High density polyethylene - hydroxyapatite composites synthetized by in situ ethylene polymerization

A novel synthesis method of obtaining polyethylene - hydroxyapatite (HDPE-HA) composites is proposed using in situ ethylene polymerization, employing Cp2ZrCl2/MAO as catalytic system. In this work, the influence of different polymerization conditions on the HA dispersion was evaluated. The parameters studied were: stirring velocity (600-2000 rpm) and temperature (10-75°C). It was found that, combining high stirring velocities (2000 rpm) and low temperatures (10 °C), it was possible to reach good filler dispersion with the HA nanocrystals interconnected in a network without the presence of agglomerates. Thermal degradation of HDPE-HA composites involved chemical degradation reaction of first order, accompanied by formation of the gas phase inside the melt polymer.