Wollastonite Foams From an Extruded Preceramic Polymer Mixed with CaCO3 Microparticles Assisted by Supercritical Carbon Dioxide

Wollastonite (CaSiO3) bioceramics have recently received great attention as hard tissue repairing material. In this paper we discuss a novel processing for open cell foams based on the mixing of a silicone resin with CaCO3 micron-sized fillers, by means of conventional polymer extrusion assisted by supercritical carbon dioxide. The novel mixing was so effective that the wollastonite yield was comparable to that achieved employing much more reactive nano-sized fillers, and led to silicone/CaCO3 extruded parts, embedding CO2. These parts can be easily converted into highly porous foams (porosity of about 80%) by a secondary low temperature treatment, before final ceramization at 900°C. Depending on the conditions of secondary treatment, it was possible to obtain foams with similar density but different pore architecture, and consequently different strength, ranging from 0.45 to 6 MPa.