Can Spectroscopy Quickly and Easily Evaluate Paint Samples?

author: Susan

2022-02-10

Can Spectroscopy Quickly and Easily Evaluate Paint Samples?

Paint and coating materials consist of ingredients such as pigments, dyes, fillers and binders, each of which is carefully mixed to help enhance product quality and performance. The ability to evaluate different coating formulations and UV protection coatings in minutes compared to hours can have a significant impact on development time and cost.
Experimental system
For quick and easy evaluation of paint samples on flat surfaces and substrates, we used an extended-range (UV-Visible-NIR) spectrometer with a broadband light source, a reflectance integrating sphere, and a diffuse reflectance standard. This modular setup allows us to quickly characterize the diffuse, specular, and total reflectance properties of each sample.

ATP5020P extended range spectrometer (200-1100 nm)
ATG1020H deuterium-tungsten halogen light source (180-2500 nm)
Integrating Spheres integrating sphere
(2) UV-VIS-1-600 600 µm extreme solarization-resistance optical fibers
Reflectance Standard Spectralon® diffuse reflectance standard
Reflectance-Holder reflectance standard holder

Since integrating spheres significantly attenuate light levels during reflectance measurements, we chose the ATP5020P as our spectrometer due to its high sensitivity in the 200-1100 nm range. The integrating sphere has a 50 mm sphere diameter and gloss trap for diffuse and total reflectance measurements. The fiber's 600 um core diameter meets the optical needs of an integrating sphere, while the fiber's extreme sunfastness mitigates degradation that can occur in fibers in the UV region. The Reflectance-Holder is a convenient accessory that can be used both as a reflectance standard holder and as a sample stage.

Measurements Solution

We analyzed five samples applied to a flat surface: three different white paints, a highly reflective UV aluminum tape, and a highly absorbing UV strip. Samples are measured using an integrating sphere that contains a gloss trap, so for samples applied to the middle strips (regions) of a flat surface, both total reflectance (gloss trap closed) and diffuse reflectance (gloss trap open) can be measured. In addition, measurements were performed on high and low UV reflectance samples as well as the top, middle and bottom strips (unpainted) of the surface. Each sample was measured at three different locations and the spectral data were averaged. All samples were referenced to a spectral reflectance standard, which was stored in the reflectance standard holder. Connect the light source and spectrometer to the appropriate ports on the integrating sphere using sun-resistant fiber optics. The integrating sphere is then inverted so that the port of the sphere can be placed on the sample supported by the reflectance standard holder. With the gloss trap turned on and then off, the reflectance was measured at three different locations on each sample (Figure 1). To avoid setup variability due to fiber movement during measurements, lift the sphere slightly to change the sample, rather than moving the sphere between samples.

Figure 1. The total reflectance spectrum here is the average of the spectrum measured at three locations in the middle strip on the flat surface.
Data were also obtained for coatings applied to the areas above and below the middle strip.
There may have been some errors in the reflectance data related to the missing gloss trap piece for the integrating sphere,
which we fixed by modifying the attachment slightly.

Why Paint Quality Matters
There's a lot more to paint than just how fast it dries or how a certain color looks in your living room. For example, coatings have additives designed to absorb UV wavelengths, help prevent fading and degradation, and even provide sanitizing properties. Broadband spectroscopy systems can help coatings researchers test new formulations more efficiently, and manufacturers can produce higher-quality, longer-lasting, safer coatings.

Related Products

  ATP5020P Deuterium Halogen ATG1020H   Integrating Spheres UV-VIS-1-600   Reflectance Standard
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