Cellulose nanofibers isolated by TEMPO-oxidation and aqueous counter collision methods

2020

Sci Rep

Self Cite

Since cellulose nanofiber (CNF) has unique characteristics in terms of renewability, high specific elastic modulus and strength and transparency, it is attractive for a building block of future materials. cnf can be extracted from various natural resource by several means. However, the size of the extracted cnf is very broad and uniformity of the extracted cnf is very important for many applications. thus, a fractionation process is necessary to obtain a uniformly sized cnf. in this paper, a simple centrifugal fractionation was carried out to reduce the size distribution of the extracted cnf suspension from hardwood pulp by the combination of TEMPO oxidation and aqueous counter collision methods. The original CNF suspension was diluted and centrifuged under low speed to remove cellulose microfibers then centrifuged under high speed to separate very small CNF. The centrifugation condition is 10 k rpm for 1 h followed by 45 k rpm for 4 h. The fractionated CNF was analyzed by an atomic force microscopy, and the length and width distribution histogram analysis was utilized. UV-visible analysis, ft-iR and XRD crystallinity analysis were carried out to analyze all fractionated cnfs and the original cnf. After centrifugal fractionation, the width and length distribution range were reduced by 62% and 70%, respectively. It is shown that the centrifugal fractionation is an easy and efficient method to fractionate a uniform cnf suspension. The tallest tree in the world which is 115 m high sustains itself for more than 600 years under its own weight and harsh environment of winds, snows, and rains 1. Wood is a fiber reinforced polymer composite produced in nature, which exhibits marvelous structural behaviors. It is a natural composite of cellulose fibers embedded in a matrix of lignin and hemicellulose. Typically, cellulose fibers in the wood are hierarchically composed of macrofibrils and microfibrils surrounded by hemicellulose and lignin. The microfibril is formed with crystalline domain and short amorphous domain 2. The microfibril, so called cellulose nanofiber (CNF), has unique characteristics in terms of renewability, high specific elastic modulus and tensile strength, low thermal expansion coefficient 3. During the biosynthesis process, cellulose molecules can form into microfibrils through the formation of inter-and intra-molecular hydrogen bonds 4. CNF is a material composed of nanosized cellulose fibrils with a high aspect ratio (length to width ratio). The width of CNF is typically in the range of 5-20 nm and length is typically up to microns 5,6. CNF is attractive for many applications, for instance, coatings, fillers, additives, structural composites, cosmetics, flexible electronics and flexible displays 7-12. CNF extracted from plants by top-down approach can be a building block of future materials. CNF can be extracted by mechanical, chemical and biological methods 13-16. However, the length of the extracted CNF is very broad depending on the extraction method and pretreatment of cellulose resources. Uniform...

Section: Width and Length Distribution Analysis The Length And Widthsupporting

confidence: 94%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simple centrifugal fractionation to reduce the size distribution of cellulose nanofibers

Zhai

2020

Sci Rep

Self Cite

“…The ACC method uses encountered water jets with a collision pressure of 200 MPa to selectively break up only weak hydrogen bonds without destroying solid bonds in the intermolecular structure of the cellulose chain. Thus, ACC is a strategic and efficient physical method that can isolate long CNF from pretreated cellulose resources 20 . Based on the optimized results of the previous study, the preparation of CNF includes 60 min of TEMPO treatment time, 30 passes of ACC process, and centrifugal fractionation at 45 k rpm for 4 h. The hardwood pulp (bleached acacia kraft pulp) was purchased from Hansol paper, South Korea, and the CNFs used in the study have average width and length of 2.0 ± 0.6 nm and 639 ± 387.3 nm, respectively 19 .…”

Section: Methodsmentioning

confidence: 99%

High-strength cellulose nanofiber/graphene oxide hybrid filament made by continuous processing and its humidity monitoring

Panicker

et al. 2021

Sci Rep

Self Cite

Human-made natural-fiber-based filaments are attractive for natural fiber-reinforced polymer (NFRP) composites. However, the composites' moisture distribution is critical, and humidity monitoring in the NFRP composites is essential to secure stability and keep their life span. In this research, high strength and humidity sensing filament was developed by blending cellulose nanofiber (CNF) and graphene oxide (GO), wet-spinning, coagulating, and drying, which can overcome the heterogeneous mechanical properties between embedded-type humidity sensors and NFRP composites. The stabilized synthesis process of the CNF-GO hybrid filament demonstrated the maximum Young's modulus of 23.9 GPa and the maximum tensile strength of 439.4 MPa. Furthermore, the achieved properties were successfully transferred to a continuous fabrication process with an additional stretching process. Furthermore, its humidity sensing behavior is shown by resistivity changes in various temperature and humidity levels. Therefore, this hybrid filament has excellent potential for in-situ humidity monitoring by embedding in smart wearable devices, natural fiber-reinforced polymer composites, and environmental sensing devices.

Journal of Industrial Textiles

“…As TEMPO oxidation at controlled conditions expected to reduce the amorphous region of cellulose fibers and transversely increase the crystalline domains of the treated sample [53], finally a reduction is noticed in the size of cellulose fibers from the micron to nano meter scale. Figure 5(a) provides the TEM images of CNF fibrils which show that the samples fined down to the smallest elements next to the cellulose molecules after the TEMPO oxidation.…”

Section: Transmission Electron Microscopy Analysismentioning

confidence: 99%

Structure and properties of high quality natural cellulose nano fibrils from a novel material Ficus natalensis barkcloth

Farooq

Jiang

Farooq

et al. 2019

We report for the first time the extraction of cellulose nano fibrils from Ficus natalensis barkcloth fibers by means of chemical treatments and catalytic oxidation of cellulose fibers by using 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO). After every stage of treatments, the structural properties of barkcloth fibers powder (BC-PW), cellulose fibers (BC-NB) and cellulose nano fibrils (BC-CNF) were carefully characterized by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for morphological analysis, Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction techniques for chemical analysis, and thermal properties were done by thermo-gravimetric analysis. FTIR results revealed the progressive removal of non-cellulosic contents and X-ray diffraction (XRD) analysis showed that the crystallinity increased with the successive alkali and bleaching treatments. Finally, by evaluating the TEM images, the average diameter of the nano-cellulose fibrils from Ficus natalensis barkcloth was also confirmed as 28 ± 0.6 nm and the length in hundred nano meters was recorded. The resultant cellulose nano fibrils maintaining the cellulose I structure had dimensional properties in nano-scale, higher crystallinity (68.5), and better thermal stability (305.62°C). The barkcloth cellulose nano fibrils can be used in nano technology like food packing material, nano composites and medical textiles.