Textures cellulosics

U.S. Pat. No. 6,207,729 (March 27, 2001). M. Medoff and A. Lagace. Texturized cellulosic and lignocellulosic materials and compositions and composites made therefrom. 

Cellulose has been dissolved in A-methylmorpholine iV-oxide at high temperature and the recrystallization of the polysaccharide upon cooling investigated." The crystallization system is analogous to the solidification of binary mixtures of polymer and diluent, which present unusual thermodynamic and morphological properties. The system provides a new method of texturing cellulose. 

Mulder B.M., Schel J.H.N., and Emons A.M.C. 2004. How the geometrical model for plant cell wall formation enables the production of a random texture. Cellulose 11 395-401. 

Ultrafiltration utilizes membrane filters with small pore sizes ranging from O.OlS t to in order to collect small particles, to separate small particle sizes, or to obtain particle-free solutions for a variety of applications. Membrane filters are characterized by a smallness and uniformity of pore size difficult to achieve with cellulosic filters. They are further characterized by thinness, strength, flexibility, low absorption and adsorption, and a flat surface texture. These properties are useful for a variety of analytical procedures. In the analytical laboratory, ultrafiltration is especially useful for gravimetric analysis, optical microscopy, and X-ray fluorescence studies. 

The texture or crystal size of phosphate coatings can conveniently be recorded by making an impression on clear cellulose tape moistened with acetone. Uniformity of crystal size is of importance for coatings which are to resist wear and assist metal working. Surface roughness may also be studied by means of a Talysurf meter. 

SPAN module. It was mentioned at the beginning that the special polyacrylonitrile fibers of SPAN have a wall thickness of 30 gm, which is considerably thicker than the 8 gm wall thickness of the SMC modules [19]. As a consequence, the presence of stronger capillary effects from the special porous fiber material of the SPAN module would be a reasonable conclusion. Furthermore, the texture of the special polyacrylonitrile fibers is expected to have better surface properties, supporting the permeation of molecules as compared with synthetically modified cellulose. In conclusion, both convection and diffusion effectively contribute to the filtration efficiency in a SPAN module, whereas for the SMC membrane, diffusion is the driving force for molecular exchange, the efficiency of which is also considerable and benefits from the large surface-to-volume ratio. 

Many other properties have to be considered, especially for apparel fibres, e.g., moisture absorption, ability to dye, drape, texture, weaving characteristics, etc. Many of the properties are influenced by the cross-section profile of the fibre. Thus cotton and some rayons (an artificial synthetic fibre derived from cellulose) are a hollow round fibre silk has a triangular shape giving it a fine lustre and drape. 

Oxidized cellulose is very similar to normal cotton but with a defined texture and an acid taste. The material tends to disintegrate on handling. Under the microscope, the fibers are very similar to those of normal absorbent cotton. Oxidized cellulose is used as an absorbable haemostatic in many types of surgery. It is incompatible with penicilline and can not be heat-sterilized. 

Figure 81 is an electron micrograph of section of cellulose fibre, enlarged 39,000 times. The micellar texture of the fibre is clearly visible. 

At the present moment it is difficult to decide which of the two hypotheses concerning the structure of cellulose is correct the idea of an amorpho-crystalline structure, or that postulating solely an amorphous texture. Nikitin assumes that the first hypothesis is the more probable, more especially as it is well in line with the most recent work of Zaydes and Sinitskaya [45] who conclude on the basis of electron diffraction investigations that in the natural cellulose fibre of Chinese nettle, there exist phases having a distinct microcrystalline structure. This suggests that structures shown in Figs. 78, 79 and 80 are the most probable. 

Further evidence in favour of the amorpho-crystalline texture was recently provided by Ranby [46]. In a series of his papers several questions connected with the microstructure of cellulose are made clear. Cellulose to be examined in an electron microscope was initially dispersed by means of ultrasonic waves. In this way Ranby has isolated elementary thread-like micelles of about 70 A dia. Any dimension characterizing the length of the micelle is however missing. 

Stabilizers and Thickeners. Many food products receive their textural properties from a group of compounds known as hydrocolloids. Hydrocolloids fall into Iwo classes polysaccharides and proteins. They include loeust bean gum. guar gum, gum arabic. carrageenan, xanthan gum. cellulose. agar, starch, pectin, alginates, and gelatin. See also Stablizer. 

Carrier properties. Carriers can be shaped and configured as films, fibers, planar surfaces, or spheres. Surface morphology, i.e., surface texture and porosity, can exert a decisive influence as can carrier materials the most important are inorganic materials such as ceramics or glass, synthetic polymers such as nylon or polystyrene, and polysaccharide materials such as cellulose, agarose, or dextran. 

Cellulose acetate forms strong, transparent films and has enjoyed many applications such as photographic film, transparent tape, and blister packaging. It can also be spun into satin fibers. Satin not only means a somewhat shiny fabric woven from cellulose acetate fiber, but also refers to something with a soft texture, which the acetate fiber has. 

Cellulose fibers (e.g., Interfibe RT Cellulose Fiber from Interfibe) are perhaps the best accepted thixotrope of this group. This material provides good thixotropy, reinforcement of the bulk polymer, minimal surface texture, and low cost. Cellulose fibers are claimed to provide greater formulation latitude than the other thixotropes at reduced cost. 

Sodium Glycolate Sample Solution Transfer about 500 mg of sample, accurately weighed, into a 100-mL beaker, moisten thoroughly with 5 mL of glacial acetic acid, followed by 5 mL of water, and stir with a glass rod until solution is complete (usually about 15 min). While stirring, slowly add 50 mL of acetone, then add 1 g of sodium chloride, and stir for several minutes to ensure complete precipitation of the Cellulose Gum. Filter through a soft, open-textured paper, previously wetted with a small amount of acetone, and collect the filtrate in a 100-mL volumetric flask. Use an additional 30 mL of acetone to facilitate transfer of the solids and to wash the filter cake, then dilute to volume with acetone, and mix. 

The plant cell wall is a composite of cellulose (the main fibre) plus shorter lengths (hemicellulose) that help bind the fibre, plus pectin (the main matrix adhesive) and some proteins. There are fruits that have a soft melting texture when ripe (e.g., avocado and blackberry) in which the cell wall swells noticeably. This swelling is related to the degree of solubilisation of the pectin (Redgwell et al. 1997) which can be removed in vitro using enzymes or other chemicals. 

Marinading can also transform texture. In animal tissues, dilute acid (e.g., acetic or citric) or salt solution destroys collagen-collagen interactions and so softens the fibres. Presumably in plant material, for which this treatment is also effective, it is the pectins that are altered, since the cellulose crystallites are too tightly bonded to be affected. 

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