In the journal Nano Letters, researchers at the Helsinki University of Science and Technology describe a process for combining strong, disc-shaped clay platelets with the soft polymer polyvinyl alcohol. When mixed together in water, the polymer coats the discs to create a slurry that can be made into paper or painted over a surface such as a wall. The resulting paper or coating is made up of discs of the so-called nanoclay stacked in rows like plates in a cupboard with the polymer surrounding them, a structure very similar to that found in nacre.
The Helsinki coatings are very strong and lightweight, but still too prone to fracture to be used in the way structural materials such as steel are used today. Their material properties are similar to those of fiberglass, says Andreas Walther, one of the Helsinki researchers. The first application for the material may be as a reinforcing coating for walls. Experiments with flamethrowers showed that the coatings can act as a heat and fire shield.
“Stiffness and strength are a start, but it needs to be tougher to be interesting,” says Berkeley’s Ritchie of the material. Walther says the method is compatible with a range of polymers, which provide the toughness in these composites, and that the group is experimenting with softer polymers in hopes of making tougher coatings. If they succeed in making the material tougher, it could be suitable for armor and for replacing structural materials in airplanes.