Effect of rock sugar as a pore-forming material on the physical and mechanical properties of hydroxyapatite scaffold

Hydroxyapatite (HA) ceramic scaffold had been made using the pressureless sintering method for bone scaffold applications. Micron- and nano-sized HA as the primary material with the addition of polyvinyl alcohol (PVA) as a binder and rock sugar (RS) sized 298-420 μm as pore-forming material had been prepared. RS was applied to produce interconnecting pores in the HA scaffold. The green body was made by uniaxial pressing method at a pressure of 200 MPa. Preheating was carried out at a temperature of 700°C with a holding time of 1 h, aimed at eliminating PVA and RS, and then the temperature was increased to 1200°C with a holding time of 2 h. During the sintering process, the heating rate and cooling rate were maintained at 3°C/min. Physical and mechanical properties were tested respectively, including porosity and compressive strength testing. The results showed that the 23.0% porosity obtained a compressive strength value of 15.6 MPa at a ratio of HA:RS of 65:35 wt%. The highest porosity of 48.4% was obtained with a compressive strength of 4.9 MPa at a ratio of 55:45 wt%. In this study, the maximum addition of RS was only at 45 wt%, while the addition of RS reaching 50 wt% or more could affect the tangential bonding between HA powders during the sintering process.