Preparation Of Hydroxyapatite And Collagen Composite

Hydroxyapatite(HAP) and its collagen(Col) composite have great applications for biomaterials due to their excellent biocompatibility and bioactivity. Three hydroxyapatite powders (HAP1, HAP2 and HAP3) were prepared by hydrolyzation process using brushite, precipitation method using calcium hydroxide and ammonium phosphate and neutralization method using calcium hydroxide and phosphoric acid, respectively. Hydroxyapatite/collagen composite was prepared by in situ precipitation method using calcium hydroxide, phosphoric acid and bovine collagen which was extracted from the fresh bovine tendons. TG / DTG, XRD, FTIR, TEM, SEM as well as specific surface area analysis and pore size distribution analysis were employed to characterize hydroxyapatite and its collagen composite. The sinterability of HAP2 powder which was precalcined at 600℃ and isopressed at 180MPa was studied. After being isopressed at 180MPa, the mechanical property of hydroxyapatite/collagen composite was tested. The results show:(1) Hydroxyapatite powders prepared by hydrolyzation process, precipitation method and neutralization method are in the shape of rod (400nm length, 40nm width), graininess (20-30nm) and sheet (50-80nm), respectively, and their aggregation particle size distributions are in the range of 1-10μm.(2) With the increasing of calcination temperature, the specific surface areas of HAP2 powders decrease. The specific surface area of the powders calcined at 600℃ is 49.1m~2/g. Samples for sintering were precalcined at 600℃ and isostatically compacted at a pressure of 180MPa. The sintered body has a dense microstructure with a relative density of 98.6%. The grain size of the sintered body is in the range of 0.4-0.8μm(3) Hydroxyapatite/collagen composite prepared from calcium hydroxide, phosphoric acid and bovine collagen has a HAP/Col mass ratio of 53:33. HAP /Colcomposite structure was formed via the intertwined assembly of Col fibers surrounded by HAP agglomerates. There are interactions existed between HAP and Col molecular.(4) The average 3-point bending strength of the Hydroxyapatite/collagen composite is 41.96MPa, and the Young's modulus is 4.60GPa. The composite has pore structures with average pore size of 0.26/im.