Cellulose fibers, structure

Cuculo, J.A., Aminudin, N., and Frey, M.W., Solvent Spun Cellulose Fibers, Structure Formation in Polymeric Fibers, Salem, D.R., Ed., Hanser Publishers, Munich, 2001, pp. 296-328. 

Saito T and Kawase M, Coloring of cellulosic fiber structure containing protein fiber , Jpn. Kokai Tokkyo Koho, 4pp, JP 04257378 A2 920911. 

Scheme of typical cellulose fiber structure before and after alkaline treatment. 

As Figure 25 8 shows the glucose units of cellulose are turned with respect to each other The overall shape of the chain however is close to linear Consequently neigh boring chains can pack together m bundles where networks of hydrogen bonds stabilize the structure and impart strength to cellulose fibers... 

In the case of grinding, the cellulose fibers go over a state of fine fibrillation into a more or less powdery substance. This mechanical severance of cellulose may break main valence bonds and will, therefore, decrease its degree of polymerization. In addition, the crystal structure of cellulose fibers is nearly lost [32]. Grinding of the cellulose fibers also, appreciably increases its surface area. 

These results may be of particular value especially in connection with studies of technical cellulose fibers and cellulose derivatives the above results may be of value for estimation of the state and structure of the material. The work of Fyfe and coworkers 1S,16) indicates that in microscrystalline rayon (cellulose II), hydrolyzed tire cord (cellulose III) and hydrolyzed rayon (cellulose IV) the identification of... 

The following brief account is concerned with factors that affect the acces-sibihty of the OH groups of cellulose, since this is the determining factor for its dissolution, hence subsequent derivatization. Electron microscopy. X-ray scattering and porosimetry of cellulose fibers have clearly shown the presence of non-uniform pores, capillaries, voids and interstices in the fiber surface [25]. Consequently, the total surface area of cellulose fibers exceeds by far the geometrical outer surface. Pore structure determines the internal... 

FIGURE 1.9 The different structural levels of a typical cellulose fiber the fiber wall consists of closely packed cellulose microfibrils oriented mainly in the direction of the fiber. 

FIGURE 20-29 Cellulose structure. The plant cell wall is made up in part of cellulose molecules arranged side by side to form paracrys-talline arrays—cellulose microfibrils. Many microfibrils combine to form a cellulose fiber, seen in the scanning electron microscope as a structure 5 to 12 nm in diameter, laid down on the cell surface in several layers distinguishable by the different orientations of their fibers. 

In Section III, it was mentioned that cell wall is a complex structure formed by different polysaccharides connected to glycoproteins. Hydroxy-L-proline-rich glycoproteins, such as extensin, have been found in almost all plants surveyed, and in some algae.203,281 A network of protein, pectic polymers, and xyloglucan, serving to cross-link the cellulose fibers of the cell wall, has been proposed.282,283 However, covalent links between the different components have not been demonstrated moreover, some of them can be extracted separately,284 and some associations may be artificial.285 Nevertheless, results are consistent with interactions through dipole-dipole (such as hydrogen bonds) or hydrophobic bonds. 

The elastomers exhibited rubber-like behavior. From an examination of electron photomicrographs of cross sections of the elastomers, the fibrillar structure of the cellulose fibers apparently formed a network, and poly (ethyl acrylate) was distributed uniformly among the fibrils. The rigid crystalline regions of the cellulose fibers apparently stabilized the amorphous, grafted poly (ethyl acrylate) to determine the mechanical properties of the elastomers (43, 44). For example, typical elastic recovery properties for these elastomers are shown in Table X. 

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