This work presents the experimental steps taken towards the preparation of 3D printable bionanocomposites using polylactic acid (PLA) biopolymer containing 0.1, 0.5 and 1 wt% CNCs.

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.

There is a growing need to address waste generated from Fused Filament Fabrication (FFF) 3D printing activities. This study explores the mechanical recycling of waste polylactic acid (PLA) accumulated from failed 3D printing operations and PLA biocomposite filaments containing nanocellulose fibres. FFF 3D printable filaments were produced via melt mixing and extrusion of virgin PLA containing varying amounts of waste PLA. The chemical, thermal and thermomechanical characterisation of each specimen was evaluated using Fourier‐transform infrared spectroscopy (FTIR), simultaneous thermal analysis (SDT), dynamic mechanical analysis (DMA), and uniaxial tensile analysis (UTA). A desktop FFF 3D printer was used to fabricate UTA and DMA test specimens. The thermal stability of the filament specimens containing waste derived from the failed 3D prints were comparable with that of the commercial filaments. However, a 11% decrease in the onset of thermal degradation is observed for the filament containing waste biocomposites. The specimens containing waste PLA exhibited higher crystallinity and storage modulus. UTA results revealed similar tensile strength and % elongation, except for the specimen containing 50% waste PLA which exhibited a 29% decrease in tensile strength. This work successfully demonstrates mechanical recycling as a viable waste management strategy for waste materials generated during FFF 3D printing.

This paper deals with the development of cellulose nanofibres (CNFs) reinforced biopolymers for use in packaging applications. Cellulose nanofibres were extracted from sawdust by a combination of chemical and mechanical treatments. The extracted cellulose nanofibres were chemically modified (fCNFs) and characterised by Fourier Transform Infrared Spectroscopy (FTIR). Bionanocomposites were prepared from biopolymers polylactic acid/polybutylene succinate (PLA/PBS) and cellulose nanofibres by compounding in a twin-screw extruder followed by injection moulding. The developed bionanocomposites were subjected to mechanical and thermal characterisation. As part of product development, CNF-biopolymer pellets were also extruded into filaments which were then 3D printed into prototypes. This work is a successful demonstration of conversion of waste residues into value-added products, which is aligned to the principles of circular economy and sustainable development.

There is a growing need for diversified material feedstock for 3D printing technologies such as fused deposition modelling (FDM) techniques. This has resulted in an increased drive in the research and development of eco-friendly biopolymer-based composites with wide applications. At present, bionanocomposites of polylactic acid (PLA), biopolymer, and cellulose nanocrystals (CNCs) offer promising technical qualities suitable for FDM 3D printing applications due to their biodegradability and wide-ranging applications. In this work, the applicability of the PLA/CNCs bionanocomposites in 4D applications was investigated by studying its shape-recovery behaviour. Tensile and dynamic mechanical analysis (DMA) was used to elucidate the mechanical and flexural properties of the 3D-printed specimens. The results revealed improvement in the deflection temperature under load (DTUL), creep deformation, and recovery of the PLA/CNCs bionanocomposites. Tensile and static 3-point bending analyses of the bionanocomposites revealed improved tensile strength and modulus of the 3D printed parts. The potential 4D application of the PLA/CNCs bionanocomposites was also investigated by successfully printing PLA/CNC bionanocomposites directly onto a nylon fabric. The PLA/CNCs-fabric prototype included a foldable cube and grid-patterned designs. Additionally, the heat-induced shape memory behaviour of these prototypes was demonstrated.