Extrusion-based 3D printing is widely used to fabricate precise and accurate 3D structures with nanocellulose suspensions due to its excellent material flow control and system stability. The current issues related to high concentration nanocellulose 3D structures are low printability, layers adhesion, shape fidelity, and mechanical strength. Herein, the issues associated with 3D printed concentrated nanocellulose structures were resolved by mixing different concentrations of tannic acid. The printing parameters of a twin-screw extruder, tannin acid content, and drying conditions were optimized for concentrated nanocellulose paste. The mechanical results showed that tannic acid effectively improved the adhesion between printed layers, as confirmed by a scanning electron microscope.
Piezoelectric ceramics, lead zirconate titanate (PZT), have been widely used for sensors and actuators due to their high electromechanical properties. However, the brittle nature of ceramics limits their applications to only small deformations as the flexibility and durability of these materials are the main essential factors required for practical applications. The flexible piezoelectric materials can be developed by blending PZT with flexible polymeric materials such as nanocellulose fibers. The bio-based nanocellulose fibers (CNF) have been reported as a type of electroactive polymer with a piezoelectric response exhibiting excellent mechanical strength and modulus. In this regard, the present study focuses on enhancing the mechanical strength and load-bearing capability of PZT by blending 20 and 30wt% of PZT powder with 80 and 70wt% CNF to obtain a flexible piezoelectric composite film via 3D printing. The 3D printed films' structural, morphological, and mechanical properties were investigated through XRD, SEM, and tensile tests. The SEM images and XRD analysis demonstrated that the PZT powder was uniformly dispersed in the CNF films and showed the morphotropic phase boundary (MPB) in PZT/CNF films. The addition of CNF in PZT has improved the mechanical strength significantly.
Graphene is a proper selection for triboelectric nanogenerators (TENGs) because of its outstanding properties such as high electrical conductivity, specific surface area, aspect ratio, mechanical strength, flexibility, and transparency. In addition, Polydimethylsiloxane (PDMS) is a triboelectric material that is transparent, flexible, and biocompatible. Nanogenerators based on graphene has several advantages over other nanogenerators including flexibility, simplicity, and structural stability. Graphene/PDMS nanocomposites can be made with good electrical and mechanical properties for use in TENGs. In the present research work, Graphene/PDMS nanocomposites with varying amounts of graphene (0, 0.05, 0.5, 1, and 1.5 wt.%) have been synthesized. The effect of chemical composition and surface modification on the properties of nanocomposites, including transparency, roughness, and contact angle has been investigated. Comparison of these results revealed the optimized nanocomposite for application in TENGs
Developing robust bio-based composites against various kinds of petroleum-derived materials has necessitated the continuous exploration and utilization of natural fiber for high-performance applications, especially those derived from bio-sources. In this scenario, cellulose nanofiber (CNF) can be a vital alternative to replace synthetic fiber commonly used as CNF-reinforced composites. In this regard, we prepared lignin-derived vanillin epoxy resin through the epoxidation of vanillin, and it was cured with a 4,4’-diamino diphenyl methane hardener. Furthermore, the solvent-epoxy mixture was impregnated with CNF film to get the CNF-reinforced vanillin epoxy composites. To confirm the compatibility of epoxy with CNF, we performed FTIR spectroscopy. Further, the bending strength of nanocomposites was evaluated. This research could lead to the manufacture of high-performance and environmentally friendly natural fiber composites that can be potentially useable in numerous applications.
The quest for bioderived resins and eco-friendly lightweight materials having remarkable mechanical performance is ubiquitous in scientific reports. In this work, we report a strong and tough biobased resin of esterified Polyvinyl alcohol-Citric acid-Lignin (E-PCL) suitable for nanocellulose fiber-reinforced polymer composites. The mechanical properties of the resin were optimized by varying the volumetric concentration of citric acid and subsequently esterified at 180°C. At 30% citric acid content, the esterified resin showed dramatic improvement in tensile strength (269.8%), toughness (1222.8%), Elastic modulus (273.5%), and hydrophobicity (48.5%). The adhesion strength of the resin to cellulose film was 31.92 MPa making it appropriate for green cellulose-based fiber-reinforced polymer composites. To validate our concept, three wet-spun nanocellulose filament was knit into mats on a loom and applied in composite fabrication through hand-layup and hot press. The lightweight yet strong and stiff structural composite displayed a record high flexural strength of 363.42 MPa and flexural modulus of 39.89 GPa with a water contact angle of 93.4°. Insights from this report offer a promising platform for utilizing environment-friendly resins and nanocellulose to engineer lightweight and robust structural composites for automotive, aerospace, and structural applications.
