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

Abstract

a b s t r a c tCommercial formulations of poly(vinyl acetate) (PVAc) and acrylic dispersions and paints commonly used by artists include a number of additives such as surfactants, coalescing agents, defoamers and thickeners, which are designed for improving shelf-life, as well as chemical and physical properties of the resulting product. Recent studies have shown that additives present in paints play an important role in the alteration processes undergone by the painting during ageing and further in cleaning tasks planed in conservation interventions. However, the identification of additives is a difficult task due to the elusive character of these substances present at low concentration in the paint.In this context, a four-step approach is proposed that includes analysis of paint samples together with analysis of their water extracted products by pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and pyrolysis-silylation-gas chromatography-mass spectrometry (Py-silylation-GC-MS). This analytical strategy enables a better characterization of common additives present in commercial PVAc and acrylic paints and dispersions. In particular, the analysis of water soluble extracts, which are mainly composed by paint additives, avoids the interference of the major polymer pyrolizates. Experimental conditions concerning sample preparation and instrumental working conditions of both Py-GC techniques are optimized.Both acrylic and PVAc paints presented poly(ethylene oxide) (POE) type fragments dominating the background of their pyrograms, especially when derivatized by means of hexamethyldisilazane (HMDS). For the first time, additives such as alkyl sulfate and alkyl ether sulfate with C 10 and C 12 alkyl chains, poly(ethoxylate) fatty alcohol and octylphenyl poly(ethoxylate) surfactants were identified, as well as polyvinyl alcohol (PVOH) protective colloids, hydrophobically modified ethoxylated urethane (HEUR) thickeners an defoamers. Their major fragments and corresponding mass spectra are discussed.

Tracing Poly(Vinyl Acetate) Emulsions by Infrared and Raman Spectroscopies: Identification of Spectral Markers

“…So far, several studies have used different techniques for the molecular characterisation of VAc-based films and paints [7,[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Within these studies, Fourier transform infrared spectroscopy (FTIR) [7,15,18,20,21,[23][24][25][27][28][29] and pyrolysis-gas chromatography and mass spectrometry (Py-GC/MS) [14][15][16][17][21][22][23]26,27] have been highly used, but other techniques such as size exclusion chromatography (SEC) [7], atomic force microscopy (AFM) [19], scanning electron microscopy-energy-dispersive X-ray microanalysis (SEM/EDX) [20] and UV-Vis spectroscopy [20], differential scanning calorimetry (DSC) [18], thermo-gravimetric analysis (TGA) [18], mechanical properties test [18] have also been used, among others. Still, most of these studies have been individually focused on a narrow set of PVAc compositions (smaller variabi...…”

A molecular study of modern oil paintings: investigating the role of dicarboxylic acids in the water sensitivity of modern oil paints

“…3 Modern artists' paints, including oil paints, can incorporate additions of metal salts, metal soaps, a variety of dispersion agents, plasticizers, llers and surfactants, amongst other materials, to inuence specic properties such as rheology, stability, drying rate, and colour. 1,[4][5][6][7][8] Among these, metal soaps and/or free fatty acids (FFA) were added to oil-based paints as dispersing agents in order to improve the wetting properties of the pigments, and their ability to be homogeneously dispersed in the oil binder. [9][10][11][12] Some modern oil paintings are now beginning to present challenges for conservation: 13 deterioration due to material composition and exposure to environment have led to surface changes, and in some cases, the migration and aggregation of chemical species occurs, leading to a range of issues such as the formation of vulnerable 'medium skins' on paint surfaces, efflorescence, protrusions, colour change and paint delamination, as well as water-and solvent-sensitivity of paint surfaces.…”

Modeling the wetting of titanium dioxide and steel substrate in water-borne paint and varnish materials in the presence of surfactants

“…However, the reasons for the improvement of these indicators are not substantiated. Study [10] shows that in various paint compositions, the introduction of surfactants makes it possible to obtain coatings with the most uniform distribution of pigment particles in the polymer matrix, due to the maximum stability of the "film-pigment-surfactant" suspensions. Moreover, for these coatings, the maximum is observed of protective resource, optical properties, gloss, concealment, and other characteristics.…”