Novel nanocellulose - microcrystalline cellulose complex with hierarchical structure reinforcing polylactic acid as 3D printing materials

Abstract

Abstract A novel nanocellulose - microcrystalline cellulose complex (NCMC) with special hierarchical structure has been prepared by grafting nanocellulose (NC) onto the surface of microcrystalline cellulose (MCC) via different silane coupling agents in this paper. The cellulose complex was easier to separate and purify from the solution in the preparation process than nanocellulose due to its large size, and was used to reinforce polylactic acid (PLA) as 3D printing materials through a melt-blending process. The results showed that NCMCs prepared by different silane coupling agents had different surface morphologies. Nanocelluloses formed a network structure on the surface of KH-550 treated NCMC, while a spherical structure wrapped by nanocellulose was formed on the surface of KH-560 treated NCMC, and KH-570 treated NCMC was the nanocellulose network with a small amount of irregular silica impurities. The mechanical properties, crystallinity of polymer and thermal stability of NCMC/PLA composites are obviously improved by adding a small amount of NCMC. Compared to pure PLA, the tensile strength, bending strength and elongation at break of the NCMC/PLA composites were increased by 40.3%, 84.1% and 34.3%, respectively. It is because NCMC had higher specific surface area and more complex surface structure than MCC, that led to more thorough grafting reaction on polylactic acid during high temperature extrusion blending process. The DSC results also showed that a small amount of NCMC could promote the crystallization of PLA as 3D printing materials. Besides, NCMC/PLA composites did not block the printing nozzle in continuous 3D printing, and the printed products had better appearances. The obtained materials are environmentally friendly, renewable and ideal for 3D printing.