Effect of polypropylene molecular weight, hydroxyapatite particle size, and Ringer’s solution on creep and impact behavior of polypropylene-surface treated hydroxyapatite biocomposites

Abstract

In this study, bovine bone was burnt at 400°C and the resulting ash was heat-treated at 900°C for 90 min to get a white powder. Chemical analysis showed that this white powder was mainly hydroxyapatite (HA). Three different average particle sizes of this powder were produced by milling at three different times. The produced HA was surface treated with a silane coupling agent. Composite samples with 40 vol.% of HA were produced by hot press molding and so mechanical testing was done on the specimens in air and Ringer’s solution. The results of these tests showed that on increasing the molecular weight of polypropylene (PP), creep strain of composites decreases proportionally, and ultimate tensile strength (UTS) and impact resistance increase dramatically. In addition, result of mechanical tests on the soaking specimens in Ringer’s solution showed that Ringer’s solution intensively decreases UTS, creep, and impact properties of PP—HA composite. Furthermore, decreasing HA particle size caused UTS rise, creep strain fall, and impact resistance rise for composites in air condition. Vice versa, in wet condition, decreasing HA particle size caused UTS, creep, and impact resistance to fall. Fracture surfaces of impact samples tests were analyzed by a scanning electron microscope.