Identification of additives in poly(vinylacetate) artist’s paints using PY-GC-MS

Abstract

Commercial poly(vinyl acetate) (PVAc) paint formulations for artists include a number of compounds in addition to the PVAc polymer and pigments to improve the physical and chemical properties of the resulting product. Among the most common additives are surfactants, coalescing agents, defoamers, freeze-thaw agents and thickeners. These products significantly influence the behaviour of the dried film. Nevertheless, they are usually difficult to detect with conventional analytical methods given their low concentration. In order to identify these additives, present in the dried film as minor components, an analytical method based on in situ thermally assisted pyrolysis-silylation gas chromatography-mass spectrometry (GC-MS) using hexamethyldisilazane as a derivatisation reagent is proposed. This method improves the conventional GC-MS analysis performed by direct pyrolysis and enables the simultaneous identification of the PVAc binding medium and the additives included by the manufacturer in the commercial paint. Five different commercial PVAc paints have been analysed, namely, armour green, burnt umber, oriental red, raw umber and white from Flashe. Internal plasticiser VeoVa consisting of C(10) fatty acids with highly branched chains has been recognised from the MS spectra. On the other hand, the differences found in the additive content of the studied paints, in particular the poly(ethylene glycol)-type surfactant, are in good agreement with their mechanical properties.

Characterization of additives of PVAc and acrylic waterborne dispersions and paints by analytical pyrolysis–GC–MS and pyrolysis–silylation–GC–MS

“…1b shows a series of peaks throughout the pyrogram of Conrayt ® , which correspond to POE fragments in their trimethylsilylated (TMS) form, with characteristic m/z 45, 73, 101, 103, 145 and 161. Such fragments have not been detected by conventional Py-GC-MS and can be ascribed to a diversity of additives, especially to surfactants [11]. Ethanoic acid in its TMS form can be found as a sharp peak at early retention times, which confirms the presence of the PVAc resin.…”

“…Py-silylation-GC-MS of VeoVa monomer produces a variety of fatty acids, which appear in their TMS form. A detailed study of these structures can be found in a previous report performed by the authors [11].…”

“…In particular, a type of additives composing the polar fraction of these waterborne formulations can be identified by this technique. Some advantages obtained by using this method to study additives in PVAc paints have been discussed elsewhere [11]. Fig.…”

“…Mass spectrum of the latter exhibits fragment ions at m/z = 158, 143, 73, 69, 41. Methacrylic acid may be included as a co-monomer in PVAc formulations in order to improve overall mechanical properties and UV resistance [11].…”

“…Recently, a report described the use of Py-GC-MS in double-shot mode for the detection of oxidation products in aged acrylic samples [28]. HMDS has been proposed by the authors to perform Py-silylation-GC-MS on a series of PVAc-Vinyl Versatate (VeoVa) paints, for studying the additives otherwise difficult to characterize by means of the conventional techniques [11].…”