Comparing the Mechanical and Thermal Properties of Polylactic Acid/Organosolv Lignin Biocomposites Made of Different Biomass for 3D Printing Applications

This work investigates the differences in mechanical and thermal properties of polylactic acid (PLA)/lignin biocomposites made of four different unmodified organosolv lignin materials, three of which were extracted from different woody biomass (maple, oak, and pine) in-house, and one sourced commercially. Filaments made from blends of 30 wt% and 40 wt% of the in-house lignin and the commercially sourced lignin as fillers in PLA were used to 3D-print experimental test samples using fused filament fabrication (FFF) process. Statistically significant differences were observed in the mechanical properties based on tension testing and Izod impact testing, while differences in thermal properties based on differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were less significant. Test samples with 30 wt% lignin had tensile strengths that were higher than those of 40 wt% lignin. Among the three in-house extracted lignin from the woody biomass resources, maple-based composites consistently yielded the highest tensile strengths while oak-based materials yielded the highest stiffness in tension testing and the most stability in impact resistance. The pine-based materials showed the most decline in strengths between 30 wt% and 40 wt% lignin loadings. The commercially obtained lignin at 30 wt% and pine-based lignin at 40 wt% yielded much higher percent elongations at failure than all other materials. This study demonstrates the influence of lignin biomass resources and their concentrations on the properties and performances of 3D printed specimens.