Influence of energy density on flexural properties of laser-sintered UHMWPE

Ultra High Molecular Weight Polyethylene (UHMWPE) is a semi-crystalline polymer that has remarkable properties of high mechanical properties, excellent wear resistance, low friction and chemical resistance, and it is found in many applications such sporting goods, medical artificial joints, bullet proof jackets and armours, ropes and fishing lines [1]. UHMWPE parts cannot be produced easily by many conventional processes because of its very high melt viscosity resulting from its very long chains [2]. Additive Manufacturing (AM) is moving from being an industrial rapid prototyping process to becoming a mainstream manufacturing process in a wide range of applications. Laser sintering of polymers is one of the AM techniques that is most promising process owing to its ability to produce parts with complex geometries, accurate dimensions, and good mechanical strength [3]. This paper reports attempts to laser-sinter UHMWPE and assesses the effects of laser energy density on the flexural properties of the sintered parts. The properties of the UHMWPE sintered parts were evaluated by performing flexural three point bending tests and were compared in terms of flexural strength, flexural modulus and ductility (deflection). Part dimensions and relative density were evaluated in order to optimise the laser sintering parameters. Thermal analysis of samples was made by differential scanning calorimetry (DSC) for the virgin powder. Results show that flexural strength, modulus and ductility are influenced by laser energy density and flexural strength and modulus of 1.37 MPa and 32.12 MPa respectively are still achievable at a lower laser energy density of 0.016 J/mm2 (Laser power of 6 W). Part dimensions and bulk density are also influenced by laser energy density.