A synthetic aragonite-based bioceramic: influence of process parameters on porosity and compressive strength

We investigate the influence of process parameters such as weight fraction and particle size of pore-former, and isostatic pressure, on porosity and compressive strength of non-sintered porous calcium carbonate biomaterials compacted at high pressure in uniaxial or isostatic mode. Experiment design and results analysis are performed according to a two-level 2k factorial design method (FDM). Results indicate that only the weight fraction of pore-former (wt fpf) influences significantly the porosity and the compressive strength. The porosity P, is described by a linear function of wt fpf, and the compressive strength σcomp, by an exponential one. For materials compacted under uniaxial pressing: P (vol%)=33.7+85.4 (wt fpf) and σcomp (MPa)=28.8 e−9.2(wt fpf) with 0.1 wt fpf 0.3. For materials compacted in isostatic mode: P (vol%)=33.9+82.1 (wt fpf) and σcomp (MPa)=24.0 e−7.0(wt fpf) with 0.15 wt fpf 0.35. The pore-former particle size has no significant influence on both properties. The increase in isostatic pressure provides slightly lower porosity and better compressive strength. For a fixed fraction of pore-former, isostatic pressing leads to a better compressive strength than uniaxial pressing. This study indicates that, for a constant amount of pore former, the size of macropores can be adjusted to reach optimal bone-ingrowth without change in compressive strength.