In this study, the effect of anionic surfactant, sodium dodecyl sulfate (SDS), on the structure and thermal insulation properties of the citric acid crosslinked CNF foam is investigated. The addition of the SDS improves the foam structure, and the prepared CNF foam indicates a porosity of around 99% and a density of around 20 mg/cm3 with very low shrinkage. SEM and FTIR are used to examine the morphology and chemical interactions. Further, the effect of the SDS on the thermal conductivity of the foam is investigated, and the foam shows thermal conductivity comparable with polyurethane foam.
Disposable plastic straws negatively impact the environment and human health while their alternatives such as paper straws are not satisfactory owing to limited mechanical performance and poor user experience. In this report, all-natural and biocompatible straws are fabricated from starch and polyvinyl alcohol slurries respectively. The functionality of the slurries is enhanced by integrating economical resources such as kraft lignin and citric acid. By doctor blading of the slurries followed by subsequent heat treatment, self-bonding straws are fabricated without the use of binders or adhesives. Through heat treatment, our straws achieve excellent strength than paper-based straws. Owing to the strong ester bond network, the straws display superior performance that surpasses commercial plastic counterparts thus meeting the requirements for practical applications. Specifically, the straws are hydro-stable for over 24 hrs. and display a desirable closed-loop degradability aspect making our straws eco-friendly substitutes for synthetic plastic straws.
The petroleum-based derived materials are used in industrial applications due to their specific properties. However, they are increasing environmental concerns because they produce toxic gases when disposed of and burned [1, 2]. Thus, biomass-derived epoxy resins have gained significant attention due to their low-cost, easy synthetic route, and environmentally friendly. CNF can be a promising approach for the future generation to design all-green materials with bio-mass-derived resins for various applications [3, 4]. This research aims to explore the strategies for hydrophilic CNF film to make it useable for high-performance applications. In this regard, the bio-based vanillin-derived epoxy resin was proposed to improve hydrophobicity of CNF film, making them ideal for TENG applications.
Depleting fossil fuels and environmental concerns have emphasized the necessity for more sustainable resources for high-performance structural applications. High strength, lightweight, and abundant bioresources make cellulose long filaments (CLFs) an excellent reinforcement for high-performance structural applications. At the same time, high strength and thermally stable vanillin epoxy can efficiently replace petroleum-based epoxies. This study introduces the combination of unidirectional CLFs and vanillin epoxy by using vacuum-assisted resin transfer molding for novel biobased composites. Owing to the low density of CLFs, the proposed composite material possessed very low density, high specific flexural strength, and excellent thermal and hydrophobic properties. The FTIR analysis demonstrated good interfacial adhesion between CLFs and vanillin epoxy. The sustainable resources, hydrophobicity, and good mechanical performance make unidirectional CLFs reinforced Vanillin epoxy composite an excellent candidate for high-performance structural applications.
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.
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.
Due to environmental concerns, replacing conventional synthetic materials with eco-friendly bio-based materials is receiving much attention from academic and industrial research. As the most abundant polymer among several bio-based materials, cellulose is widely used to produce bio-based porous materials that have been used in various applications, including packaging, thermal insulation and sound absorption. Different processing methods have been used to prepare nanocellulosic porous materials but the specific requirement and time consuming process limit the use of these methods for large-scale production. Further, the use of toxic and expensive inorganic or synthetic blowing agents or crosslinking agents limits the applications of these porous materials. Therefore, to overcome these drawbacks, we used an environmentally friendly, time-saving, economical process to produce bio-based cellulose nanofiber (CNF) foam using bio-based nontoxic and inexpensive citric acid as a green crosslinking agent. The foam is prepared by homogenizer followed by freezing, solvent exchange and oven drying. The prepared foam indicates low shrinkage and has a very low density. The foam shows a highly porous structure (more than 98% porosity) and the morphology of the foam is examined by SEM. The FTIR study confirms the covalent crosslinking, and the foam shows high compressive modulus and strength.
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.
In this study, we developed a new type of cross-linked polyvinyl alcohol (PVA)-lignin i.e., esterified PVA-CA-lignin resin by using citric acid (CA) cross-linker. Firstly, hydrogen bonded PVA-CA-lignin resin was prepared by the mixing of PVA, lignin and CA and then esterification of hydrogen bonded PVA-CA-lignin resin was carried out at 180oC. Subsequently, the esterification of PVA-CA-lignin resin was confirmed by FTIR and the morphology of the esterified PVA-CA-lignin resin was examined with the help of scanning electron microscopy.Finally, the effects of CA cross-linker on the properties of esterified PVA-CA-lignin resin, especially the tensile strength and thermal stability were evaluated and analyzed. The results demonstrated that CA was cross-linked in PVA-lignin resin matrix and the content of CAenhances the performance of esterified PVA-CA-lignin resin significantly. The esterified PVA-CA-lignin resin is applicable for the natural fibre reinforced composites.
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