Development of near-infrared reflective inorganic pigment dispersions in the continuous phase of solvent-binder medium

Abstract

Coatings containing functional pigments capable of reflecting radiation in the near-infrared (NIR) spectrum have been coveted in recent years to meet various industrial specifications. In this study, NIR reflective inorganic pigments with the chemical structure of TiO₂, CoAl₂O₄, and (Cr,Fe)₂O₃ were dispersed individually in the continuous phase of organic solvents and thermosetting acrylic polyol to form ready-to-use colorants for NIR reflective coatings. A total of ten different pigments, three TiO₂, three CoAl₂O₄, and four (Cr,Fe)₂O₃, were included. Resin-dispersant compatibility and solvent-pigment compatibility in potential paint formulations were tested prior to dispersion design. The ability of the developed pigment dispersions to maintain the primary particle size distributions was confirmed by stability tests, and UV–Vis–NIR spectra of fresh pigment dispersions drawn-down on steel plates were comparatively evaluated. Although the change in pigment particle size distribution after subjecting the dispersions to different temperatures was negligible, the favorable NIR reflectance obtained by certain pigment dispersions served to select the optimum pigment dispersions within dispersions of the same pigment chemistry. The ALTIRIS 800, 22-5600, and 30C941 dispersions exhibited higher reflectance in the NIR spectrum compared to other developed TiO₂, CoAl₂O₄, and (Cr,Fe)₂O₃ dispersions, respectively, and supported their use in paint designs suitable to autonomous vehicles.