Evaluation of CO2 and Nd:YAG lasers for the selective laser sintering of HAPEX®

This paper evaluates and compares the performance of a CO2 and Nd:YAG laser for the selective laser sintering (SLS) of a commercial hydroxyapatite reinforced polyethylene (HA-HDPE) bioactive ceramic polymer composite material. Single-line and layer specimens were produced to compare the effects of different lasers on the material sintering. It was found that the processing window was much larger for the CO2 laser as compared to the Nd:YAG laser. Furthermore, the Nd:YAG processing window was highly dependent on the pulse width and pulse repetition rate parameter settings. Furthermore, the processing windows for both the laser systems were affected by the particle size of the HA-HDPE powders. The degree and mechanism of particle fusion existing in the composites layers were greatly influenced by the laser source and particle size. The results presented in this work clearly indicate that the CO2 laser would present a better performance than the Nd:YAG laser for the SLS of HAPEX® in terms of operation range, speed, processing efficiency, and, subsequently, greater potential as an SLS processing method for bioactive implant products

Selective laser sintering of hydroxyapatite reinforced polyethylene composites for bioactive implants and tissue scaffold development

Selective laser sintering (SLS) has been investigated for the production of bioactive implants and tissue scaffolds using composites of high-density polyethylene (HDPE) reinforced with hydroxyapatite (HA) with the aim of achieving the rapid manufacturing of customized implants. Single-layer and multilayer block specimens made of HA-HDPE composites with 30 and 40 vol % HA were sintered successfully using a CO2 laser sintering system. Laser power and scanning speed had a significant effect on the sintering behaviour. The degree of particle fusion and porosity were influenced by the laser processing parameters, hence control can be attained by varying these parameters. Moreover, the SLS processing allowed exposure of HA particles on the surface of the composites and thereby should provide bioactive products. Pores existed in the SLS-fabricated composite parts and at certain processing parameters a significant fraction of the pores were within the optimal sizes for tissue regeneration. The results indicate that the SLS technique has the potential not only to fabricate HA-HDPE composite products but also to produce appropriate features for their application as bioactive implants and tissue scaffolds

Effects of material morphology and processing conditions on the characteristics of hydroxyapatite and high-density polyethylene biocomposites by selective laser sintering

Hydroxyapatite (HA), a ceramic to which bone inherently bonds, incorporated into a polymer matrix enhances the bioactivity of implants. In order to rapid-manufacture bioactive implants, selective laser sintering (SLS) has been used to fabricate HA and high-density polyethylene (HDPE) composite (HA-HDPE). The properties of SLS-fabricated specimens have been investigated. The main aspects to be considered in the SLS technology are the properties of the materials used in the process and processing parameters (PPs). HA-HDPE composite specimens have been fabricated using five different powders with variations in particle size (PS), PS distribution, and five different laser PPs. The sintering height, the width, and the shrinkage of the specimens were determined and the effects of the particles and PPs on the physical properties were investigated. The HA-HDPE specimens were found to be highly porous and the sintered density and porosity of the specimens were influenced by the PS and PPs. The interparticle connectivity and the pore size range of the specimens were found to be predominantly determined by the PS and to a lesser extent also influenced by the PPs. The strength of these specimens and the relationship with porosity are discussed