Temperature sensitive color changing pigments:
1、 Temperature variation principle
The color changing principle and structure of reversible temperature sensitive color changing pigments:
Temperature sensitive color changing pigment is a microcapsule reversible temperature sensitive color changing pigment that changes color repeatedly with increasing or decreasing temperature. It is prepared from an electron transfer type organic compound system. Electron transfer organic compounds are a class of organic chromophores with special chemical structures. At a specific temperature, the molecular structure of the organic compound undergoes a change due to electron transfer, resulting in color transformation. This color changing substance not only has bright colors, but also can achieve color changes from the "colored=colorless" and "colorless=colored" states, which are not possessed by heavy metal complex and liquid crystal reversible temperature sensitive color changing substances. Microcapsulated reversible thermochromic substances are called reversible thermochromic pigments (commonly known as temperature changing pigments, temperature sensitive powders, or temperature changing powders). The particles of this pigment are spherical in shape, The average diameter is 2-7 microns One micrometer is equal to one thousandth of a millimeter, and its interior is a color changing substance. The exterior is a transparent shell about 0.2-0.5 micrometers thick that cannot be dissolved or melted, which protects the color changing substance from other chemical substances. Therefore, it is very important to avoid damaging this outer shell during use. The basic color of temperature sensitive color changing pigments: Currently, our company produces reversible temperature sensitive color changing pigments in the following 10 colors in the color developing state: Color based
brown
Peacock Green
brown
Dark Blue
Treasure Blue
black
Light blue
black
Grass green
Light blue
2、 Principle and structure
Temperature sensitive color changing pigments are prepared from electron transfer type organic compound systems. Electron transfer organic compounds are organic chromophores with special chemical structures. At a specific temperature, the molecular structure of the organic compound undergoes a change due to electron transfer, resulting in color transformation. This color changing substance not only has bright colors, but also can achieve color changes from a "colored colorless" state, which is not possessed by heavy metal complex and liquid crystal reversible temperature sensitive color changing substances.
Microcapsulated reversible thermochromic substances are called reversible thermochromic pigments (commonly known as temperature changing pigments, temperature sensitive powders, or temperature changing powders). The particles of this pigment are spherical in shape, with an average diameter of 2-7 micrometers (one micrometer is equivalent to one thousandth of a millimeter). The interior is a discoloring substance, and the exterior is a transparent shell about 0.2-0.5 micrometers thick that neither dissolves nor melts. It is precisely this that protects the discoloring substance from the erosion of other chemical substances. Therefore, it is very important to avoid damaging this layer of shell during use.
Basic color for temperature sensitive color change: 2. Basic temperature for temperature sensitive color change: -5C, 0C, 5C, 10C, 16C, 21C, 31C, 33C, 38C43 ° C, 45C, 50C, 65C, 70C, 78C. 3. Temperature sensitive discoloration can change color repeatedly as the temperature increases or decreases. (Taking 31C red as an example, the color change form is colorless above 31 ° C and red below 31C). 4. Temperature sensitive discoloration contains microcapsule discoloration particles with a particle size ranging from 1 to 10 UM, and has the characteristics of high temperature resistance and other capsule changes.
5. The design of temperature sensitive color changing products is based on the demand for color changes in high and low temperature environments, and is mostly applied to series products that sense human body temperature, and can also be used for anti-counterfeiting design.
3．Color change temperature of temperature sensitive color changing pigments:
In fact, the color change temperature of temperature sensitive color changing pigments is not a temperature point, but a temperature range, that is, the temperature range from the beginning of color change to the end of color change (TO~T1). The width of this temperature range is generally 46C, and some varieties with higher color change accuracy (narrow range varieties, represented by "N") have a narrower color change temperature range of only 2-3 ° C. Usually, we define the temperature T1 corresponding to the completion of color change during the constant rate heating process as the color change temperature of the temperature sensitive color changing pigment.
Number of temperature sensitive discoloration cycles:
Take a small amount of the color changing pigment to be tested, mix well with 504 epoxy adhesive, and scrape the sample on white paper (thickness 0.05-0.08 mm) at room temperature above 20C and let it stand for 24 hours. Cut 10X30 MM paper pattern. Take two 600 ML beakers and inject water. The water temperature shall be no less than 5C above the upper limit (T1) of the color change temperature range of the tested sample and no less than 5C below the lower limit (TO) (for RF-65 series inks, the water temperature shall be set to TO=35C and T1=70C respectively), and the water temperature shall be maintained. Immerse the sample in two beakers in turns, and complete each cycle for 3-4 seconds. Observe color changes and record the number of reversible color change cycles (typically, the number of color change cycles for thermal fading series is greater than 4000-8000).