Mechanical properties and apatite forming ability of TiO_2 nanoparticles/high density polyethylene composite: Effect of filler content

摘要

Composite materials consisting of TiO_2 nanopar-ticles and high-density polyethylene (HDPE), designated hereafter as TiO_2/HDPE, were prepared by a kneading and forming process. The effect of TiO_2 content on the mechanical properties and apatite forming ability of these materials was studied. Increased TiO_2 content resulted in an increase in bending strength, yield strength, Young's modulus and compressive strength (bending strength = 68 MPa, yield strength = 54 MPa, Young's modulus = 7 GPa, and compressive strength = 82 MPa) at 50 vol% TiO_2. The composite with 50 vol% TiO_2 shows a similar strength and Young's modulus to human cortical bone. The TiO_2/HDPE composites with different TiO_2 contents were soaked at 36.5℃ for up to 14 days in a simulated body fluid (SBF) whose ion concentrations were nearly equal to those of human blood plasma. The apatite forming ability, which is indicative of bioactivity, increased with TiO_2 content. Little apatite formation was observed for the TiO_2/HDPE composite with 20 vol% content. However, in the case of 40 vol% TiO_2 content and higher, the apatite layers were formed on the surface of the composites within 7 days. The most potent TiO_2 content for a bone-repairing material was 50 vol%, judging from the mechanical and biological results. This kind of bioactive material with similar mechanical properties to human cortical bone is expected to be useful as a load bearing bone substitute in areas such as the vertebra and cranium.