PLA bio-nanocomposites reinforced with cellulose nanofibrils (CNFs) for 3D printing applications

This study deals with the development of 3D printable bionanocomposites using poly(lactic acid) (PLA) with <= 2% D-lactic acid content and cellulose nanofibrils (CNFs). The CNFs were extracted from the waste sawdust of Eucalyptus grandis via chemical and mechanical techniques. Thermogravimetric analysis (TGA) revealed that the CNFs were thermally stable within the intended processing temperature ranges. In this study, a combination of solvent casting and melt extrusion techniques was adopted in the production of PLA containing 1 wt% and 3 wt% CNFs. The neat PLA filament was brittle and frequently broke during fused deposition modelling (FDM) 3D printing. However, the incorporation of triacetin as a green plasticizer resulted in improved filament flexibility and eliminated the inherent brittleness. TGA analysis revealed a slight reduction in the degradation temperature of the bionanocomposites when compared to neat polymer; however, all the specimens were thermally stable within the processing temperature. The scanning electron microscopy images of the 3D printed specimens revealed the presence of voids across the fracture surfaces. The tensile analysis of 3D printed specimens revealed that the PLA/CNF bionanocomposites exhibited higher tensile modulus, and elongation (strain) when compared to PLA-based specimens. The tensile strength of the 3D-printed 1 wt% bionanocomposite specimen was 12% higher than that of the neat specimen, whereas the 3 wt% bionanocomposite remained comparable to neat PLA. In summary, the morphological, tensile and 3D printing analysis revealed that the bionanocomposite filaments possessed adequate roundness, flexibility, and strength. The as-prepared filaments performed well under low printing temperatures without warping.