Thermochromic pigment

Other name: Color change pigment, Colour changing powder, temperature sensitive pigments

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Principle and structure of color change of thermochromic pigment:

Thermochromic pigment is prepared by electron-transfer organic compound system, which is a kind of organic hair color system with special chemical structure. This color-changing substance is not only brightly colored, but also can realize the color change from the “colorless” state.

 

Basic color:

Can provide 15 color temperature (70 ℃ only provide black and dark blue) of all kinds can be mixed each other, can also add other color palette.

Colors: red rose red peach red vermilion orange yellow grass green green sky blue Turkey blue blue deep blue violet violet coffee black

 

Basic temperature point of temperature change:

– 5 ℃ and 0 ℃, 4 ℃ 8 ℃, 10 ℃, 15 ℃, 22 ℃, 25 ℃ and 29 ℃, 31 ℃ and 33 ℃, 35 ℃, 38 ℃ and 40 ℃ and 43 ℃, 45 ℃ and 55 ℃, 50 ℃, 60 ℃, 65 ℃, 70 ℃.

Discoloration can change color repeatedly with the rise and fall of temperature. (31 ℃ red, for example, color change form for 31 ℃ above show colorless, 31 ℃ below red).

 

Light fastness:

Temperature-sensitive pigment has poor light resistance, and will quickly fade and become invalid when exposed to strong sunlight. Therefore, it is suitable for indoor use. Should avoid intense sunshine and ultraviolet lamplight illuminate, be helpful for prolonging the service life of become angry pigment so.

 

Heat resistance:

Thermal color pigments in a short period of time can be 230 ℃ high temperature resistant, can be used in injection molding and high temperature curing. However, the thermal stability of the color-changing pigment is different in the hair state and achromatic state, and the former is more stable than the latter. And when the temperature higher than 80 ℃, the color system will start the degradation of organic matter, therefore color paint should avoid long-term work under temperature higher than 75 ℃.

 

Application of thermochromic powder

1.The reversible temperature-sensitive color-changing substance microencapsulated is called reversible temperature-sensitive color-changing pigment (commonly known as temperature-sensitive pigment, temperature-sensitive powder or temperature-sensitive powder).

2.This product can be used for injection and extrusion molding of polypropylene (PP), PE, PS, PU, TPU, TPR, EVA, soft polyvinyl chloride (s-pvc), ABS, silicone and other transparent or translucent plastics.

3, for injection, extrusion processing or casting, molding, molding, curing, the amount of discoloration pigment is 0.2-5% of the amount of plastic, usually 0.5-2%; Discoloration pigment and plastic particles to fully mix uniform, mixing can use a small amount of white oil.

4.Temperature: Processing temperature should be controlled under 220 ℃, the highest do not exceed 250 ℃, and try to reduce the time for heating the material (high temperature and long heat will damage the paint color performance).

 

Precautions for use

1.When coloring pigments are used in injection and extrusion, other fillers or common pigments (such as titanium dioxide, calcium carbonate, barium sulfate, carbon black, etc.) should not be used at the same time in plastics, otherwise the color changing effect will be shielded.

2.When the color-changing pigment is used in casting, molding and curing, the color-changing pigment should be added into unsaturated polyester, plexiglass or nylon monomer and stirred and dispersed evenly, and then the initiator or curing agent should be added to initiate polymerization or crosslinking reaction. Because the viscosity of the system increases sharply after prepolymerization, the addition of discoloration pigment will make a large number of pigment particles wrapped together, which is difficult to disperse evenly. In addition, a large number of bubbles will remain in the system during the stirring operation.

3.Careful selection of cross-linking agent or curing agent: in the cross-linking curing process of epoxy resin and unsaturated polyester resin, strong shrinkage stress will sometimes occur in the interior, which will lead to the rupture of the shell of the color-changing pigment microcapsule, and other chemicals will enter the interior of the pigment to make it lose its color-changing performance. This often occurs when epoxy is thicker than 0.2 mm and polyamine hardeners are used.

4, can not use the mixer, kneading machine, high-speed disperser, twin-screw extruder and other high shear equipment for plastic particles and pigment pre-mixing. These devices can seriously damage the protective layer on the surface of the discoloration pigment, making it lose its discoloration performance. In addition, the color masterbatch should be prepared to prevent the pigment from repeated extrusion granulation.

5, in the formulation of PVC resin should avoid the use of phosphorus stabilizer and plasticizer, otherwise it will make discoloration injection products in the state of achromatic produce serious residual color.

 

Storage method:

Reversible temperature-sensitive pigment itself is an unstable system (stability is difficult to change), so its light resistance, heat resistance, aging resistance and other properties are far less than ordinary pigments, should be paid attention to in use.

Store in a dry and cool place sealed away from direct sunlight.

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