Melanin is a natural molecule found in the skin of animals, as well as hair and the iris of eyes. This protein provides color and functions to protect the animal (including humans) from the damaging effects of ultraviolet light. In humans, melanin is the primary determinant of skin color.
The idea of adding melanin to furnishings is being considered not because of the color properties of the pigment, but because adding a small quantity of melanin to polyurethane helps to make the material far stronger.
Polyurethane is a polymer and it is used to make a variety of materials. Polyurethanes are used in the manufacture such products as of foam seating, wheels and tires (such shopping cart wheels), adhesives, synthetic fibers (like Spandex), carpet underlay, and condoms. It is popular because it can readily be stretched and molded, and it enables the outer coating of a material to be glossy.
Polyurethane can be prone to damage, however, and materials scientists and chemistry are working on ways to strengthen the material. Attempts to improve durability include adding silica, carbon nanotubes and graphene oxide. While these enhance tensile strength they do not address the issue of toughness.
In a breakthrough, Jiangnan University researchers, led by Mingqing Chen and Weifu Dong, have found that adding melanin provides the required levels of strengthening. In a study, the Chinese researchers discovered that adding just two percent of the biomolecule melanin (extracted from cuttlefish ink) improved both tensile strength and toughness ten-fold.
Physically, untreated polyurethane has the physical properties of 5.6 megapascals and 33 megajoules per cubic meter. By adding the melanin, these measures of force and energy absorption rose to 51.5 megapascals and 413 megajoules per cubic meter. In addition, the modified material had greater stretchability, up to 1,880 percent before it ruptured.
The research has been published in the journal Biomacromolecules. The research paper is titled “Superior Performance of Polyurethane Based on Natural Melanin Nanoparticles.”
