Thermochromic luminescent fiber based on yellow thermochromic microcapsules: preparation, properties, and potential application areas

Luminescent fibers are widely used in textile fields because of their excellent luminescence performance. However, the lack of its sensing property limits the fiber’s application. In this work, two rare earth luminescent materials, SrAl2O4:Eu2+, Dy3+ (SAOED) and Sr2ZnSi2O4:Eu2+, Dy3+ (SZSO), were used as luminous sources, and a yellow thermochromic microcapsule (YTM) was used as a light conversion agent to prepare a thermochromic luminescent fiber (TLF) through wet spinning. The micro-morphology of the TLF was analyzed using scanning electron microscopy (SEM). Three particles were uniformly incorporated in the cellulose fibers, which provide the fibers with a rough surface. Interestingly, the YTM content had no negative effect on the breaking strength of the TLF. Nevertheless, as the concentration of YTM increased from 3 to 10 %, the elongation at break tended to decrease. X-ray diffraction (XRD) results indicate that the cellulose matrix and the wet spinning process did not destroy the phase of rare earth luminescent materials in the fiber. The thermodynamic stability and dynamic phase structure were investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The TLF was stable below 100 °C. The fluorescence spectra and absorption spectra measurements show that TLF exhibits good thermochromic luminescence performance. The TLF appeared white at room temperature (25 °C) and emitted green light, but when the temperature increased (50 °C), the fiber faded and emitted indigo light. Herein, the potential application areas of the TLF can be used in optical materials and thermal sensors.