Preparation of lignin nanoparticles by ultrasonication and its incorporation in DLP 3D printing UV-curable resin as bio-filler

As 3D printing technology continues to evolve and become more widely utilized across various fields, there is a growing need to enhance the performance of 3D printing materials. The incorporation of lignin as a bio-filler has the potential to enhance the performance of 3D-printed composites. However, the current limitations of lignin dispersion and stability in UV-curable resins restrict its broader application. Therefore, we prepared lignin nanoparticles (LNPs) by ultrasonication under different conditions. By characterizing the properties of the LNPs and comparing them with the pristine lignin, it was shown that both the increase in power and time during ultrasonication resulted in a decrease in the size of the lignin particles. The obtained LNPs were well dispersed in the acrylic resin and retained good stability. The LNPs were added to the acrylate matrix at different content to obtain LNPs/acrylate UV-curable resins, and their mechanical, thermal and morphological properties were investigated after curing. The results showed that the cured LNPs/acrylate resin had superior mechanical properties in comparison to the pure acrylic resin. The optimal mechanical performance was observed at LNPs content of 2.0 wt% (tensile strength: 2.42 MPa, Young's modulus: 25.7 MPa, toughness: 113.6 MJ/m3, and Shore D hardness: 82.1 HD). The cross-section of the cured LNPs/acrylate composites was analyzed by SEM and it was found that the grid structure formed inside the material may be the key to its improved performance. The thermal stability of the cured LNPs/acrylate composite improved with the increase of LNPs content. Finally, digital light processing (DLP) 3D printing was performed with the LNPs/acrylate UV-curable resin (2.0 wt% LNPs content), and it was found to have good printing accuracy and perfectly meet the requirements of DLP 3D printing. These results demonstrate the potential of LNPs as enhanced bio-fillers in DLP 3D printing.