Nature inspires greener way to make colourful plastics

Scientists have developed a new kind of coating that gives plastic its colour without the use of dyes.
Long before humans figured out how to create colours, nature had already perfected the process in the form of the stunning, bright butterfly wings of many different hues, for example.
Now scientists at The Technical University of Denmark (DTU) are are tapping into those secrets to develop a more environmentally friendly way to make coloured plastics.
The method uses structure - or the shapes and architectures of materials - rather than dyes, to produce colour.
Investigators N Asger Mortensen, Anders Kristensen and colleagues point out that currently, plastic manufacturers add pigments to their products. That gives them the range of colours customers have come to expect in everything from toys to tools.

But these additional ingredients add to the growing waste stream of plastics manufacturing and make it difficult to recycle products.

To come up with a more eco-friendly alternative, Mortensen's team turned to highly advanced materials that can be made to appear in different colours - purely by designing their surface structures at the nanoscopic level.
They layered materials, including ultra-thin, nano-sized aluminum disks, in a way that manipulates light and creates a new kind of coloured surface.
To protect it from damage, the scientists topped it off with a scratch-resistant film. Using this method, they created a wide spectrum of colours that could be added to plastics.

The research appears in the American Chemical Society (ACS) journal Nano Letters.