| Hydroxyapatite (HA) ceramics are attractive in hard tissue repair because of its excellent biocompatibility and osteoconductivity, which is the research focus of bone repair and substitute materials in recent 20-30 years. However, due to the brittleness, hard molding, mechanical matching problem with human bone, and high modulus and fatigue failure in vivo, it has been restricted in clinic for un-load bearing bone repair. Therefore, development of biocomposites with high bioactivity, good mechanical property and biocompatibility with natural bone to meet the need of hard tissue repair is a hot topic of international biomaterials research.It is well known that the natural bone consists of nanoapatite crystals and collagen. Simulation of the structure and function of natural bone, the fabrication of apatite/polymer composite with the bioactivity of apatite and the toughness of polymer has brought the largest interest and abroad attention of many researchers in recent years.Polymer has good toughness and a modulus close to human bone, but it has not bioactivity. As the main mineral constituent of human hard tissues, HA has shown excellent bioactivity and can integrate with natural bone. In order to enhance the toughness of HA bioceramics, studies on HA and polymer composite are highlighted. Up to date, various composites have been explored as bone substitute materials, including HA reinforced polyethylene, polylactide, collagen and Polyactive? etc.In this research, a new method of calcium nitrate and sodium phosphateas reactants was employed to prepare apatite precipitate. The apatite precipitate is hydrothermally treated to fabricate nanoapatite crystals under normal pressure at different temperature, and N, N-dimethyl acetamide is used as dispersant in synthesizing nanoapatite crystals. The results indicate that the prepared nanoapatite crystals have similarity in composition, structure, size, morphology and crystallinity to those of bone apatite crystals. The nanoapatite crystals contain OH', CO32', Na+ and HPO42- ions in their crystal structure. Therefore, the nanoapatite crystals can be called bone-like apatite crystals.Different hydrothermally treated conditions have obviously effect on the morphology, crystallinity and the size of nanoapatite crystals. The size and crystallinity of the nano-apatite crystals increase with hydrothermal temperature, treatment time, and surface activity of apatite precipitation. The morphology of the nanoapatite crystals is rod-like under pressure and needle-like with a bigger aspect ratio under normal pressure. The freshness of the. starting apatite precipitates affects the growth of the nano apatite crystal. The size of nano apatite crystals hydrothermally treated after as-prepared is much bigger than that from the apatite precipitates stored for a period of time.It is clear that the higher the HA content in the polymer, the better the bioactivity of the composite. To achieve the desired bioactivity, it is necessary to increase HA content in composite. However, at present, most HA/polymer composites are prepared by directly mixing HA powder with polymer resin, which is difficult to fabricate composite with high HA content.It is known that the smaller the HA particles are, the higher the HA content could be in the polymer. Therefore, n-HA crystals should be selected to fabricate high bioactive composites. However, due to its high surface activity, when n-HA slurry is dried in air, it will clog into micrometer-sized HA particles. Try to solve this problem, undried HAn-HA slurry is used directly to prepare n-HA/polymer biocomposite with a new co-solution method under normal atmospheric pressure in this study.The results show that the novel biocomposite of n-HA/PA66 prepared by co-solution method has good homogeneity, high n-HA content (65wt%), and excellent mechanical properties, which are close to the natural bone. Strong molecular interactions and chemical bonding are present between the n-HA crystals and PA66 polymer. The synthetic nano-composite could be one of the best bioac...
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