Processing of homogeneous ceramic/polymer blends for bioresorbable composites
Three methods to mix ceramic fillers, hydroxyapatite or β-tricalcium phosphate, with a polymer matrix, a poly l-lactic acid, are investigated as a first step prior to supercritical foaming to prepare porous composite structures for biomedical applications. First the dry process consists in mixing ceramic powder and polymer pellets before a compression molding step. The second technique is based on the dispersion of ceramic fillers into a polymer–solvent solution. The third method is a melt extrusion of a ceramic/polymer powder mixture. Each technique is first optimized by defining the processing parameters suitable for the bioresorbable materials considered. Then comparison of the three methods shows that solvent or melt processing results in a more homogeneous filler distribution than the dry technique. Extrusion leads to composites with a higher modulus than solvent prepared compounds and is a solvent-free approach. The former technique is therefore selected to prepare ceramic/polymer blends before supercritical CO2 foaming.