Cellulose nanofibres

Bhatnagar, A., Sain, M., 2005. Processing of cellulose nanofibre-reinforced composites. Journal of Reinforced Plastics and Composites 24 (12), 1259—1268. 

Eichhorn, S. J., Dufresne, A., and Aranguren, M. (2010). Review Current international research into cellulose nanofibres and nanocomnosites. I. Mater. Set. 45(1), 1-33. 

Details of vegetable oil-based polymers conventional composites have been discussed in an earlier chapter. In this chapter, nanocomposites of vegetable oil-based polymers are discussed. Certain questions arise as to how much difference there is between these composites. The questions are significant when the same reinforcing agent is used in both cases. As an example, a vegetable oil-based polyurethane with alkali-treated chopped jute fibres in a conventional composite and cellulose nanofibres (obtained from jute fibres) in a vegetable oil-based polymer nanocomposite are discussed. The... 

Three different types of nanomaterials, based on their dimensional characteristics, are generally used to prepare polymer nanocomposites. These include nanomaterials with only one dimension in the nanometre range (e.g. nano-clay), those with two dimensions in the nanometre scale (e.g. carbon nanotubes) and those that have all three dimensions in the nanometre scale (e.g. spherical silver nanoparticles), as stated earlier. Thus nanosize thin layered aluminosilicates or nanoclays, layer double hydroxide (LDH), a large number of nanoparticles of metals and their oxides, carbon nanotubes and cellulose nanofibres are used as nanomaterials in the preparation of vegetable oil-based polymer nanocomposites. 

Nogi et al. [40], in 2005, used bacterial cellulose nanofibres to reinforce transparent polymers. The composites exhibited a highly luminous transmittance at a fibre content as high as 60 wt%, and a low sensitivity to matrices with a variety of refractive indices. The optical transparency was also insensitive to temperature increases up to 80°C. 

P. M. Visakh, S. Thomas, K. Oksman and A. P. Mathew, Cellulose Nanofibres and Cellulose Nanowhiskers Based Natural Rubber Composites Diffusion, Sorption, and Permeation of Aromatic Organic Solvents, Journal of Applied Polymer Science, 2012, 124, 1614. 

Abstract This chapter deals with the structure, properties and applications of natural fibres. Extraction methods of Natural Fibres from different sources have been discussed in detail. Natural fibres have the special advantage of high specific strength and sustainability, which make them ideal candidates for reinforcement in various polymeric matrices. Natural fibres find application in various fields like construction, automobile industry and also in soil conservation. It is the main source of cellulose, an eminent representative of nanomaterial. Extractions of cellulose from plant-based fibres are discussed in detail. Various mediods used for characterization of cellulose nanofibres and advantages of these nanofibres have also been dealt with. 

Keywords Animal fibre Cellulose Nanofibre Plant fibre... 

Several sources of cellulose have been used to obtain cellulose nanofibres including banana residues [87, 90], soybean souree [99], cotton [100], wheat straw [86], bacterial cellulose [101-104], sisal [88, 105], hemp [89, 106], sugar beet pulp [107, 108], potato pulp [109], bagasse [110], stems of cacti [111] and algae [112],... 

Detailed stractural examinaticm is essential to investigate the potential of cellulose nanofibre as reinforcement in polymer composites. Several characterization techniques were used to study the ultrasfructure of cellulose obtained from various sources. Various techniques such as TEM, field emission scanning electron microscopy (FESEM), SEM, AFM and wide-angle X-ray scattering (WAXS) have been used to characterise the morphology of cellulose nanofibres. TEM and AFM aid... 

Table 1.2 Examples of cellulose nanofibre preparation procedures... 

Alemdar and Sain [86] extracted Cellulose nanofibres of wheat straw and soy hulls, by a chemi-mechanical technique. They analysed the morphology and physical properties of the nanofibres by scanning and transmission electron microscopy. The wheat straw nanofibres have diameters in the range of 10-80 nm and lengths of a few thousand nanometres, and the soy hull nanofibres have diameters in the range of 20-120 nm and shorter lengths than the wheat straw nanofibres. Fig. 1.21a and b shows the TEM pictures of the wheat straw and soy hull nanofibres. The image shows the separation of the nanofibres from the micro-sized fibres. The thermal properties of the nanofibres were studied by the TGA technique and found that the... 

Cherian et al. [87] extracted cellulose nanofibres from the pseudo stem of the banana plant by using acid treatment coupled with high pressure defibrillation. Characterization of the fibres by (Scanning Force Microscopy) SFM and TEM showed that there is reduction in the size of banana fibres to the nanometre range (below 40 nm). The average length and diameter of the developed nanofibrils were found to be between 200-250 nm and 4-5 nm, respectively. Figures 1.22a, b and 1.23 show the SFM and TEM pictures of banana nanofibres, respectively. 

Fig. 1.24 (a) Atomic force micrographs of cellulose nanofibres of PALF (b) TEM of cellulose... 

