Functional nanostructures for plastic - a manufacturing breakthrough
An EU-funded project has developed moulds capable of embedding nanostructures onto the surface of plastic parts. This innovation could help carmakers and other industries using plastics improve their manufacturing processes and products - boosting competitiveness.
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“At the moment, a car part like an anti-fog light achieves anti-glare properties by being coated in a chemical film, which is expensive and wears off,” explains Anders Kristensen, project coordinator of the EU-funded PLAST4FUTURE project and a professor at the Technical University of Denmark.
“The same goes for anti-glare reading glasses. What we’ve done is achieve the same functionality by applying nanostructures directly onto the surface of this part through advanced injection plastic moulding, removing the need to apply an additional coating.”
Manufacturers would also be able to use nanostructures to colour plastics without the need to add pigments or film, he adds. This phenomenon can be found in nature: for example, the wings of the brilliant blue morpho butterfly achieve their intensity because nanoscale structures interfere with light in particular way.
Similarly, the PLAST4FUTURE team has been able to show that plastic can be injection moulded in such a way that light is reflected off the nanostructured surface to give a particular colour. This means colour functionality has been achieved during production of the plastic part – colour does not have to be added at a later stage.
How industry benefits
“Innovation has been achieved all along the value chain, beginning with the steel injection moulding tools used in plastic manufacturing,” says Kristensen. “The semiconductor industry has for years used state-of-the-art etching to add functionality to silicon surfaces. The project took this as the starting point and adapted semiconductor etching technology for shaping plastic objects.”
The project then developed hard and durable moulds with just the right properties for etching, while new production tools were also developed by SME project partners. “The SMEs behind the new steel moulds have just taken their first orders,” adds Kristensen.
Next, a novel surface polishing process was integrated into a milling machine for automated robotic polishing. The mould surface must be smooth to the nanometre level for nanostructure functionalities to be embedded.
As Kristensen points out, companies involved in designing injection moulds are potential end users of this technology as much plastics manufacturers. One of the project’s key aims is to create demand for advanced nanotech moulds.
The project also follows the ‘cradle to cradle’ philosophy of production – using nanostructures makes products and parts easier to recycle.
“Think of it this way,” says Kristensen. “If you have red and blue plastic pen cylinders that you want to recycle you would first have to sort them out by colour. However, if both sets of cylinders are made from exactly the same material and the colour is simply caused by light reflecting the surface texture, then you would simply just grind them down, melt them and pour back into the mould, making them cheaper and more efficient to recycle.”
The consortium is already looking to the future. Some members of the team recently joined forces with another EU-funded project to secure funding for a project under the Horizon 2020 programme.
“The aim of this is to take our project to the next level and combine plastic and composite materials in order to deliver real products and car parts,” says Kristensen.