Three : color changing temperature of Thermochromic Pigment
1: Color changing temperature,the color changing temperature of the Thermochromic Pigment is not a point, but a temperature range. It’s the range contains from the beginning to the end of the color changing(T0 T1) .The width of this temperature range is commonly 4 to 6 ℃.Some varieties which have high precision of discoloration (narrow range of varieties, expressed as a "N") its color changing range is narrow, only from 2 to 3 ℃.
2: Due to the curve of heating and cooling process of the Reversible Thermochromic Pigment Can not be coincided completely.So there be a certain hysteresis interval. To make the measurements can be reproduced, Must choose the Heat up Method to measure the color changing temperature and the range.
Method are as below:
Take a little bit Thermochromic Pigment tuning into ink. Take a little sample on the white paper . Fully dry at room temperature . Shearing of 10 x 30 mm ( can also directly select the ink printing products). The opposite sealed with colorless transparent OPP tape.Take a 600 ml beaker. Injected the water.Insert an electronic digital thermometer which after the correction . Adjust the water temperature below the range (T0) of the testing sample,and not less than 7 ℃ (for the RF - 65 series inks, water temperature of 35 ℃).Put the beaker on the magnetic stirrer and stirring in a blender.Put half of sample which was sealed by OPP tape into the water, elevated the water temperature slowly, then look carefully.Mark the temperature of when color began to change( T0) and when it no longer change (T1).(T0) ~ (T1) is the range of the color changing temperature , T1 is the the color changing temperature of the sample.
3 : Color changing cycles:
Take a few of testing pigments, mix evenly with 504 epoxy resin . Scraping the sample on white paper (0.05~0.05 mm thick) let stand for 24 hours at room temperature. Then cured at 120 ℃ for 10 minutes.Shearing pattern of 10 x 30 mm for sample.Take two 500 ml beakers, injected with water.The water temperature is respectively be 5 ~ 20 ℃ higher than the Upper limit (T1) and 5 ℃ lower than the lower limit (T0) of the testing sample.(for the RF - 65 series inks, water temperature respectively be T0 = 35 ℃,T1 = 70 ℃) and keep the water temperature.Take turns put the testing sample which were sealed by OPP tapes immersed into the two beakers. Observation of the changes the colors ,record the reversible color changing cycles respectively (usually, the change numbers of heat dissipation color series is more than 3000 ~ 10000 times)
View more Reversible Thermochromic Pigment ，please check :http://www.smarol.com/Reversible-Thermochromic-Pigment.html
