Hydroxyapatite-polymer composites with tannin as a chelating agent: crystal structure and mechanical properties

Hydroxyapatite is the main minerals in the bone as a biomaterial. The synthesis of hydroxyapatite requires additional materials to improve its mechanical properties. This research aimed to observe the ability of tannins as a chelating agent in hydroxyapatite synthesis. Hydroxyapatite was synthesized from Ca(OH)2, (NH4)2HPO4, Ca(OH)2, H3PO4, and tannin as chelating agents with precipitation method. Hydroxyapatite made from calcium and phosphate as a precursor and control the pH was 12 with the addition of Sodium Hydroxide. Then, added tannin and stirrer about 1 hour. The precipitate was dried in oven at 40°C for Hydroxyapatite using H3PO4 precursor. All the samples were characterized using FTIR, XRD, SEM and Hardness tester. Two compounds (calcium carbonate and hydroxyapatite) were obtained by using XRD analysis. The crystal size of the hydroxyapatite of 15-27 nm and hydroxyapatite-tannin of 10-29 nm. The SEM results show the surface morphology of hydroxyapatite was obtained as agglomerates or clumping. Hydroxyapatite-tannin was obtained with particle size in fields from 0.1-0.4 µm. The Hardness Tester received an average value was 28.36 N and 27.81 N for hydroxyapatite and 34.43 N dan 33.92 N for hydroxyapatite-tannin. Tannin acts as a chelating agent in the synthesis process of hydroxyapatite by the precipitation method.