HDPE@UHMWPE Powders for Power Bed Fusion Based Additive Manufacturing

Commercial UHMWPE powder of 60 µm size (d50) embossed with 2–5 wt% of nanosilica is used as a support for the preparation of core–shell HDPE@silica@UHMWPE particles. The HDPE shell is generated by polymerization of ethylene in toluene slurry after treatment of the silica@UHMWPE with a methyl aluminoxane activated bisimine pyridine iron complex. Heat pressing the powder gives a solid material with identifiable original UHMWPE particles and a layer from fusion of UHMWPE and the surrounding HDPE shell; the properties match those of the UHMWPE base material. The powder flow properties of the HDPE@silica@UHMWPE are insufficient for a powder bed fusion process, a value for the flow function between 2 and 3 is measured in a ring shear tester. Additivation with nanosilica helps to overcome the insufficient flowability and allows the material to be recoated in a power bed fusion system. Laser sintering gives evidence for a substantial mixing and welding of the HDPE shells and UHMWPE. Caking at the surface of the built parts hinders the manufacturing of isolated parts. Further additivation with carbon black reduces the caking; however, the welding within the HDPE@silica@UHMWPE material is much less strong.