An evaluation of mechanical property and microstructural development in HAP-Ca polycarboxylate biocomposites prepared by hot pressing

A hot-pressing technique was used to prepare composites anticipated to be bio-compatible. Ca₄(PO₄)₂O (TetCP) was reacted with an acrylic-itaconic copolymer (COP) in the absence of a solvent to form composites comprised of Ca₁₀(PO₄)₆(OH)₂, (hydroxyapatite, or HAp) and the Ca polyalkenoate salt. The effect of temperature, pressure, and hot-pressing time on the mechanical properties and microstructure of the composites were studied. Results showed that both tensile strength and elastic modulus increased when temperature and time were increased. When the compaction pressure was increased, these properties initially increased but decreased at high pressures. These variations in the mechanical properties were correlated with the microstructure of these composites. The mechanism of the reaction was also studied. Reaction starts when the copolymer is heated to above its T(g) permitting it to flow and react with the TetCP grains. The COOH groups on the polymer are neutralized by Ca²⁺ ions liberated from the TetCP. At the end of reaction, a network of the Ca polyalkenoate salt is formed in which HAp crystals are embedded. (C) 2000 John Wiley and Sons, Inc.