Effect of heat treatment of hydroxyapatite on its dispersibility in aqueous medium

Dispersibility of hydroxyapatite (HAP) powder, as received and heat treated, in aqueous medium has been studied in presence of three anionic polyelectrolytes, namely Darvan 821 A, Darvan 811 and Darvan C using techniques like surface charge characterization by particle charge detector (PCD), flow point and capillary suction time (CST) measurement. Studies revealed that as received powder has very reactive surfaces and comparatively higher surface charges compared to heat-treated one. It has been also observed that performance of most bulkier dispersant, namely, Darvan C was the poorest in both the cases. Flow points measurements indicated that it may be possible to prepare slurry with high solid loading using both the powder, but CST measurement established that heat-treated powder stayed agglomerated and consequently has poor dispersibility.