Cellulose microfibril

About: Cellulose microfibril is a research topic. Over the lifetime, 679 publications have been published within this topic receiving 29188 citations.

TEMPO-oxidized cellulose nanofibers

Abstract: Native wood celluloses can be converted to individual nanofibers 3–4 nm wide that are at least several microns in length, i.e. with aspect ratios >100, by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation and successive mild disintegration in water. Preparation methods and fundamental characteristics of TEMPO-oxidized cellulose nanofibers (TOCN) are reviewed in this paper. Significant amounts of C6 carboxylate groups are selectively formed on each cellulose microfibril surface by TEMPO-mediated oxidation without any changes to the original crystallinity (∼74%) or crystal width of wood celluloses. Electrostatic repulsion and/or osmotic effects working between anionically-charged cellulose microfibrils, the ζ-potentials of which are approximately −75 mV in water, cause the formation of completely individualized TOCN dispersed in water by gentle mechanical disintegration treatment of TEMPO-oxidized wood cellulose fibers. Self-standing TOCN films are transparent and flexible, with high tensile strengths of 200–300 MPa and elastic moduli of 6–7 GPa. Moreover, TOCN-coated poly(lactic acid) films have extremely low oxygen permeability. The new cellulose-based nanofibers formed by size reduction process of native cellulose fibers by TEMPO-mediated oxidation have potential application as environmentally friendly and new bio-based nanomaterials in high-tech fields.

Cellulose microfibrils from potato tuber cells: Processing and characterization of starch–cellulose microfibril composites

Abstract: The ultrastructure and morphology of potato (Solanum tuberosum L.) tuber cells were investigated by optical, scanning, and transmission electron microscopies. After removal of starch granules, pectins and hemicelluloses were solubilized under alkaline conditions. The alkaline insoluble residue consisted mainly of primary cell wall cellulose, which can be disintegrated under shearing to produce a homogenized microfibril suspension, as reported in a previous work.40 Composite materials were processed from this potato cellulose microfibril suspension, gelatinized potato starch as a matrix and glycerol as a plasticizer. After blending and casting, films were obtained by water evaporation. The mechanical properties and water absorption behavior of the resulting films were investigated, and differences were observed depending on the glycerol, cellulose microfibrils, and relative humidity content. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 2080–2092, 2000

Structure and properties of the cellulose microfibril

Abstract: The current structural models of the cellulose microfibril as well as its mechanical and thermal properties are reviewed. The cellulose microfibril can be considered as a single thin and long crystalline entity with highly anisotropic physical properties. The contribution and limit of different methods employed such as electron microscopy, infrared spectroscopy, X-ray scattering and diffraction, solid state nuclear magnetic resonance spectroscopy, and molecular modeling are also discussed.

Cellulose microfibril angle in the cell wall of wood fibres

Abstract: The term microfibril angle (MFA) in wood science refers to the angle between the direction of the helical windings of cellulose microfibrils in the secondary cell wall of fibres and tracheids and the long axis of cell. Technologically, it is usually applied to the orientation of cellulose microfibrils in the S2 layer that makes up the greatest proportion of the wall thickness, since it is this which most affects the physical properties of wood. This review describes the organisation of the cellulose component of the secondary wall of fibres and tracheids and the various methods that have been used for the measurement of MFA. It considers the variation of MFA within the tree and the biological reason for the large differences found between juvenile (or core) wood and mature (or outer) wood. The ability of the tree to vary MFA in response to environmental stress, particularly in reaction wood, is also described. Differences in MFA have a profound effect on the properties of wood, in particular its stiffness. The large MFA in juvenile wood confers low stiffness and gives the sapling the flexibility it needs to survive high winds without breaking. It also means, however, that timber containing a high proportion of juvenile wood is unsuitable for use as high-grade structural timber. This fact has taken on increasing importance in view of the trend in forestry towards short rotation cropping of fast grown species. These trees at harvest may contain 50% or more of timber with low stiffness and therefore, low economic value. Although they are presently grown mainly for pulp, pressure for increased timber production means that ways will be sought to improve the quality of their timber by reducing juvenile wood MFA. The mechanism by which the orientation of microfibril deposition is controlled is still a matter of debate. However, the application of molecular techniques is likely to enable modification of this process. The extent to which these techniques should be used to improve timber quality by reducing MFA in juvenile wood is, however, uncertain, since care must be taken to avoid compromising the safety of the tree.