Recently, extrusion-based 3D printing has been widely used to manufacture precise and accurate 3D structures with high nanocellulose concentrations due to excellent materials flow control and system stability. With the extrusion-based 3D printing technique, the main challenges for precision and accuracy in high concentration nanocellulose 3D printed structures are proper printing parameters and appropriate adhesion between printed layers. Therefore, this study aims to improve the adhesion between high content nanocellulose printed layers by blending different lignin concentrations and optimizing the twin-screw extruder printing parameters. The lignin concentrations are optimized in nanocellulose paste by assessing the mechanical properties, shape retention, and shrinkage of 3D printed structures. To ease shape retention, the 3D printed structures are dried at controlled humidity (45%) and temperature (25oC). The surface morphology of the 3D printed structures is observed by scanning electron microscope.
KEYWORDS: 3D printing, 3D modeling, Structural engineering, Scanning electron microscopy, Manufacturing, Humidity, Electron microscopes, Computer simulations, Additive manufacturing
3D printing, commonly referred to as additive manufacturing (AM), is a rapid technique of making three-dimensional structures from a computer-based design model. Various materials have been used to manufacture 3D structures for different engineering applications, including synthetic and natural materials. In the case of natural materials for 3D printing, nanocellulose gain much attention as a feedstock material for AM techniques due to its high strength, lightweight, and biocompatibility. However, the mechanical properties exhibited in high concentration nanocellulose printed 3D structures are unsatisfactory, as demonstrated in their building blocks due to drying issues. Therefore, this research aims to optimize the proper drying conditions for 3D printed high concentration nanocellulose structures. The 3D printed structures are dried at different humidity and temperature conditions and evaluated their mechanical properties. The scanning electron microscope is utilized to observe the morphology of 3D printed high concentration nanocellulose structures. The research results will significantly help nanocellulose-based industries to overcome the drying issues in 3D printed high concentration nanocellulose structures.
Cellulose is attractive for in fabricating renewable triboelectric nanogenerators (TENGs) due to its lightweight, flexibility, renewability, and biodegradability. However, the insufficient functional groups and weak polarization on the surface restrict its progress towards high-performance TENGs. Therefore, this research has developed flexible environment-friendly TENGs with significant output performance based on polyvinyl alcohol (PVA)/graphene oxide (GO) and cellulose films. Furthermore, the specific contact surface area of the films is improved by patterning rectangular dots using a photolithography technique. Moreover, the concentration of GO, size of friction layers, and thickness are optimized in terms of triboelectric output performance. The scanning electron microscope is used to observe the surface morphology of the prepared TENGs films. We believe that the fabricated TENGs have the potential to be applied for self-powered biomedical applications.
Twin-screw extruder (TSE) based additive manufacturing technology can effectively print high viscous materials into precise and complex shapes. The dimensional accuracy and quality of the printed parts depend on the correct selection of the extruder machine's processing parameters to the printing materials. Hence, this paper presents an experimental study on optimizing the processing parameters of TSE for high concentration nanocellulose paste. The optimized parameters include twin-screw speed, feeding rate, printing speed to the nozzle diameter, and nanocellulose paste concentration. The feed rate of 1.2 ml/min, screw speed of 150 rpm, and the printing speed of 9.37 mm/s were the optimum process parameters for high accuracy and high-quality 3D printed structures 25wt% nanocellulose paste. Furthermore, pyramid-shaped and star-shaped structures were printed to verify the optimized parameters.
Nanocellulose has a great potential as a renewable material due to its high mechanical strength, high Young’s modulus, low density and eco-friendliness. Once a bulk material is made with it, then the bulk material made with nanocellulose can be a renewable bulk material, which is eco-friendly, lightweight and strong. This paper aims at testing the feasibility bulk material processing by using nanocellulose, specifically cellulose nanocrystal (CNC). The fabrication is carried out through steam with high temperature and high pressure to form hydrogen bonds between CNCs, followed by heat and pressure molding. Crystalline structures of the prepared bulk materials are investigated by using X-ray diffraction and morphology and mechanical properties are investigated by using scanning electron microscope and dynamic mechanical analysis. Also, machining behavior for the nanocellulose bulk material is tested by using end mill to see its manufacturing possibility. In addition, the surface roughness is measured by using optical surface profiler with endmill machining part. Machining heat generation is investigated by thermal imaging camera between endmill tool and machined surface of the sample.
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