| Hydroxyapatite (HA, Ca10(PO4)6(OH)2) has been used for orthopedic/dental implants by its similar chemical composition and structure to the mineral phase of human bone, and it can promote sufficient new bone formation for the firm attachment of juxtaposed bone. However, duing to low fracture toughness, HA cannot serve as a bulk implant material under the high physiological loading condition. Therefore, development of biocomposites with good mechanical property, excellent bioactivity and biocompatibility similar to natural bone to meet the need of hard tissue repair has been a hot topic for over thirty years. To obtain an advanced mechanical performance of the bioactive composite, bioceramic particles were usually incorporated into the polymer matrix using conventional plastics processing technology.Nano hydroxyapatite (n-HA) reinforced polyamide 66 (PA66) (n-HA/PA66) biocomposites for load bearing bone repair were firstly prepared by a group leaded by Yubao Li. In the composite, HA crystals can keep their nano grade dispersion in the PA66 matrix and the content of n-HA can reach 65wt%. The bending strength, tensile strength and compressive strength of the composite with 64.25 wt% n-HA are 95, 79 and 117MPa, respectively, which are close to the natural bone (80-100, 60-120, 50-140MPa separately), and the elastic modulus of this composite is 5.6GPa. However, the elastic modulus of bioceramics and medical metals are much higher (70-300GPa) than that of the natural bone (3-25GPa) and thus often cause stress stimulation or shielding effect, resulting in bone resorption and loosening of implants. Therefore, the mechanical...
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