PLLA/PCL composite filaments reinforced with buffalo bone-derived carbonated hydroxyapatite for fused deposition modeling

This study presents the development and characterization of poly(L-lactic acid) (PLLA)/polycaprolactone (PCL) composite filaments containing buffalo bone-derived carbonated hydroxyapatite (CHA) for potential fused deposition modeling (FDM) applications. Composite filaments containing 10, 20, and 30 wt% CHA were fabricated using a 70:30 PLLA/PCL matrix and characterized in terms of chemical structure, thermal behavior, morphology, mechanical properties, and preliminary mineralization-related response. FTIR analysis indicated retention of the characteristic functional groups of the PLLA/PCL matrix and spectral features consistent with the CHA reference after extrusion; however, overlapping bands prevented definitive assignment of phosphate and carbonate groups in the filament spectra. DSC analysis showed composition-dependent changes in PLLA crystallization behavior, with T cc shifting to higher temperatures following CHA incorporation. The highest calculated crystallinity of 56.75% was observed at 20 wt% CHA, decreasing to 35.74% at 30 wt% CHA. Tensile testing showed a statistically significant effect of CHA loading on tensile strength, whereas elongation at break did not differ significantly among formulations. The neat PLLA/PCL blend exhibited the highest tensile strength (40.83 MPa), whereas 20 wt% CHA showed the highest mean elongation at break (6.53%), representing a descriptive numerical trend rather than a statistically confirmed improvement. After 7 days of simulated body fluid immersion, SEM revealed surface deposits accompanied by localized Ca and P/Mg-region signals in EDX analysis. However, the deposited phase could not be conclusively identified. Overall, CHA loading influenced the thermal, morphological, mechanical, and surface mineralization-related characteristics of the composite filaments. These findings provide a preliminary basis for further investigation of buffalo bone-derived CHA/PLLA/PCL filaments as potential FDM feedstock materials.