Bio-based cellulose-filled vitrimers for 3D printing via liquid deposition modeling: Rheological tuning and environmental assessment

To address the need for sustainable materials in 3D printing applications, a bio-based vitrimer was developed using an epoxy resin derived from cardanol and cystamine as a cross-linker. Cystamine was chosen due to its dynamic disulfide bonds, bio-based nature and highly reactive aliphatic amine groups, enabling rapid network formation under mild thermal conditions. Microfibrillated cellulose (MFC) and ultrafine cellulose (UFC) were used as bio-based fillers and rheology modifiers to formulate printable pastes. The curing process was thoroughly investigated by DSC and FTIR-ATR, confirming efficient cross-linking under the selected conditions. Thermal and structural properties of the vitrimers were characterized by gel content, swelling, and heat resistance analyses. The printability of the pastes via Liquid Deposition Modeling was evaluated through rheological analysis, and a concentration of 13 wt% MFC and 13 wt% UFC was identified as the optimal compromise between shear-flow behavior and post-print structural integrity. Simple and more complex geometries were printed and then cured at 30–80 °C, ensuring high shape fidelity (87.0 %). The vitrimer behavior was confirmed by stress-relaxation experiments, showing an overall activation energy in the range of 63–65 kJ mol−1, and by successful mechanical recyclability. Finally, a preliminary Life Cycle Assessment underscored the potential of these materials for sustainable additive manufacturing.