Coatings chemists and paint formulators face the challenge of developing products that are not only durable and aesthetically pleasing, but that address sustainability issues and have added functionality. The technology of infrared-reflecting (IR) pigments addresses both sustainability and the desire for functionality by allowing the development of coatings that can reduce energy usage and meet building code-related certifications and requirements. There are three main classes of IR pigments that work with different mechanisms and can be utilized individually or together for maximum performance. This article is meant as an introduction into the fundamental properties of the pigments to better understand how they can be used in fully formulated products.
First, a basic understanding of the complete solar spectrum is needed. Standard coatings are primarily concerned with color, which is determined by the visible, and the ultraviolet (UV) wavelengths of light, which impacts the durability of a paint or coating. The near-infrared (n-IR) part of the solar spectrum is often ignored. The UV (295-400 nm) spectrum is only a small percent of the sun’s energy, with the rest divided up roughly in half between the visible (400-700 nm) and the invisible near-infrared (700-2500 nm) spectrums.