Science Buddies: "Ask an Expert"

For my project I need to have plastic that can change color at a certain temperature. I was hoping to use leuco dyes to achieve this but I cannot find any information (on the internet) about whether or not Leuco dyes can be set to change at a specific temperature (for example 40 degrees F). How can I find out about this?

Hi rose-02,

The short answer seems to be yes, Leuco dyes can be temperature sensitive when combined with appropriate chemical. Try a Google search for "thermochromic dyes", and you'll find a lot of information. This Wikipedia article, for example, gives some general background (http://en.wikipedia.org/wiki/Thermochromism), as does this manufacturer's website (http://www.colorchange.com/leuco-dyes).

The temperature sensitivity of leuco dye thermochroic pigments isn't fantastic--you're not going to get +/1 degree C precision. But, if you are looking to qualitatively evaluate larger (several degree or more) changes in temperature, they may be a viable option. Different products are sensitive to changes over different temperature ranges, so you will need to consider the range of temperatures you are interested in.

If you can provide some additional details about what the plastic will be used for, why the temperature sensitivity is important, and what your experiment will be, we may be able to help you figure out an option that will work well for your specific project.

All the best,