(65d) Demethylated Lignin As the Interface Enhancer in FDM 3D Printing for PA12 Composites

Fused deposition modeling (FDM) is a widely used 3D printing technique. One of the big challenges of FDM is the weak interface bonding among the layers which limits the mechanical properties of the printed items. In the current work, lignin, the most abundant aromatic biopolymer, was modified by converting its methoxy group to hydroxyl group, forming more phenolic OH groups. Quantitative ³¹P NMR along with ¹H NMR technique was used to track the changes of phenolic OH and methoxy group, and results showed that the content of phenolic -OH group increased from 2.86 to 4.76 mmol/g while the -OMe group dropped from 15.66 to 5.00 mmol/g. The modified lignin (M-Lignin) was then applied in the FDM 3D printing with polyamide 12 (PA12). Due to the enhanced interaction between PA12 and M-Lignin, the melt viscosity increased significantly for the PA12/M-lignin blend during the filament extrusion. For the mechanical performance of the printed samples, the PA12/M-lignin composites with 10 wt% of the M-lignin had the highest tensile strength around 52.7 MPa (46.2 MPa for pure PA) and the Young’s modulus of 1.98 GPa (1.69 GPa for pure PA12), while the elongation at break remained 46% (58% for pure PA). In addition, the M-lignin could also be potential to prevent the aging of PA12 in practical use.