Three-Dimensional Printing of Highly Crosslinked and Concentrated Nanocellulose for Environmentally Friendly Structural Applications
Muhammad Latif, Yangxiaozhe Jiang, Bijender Kumar, Hyeon Cheol Cho, Jong Min Song, Jaehwan Kim
Abstract
In recent years, three-dimensional (3D) printing of environmentally friendly structures with a high concentration of nanocellulose (NC) has gained much attention because of health and environmental issues. However, there remain challenges due to poor adhesion between printed layers, resulting in low mechanical properties and shape fidelity. This research demonstrates an economical approach to printing environmentally friendly 3D structures by directly extruding high-concentration NC (∼25.5 wt %) paste to deal with the challenges. Different low concentrations (2.5, 5, and 10 wt %) of polyvinyl alcohol (PVA) were mixed with NC as a crosslinker to facilitate the adhesion between the printed layers. A twin-screw extrusion machine was used to eject the high-concentration NC paste for 3D printing. After the printing process, the final structures were dried at a controlled relative humidity of 45% and a temperature of 25 °C. An optimum 5 wt % PVA-crosslinked high-concentration NC paste showed the highest flexural strength of 121 ± 2 MPa (233% improvement) and a flexural modulus of 15.0 ± 0.1 GPa (263% improvement), which are much higher than the previously reported results until now. It suggests that the extremely low content of PVA effectively improved the bilayer adhesion, resulting in high shape fidelity and mechanical strength of the 3D printed structures for environmentally friendly structural applications.