Effect of Licorice Residue Biomass Filler on Structure and Properties of Amorphous Polylactic Acid 3D ‐Printed Composites

To achieve the high‐value utilization of licorice residue (LR), polylactic acid (PLA)/LR composite monofilaments were prepared via the melt blending‐extrusion process using amorphous PLA as the matrix and LR as the filler. The effect of LR content (4, 8, and 12 wt%) on the supramolecular structure of PLA was analyzed. The SEM of the cross‐section of the composite monofilaments showed that LR was uniformly dispersed in the PLA matrix. Calculations from the second DSC heating curve revealed that the crystallinity of the composite monofilament reached 7.9% at an LR mass fraction of 4%, while that of neat PLA monofilament was 6.7%, indicating that LR exerted a weak heterogeneous nucleation effect on amorphous PLA. However, the crystallinity decreased to 5.8% and 5.0% when the content of LR is 8 and 12 wt%, respectively, as the densely dispersed LR inhibited the crystal growth of PLA. Thermal stability tests showed that even at an LR content of 12 wt%, the mass loss of the composite monofilament was only 1% below 300°C, which meets the processing temperature requirement for 3D printing (≤ 250°C). In terms of mechanical properties, the tensile strength at break of the composite monofilaments ranged from 42.6 to 48.6 MPa, which was comparable to that of neat PLA (47.6 MPa), and the elongation at break remained at approximately 2.3%, suggesting that the flexibility was not significantly affected. 3D printing experiments demonstrated that the extrusion of PLA/LR composites proceeded basically smoothly with good 3D printing formability.