Silvia Berretta

Poly Aryl Ether Ketones (PAEKs) and carbon-reinforced PAEK powders for laser sintering

This paper discusses various methods of fabrication of plain and carbon-reinforced composite powders, as well as a range of powder characterisation test methods suitable for defining powders for laser sintering. Two milling processes (based on disc blades and rotatory cutting knives) were used as methods of fabrication of powders, starting from injection moulding granule grades, for comparison with current powders obtained directly from polymerisation processes. It was found that the milling process affects the particles properties. The rotary milling produced powders with superior properties in comparison with the disc milling method. Tests including particle size distribution, angle of repose, aspect ratio, sphericity and roundness of particles were employed to compare and assess the suitability of powders for laser sintering. The Brunauer–Emmett–Teller test was identified as a useful method to define surface roughness and porosity of the particles. The carbon fibre (Cf) Poly Ether Ketone (PEK) granules milled well and after an additional sieving process created a good quality powder. This is the first attempt to investigate properties of PEK powder with encapsulated Cf and follow their sintering profile through hot-stage microscopy. It is expected that this type of composite powder will create isotropic structures in comparison with the highly anisotropic properties given by the known dry mix composite powders, currently used in laser sintering.

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

High-temperature laser sintering (HT-LS) is an additive manufacturing technology whose potential could be limited by the restricted number of materials optimised for the process. Poly ether ether ketone (PEEK) with different melt viscosity values, PEEK 150PF and PEEK 450PF, have been used in parallel with the commercial grade, poly ether ketone (PEK) HP3, to investigate the role of material viscosity on particle coalescence, structure and mechanical performance of components manufactured in HT-LS. The material with lower viscosity, PEEK 150PF, was found to exhibit faster coalescence and lower tensile strength than the grades with higher viscosities, PEEK 450PF and PEK HP3.