High Content Nanocellulose 3D‐Printed and Esterified Structures with Strong Interfacial Adhesion, High Mechanical Properties, and Shape Fidelity

Abstract

Wood‐derived biopolymers such as nanocellulose are an attractive engineering material for 3D printing due to their abundance and environment‐friendliness, but their processing into complex structures remains challenging. The most challenging issues in 3D printing high cellulose content structures include printability, interfacial adhesion between layers, mechanical properties, and shape fidelity. Here, a simple and economical approach is presented to manufacture 3D structures by directly extruding high concentration nanocellulose (≈25.94 wt.%) paste cross‐linked with different citric acid (CA) contents. The CA, a green cross‐linker, is optimized in nanocellulose paste to cross‐link between cellulose layers substantially. Furthermore, esterification is achieved by heating the 3D‐printed structures at 140 °C for 20 min in a vacuum oven, as confirmed by Fourier transform infrared spectroscopy. The optimum CA content in nanocellulose paste (CNC:CA:CNF = 20:2:1) exhibits the flexural strength of 82.78 ± 2.79 MPa (128% improvement) and Young's modulus of 6.97 ± 0.38 GPa after 3D printing followed by esterification, which is the best achievement in nanocellulose 3D printing. In addition to the high mechanical strength, the shrinkage of the esterified 3D‐printed structures is below 9%, which demonstrates their high shape fidelity without any interfacial adhesion issues.

Construction of CNC@SiO2@PL Based Superhydrophobic Wood with Excellent Abrasion Resistance Based on Nanoindentation Analysis and Good UV Resistance

“…CNC is a rod-like structure material, which is mainly made of plant fibers by acid hydrolysis, and it has negatively charged sulfonic acid groups on its surface. It has emerged as a strengthening material in recent years [ 20 , 21 ]. As in our previous study [ 6 ], we proposed using the CNC@SiO 2 rods instead of pure SiO 2 nanoparticles to build the rough structure of the superhydrophobic coating.…”

Additively-Manufactured High-Concentration Nanocellulose Composites: Structure and Mechanical Properties

“…The most significant aspects of 3D printing are removing restrictions in designing and constructing complex geometries and reducing material wastage [ 27 , 28 , 29 ]. Based on the ASTM 52900:2015 standard, AMT has seven classifications: direct energy deposition, material jetting and binder jetting technology, fused deposition modeling, vat photopolymerization, and material extrusion method [ 30 ]. Among different 3D printing technologies, material extrusion AMT is well-known for nanocellulose materials [ 31 ].…”

Crystalline and Hairy Nanocelluloses for 3D Printed Hydrogels and Strongly Structured Cryogels

“…The advantages of CNC and CNF in 3D printing include their surface modification characteristics and shear-thinning behavior in aqueous media . However, dilute suspensions of CNC and CNF are not fully suitable for 3D printing due to their low viscosity and drying shrinkage . Increasing the nanocellulose solid content (e.g., 30–40 wt % CNC) surmounts these issues but causes other problems such as nozzle clogging. − Thus, optimizing the solid content in inks (hydrogels) is a major challenge.…”

“…However, dilute suspensions of CNC and CNF are not fully suitable for 3D printing due to their low viscosity and drying shrinkage . Increasing the nanocellulose solid content (e.g., 30–40 wt % CNC) surmounts these issues but causes other problems such as nozzle clogging. − Thus, optimizing the solid content in inks (hydrogels) is a major challenge. A viable approach to tuning hydrogel rheology for high-fidelity 3D printing is to tune the interparticle interactions, which can be achieved by the addition of secondary materials such as polymers, nanoparticles, and salts …”