Physico-chemical behaviour of Poly (Ether Ketone) (PEK) in High Temperature Laser Sintering (HT-LS)

Abstract

Laser sintering (LS) of polymers has high potential for growth as a manufacturing technique into a wide range of applications provided the range of engineering polymers available for LS expands and machines and SLS process conditions are optimised for such materials. This study is the first investigation into laser sintering of both virgin and used polyether ketone PEK powder using a bespoke high temperature polymer laser sintering machine (EOS P800). The physicochemical results reveal that, in spite of polymer degradation, used PEK has a viable processing processing window for LS manufacturing which, combined with optimisation of specific parameters can successfully lead to manufacture of good quality parts. The proposed sintering mechanism of both, virgin and used powders is supported by the experimental data. The incorporation of 30 % used HP3 PEK powder led to an approximately 17% drop in tensile strength. Virgin PEK (~41% crystallinity)Used PEK (~52% crystallinity ) Shorter chainsCross-linked region First investigation into laser sintering of virgin and used polyether ketones (PEK) using a bespoke high temperature selective laser sintering system The incorporation of 30 % used PEK powder led to an approximately 17% drop in tensile strength The use of a higher laser power improves the surface finish but it doesn't affect the porosity and mechanical strength of the parts incorporating reused powder The used PEK powder suffers degradation which affects the particle coalescence process This study is the first investigation into laser sintering of both virgin and used polyether ketone PEK powder using a bespoke high temperature (HT) polymer laser sintering machine (known commercially as EOSINT P800). The physico-chemical results reveal that, in spite of polymer degradation, used PEK has a viable processing window for LS manufacturing which, combined with optimisation of specific parameters can successfully lead to manufacture of good quality parts. The proposed sintering mechanism of both, virgin and used powders is supported by the experimental data. The incorporation of 30 % used HP3 PEK powder led to an approximately 17% drop in tensile strength.

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

“…62.7 ± 3.2 XRD crystal size (nm) 9.2 ± 2.7 14.9 ± 3.5 17.1 ± 3. 8 15.5 ± 3.6 The crystal size between IM-PEK and HT-LS PEK HP3 was found to be very different. HT-LS PEK samples showed bigger crystals than IM-PEK samples.…”

“…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.…”

“…Ghita et al [8] studied virgin and used (material that has already been through the HT-LS manufacturing process) PEK HP3 particles in terms of particle sintering mechanism, melting temperature, crystallisation temperature and mechanical performance of the laser sintered components. HT-LS PEK HP3 samples made with used powder showed a tensile strength drop of 17% between PEK HP3 pure virgin powder.…”

Processability of PEEK, a new polymer for High Temperature Laser Sintering (HT-LS)

“…The parameters of build 5 corresponding to the energy density of 0.029 J/mm² were then used as an optimal set for the next builds of this work. In Figure 6, the tensile strength values found for PEEK 450PF-Build 5 has been plotted in comparison to the tensile strength value of HP3 PEK [4]. The tensile strength of PEEK 450PF is approximately 20 MPa lower than the value found for PEK HP3, but still acceptable for a wide range of engineering applications [31].…”

“…A higher shrinkage for samples built in the middle of the building chamber of the system and a drop of the tensile properties for samples built along the Z direction were presented. In another work, Ghita et al [4] sintered and studied for the first time HP3 PEK samples blended with used HP3 PEK powder (material that had already been through the manufacturing process). Both raw powders and sintered specimens were analysed.…”