Color change as desired – Thermochromic polymers
Thermochromic effects are caused by either structural changes of dyes or a change in the lattice arrangement of periodic structures. The focus of the work at Fraunhofer IAP lies on dye systems based on leuco or pH indicator dyes. In the case of the leuco dye systems, we distinguish between a color-to-colorless switching with an increase in temperature and an inverse switching from colorless to color with increasing temperatures.
In our material development, the thermochromic effects are converted into polymer matrices - thermoplastics, thermosets, elastomers, paints and coatings - without significantly changing their material-specific properties. The thermochromic additives to be developed for this purpose not only have to be stable in the polymer matrix, but also survive their processing process unscathed. In the case of thermoplastics, this is the processing by means of extrusion processes, in the case of thermosets and elastomers the crosslinking process and in the case of coatings the application and curing process. All of these matrices place different demands on the chemical, mechanical and thermal stability of the thermochromic additives.