S. Pakdaman - epartment of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran, Iran
M. Khatibzadeh - epartment of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran, Iran

The present study reports the colorimetric properties of blue leuco dye-based thermochromic ink with 40 ºC activation temperature which was applied on white cotton fabric. Attenuated Total Reflection (ATR) was used to characterize the properties of the printed fabric by the mentioned thermochromic ink. Also the spectra of the samples were studied using spectroradiometer. The study was done for the both colored and colorless phases of the samples. The spectra characterizations of the printed fabrics were investigated after repetition of heating and cooling for 1200 times between 28ºC and 40ºC. The color of the ink was dependent on temperature as well as the thermal history of the sample, which shows a color hysteresis. The area of the observed hysteresis loop in CIELAB color space determines how different colors appear on the sample during the comparison of the decolorization and colorization processes. The spectra data were compared from the first time before and after the 1200 time by heating and cooling. The results indicated that the reversible thermochromic process depended on temperature which can be shown by change of lightness L* as a function of temperature. After repetition the heating and cooling the samples for 1200 times, L* became higher. Finally after this repetition, the lactone ring closed and caused the sample went to colorless form and did not return to primary color in environment temperature.

Thermochromic- Activation temperature- Colorimetric properties- CIELAB- Life cycle