Recent technological developments have enabled the application of laser sintering in the direct production of intricate parts from computer aided design data without the involvement of any expensive mould tool. Significant research focus has shifted to this area as it has immense potential to revolutionized both commercial and industrial production processes. However, this technique has hit a snag in that it lacks powder materials that can be effectively employed. Over the years, polyamides (PA11 and PA12) have predominantly been used for a standard laser sintering process, due to their excellent processability.
The incorporation of reinforcement to polyamides can lead to composite components with improved performance and widened applications. Unfortunately, in harsh environments, such as: aerospace, defense and gas applications, the currently available polymers for laser sintering do not meet the threshold requirements. Preceding studies have established that nanofillers, such as graphene coupled with inorganic fullerene-like tungsten disulphide (IF-WS2) have improved thermal stability against oxidation at elevated temperatures. Nonetheless, high performance polymeric materials that are suitable for laser sintering processing need to be developed.
Recently, University of Exeter researchers led by Professor Yanqiu Zhu from the College of Engineering, Mathematics and Physical Sciences conducted a study in which they described a generically novel technique for creating composite powders suitable for High Temperature Laser Sintering (HT-LS) using graphene nanoparticles and Carbon-coated IF-WS2 as the nanofillers. The research team used a salt template as a spacer and adapted a partial melting process to purposely create a ‘weak’ porous composite block. Their work is currently published in the research journal, Composites Science and Technology.
The researchers produced the composite powders via the partial melting of porous Poly Ether Ether Ketone (PEEK) blocks followed by grinding, without changing the physical properties of each constituent. The structure and morphology of the resultant powder was then characterized. Particle size distribution procedures were then undertaken followed by powder rheology tests. Materials used for this study were PEEK 450PF, graphene nanoplatelets (GNP) and sodium chloride.
The authors observed that the IF-WS2 and GNP nanofillers were encapsulated inside the PEEK matrix, and that the surface of the composite particles was smooth and round, which makes them potentially suitable for HT-LS applications. Additionally, the powder rheology studies showed that the nanocomposite powders exhibited improved powder rheology when compared with the plain PEEK 450PF. Moreover, it was noted that the PEEK-IF-WS2 thin film showed less cavity and exhibited a smoother surface than those of PEEK-GNP.
In summary, University of Exeter scientists successfully developed a novel, cost-effective and environmentally friendly technique for the creation of various novel composite powders, suitable for HT-LS additive layer manufacturing. Remarkably, the team was able to validate that the resulting composite powders were suitable for HT-LS applications. Altogether, the new strategy reported here brings in great potential for the additive layer manufacturing of high performance polymeric composite components with improved mechanical and added functionalities by choosing the proper matrix and filler combination.
Bahareh Yazdani, Binling Chen, Luiza Benedetti, Richard Davies, Oana Ghita, Yanqiu Zhu. A new method to prepare composite powders customized for high temperature laser sintering. Composites Science and Technology, volume 167 (2018) page 243–250.Go To Composites Science and Technology