Tunicin

ONOZUKA P 500 PYROCELLULOSE RAYOPH-ANE RAYWEB Q REXCEL SIGMACELL Q SOLKA-FIL SOLKA-FLOC SOLKA-FLOC BW SOLKA-FLOC BW 20 SOLKA-FLOC BW 100 SOLKA-FLOC BW 200 SOLKA-FLOC BW 2030 SPARTOSE OM-22 SULFITE CELLULOSE TOMOFAN TUNICIN WHATMAN CC-31... 

Surprisingly, the association between TPS and cellulose fibres (polysaccharide-based composites) has been little analysed. In the literature, cellulose fillers used in association with a plasticized starch matrix are commercial paper fibres,10 potato pulp microfibrils,11 12 tunicin whiskers and paper bleached pulp.13-14 The literature reports that these cellulose fillers improve the tensile strength. Besides, the composite water sorption seems to be decreased. This behaviour is related to the well known lower water uptake of cellulose compared to starch.10-14... 

The crystal structure and hydrogen-bonding system in cellulose ip was elucidated by the combined use of synchrotron X-ray and neutron fiber diffraction." Oriented fibrous samples were prepared by aligning cellulose microcrystals from tunicin, reconstituted into oriented films. These samples diffracted both synchrotron X-rays and neutrons to a resolution better than 1 A, yielding more than 300 unique reflections and an unambiguous assignment of the monoclinic unit-cell dimensions (a = 7.784 A,... 

Fig. 19. Molecular model of a microfibril of cellulose, projected along the fibril axes compared with the typical morphologies observed for Valonia cellulose and tunicin, along with the CPK (Corey-PauUng-Koltun) representation of the main crystalline faces for cellulose 1. (See Color Plate 12.)...

Fig. 20. Range of microfibril sizes for different sources of cellulose R is the ratio of the number of surface chains over the total number of cellulose chains. The estimated number of cellulose chains in one crystalline microfibril according to the origin of cellulose Valonia, 1200 Micrasterias, 900 tunicin, 800 cotton, 80 wood, 35 and parenchyma, 20.

Fig. 22. Transmission electron micrographs of tunicin. (A) Microciystals negatively stained with uranyl acetate. (B) Ultiathin section of microfibrils in bright field. (C) Transmission election miciographs of cellulose miciociystals n atively stained with uranyl acetate. (D) Ultiathin section of a cotton fiber in bright field. (E) Transmission electron micrographs of parenchyma cellulose miciofibrils n atively stained with uranyl acetate. (F) Ultiathin section of microfibrils in bright field. (G) X-ray diftiaction diagrams of cellulose microoystal (a) tunicin cellulose (b) cotton and (c) parenchyma. ...

It may be estimated that the surface chains in tunicin microfibrils constitute no more than 5% of the total number of tunicin chains, whereas surface chains may constitute 70% of the total number in parenchyma microfibrils. The result of increasing number of surface chains and decrease in whisker diameter can also be evidenced by infiared spectroscopy, with a broadening of tire absorption bands and loss of resolution. A peak at 1635 cm may be attributed to vibrations arising from water molecules absorbed in the noncrystalline regions of cellulose. 

P. S. Belton, S. F. Tanner, N. Cartier, and H. Chanzy, High-resolution sohd-state C nuclear magnetic resonance spectroscopy of tunicin, an animal cellulose. Macromolecules, 22 (1989) 1615-1617. 

ANG 01 ] Angles M.N., Dufresne A., Tlasticized starch/tunicin whiskers nanocomposite materials. 2. Mechanical behavior , Macrawo/ecufes, vol. 34, no. 9, pp. 2921-2931,2001. 

MAT 02] Mathew A.P., Dufresne A., Morphological investigation of nanocomposites from sorbitol plasticized starch and tunicin whiskers . Biomacromolecules, vol. 3, no. 3, pp. 609-617,2002. 

Figure 2.2 shows a TEM micrograph of cellulose whiskers prepared from cotton. Geometrical characteristics of cellulose whiskers depend on the origin of cellulose microfibrils and on the conditions of the acid hydrolysis process such as time, temperature, and purity of materials. Samir et al. [75] have reported the dimensions of cotton and tunicin whiskers. The length (L) and lateral dimension (D) of cotton whiskers were around 200 and 5 nm, respectively (ratio L/D = 40). The length and lateral dimension of tunicin whiskers were reported to be around 1,000 and 15 nm, respectively (ratio L/D = 67). De Souza [76] studied cotton and tunicate whiskers in aqueous suspensions as well. The average size whisker dimensions reported were L = 255 nm and D = 15 nm for cotton whiskers (ratio L/D — 17) while the values were L — 1,160 nm and D = 6 nm (ratio L/D = 72.5) for tunicate whiskers. 

Angles, M.N., Dufresne, A. Plasticized starch/tunicin whiskers nanocompositcs 2. mechanical behavior. Macromolecules 34, 2921-2931 (2001)... 

Cellulose was defined as a chemical substance related to polysaccharides in 1838 thanks to the works of French chemist Anselme Payen, who isolated it from plant matter and determined its chemical formula (Payen, 1838). Cellulose is the most abundant organic matter on Earth. Total resources of cellulose in nature reach one trillion tons (Klemm et al., 2005). Moreover, being renewable in nature, a mass of this biopolymer increases by approximately 100 billion tons annually as a result of photobiosynthesis (Field et al., 1998). Cellulose is present in all plants and algae cellulose of the tunicin type forms the shells of certain marine creatures, and it is also synthesized by some microorganisms, for example, Gluconacetobacter xylinus. 

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