This plastic sheet is printed with thermochromic liquid crystals that change colour from black to green to blue and then back to black as the sheet is heated through its temperature range. The colour change is reversed when the temperature is lowered. The colour change happens within a five degree temperature range and there are different variants for temperature ranges between -30°C and 120ºC. MaterialSampleShop stocks a limited selection of variants.
It is used for flat thermometers that can be glued to surfaces. It is also used for science experiments and thermal mapping in R&D.
The sheet will degrade with time and the degradation is accelerated if the sheet is exposed to UV light or if heated to high temperatures. Thermochromic sheets can easily be cut to the desired geometry.
Use this technology to monitor machine temperatures.
You can see the colour change by heating the sheet between your palms.