade Federal de Minas Gerais (UFMG, Brazil) were conducted.