Characterization of porous β-tricalcium phosphate fabricated by physical foaming with a nonionic surfactant: Effect of adding a thickener

Carboxymethylcellulose with ammonium functional groups (CMC-NH4), acting as a thickener, was included in the preparation of porous beta-tricalcium phosphate (β-TCP) based on foaming via physical agitation. The physical properties of the resulting porous products were evaluated. The viscosities of the slurry and resulting foam were increased markedly as the amount of added CMC-NH4 was increased. A polyoxyethylene alkyl ether surfactant was also found to significantly promote foaming, although the foam became less stable over time. The incorporation of CMC-NH4 increased foam stability even though an excess of this agent gave an overly high viscosity that inhibited foaming. Sintered porous β-TCP generated in this study was a single-phase material with no by-products. Cross-sectional scanning electron microscopy images of the porous β-TCP showed that the pore size and distribution were changed as the proportion of CMC-NH4 was increased. The addition of 1.0 g of this agent to 30 g β-TCP gave a material containing primarily macro-sized pores with a porosity of approximately 80 % and compressive strength on the order of 2 MPa. Both micro-sized pores (0.2–0.6 µm with an average of 0.32 µm) and macro-sized pores (10–200 µm with an average of 80 µm) were found to be connected in the specimens. Controlling the slurry viscosity was determined to be important because this variable affected the pore size and size distribution.