Study on preparation, characterization and application of mixed-colorants thermochromic microcapsules

In order to expand the color-change range and make the discoloration temperature suitable for the daily textiles, a new formulation of mixed-colorants thermochromic core material is designed, in which crystal violet lactone (CVL) is the basic color former, bisphenol A (BPA) is the developer, especially the solvent-based dye and dodecyl dedecanoate are used as the extended dye and the solvent, respectively. Scanning electron microscope (SEM), differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA) were applied to study the morphology, encapsulation rate, non-isothermal crystallization behavior and thermal stability of the mixed-colorant thermochromic microcapsules (MCTMs) prepared by in-situ polymerization. The results show that MCTMs have good sphericity, uniform particle size, good thermal stability and the encapsulation rate can reach 86.73%. Under the non-isothermal conditions, the encapsulation of formaldehyde-melamine resin wall material can slightly reduce the crystallization rate of the solvent, but does not affect the relative crystallinity, thermal properties and discoloration sensitivity of the core materials. With the variety of ambient temperatures in the range of 20–35 °C, the printed cotton fabrics with MCTMs could change color reversibly between different tones with good reliability and durability, and exhibit more gorgeous colors than the common thermochromic materials.