sydpins

This is a thermochromic badge(Changes color as temperature rises) produced in 2021.The thermochromic badge uses a waterbased paint, which is widely used on chip thermometers and propane 
level indicators.Later it was also used in car painting and some handicrafts.The most widely known product is the Mood ring.

There are four types of coatings:

1. Basic type (no dilution or addition, 3~4 layers are required for brushing, it is sticky and difficult to apply).
2. Concentrated type (need to be diluted with pure water and then sprayed with a high power spray gun for 4~5 layers).
3. Low PSI type (can be sprayed with a model airbrush without dilution, but 7~10 layers are required).
4. Brush type (only 1~2 layers are required, it will slightly repel the smooth surface/ paint surface, the paint will easily gather into drops due to tension during brushing,  and will leave obvious traces of brushstrokes after drying).

Warm change badge video appreciation

Thermochromic Test

I bought 4 types of paint for testing and found that ordinary spraying and brushing are not suitable for coloring badges.The advantage of spraying is that it can evenly cover all details and internal chamfers. The disadvantage is that it needs to be sprayed multiple times to ensure the saturation when changing color, and it is difficult to cover and isolate the outer edge of the badge.After the paint dries, a layer of adhesive film is formed. If the paint covers the outer edge of the badge, the later resin sealing layer will not be tightly combined with the badge body and will be easily damaged. (Moreover, this layer of adhesive film will have poor viscosity and extremely low adhesion.)The effect of brushing (thin coating) is worse, and the traces of brushstrokes are obvious.

The final optimization scheme obtained through repeated trials is as follows:

• The badge base is made of epoxy electrophoretic black, which is more uniform and smooth than spray coating.
• Clean the badge base to remove surface impurities.
• Depending on the surface coating, determine whether it is necessary to enhance the adhesion of the substrate.
• Use a paintbrush to thickly apply (accumulate) the paint in the groove of the badge, slightly higher than the plane of the base. Use the tension of the paint to evenly cover the inner chamfered bevel after it dries (the same surface as the painted badge) color method).
• When waiting for drying after coloring, it needs to be covered to prevent falling into dust, and can also be put into the oven to speed up drying.
• Use transparent resin to seal the layer and use water wax to polish the resin after curing.

The temperature range is 16°C – 36°C

The room temperature was below 16°C when the video was shot, resulting in the badge color did not gradually change from black. In order to speed up the color change process, the video speed is 1.25 times faster on the right side because the hot air from the hair dryer is heated frThe room temperature was below 16°C when the video was shot, resulting in the badge color did not gradually change from black. In order to speed up the color change process, the video speed is 1.25 times faster on the right side because the hot air from the hair dryer is heated from the right side.om the right side.

black

brown

yellow

green

cyan

blue

purple

pink

green

cyan

blue

The discoloration temperature range of the paint is 16°C – 36°C, and the color changes are: Black,brown,yellow, green,cyan,blue,purple,pink,green,cyan,blue.The principle of discoloration is that changes in temperature will cause changes in the spacing between crystal layers in the paint.Light passing through the crystal undergoes Bragg diffraction at these crystal layers, and the wavelengths with maximum constructive interference are reflected back into the perceptible spectral colors, so the color of the paint can continuously change color, from a non-reflective color (black) to color and back to black, the specific color change depends on the ambient temperature.

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