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3D Printed PLA/HAp Biocomposites
adhesion. However, the high calcination temperature 3.4. Mechanical properties
might have also caused aggregation which prevented good The tensile stress-strain curve of PLA/HAp biocomposites
dispersion of HAp powders in the PLA matrix . The few is shown in Figure 6A. The HAp indeed had a reinforcing
[14]
prominent peaks of HAp were observed to be overlapped effect, as the elastic moduli and tensile strengths both
by the more intense peaks of PLA, approximately around increased compared to pure PLA. As the powder loading
1100–900 cm . Moreover, no new covalent bonds formed was increased, the elastic modulus increased compared
−1
within the PLA/HAp composites, suggesting that the HAp to pure PLA (2.3–~3.5 GPa), but the modulus remained
fillers were embedded in the polymer matrix through consistent despite the further increase in HAp loading
mechanical manner rather than by chemical means. (Figure 6B). Unsurprisingly, the tensile strength decreased
3.3. Crystallinity at 15 wt% HAp loading as the powder loading increased.
This may be primarily due to the HAp agglomeration and
XRD of HAp, PLA, and the printed PLA/HAp poor dispersion, as well as the formation of macro voids
biocomposites is shown in Figure 5. The HAp between neighboring filament beads. Nevertheless, HAp
diffractogram displayed the crystalline nature of the has shown to improve the strength of pure PLA (32.7–
powder. Prominent peaks and their corresponding planes 47.3 MPa). HAp might also act as nucleation sites where
were noted at approximately 26° (002), 33° (112), 47° PLA molecule chains could have entangled itself through
(222), and 49° (213). The (211) plane at ca. 32° is inherent mechanical interlocking effects.
to and characteristic of pure HAp . The stiffness of both PLA/10H and PLA/15H
[12]
Pure PLA (PLA/0H) exhibited a broad spectrum similarly generated 3.5 GPa elastic modulus which is
indicating the amorphous structure of the polymer . within the range of the human cancellous bone tissue ;
[23]
[15]
The composite samples exhibited diffraction peaks hence, these formulations have the potential for the repair
characterized by the presence of HAp in the polymer of smaller bone tissues.
matrix. The peak intensity increases as a function of the The fracture surface after the uniaxial tensile
increase in HAp powder loading. testing of PLA/HAp biocomposites are shown in

Figure 5. X-ray diffractograms of hydroxyapatite (HAp), and varying powder loading in 3D printed polylactic acid/HAp composites
(0–15 wt. %).

118 International Journal of Bioprinting (2021)–Volume 7, Issue 1