Shenzhen Xingsheng Pearl Chemical Pignent .Co., Ltd.
Contact: Mr. Zhang
Phone: 86 0755 29497723
Fax: 86 0755 32998090
Email :info@xs-color. com
Address: Lougang South Industrial Zone, Songgang Street, Baoan District, Shenzhen
Website : en.xs-color.com
First, the principle and structure of the color change of thermochromic pigments:
The thermochromic pigment is prepared from an electron transfer type organic compound system. Electron-transfer organic compounds are a class of organic chromonic systems with a special chemical structure. The color transition of the organic substance is changed by electron transfer at a specific temperature. This color-changing substance is not only bright in color, but also can change the color from the "colored === colorless" state, which is not possessed by the heavy metal complex salt complex type and the liquid crystal type reversible thermochromic substance.
The microencapsulated reversible thermochromic substance is called a reversible thermochromic pigment (commonly known as: warming pigment, temperature sensitive powder or warming powder). The pigment particles are spherical in shape and have an average diameter of 2 to 7 microns (one micron is one thousandth of a millimeter). The inside is a color-changing substance, and the outside is a transparent shell with a thickness of about 0.2 to 0.5 μm that neither dissolves nor melts. It protects the discolored material from other chemicals. Therefore, it is important to avoid damaging this layer of the casing during use.
1, the basic color of temperature change:
2, temperature change basic temperature: -5 ° C, 0 ° C, 5 ° C, 10 ° C, 16 ° C, 21 ° C, 31 ° C, 33 ° C, 38 ° C, 43 ° C, 45 ° C, 50 ° C, 65 ° C, 70 ° C , 78 ° C.
3, temperature change color can be changed with the temperature rise and fall and will change color. (In the case of red at 31 ° C, the color change form is colorless above 31 ° C and red under 31 ° C).
4, temperature-sensitive discoloration contains microcapsule color-changing particles, the particle size is between 1~10UM, and has the characteristics of high temperature, anti-oxidation and other capsules.
5. The design of temperature-sensitive color-changing products is based on the color change in high-temperature environment and low-temperature environment, and is mostly applied to human body temperature-sensing products, and can also be used for anti-counterfeiting design.
Second, temperature sensitive color powder application:
1. The thermochromic powder is a microencapsulated reversible thermochromic substance called reversible thermochromic pigment (commonly known as: temperature change pigment, temperature sensitive powder or warming powder).
2. This product can be used for injection molding and extrusion molding of transparent or translucent plastic such as polypropylene (PP), soft polyvinyl chloride (S-PVC), AS, ABS and silica gel. It can also be mixed with an unsaturated polyester, epoxy resin, plexiglass or nylon monomer to cast, mold, and cure a suitable ink substrate.
3. For injection molding, extrusion processing or casting, molding, solidification molding, the amount of color-changing pigment is 0.4~3.0% of the plastic amount, usually 0.6-2.0%. The color-changing pigment should be thoroughly mixed with the plastic particles (a small amount of white oil can be used when mixing). If the ordinary pigment is color-matched with the color-changing pigment, the ordinary pigment (or dye) is used in an amount of about 0.5 to 2.5% of the color-changing pigment.
4, color masterbatch:
In mass production, color-changing pigments can be added to polyethylene wax or polystyrene wax to prepare a color masterbatch with a pigment content of 10%, and then mixed with plastic particles. This allows the discoloration pigment to be more uniformly dispersed. For the preparation method of color masterbatch, please refer to the technical data provided by the company.
The processing temperature should be controlled below 200 °C, the maximum should not exceed 230 °C, and the heating time of the material should be minimized. (High temperature, long-term heating will impair the discoloration performance of the pigment).
A: When using color-changing pigments in injection molding and extrusion, other fillers or common pigments (such as titanium, calcium carbonate, barium sulfate, carbon black, etc.) should not be used in the plastic at the same time, otherwise the color change effect will be shielded.
B: When using color-changing pigments in casting, molding and solidification, the color-changing pigment should be added to the unsaturated polyester, plexiglass or nylon monomer to stir and disperse uniformly, and then the initiator or curing agent is added to start the polymerization or crosslinking reaction. Since the viscosity of the system rises sharply after the prepolymerization, the addition of the color-changing pigment at this time causes a large amount of pigment particles to be wrapped together and is difficult to disperse uniformly. In addition, the agitation operation at this time also causes a large amount of air bubbles to remain in the system.
C: Careful selection of cross-linking agent or curing agent: During the cross-linking curing process of epoxy resin and unsaturated polyester resin, strong shrinkage stress sometimes occurs inside the epoxy resin and microcapsule shell, and other chemicals enter. The interior of the pigment loses its discoloration properties. This is often the case when the epoxy resin is cured to a thickness greater than 0.2 mm and a polyamine curing agent is used.
D: Premixing of plastic particles and color-changing pigments cannot be carried out using high shear equipment such as mixers, kneaders, high-speed dispersers, and twin-screw extruders. These devices can severely damage the protective layer on the surface of the color-changing pigment, causing it to lose its discoloration properties. In addition, the color changing pigment should be prevented from undergoing repeated extrusion granulation operations in the preparation of the color masterbatch.
E: Phosphorus-containing stabilizers and plasticizers should be avoided in the formulation of PVC resin, otherwise the color-changing injection molded products will produce severe residual color in the decolorized state.
Third, the storage method:
The reversible thermochromic pigment itself is an unstable system (it is difficult to change when it is stable), so its resistance to light, heat, and aging is far less than that of ordinary pigments, and should be noted in use.
1, light resistance:
Thermochromic pigments have poor lightfastness and can quickly fade under intense sunlight, so they are only suitable for indoor use. Radiation from strong sunlight and UV light should be avoided, which will help extend the life of the color-changing pigment.
2, heat resistance:
The thermochromic pigment can withstand 230 ° C high temperature (about 10 minutes) in a short time, and can be applied to injection molding and high temperature curing. However, the color-changing pigment has different thermal stability in the chromophoric state and the decolorized state, and the stability of the former is higher than that of the latter. In addition, when the temperature is higher than 80 ° C, the organic matter constituting the color changing system also starts to degrade. Therefore, color-changing pigments should avoid long-term operation at temperatures above 75 °C.
Light resistance, heat resistance, aging resistance and other properties are far less than ordinary pigments, should be noted in the use.