Effect of stearic acid on the mechanical and rheological properties of PLA/HA biocomposites

In this study, biocomposite filaments of polylactic acid (PLA) combined with stearic acid (SA)-coated nano-hydroxyapatite (HA) filler were prepared and characterized. These filaments were then used in material extrusion (MEX) additive manufacturing via fused deposition modeling (FDM) to create scaffolds for bone tissue engineering (BTE). Initially, HA was characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and the Rietveld method. Particle size distribution was examined through dynamic light scattering (DLS), and its specific surface area was determined by the Brunauer-Emmett-Teller (BET) method. Subsequently, the HA nanoparticles were coated with stearic acid (SA) to explore its potential as a surfactant for PLA/HA nanocomposites. For composite fabrication, pure HA and SA-coated HA were mixed with PLA in a torque rheometer to obtain PLA/HA and PLA/HA-SA biocomposites. Their flow behavior was evaluated using a slit die rheometer, demonstrating that the SA coating improved rheological properties. The composites were extruded to produce 1.75 mm diameter filaments, which were analyzed by mechanical tensile testing, showing that the SA coating reduced the fragility of the PLA/HA filaments. The filaments exhibited high repeatability in terms of quality, facilitating scaffold printing. The FDM-manufactured scaffolds were analyzed through compressive testing, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and AlamarBlue Cell Viability Analysis. The results demonstrated that these scaffolds possess the required mechanical, thermal, and cytotoxicity properties for applications in bone tissue engineering. [Display omitted]