The research team from Nottingham’s School of Chemistry and Faculty of Engineering used supercriticial carbon dioxide to create an ‘efficient and clean’ process to coat PA-12 polymer particles used in a 3D printing process.
The researchers said they have successfully demonstrated that the coatings can add colour and anti-mould and fungal properties to the printing process.
Currently, one of the most common commercial 3D printing techniques is powder bed fusion or laser sintering. In this process a layer of free-flowing polymer powder is laid down and a laser is guided by a computer generated design to melt the powder layer-by-layer.
A new layer of powder is applied to the previous layer and once again the laser melts the powder together whilst simultaneously anchoring it to the layer below. This process continues until the designed part is complete, often consisting of thousands of layers.
The strong plastic polyamide-12 (PA12) is often used in the 3D printing industry to print complex and detailed parts, commonly deployed in the automotive or aerospace industries, which the research team aimed to make more functional through their new coating process.
In a statement, Christopher Tuck, Professor of Materials Engineering in Nottingham’s Centre for Additive Manufacturing in the Faculty of Engineering, said: “The real benefit of 3D printing or additive manufacturing 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.
“This new process provides an easy route to the development of a wide range of material capabilities without compromising processability.”
Colours, mould & fungi
The research team said the only options for manufacturers are grey or white powders with the colour added afterwards, whereas they have created a range of coloured polymers that coat the PA-12 particles.
“There are a few challenges facing the 3D printing industry due to limitations on the functionality of the polymers used. To tackle some of these challenges we have created a simple but effective approach to adding functionality by coating the particles,” said Professor Steve Howdle, head of Nottingham’s School of Chemistry.
“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.”
Additionally, as the new shell coating prevents the growth of mould and fungi, the researchers said that objects made using PA-12 can now be used in moist environments, 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,” said Professor Howdle.
The research paper, published in Nature Communications, can be read in full here.
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