Hydrolysis of tetracalcium phosphate in the presence of a poly(alkenoic acid)

Abstract

Ca4(PO4)2O (TetCP) reacts with an acidic polyelectrolyte in the absence of a solvent to form a composite composed of Ca10(PO4)6(OH)2 (hydroxyapatite, or HAp) and the Ca salt of the polyelectrolyte. Mixtures of an acrylic copolymer and TetCP powders were hot-pressed, and the effects of temperature, pressure, and time on HAp formation were studied. Reaction starts when the copolymer is heated to above Tg. Initial carboxyl site neutralization liberates water, continued TetCP hydrolysis, liberates Ca2+ ions, which react with the copolymer forming its Ca salt. When 90% conversion to HAp was achieved, the composite had an average tensile strength of 51 MPa, a Vickers hardness of 145 kg/mm2 and a Tg ˜50 °C.