Cherian et al. [119] also extracted cellulose nanofibres from pineapple leaf fibres using acid-coupled steam treatment. The strucmral and physicochemical properties of the pineapple leaf fibres were studied by environmental scanning electron microscopy (ESEM), AFM and TEM and X-ray diffi action (XRD) techniques. The acid-coupled steam explosion process resulted in the isolation of PALF nanofibres having a diameter range of 5-60 nm. Figure 1.24a and b shows the AFM and TEM images of nano fibres obtained from pineapple leaf fibres. AFM and TEM support the evidence for the isolation of individual nanofibres from PALF. 

Wang et al. [89] extracted the cellulose nanofibres of hemp fibre by a chemi-mechanical process, and the structural details were studied with SEM, TEM and... 

AFM. The widths of unbleached nanofibres of hemp were estimated between 50 and 100 nm, and most of them had a diameter range of 70-100 nm. Bleached nanofibres of hemp produced smaller widths (30-100 nm) compared with that of unbleached nanofibres, and most of the bleached nanofibres had a diameter range of 30-50 nm. Aspect ratios of the extracted cellulose nanofibres were estimated from transmission electron micrographs. The aspect ratio of the bleached and unbleached nanofibres were found to be 82 and 88, respectively. TEM and AFM images of hemp nanofibres are shown in the Figs. 1.25 and 1.26, respectively. TEM and AFM images showed that the high-pressure defibrillation leads to individualization of the cellulose nanofibres from the cell wall. 

Wang and Sain [99] extracted cellulose nanofibres from a soybean source by combining chemical and mechanical treatments. Isolated nanofibres were shown to have diameter between 50 and 100 nm and the length in micrometre scale, which... 

Wang B, Sain M (2007) Isolation of nanofibres from soybean source and their reinforcing capability on synthetic polymers. Compos Sci Technol 67 2521-2527 Teixeira EM, Correa AC, Manzoli A, Leite FL, Oliveira CR, Mafioso LHC et al (2010) Cellulose nanofibres from white and naturally colored cotton fibres. Cellulose. doi 10.1007/ si 0570-010-9403-0... 

De Rodriguez NLG, Thielemans W, Dufresne A et al (2006) Sisal cellulose whiskers reinforced polyvinyl acetate nanocomposites. Cellulose 13 261-270 Bhatnagar A, Sain M (2005) Processing of cellulose nanofibres-reinforced composites. J Reinf Plas Compos 24 1259-1268... 

Ifuku S, Nogi M, Abe K et al (2007) Surface modification of bacterial cellulose nanofibres for property enhancement of optically transparent composites dependence on acetyl-group DS. Biomacromolecules 8 1973-1978... 

Nakagaito AN, Yano H (2008) Toughness enhancement of cellulose nanocomposites by alkali treatment of the rein- forcing cellulose nanofibres. Cellulose 15 323-331 Nakagaito AN, Iwamoto S, Yano H (2005) Bacterial cellulose the ultimate nano-scalar cellulose morphology for the production of high-strength composites. Appl Phys A Mat Mater Sci Process 80 93-97... 

Saito T, Kimura S, Nishiyama Y et al (2007) Cellulose nanofibres prepared by TEMPO-mediated oxidation of native cellulose. Biomacromolecules 8 2485-2491 Saito T, Hirota M, Tamura N et al (2009) Individualization of nano-sized plant cellulose fibrils by direct surface carboxylation using TEMPO catalyst under neutral conditions. Biomacromolecules 10 1992-1996... 

Teixeira EM, Correa AC, Manzoli A et al (2010) Cellulose nanofibres from white and naturally colored cotton fibres. Cellulose 17 595-606... 

The reinforcement by cellulose nanofibres instead of micro-sized fibres is recognized as being more effective due to interactions between the nano-sized elements that make up a percolated network connected by hydrogen bonds or entanglements. 

Potential of nanocellulose has been established as the next generation renewable reinforcement for the production of renewable high performance biocomposites by the researchers. The tensile modulus and strength of most cellulose nanocomposites has been reported hnearly with the tensile modulus and strength of the cellulose nanopaper structures. Uniform dispersion of individual cellulose nanofibres in the polymer matrix may improve the composite properties [54]. In last few decades... 

Kose and Kondo studied tbe size effects of cellulose nanofibres on the crystallization behaviour of PLA. They discovered that the smaller size of cellulose nanofibres on tbe nanoscale does not necessarily make a better nucleating agent for PLA. Table 9.1 summarizes the Avrami kinetic parameters for the isothermal crystallization of the PLA and PLA biocomposites with different types of nanocelluloses as compared to PLA composites with talc and nanoclay. With the addition of unmodified and silylated CNCs as nucleating agents, the t 2 value increases with increasing T similar to that of nanoclay and com starch, but opposite to that of talc. Comparing the... 

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