Optical properties of polymer-based coatings containing metallic particles: effect of particle shape and binder

Polymer-based coatings containing metallic microparticles are a kind of functional material with effective spectral selectivity. The spectral radiative transfer model of polymer-based coatings is built based on geometrical optics, and the spectral radiative characteristics of the coatings were investigated by Monte Carlo ray-tracing method. The coatings consist of aluminum particles with different shapes as fillers and four kinds of polymer resins as binders, respectively. After verifying the reliability of the method, the effect of particle shape and binder on the infrared emission properties in the range of 8–14 μm is systematically investigated. The results demonstrate that adding flake particles into the coating can obtain lowest infrared emissivity, which is at most 86.79% lower than the coating containing spherical particles when the volume fraction is 30%. The mean emissivity of Al/acrylic resin, Al/polyetherimide (PEI), Al/polymethyl methacrylate, and Al/polystyrene (PS) composite coatings is 0.46, 0.48, 0.41, and 0.22, respectively. Al/PS composite coating has the minimum mean infrared emissivity among these four kinds of polymer-based coatings, which is 54.2% lower than Al/PEI composite coating. The method proposed in this work will provide theoretical guidance for experimental research.