Influence of porosity and pore size on the compressive strength of porous hydroxyapatite ceramic

Porous hydroxyapatite (HAp) ceramics with porosity volume fractions varying from 33% to 78% were fabricated using poly vinyl butyral (PVB) as a pore-forming agent. Three types of PVB particle, of size 0.093 mm, 0.188 mm, and 0.42 mm, were employed corresponding to the porous HAp of different macropore sizes. The compressive strength of the porous HAp was investigated in terms of porosity and pore size. The compressive strength behaviour of the porous HAp can be correlated exponentially with porosity volume with a correlation factor greater than 0.96. The porous HAp consisting of smaller macropore exhibits higher strength in comparison with those of larger macropore; however, a greater porosity-dependent strength is observed for the porous HAp ceramic consisting primarily of smaller macropores. Experimental analysis also revealed that for a given porosity volume, the compressive strength behaves roughly linearly with macropore size; a smaller macropore corresponds to a higher compressive strength. These findings suggest that an optimum design of porous HAp with a variety of porosities and with sufficient strength is feasible.