Fluoropolymer‐based clear and white paint coatings composition analysis by X‐Ray fluorescence

Abstract

A new method for the quantification of organic and inorganic phase fractions was developed for fluoropolymer/acrylic-blend paints -clear and white paint coatings -on aluminum panels by using wavelength dispersive X-ray fluorescence spectrometry (WDXRF). The method was developed for clear coat samples (only containing fluoropolymer and acrylic phases) as well as white paint samples by also measuring silica and titanium dioxide levels. Both WDXRF and X-ray photoelectron spectroscopy (XPS), a surface technique, were investigated. For clear coat samples, we found that WDXRF provided far superior quantitative results to XPS, likely related to the extreme surface sensitivity of XPS, in this case a drawback more than a strength. For white paint samples, the X-ray fluorescence spectrometry method achieved a relative accuracy typically better than 5% for the organic phases and better than 2% for the inorganic phases, for measurements on 8-mm diameter samples. Copyright © 2013 John Wiley & Sons, Ltd. IntroductionFluoropolymer-based coatings are used in a wide variety of applications including outdoor architectural coatings, [1][2][3] medical devices, [4] marine coatings, [5,6] or cookware, to name a few. In the architectural market, fluoropolymer-based paint formulations represent the high-end segment because of their chemical resistance and weatherability, allowing decades of unaltered outdoor color and performance. Paints using poly (vinylidene fluoride) in particular have a 50-year record history of outstanding performance linked to chemical resistance, durability, adhesion, and low dirt retention, as well as good moisture and fungus resistance. [1][2][3] Classic paint formulation on organic solvent technology, whereas modern paint formulation is based on latex technologies where the polymeric phases and pigments are suspended in an aqueous solvent, thus eliminating the negative environmental impact of the use of organic solvents. Such formulations involve multiple components addressing the need for longevity (weatherability), adhesion, color, and structural integrity. The analysis of dry paints (coatings) typically involves a number of techniques aimed at analyzing the organic and inorganic components of the paint. Spectroscopy techniques such as Fourier transform infrared/attenuated total reflectance, nuclear magnetic resonance (NMR), pyrolysis gas chromatography mass spectroscopy, matrix-assisted laser desorption/ionization mass spectroscopy, and thermal gravimetric analysis among others can contribute information to the identification and/or quantification of some of the components, organic or inorganic, that are part of the coating composition. [7,8] X-ray-based techniques could also be a valuable asset by providing information on the organic and inorganic paint components while achieving speed of analysis similar to vibrational techniques, an important aspect for quality control considerations. Christensen et al.[9] used energy-dispersive X-ray fluorescence to measure a series of elements ranging from aluminum to ...