Effects of zinc oxide filler on the curing and mechanical response of alkyd coatings

Abstract

Please cite this article as: L.F. Sturdy, M.S. Wright, A. Yee et al., Effects of zinc oxide filler on the curing and mechanical response of alkyd coatings, Polymer (2020), doi: https://doi. AbstractThe mechanical properties of an alkyd resin filled with zinc oxide pigment were studied at different concentrations over a wide range of time scales using dynamic mechanical analysis, quartz crystal rheometry and nanoindentation. The motivation for this work stems from the interest in accessing the long-term properties of paint coatings by studying the mechanical properties of historic paints. In this foundational work, we compare three different modalities of mechanical measurements and systematically determine the effect of pigment filler loading on the measured properties. Quantitative agreement between the methods is obtained when the characteristic time scales of each of the methods is taken into account. While nanoindentation is the technique most readily applied to historic paint samples, the rheometric quartz crystal microbalance (rheo-QCM) is the best suited for obtaining mechanistic information from measurements of paint properties over time, provided that appropriate thin-film samples can be produced. In these studies we find that ZnO increases the rate of oxidation of the alkyd during the initial stages of cure by an amount that depends on the ZnO content. J o u r n a l P r e -p r o o f Journal Pre-proof 2. Materials and Methods 2.1. Materials The alkyd films were prepared from Gamblin Artists Colors (Portland, OR) Galkyd mixed with Fischer Z50 zinc oxide ranging from 0.05 to 0.60 wet weight fraction. When necessary to change 2 J o u r n a l P r e -p r o o f Journal Pre-proof J o u r n a l P r e -p r o o f Journal Pre-proof J o u r n a l P r e -p r o o f Journal Pre-proof 7 J o u r n a l P r e -p r o o f Journal Pre-proof Thermogravimetric (TGA) experiments were conducted on naturally aged 5-month-old alkyd samples for four of the zinc oxide filler loadings listed in Table 1 to confirm the amount of zinc oxide pigment present relative to the binder after solvent evaporation. These results are shown in Figure 8 J o u r n a l P r e -p r o o f Journal Pre-proof J o u r n a l P r e -p r o o f Journal Pre-proof J o u r n a l P r e -p r o o f Journal Pre-proof J o u r n a l P r e -p r o o f Journal Pre-proof J o u r n a l P r e -p r o o f Journal Pre-proof -Zinc oxide accelerates the oxidative curing of alkyd paints. -Consistent results obtained with nanoindentation, dynamic mechanical analysis and high frequency rheometry. J o u r n a l P r e -p r o o f Journal Pre-proof J o u r n a l P r e -p r o o f Journal Pre-proof Declaration of interest: none J o u r n a l P r e -p r o o f Journal Pre-proof

After the paint has dried: a review of testing techniques for studying the mechanical properties of artists’ paint

“…More recent studies using nanoindentation have incorporated comparisons of the data from nanoindentation with data from DMA and dynamic vapor sorption to understand how each technique showed the changes in mechanical properties when subjected to variations in RH [100]. Measurements on the same zinc oxide filled alkyd samples with DMA, QCM and nanoindentation have confirmed the compatibility of the three techniques when the frequency of the measurement is appropriately taken into account [17]. Fujisawa et al add a compliance term to their determination of mechanical properties to account for edge effects of the stiffer embedding resin on a paint sample [101].…”

“…Some studies focused on the mechanical properties of paint have used a measurement of pigment content based on volume, pigment volume concentration (PVC), instead of pigment-to-binder ratio, which is a weightbased measurement [15][16][17]. Mathematical models have also been developed to describe the effects of pigment particle concentration and shape on the stiffness of the sample and have been explored in some of the studies that will be highlighted in Section 2 [18,19].…”

“…The application of time-temperature superposition to DMA data collected over a range of temperatures allows researchers to access a much wider range of measurement frequencies than typically accessed with other methods. Sturdy et al used DMA to understand the material response of a commercially produced alkyd based binding medium (Galkyd) as a function of curing time and filler content of zinc oxide, providing a survey of the effects of filler content and the compatibility between DMA, the quartz crystal microbalance (QCM), and nanoindentation for studying paint materials [17,69]. These studies also compared the material responses measured using DMA and the QCM, demonstrating that both techniques are able to capture the glassy material response well.…”

“…The curing behavior of a commercial alkyd binding medium was measured over the course of three years, as well as the effects of temperature and the filler effects when zinc oxide was added [17,69,95]. Analyzing both the mass and the mechanical properties of a sample can provide a clearer picture about how the material responses of paint films change as a function of their environment as demonstrated in Fig.…”

A Review of Microwave Synthesis of Zinc Oxide Nanomaterials: Reactants, Process Parameters and Morphologies

“…ZnO is used as an ultraviolet (UV) radiation filter in sunscreen cosmetics (creams, balms, lotions). Nowadays ZnO is commonly used as an additive in such products as pigments (zinc white, zinc green), flame retardants, cements, ceramics, porcelain, glass, plastics, sealants, adhesives, lubricating oils and paints [ 70 , 76 , 89 , 90 , 93 , 94 ]. The presence of ZnO in paint, apart from changing the colour, contributes also to providing the paint coat with anti-corrosion and antifouling properties.…”