Morphology of polymeric powders in Laser Sintering (LS): From Polyamide to new PEEK powders

Abstract

In an attempt to expand the range of engineering polymers used for laser sintering, this paper examines the morphology, flowability and interparticle interactions of two commercially available poly (ether ether) ketone (PEEK) powders, not yet optimised for the LS process, by comparison with the LS optimised Polyamide (PA) and Polyetherketone (PEK) powdered polymers . The effect of incorporating fillers and additives on the flow behaviour is also analysed. The Particle Size Distribution (PSD) results alone do not allow ranking the powder materials in relation to the flow behaviour. The particle morphology has a stronger influence on the flow characteristics for materials with similar PSDs. The work also provides additional characterization parameters to be considered when analysing LS powders. Graphical abstract

Glass bead filled Polyetherketone (PEK) composite by High Temperature Laser Sintering (HT-LS)

“…The glass beads have almost perfect spherical shape, while the PEK powders have a flake like appearance. Previous particle analysis [24] of HP3 PEK powder showed that 50% volume frequency had particle size in range of 37.5-63 µm whereas the glass beads, 52% volume frequency had diameter in range of 16-27.5 µm.…”

Polymer viscosity, particle coalescence and mechanical performance in high-temperature laser sintering

“…Highly circular and round particles with smooth surfaces and fully dense structure were found to achieve higher flow behaviour. In a previous publication the authors showed that [5] particles with smoother surfaces, rounder and circular shapes exhibited a better flow behaviour. Circularity is a shape descriptor that quantifies how much a given particle shape is similar to a circle overall, roundness is instead a shape descriptor that indicates how round the edges of a particle are.…”

“…Berretta et al [5] quantitatively analysed size and morphological characteristics of new potential candidate HT polymers and their composites in parallel with established Laser Sintering (LS) materials such as PEK HP3 and PA 2200. The study highlighted that a simple particle size analysis is not sufficient when searching for new HT-LS powder candidates.…”

“…The roundness and circularity data sets of PEEK 450PF before and after thermal conditioning is displayed in Figure 6. The details of this quantitative analysis can be found elsewhere [5]. …”

“…Using the EOSINT P 800 system, LS of commercial HP3 PEK grade and off-the-shelf Victrex PEEK 150PF and 450PF powders has been proven [3][4][5][6][7][8][9], however these studies mostly focussed in assessing the mechanical performance and microstructure of the laser sintered parts rather than the particle coalescence or the polymer viscosity.…”