Thermochromic paint with three‐stage colour transition effect based on thermochromic microcapsules and its crosslinking modification

Abstract To expand the colour change range of thermochromic materials, two types of thermochromic microcapsules (TCMs) with different colour change temperatures and effects were utilised to prepare a TCMs blending system exhibiting a three‐stage colour transition at temperatures ranging from 10 to 60°C. Thermochromic paints were then prepared based on this TCMs blending system using a modified waterborne polyurethane (WPU). The thermochromic properties of the TCMs blending system and the impact of crosslinking modification on the coating properties were investigated. The findings revealed that the ratio of TCMs influences the colour change effect and temperature of the blending system. With temperature variations, the colour of the TCMs blending system can reversibly transition between blue, green and yellow, offering a more vibrant thermochromic effect compared with conventional thermochromic materials. The modified WPU enabled the preparation of paint from the blending system, which was applied to fabric surfaces to create multistage thermochromic fabrics. The mechanical properties, water resistance and adhesion of the modified coating were enhanced, and the colour fastness to washing of the fabrics improved by two grades. This study has practical significance for the application of TCMs and the development of colour‐changing textiles.