THE FORMATION OF HYDROXYAPATITE-GELATIN COMPOSITES AT 38-DEGREES-C

Composites comprised of calcium deficient hydroxyapatite (CA/P = 1.5) and gelatin form in about 4 h at 38 degrees C. The solid reactants use d are CaHPO4 and Ca-4(PO4)(2)O and the liquid reactant is gelatin solu tion. The reaction forming hydroxyapatite occurs in several steps. Bas ed on the measurement of heat liberation, there is an initial period w here the reaction rate is low. This is followed by a period of constan t reaction until the reaction is complete. Analysis of the variation i n pH shows that hydroxyapatite formation occurs at a steady state pH n ear 8.2. Analyses of the evolution of crystalline phases indicates tha t Ca-4(PO4)(2)O is consumed prior to complete reaction resulting in a phase assemblage of hydroxyapatite (CA/P > 1.5) and CaHPO4. Further re action results in compositional adjustments in hydroxyapatite as CaHPO 4 is consumed. Microstructurally, the composites which form consist of clusters of hydroxyapatite embedded in a gelatin network. The presenc e of gelatin does not influence the morphology of the hydroxyapatite w hich forms nor does it retard its rate of formation. (C) 1994 John Wil ey and Sons, Inc.