New fireproof plastic coating mimics mother of pearl

Plastic is a very versatile material, but it is hardly fireproof without adding usually toxic fire-retardants. Looking at nature, however, researchers at the University of Connecticut found a quick way to create a fireproof plastic coating, mimicking mother of pearl.

Mother of pearl, or nacre, is the shiny pearl-like material found in the inner shell of some molluscs. It is built up of layers of the mineral aragonite separated by organic polymers such as chitin. The material is surprisingly strong, without being brittle or dense.

Artificial materials mimicking mother of pearl are can provide a protective coating in many situations. However, making these materials is a slow process, as they have to be build layer by layer.

However, the researchers at the University of Connecticut found a way to make the material in one go. To make the material, the team mixed a type of clay that sheds layers when exposed to ultrasonic pulses with a polymer to stick the layers together. They then dipped strips of plastic in the material to coat them.

When the coated sheets of plastic are hung up like drying laundry, the thin liquid layer flows towards the ground, pulling the nanometre-thick sheets of clay into alignment with one another like neatly laid bricks. This is crucial for keeping the coating strong and airtight. Finally, the material was placed in an oven, drying the sticky polymer sandwiched between the clay layers. The whole process can be completed in a matter of minutes.

Using their quick method, the researchers were able to make a thin film coating that is 60 per cent stronger than stainless steel. A plastic sheet covered by this new material was over 13,000 times less permeable to air and other gasses than on its own. When the team tried to set it on fire, the material became scorched where the flame directly touched the coated sheet, but would not ignite.

Because of the method’s speed and environmentally friendly components, it would be easy to apply it to a variety of applications that require an airtight or flame-retardant coating. It could, for instance, also make biodegradable plastics fire-retardant.

Photos: UConn / Wikimedia / Max Pixel