Cellulosic fibers, density

Cellulosic fibers, density of, V, 121 Celtrobionic acid, I, 44 Celtrobiose, I, 44... 

The bulk properties of regenerated cellulose are the properties of Cellulose II which is created from Cellulose I by alkaline expansion of the crystal stmcture (97,101) (see Cellulose). The key textile fiber properties for the most important current varieties of regenerated cellulose are shown in Table 2. Fiber densities vary between 1.53 and 1.50. 

Filter aids should have low bulk density to minimize settling and aid good distribution on a filter-medium surface that may not be horizontal. They should also be porous and capable of forming a porous cake to minimize flow resistance, and they must be chemically inert to the filtrate. These characteristics are all found in the two most popular commercial filter aids diatomaceous silica (also called diatomite, or diatomaceous earth), which is an almost pure silica prepared from deposits of diatom skeletons and expanded perhte, particles of puffed lava that are principally aluminum alkali siheate. Cellulosic fibers (ground wood pulp) are sometimes used when siliceous materials cannot be used but are much more compressible. The use of other less effective aids (e.g., carbon and gypsum) may be justified in special cases. Sometimes a combination or carbon and diatomaceous silica permits adsorption in addition to filter-aid performance. Various other materials, such as salt, fine sand, starch, and precipitated calcium carbonate, are employed in specific industries where they represent either waste material or inexpensive alternatives to conventional filter aids. 

Anthraquinoid compounds have also been employed as mediators for reduction of dispersed organic compounds, particularly for dyestuffs used in dyeing of cellulose fibers in 0.1 M NaOH [67], The reduction efficiency is characterized by comparing the maximum cathodic current of the anthraquinoid solution containing the dyestuff with the cathodic peak current without reducible vat dye. The limiting current density depends on the diffusion transport of the anthraquinoid compound, whereas the addition of dispersed dyestuff has a minor influence. 

Zempl i, of aldononitriles, IV, 138 AVDehydroandrosterone, IV, 93 Dehydrocholic acid, IV, 106 Dehydrodesoxycholic acid, IV, 92 Dehydrohalogenation, of halo carbohydrates, III, 102 Density of cellulosic fibers, V, 121 Depolymerase, action on pectic acids, V, 82, 92... 

INTEX SOFTENER 215 produces the slick hand generally associated with the high density grade polyethylenes. It has been found to produce on excellent hand on many fabric blends, particularly those containing substantial percentage of cellulosic fibers. 

Antioxidants slow down the plastic degradation under high tanperature, attrition, and so on, hence, minimize the VOC formation and the respective decrease of density. Moisture in the ingredients also leads to a decrease of the final density of the material, hence, cellulose fiber should be dried, if necessary. Last, but not the least, vented extruders remove VOCs and steam from hot melt and greatly increase density of the final product. 

Pure cellulose fiber has a relatively low density, such as 1.0-1.1 g/cm However, being penetrated with lignin and hemicellulosics, its density, such as in wood flour or rice hulls, reaches 1.3-1.5 g/cm When ashed at 525°C (977° F), wood flour leaves 0.13-0.40% of ash and rice hulls—as much as 18.8% of ash. This... 

In the 1980s, more attention has been increasingly paid to improving the physical properties, such as mechanical strength, stiffness, resistance to thermal deformation, and so forth, of the fiber-plastic composite products. It was recognized that moisture in cellulosic fiber leads to steam formation in the compounder and the extruder, increases porosity of the final product and decreases its density, accelerates the oxidation of the hot melt during processing, and makes the final product weaker and less durable. 

Specific gravity of lignified cellulose fiber (wood flour, saw dust, and rice hulls) in WPCs typically is between 1.3 and 1.5 g/cm. Rice hulls lignocellulosic matrix in WPC materials is of about the same density as that of wood flour, and they are equal to about 1.35 g/cm and 1.30-1.35 g/cm, respectively. However, because rice hulls contain 19% of silicates (specific gravity approximately 2.8 g/cm ), the resulting specific gravity of rice hulls as a tiller is around 1.50 g/cm. ... 

Density (specific gravity) of WPCs does not depend on the particle size of the wood flour. It appears that during compounding and extrusion, cellulose fiber is compressed to the maximum density of 1.3-1.5 g/cm. ... 

TABLE 4.2 Effect of specific gravity of fillers on density of the filled plastic. Cellulose fibers (wood Hour, rice hulls) typically have specific gravity of 1.3 g/cm calcium carbonate and talc typically have specific density of 2.8 g/cm. ... 

One can see that the presence of 20-40% of mineral fillers significantly increases density of filled HDPE and polypropylene compared with the plastics filled with cellulose fiber. 

Data in Table 4.6 show that both calcium carbonate and talc increase flexural modulus by about 40-60%, decrease impact resistance and energy to break by about 30-40%, and slightly increase moisture absorption. All these effects are generally known in the composite research and development, and slightly vary quantitatively by changing the particle size of minerals, a type of plastic, a type of cellulose (wood) fiber, density (specific gravity) of the matrix, and so on. 

It is practically impossible to make industrial WPC boards without any porosity, hence, without any decrease in density compared to its theoretical value. Even traces of moisture in wood/cellulose fiber create steam at hot melt tempera-tnres, hence, porosity. Plastic decomposition during processing prodnces volatile organic compound (VOC), hence, porosity. Wood extractives decomposition prodnces VOC, hence, porosity. Wood fibers lignin decomposition at plastic hot... 

GeoDeck composite deck boards often utilize HDPE with the density of 0.955 g/cm Its coefficient of friction is about 0.15. However, when rice hulls and a granular blend of calcium carbonate/kaolin and delignifled cellulose fiber are incorporated into the plastic matrix, the static coefficient of friction increased to 0.53, that is, to 350% compared to the initial HDPE. 

The circular shape of the cross section of the fibril accprding to Manley, and the cylindrical hole in the middle of the fibril are difficult to reconcile with the measured density of the fiber wall, known to be as high as about 1.5. For pure crystalline cellulose a density of 1.59 is calcu-... 

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