Development of P(3HB-co-3HHx) nanohydroxyapatite (nHA) composites for scaffolds manufacturing by means of fused deposition modeling

This work reports on the development of nanocomposites based on poly(3hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HHx)] and nanohydroxyapatite (nHA) for the development of scaffolds by means of a two-stage extrusion process followed by a 3D printing process. Tensile test samples were produced for the characterization of the materials. Each processing thermal cycle promoted a slight thermal degradation, identified by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Also, a viscosity reduction was observed in the rheological measurements. The 3D-printed tensile test samples exhibited increasing stiffness at increasing nHA content (with elastic modulus values close to 1000 MPa), while tensile strength and strain at break were reduced. Nonetheless, the deposition direction oriented with the tensile direction (raster angle of 0 degrees C) exhibited the highest tensile strength (18 MPa) but lower elongation at break than the 45 degrees/-45 degrees C deposition, which resulted in the highest strain (up to 17%). Regarding the scaffolds, they were degraded in phosphate-buffered saline at 37 degrees C for 8 weeks. This degradation was identified by a reduction of their weight (between 1.5% and 3.0%) and reduced mechanical behavior measured by means of a compression test. Scaffolds showed a decrease of the compression strength (from values close to 13 MPa to 9 MPa).