1. Temperature for thermochromic color change

In fact, the color-changing temperature of thermochromic pigments is not a single temperature point, but a temperature range, that is, the temperature range (T0~T1) from the beginning to the end of the color change. The width of this temperature range is generally 4 to 6°C. Some varieties with higher color-changing precision (narrow-range varieties, indicated by "N") have a narrower color-changing temperature range, only 2 to 3°C.

Usually, in the process of uniform heating, the temperature T1 corresponding to the basically completed color change is defined as the color-changing temperature of the thermochromic pigment.Pearlescent pigment, Color-changing pigment, Fluorescent pigment

2. Number of thermochromic color change cycles:

Take a little of the tested color-changing pigment, mix it evenly with 504 epoxy glue, scrape the sample on white paper (thickness 0.05 - 0.08 mm), and let it stand at room temperature above 20°C for one day. Cut a 10×30 mm paper sample. Take two 600 mL beakers and fill them with water. The water temperatures are 5 - 20°C above the upper limit (T1) and not less than 5°C below the lower limit (T0) of the color-changing temperature range of the tested sample (for RF-65 series inks, the water temperatures are set at T0 = 35°C and T1 = 70°C), and keep the water temperature. Immerse the sample in the two beakers alternately, and the time for each cycle is 3 - 4 seconds. Observe the color change and record the number of reversible color change cycles (usually, the number of color change cycles of the heat-fading series is greater than 4000 - 8000 times).