Cellulose, fine

Figure 6.2 The effect of pH on the zeta potential of cellulosic fines and fibres as measured by streaming potential and microelectrophoresis (figures in brackets are negative).

Millett, M. A. Goedken, V. L. Modification of Cellulose Fine Structures—... 

Starch is added to the papermaking furnish for a variety of applications paper formation control furnish drainage improvement filler and cellulose fines retention size retention internal paper strength improvement surface strength enhancement and reduction of waste water pollution. 

Uptake of iron II by NDF suspended in solutions of the composition described below and buffered at pH 6.4 is rectilinear up to iron concentrations of about 1.5 ug/ml (13). Above the latter concentration, the iron becomes unstable and the results erratic. The quantity of iron bound by NDF of wheat exceeded that bound by the NDF of maize by about 25 %. Binding by ADF and by cellulose (finely divided filter paper or absorbent cotton) were equal and about half of the amount of iron bound by wheat NDF. For measurement of binding,... 

That such features of cellulose as the crystal lattice form are significant determinants of cellulase action has only recently been established (19), although a great deal remains to be learned about the enzymatic importance of cellulose fine structure. It is clearly established, however, that each of the three water-stable crystal forms of cellulose is distinct in the rate at which it is hydrolyzed and in its properties as an inducer of cellulase. For example the Trichoderma viride cellulase from culture extracts exhibits a lower activation energy in attacking the crystal lattice form used in culture growth, than in attacking the other lattice forms (Table I). 

Dry Grass, Sphagnum, Ferns Cellulose, Fine Papers, Cotton, Sugar Wheat Straw (dry)... 

Two different strength properties of the handsheets are compared in Fig. 5.18. According to the figure, an increased amount of fines significantly enhances the tensile strength of the new composite paper. Nanofibrillar cellulosic fines contribute... 

Carbon disulphide is an excellent solvent for fats, oils, rubber, sulphur, bromine and iodine, and is used industrially as a solvent for extraction. It is also used in the production of viscose silk, when added to wood cellulose impregnated with sodium hydroxide solution, a viscous solution of cellulose xanthate is formed, and this can be extruded through a fine nozzle into acid, which decomposes the xanthate to give a glossy thread of cellulose. 

Fibrillated Fibers. Instead of extmding cellulose acetate into a continuous fiber, discrete, pulp-like agglomerates of fine, individual fibrils, called fibrets or fibrids, can be produced by rapid precipitation with an attenuating coagulation fluid. The individual fibers have diameters of 0.5 to 5.0 ]lni and lengths of 20 to 200 )Jm (Fig. 10). The surface area of the fibrillated fibers are about 20 m /g, about 60—80 times that of standard textile fibers. These materials are very hydrophilic an 85% moisture content has the appearance of a dry soHd (72). One appHcation is in a paper stmcture where their fine fiber size and branched stmcture allows mechanical entrapment of small particles. The fibers can also be loaded with particles to enhance some desired performance such as enhanced opacity for papers. When filled with metal particles it was suggested they be used as a radar screen in aerial warfare (73). 

Steeping. Sheet, roU, or suitably milled flock pulp is metered into a pulper along with vigorously stirred 18% sodium hydroxide solution at 50°C. The resulting slurry, containing about 5% finely dispersed pulp, passes to a buffer tank from which it is metered to a slurry press that sieves out the swollen fiber and returns the pressings soda for concentration correction and reuse. The cellulose reacts with the soda as a complex alcohol to form the sodium salt or alk-ceU. 

The dark blue solution containing 5—10% of cellulose with a DP of 1000—2000 is filtered through a series of plate-and-frame filter presses using fine mesh metal screens to remove any particles that might block the spinneret holes. It is then deaerated under vacuum and stored ready for spinning. Unlike viscose dope, the cuprammonium cellulose [9050-09-3] solution is relatively stable. 

Other fibrous and porous materials used for sound-absorbing treatments include wood, cellulose, and metal fibers foamed gypsum or Pordand cement combined with other materials and sintered metals. Wood fibers can be combined with binders and dame-retardent chemicals. Metal fibers and sintered metals can be manufactured with finely controlled physical properties. They usually are made for appHcations involving severe chemical or physical environments, although some sintered metal materials have found their way into architectural appHcations. Prior to concerns regarding its carcinogenic properties, asbestos fiber had been used extensively in spray-on acoustical treatments. 

Paper consists of sheet materials that are comprised of bonded small discrete fibers. The fibers usually are ceUulosic in nature and are held together by hydrogen bonds (see Cellulose). The fibers are formed into a sheet on a fine screen from a dilute water suspension. The word paper is derived from papyms, a sheet made in ancient times by pressing together very thin strips of an Egyptian reed Cjperuspapyrus) (1). 

Fractionation separates fines and short, weak cellulose fibers from longer, stronger cellulose fibers (52). Its primary appHcation is ia processiag old cormgated coataiaers iato aew packagiag products. 

An important chemical finishing process for cotton fabrics is that of mercerization, which improves strength, luster, and dye receptivity. Mercerization iavolves brief exposure of the fabric under tension to concentrated (20—25 wt %) NaOH solution (14). In this treatment, the cotton fibers become more circular ia cross-section and smoother ia surface appearance, which iacreases their luster. At the molecular level, mercerization causes a decrease ia the degree of crystallinity and a transformation of the cellulose crystal form. These fine stmctural changes iacrease the moisture and dye absorption properties of the fiber. Biopolishing is a relatively new treatment of cotton fabrics, involving ceUulase enzymes, to produce special surface effects (15). 

Bacterial Cellulose. Development of a new strain of Acetobacter may lead to economical production of another novel ceUulose. CeUulon fiber has a very fine fiber diameter and therefore a much larger surface area, which makes it physicaUy distinct from wood ceUulose. Its physical properties mote closely resemble those of the microcrystalline ceUuloses thus it feels smooth ia the mouth, has a high water-binding capacity, and provides viscous aqueous dispersions at low concentration. It iateracts synergisticaUy with xanthan and CMC for enhanced viscosity and stabUity. 

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