Experimental study on pigmented coatings using two particle types with complementary optical features

Abstract

One effective measure for building energy reduction is to pigment coatings on building exteriors. Conventionally, most coatings are designed using single particle types. Due to the limited particle optical features, these coatings usually perform well in one performance (e.g., thermal aspect) but poorly in another (e.g., aesthetic aspect). Thus, in practice they may not be able to meet the user-required performance in both aspects. Using particles with complementary optical features, such requirements may be fulfilled. To this end, this study experimentally investigates double-layered coatings using two particle types (i.e., CuO and TiO2) with complementary features. The performance of 24 coating samples is evaluated with selected total particle masses and mass ratios. Results show that in comparison with the conventionally designed coatings, the two proposed ones (i.e., TiO2 - CuO and CuO - TiO2 coatings) provide more performance alternatives under varied mass ratios; and they also present significant performance differences. For instance, when the TiO2 mass ratio increases, the total solar reflectance of the CuO-TiO2 coating increases slowly at first but quickly afterwards; while that of the TiO2-CuO coating increases quickly in the beginning but experiences a slow increase afterwards. It also illustrates that as the same required performance is met, the final choice of the two coatings is mainly determined by the initial costs of the utilized particles. Considering the optimal design in practice, the proposed coating is modelled. Validation results are shown at last.