Effect of particle morphology and polyethylene molecular weight on the fracture toughness of hydroxyapatite reinforced polyethylene composite.

Fracture toughness testing has been performed on hydroxyapatite-polyethylene composites. Sintered and unsintered grades of hydroxyapatite and two grades of high-density polyethylene were used to make 40 vol % hydroxyapatite composites. Compact tension testing was performed at both room temperature and at 37 degrees C and at three strain rates. The effect of increasing the loading rate from 2 to 200 microm s(-1) was to increase the fracture toughness. Increasing the testing temperature or decreasing the surface area of the reinforcing particles also increased the fracture toughness. However, using a lower molecular weight, injection moulding, grade of polyethylene reduced the fracture toughness. Thus for higher fracture toughness, a low surface area sintered hydroxyapatite in a high-molecular weight polyethylene is required.