A team of scientists and engineers from the University of Nottingham’s School of Chemistry and Faculty of Engineering has developed a new coating for plastic particles that are used in 3D printing that significantly increases their functionality and opens up new possibilities for commercial applications.
The researchers used supercriticial carbon dioxide to create an efficient, effective and clean process to coat polyamide-12 (PA12) polymer particles used in a 3D-printing process. They then demonstrated that the new coatings have the ability to add colour and anti-mould and anti-fungal properties to the printing process.
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Powder bed fusion or laser sintering is one of the most common commercial 3D-printing techniques. In this process, a layer of free-flowing polymer powder is laid down and a laser is used to melt the powder. A new layer of powder is applied to the previous layer and once again the laser melts the powder particles together while simultaneously anchoring them to the layer below. This process continues until the designed part, often consisting of thousands of layers, is complete.
PA12 is a strong plastic that’s often used in the 3D-printing industry to print complex and detailed parts, commonly deployed in the automotive or aerospace industries.
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‘The real benefit of 3D printing is in the design and production of bespoke and unique objects, but its limitations are in the materials and palette of available properties that limit the overall application space,’ said Professor Christopher Tuck, professor of materials engineering in the Centre for Additive Manufacturing in the Faculty of Engineering. ‘This new process provides an easy route to the development of a wide range of material capabilities without compromising processability.’
Two key capabilities the new process can deliver are the addition of coatings for colour and for anti-fungal and anti-mould properties. Currently, the only options for manufacturers are grey or white powders – colour is added afterwards. The team created a range of coloured polymers that coat the PA-12 particles.
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‘There are a few challenges facing the 3D-printing industry due to limitations on the functionality of the polymers used,’ said Professor Steve Howdle, head of the School of Chemistry. ‘To tackle some of these challenges, we have created a simple but effective approach to adding functionality by coating the particles. We’ve designed the coloured shell polymer so that it matches the mechanical and thermal properties of the printing polymer. Most importantly, we’ve demonstrated this with the key polymer (PA-12) that is ubiquitous to the industry. Our new coloured polymeric powders work perfectly in the existing commercially deployed machines.’
Currently, objects made using PA-12 can’t be used in moist environments due to the growth of mould and fungi. The new shell coating can also be used to develop coatings that prevent this from happening, opening up new possibilities for the use of 3D-printed objects in new areas.
‘A key benefit of this process is that it can easily be incorporated into current commercial 3D-printing processes and this could be potentially transformative for the industry in widening scope by introducing new functionality, simplifying processes and, importantly, achieving all of this sustainably,’ Professor Howdle added.
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The research has been published in Nature Communications.