Preparation and Thermal Modification of Disentangled Ultrahigh‐Molecular‐Weight Polyethylene Particles for Powder‐Based Additive Manufacturing

Polymerization of ethylene at 5 bar pressure by a supported bisimine pyridine iron dichloride catalyst yields round particles with a broad distribution but good flowability of disentangled ultrahigh‐molecular‐weight polyethylene (dUHMWPE). The catalytic support is obtained by treating spray‐dried silica particles with trimethyl aluminum and subsequently with the iron complex. High activity is generated by heating the loaded support to 50 °C. The prepared dUHMWPE powder has a bulk density of 0.26 g mL⁻¹. Thermal analysis, comprising fast and slow heating, holding, and cooling procedures, shows that the initial high state of disentanglement is not lost on melting and that crystallization from the melt basically reestablishes this state. Thermal treatment at 110 °C of the powder is possible without loss of the low viscosity to yield more compact particles (0.30 g mL⁻¹). Injection molding of dUHMWPE and thermally treated dUHMWPE is readily achieved. The ultimate tensile strength of the dUHMWPE is 29 MPa at 220% strain; the treated dUHMWPE exhibits an ultimate tensile strength of 30 MPa at 100% strain. Laser‐sintering experiments of the dUHWMPE powder along the directed energy deposition technique give a dense cohesive surface: small hatch distances and longer pulse durations are favorable parameters.