Ternary mixture thermochromic microcapsules for visible light absorption and photothermal conversion energy storage

Thermochromic microcapsules with photothermal conversion properties were prepared by melamine urea formaldehyde resin (MUF) coated ternary mixtures (color coupler, color developer and solvent). The particle characteristics, chemical structure, heat storage properties, discoloration effect, thermal cycling durability and photothermal conversion properties of microcapsules were analyzed and characterized by ESEM and LPSA, FTIR and XRD, DSC and TGA, SC-10 and UV–Vis, thermal cycling test and solar simulator. The thermochromic and photothermal conversion mechanisms of microcapsules were analyzed. The results showed that the thermochromic microcapsules with a core material ratio of (1:3:60) have the best comprehensive performance. The chromatic aberration value of RTPCMs-C3 and RTPCMs-O3 is 23.35 and 12.14, respectively, which has a certain visible light absorption capacity and excellent thermal cycle durability. The photothermal conversion efficiencies of RTPCMs-C3 and RTPCMs-O3 under simulated solar irradiation were 55.4% and 72.9%, respectively. The conjugated organic polymer core material selectively absorbs the electromagnetic radiation frequency which are matching its internal electronic transition, causing the atomic lattice vibration to generate heat. The heat changes the state of the core material and dissociates the internal conjugated double bonds, eventually causing the microcapsules to change color.