White sheets without titanium dioxide
There is currently no alternative to the white pigment titanium dioxide for paints and coatings. However, new competitors could be white sheets which, thanks to bionic materials, do not require titanium dioxide at all.
In nature, there are also other ways to produce a brilliant white. The beetle Cyphochilus insulanus, for example, uses nanostructures in its chitin armour, which provides the necessary refraction of light. The paint industry and the research community have also looked into these structures from time to time. However, a technically useful implementation as a pigment for paints and varnishes has not yet succeeded.
The situation is now different with plastic sheets. Researchers at the Karlsruhe Institute of Technology (KIT) have now developed a polymer sheet that is similar to the porous beetle shell. “Based on this model, we use polymers to produce solid, porous nanostructures that resemble a sponge,” explains Professor Hendrik Hölscher from the Institute of Microstructure Technology at KIT.
The films are extremely thin and flexible, yet mechanically stable, according to the KIT. It is hoped that they can thus be applied to a broad range of different materials and substances. At a thickness of nine micrometers, the new sheets reflect 57% of the incident light, but with a correspondingly thicker sheet, 80-90% is also possible.
In addition to sheets, it should also be possible to dye entire objects white. To this end, the researchers plan to produce small beads that can then be mixed into other materials.
Book tip
Jochen Winkler’s reference book Titanium Dioxide is now one of the classics of paint literature and provides both a broad overview and deep insights into the subject of titanium dioxide.
