Application of thermochromic pigments in plastic products

Application of thermochromic pigments in plastic products:

1. R series thermochromic pigments are suitable for injection molding and extrusion:

R series (plastic grade) is a variety of color-changing pigments specially developed by our company for plastics. Its characteristics are: thick capsule wall, high strength, good heat resistance, easier to disperse evenly, and less residual color during decolorization.

2. Scope of application:

This product can be used for injection molding and extrusion molding of transparent or translucent plastics such as polyethylene (PE), polypropylene (PP), polystyrene (PS), soft polyvinyl chloride (S-PVC), AS and ABS. It can also be mixed into unsaturated polyester, epoxy resin, plexiglass or nylon monomers for casting, molding and curing.

3. Dosage:

When used for injection molding, extrusion processing or casting, molding, curing molding, the amount of color-changing pigment is 0.4~3.0% of the amount of plastic, usually 0.6~2.0%. The color-changing pigment and plastic particles should be fully mixed evenly (a small amount of white oil can be used when mixing). If it is a combination of ordinary pigments and color-changing pigments, the amount of ordinary pigments (or dyes) is about 0.5-2.5% of the color-changing pigments.

4. Color masterbatch:

In mass production, the color-changing pigment can be added to polyethylene wax or polystyrene wax to make a color masterbatch with a pigment content of 10%, and then mixed with plastic particles. In this way, the color-changing pigment can be dispersed more uniformly. For the preparation method of color masterbatch, please refer to the technical information provided by our company.

5. Temperature:

The processing temperature should be controlled below 200℃, and the higher should not exceed 230℃, and the heating time of the material should be minimized. (High temperature, long time heating will damage the color change performance of the pigment).

6. Matters needing attention:

A: When using color-changing pigments in injection molding and extrusion, other fillers or common pigments (such as titanium dioxide, calcium carbonate, barium sulfate, carbon black, etc.) should not be used in the plastic at the same time, otherwise the color-changing effect will be shielded.

B: When using color-changing pigments in casting, molding and curing, the color-changing pigments should be added to the unsaturated polyester, plexiglass or nylon monomers and mixed and dispersed uniformly, and then the initiator or curing agent is added to start the polymerization or crosslinking reaction. Because the viscosity of the system rises sharply after prepolymerization, the addition of color-changing pigments will pack a large number of pigment particles together, making it difficult to evenly disperse. In addition, the stirring operation at this time will also leave a large number of bubbles in the system.

C: Carefully choose the crosslinking agent or curing agent: during the crosslinking and curing process of epoxy resin and unsaturated polyester resin, strong shrinkage stress sometimes occurs inside, causing the shell of the color-changing pigment microcapsule to break and other chemical substances to enter The interior of the pigment makes it lose its discoloration performance. This situation often occurs when the curing thickness of the epoxy resin is greater than 0.2 mm and the polyamine curing agent is used.

D: High-shear equipment such as internal mixers, kneaders, high-speed dispersers, twin-screw extruders, etc. cannot be used to pre-mix plastic particles with color-changing pigments. These devices will severely damage the protective layer on the surface of the color-changing pigment, causing it to lose its color-changing performance. In addition, the color-changing pigment should be avoided to undergo repeated extrusion and granulation operations when preparing the color masterbatch.

E: Phosphorus-containing stabilizers and plasticizers should be avoided in the formula of PVC resin, otherwise it will cause serious residual color in the discoloration state of the color-changing injection molded product.