Surface Area of Fibers

By the definition of a fiber in Chapter 1, a maximum fiber diameter (0.5 mm) should yield a surface area of only 80 cm per gram. A fiber of 5 microns diameter yields a surface area of 8000 cm per g, while a fiber of Ip diameter has a surface area of 40,000 cm per g. Some samples of the serpentine mineral, chrysotile, exhibit diameters of fibrils as small as 200 angstroms (500,(X)0 cm surface area per gram). The potential for enormous surfaces from a single 1 g sample of fiber is obvious. 

The surface of [Ca(P03)3] fibers could be estimated by a treatment of the type evolved above, because they were solid needles with smooth surfaces. [NaCa(P03)3]/i fibers could not be treated in a similar way. They were composed of many tiny fibrils that were inclined to form brushes at the tips. Measured surface areas of [NaCa(P03)3] ranged from about 1500 cm /g to about 15,000 cm /g, depending on how they were milled and the size fraction selected for measurement. The tendency of these fibers to form brushes caused them to have a very high and unexpected oil absorbency. 

The surface area of 1 cc of continuous fiber increases with the reciprocal of the radius squared. Surface tension is usually reported as y, in dyne/cm. The circumference, C, of a fiber is 

If it is assumed that the total strength of a fiber is its surface strength, then 

If F is an equilibrium force that the fiber will support as a result of surface tension, then 

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Specific surface area of fibers 2 m g initially 290 m g after etching Membrane tube diameter, thickness 6 mm 70 pm... 

Based on mass-transfer data for MBSE and MBSS of Phe in a HF contactor with a surface area of 1.4 m2 published in ref. [86] a simulation of the pilot plant for recovery of Phe was done [127]. Number of contactors needed for recovery of Phe was estimated for the unit with a feed flowrate of 100Lh 1, Phe concentration of 50 mol m 3 in the filtered broth, yield of Phe in MBSE 70%, Resell = 2.0, approach to the equilibrium at the raffinate end of contactor of 60%, and concentration factor of 10 were supposed. The estimated number of contactors of Liqui-Cel type 4" x 28" (Membrana, with an effective length of fibers of 0.6 m and surface area of fibers 19.2 m2) in series was 6 in MBSE and 5 in stripping. From simulations it followed that the number of contactors (length of fibers) in M B S E and M B S S is very sensitive to the... 

Ho et al. [141-143,146,151] published a series of papers on removal/recovery of several metals from waste solutions by pertraction through B LM E in H F contactors as shown in Table 23.4. For some metals, such as zinc and copper, scale-up of this system to pilot plant with a HF module with a surface area of fibers of 19 m2 (with diameter 10.2 and length 71.1 cm) was done and mass-transfer characteristics have been estimated [142]. Separation of phases in the dispersion from the stripping was satisfactory. 

From SEM studies, it can be observed that the untreated sisal fiber has a network structure and includes waxes and other low molar mass impurities whereas sisal fiber gets thinner after treatment. It is possible that treatment leads to microfiber fibrillation. The surfaces of the treated sisal fiber become smoother as compared to those of untreated sisal fiber. The effective surface area of fiber available for contact with the matrix also increases in composites while also reducing the diameter of sisal fibers and thereby increasing their aspect ratio. This may offer better fiber-matrix interface adhesion and improve stress transfer. These will give rise to improvement in mechanical properties [78]. 

The catalysts based on silica fiberglass materials can be efficiently used in many gas-phase and Hquid-phase catalytic processes such as acid-catalyzed isopropanol dehydration reactions. To date, the acid-base properties of fiberglass materials, including the Brpnsted acidity, were not studied in detail. The lack of detailed studies could be due to the low specific surface area of fiber-... 

The ability to measure dynamic contact angles has a major advantage. It enables us to characterize a large surface area of fibers and, therefore, to... 

The surface area of fiber decreases with the diameter of fiber, and the relationship is listed in Table 2.34. High surface can provide some special properties for fibers, such as capillary adsorption, handle, draping, color, and luster. Ultrafine fibers have been used for artificial suede for many years they can provide better comprehensive performance advantages than natural suede (Table 2.35). 

The surface areas of fibers was determined by Mesderfer et al. [75] with Direct Red 23 cation in cold water. Parallel tests were carried out... 

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). 

A special use for meltblown olefin fiber is in filtration media such as surgical masks and industrial filters (78). The high surface area of these ultrafine filament fibers permits preparation of nonwoven filters with effective pore sizes as small as 0.5 p.m. 

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... 

Sintered metal fibers with filaments of uniform size (2-40 (tm), made of SS, Inconel, or Fecralloy , are fabricated in the form of panels. Gauzes based on thicker wires (100-250 tm) are made from SS, nickel, or copper. They have a low surface area of about 10 m g. Several procedures are used to increase the surface area, for example, leaching procedures, analogous to the production of Ra-Nickel, and electrophoretic deposition of particles or colloid suspensions. The porosity of structures formed from metal fibers range from 70 to 90%. The heat transfer coefficients are high, up to 2 times larger than for random packed beds [67]. 

KoTHmex activated carbon fiber fabrics AW-1101 (BET specific surface area of 880m /g, average pore diameter of 2nm) was provided by Taiwan Carbon Technology Co. Ltd. The support is pretreated in a boiling aqueous solution of 6.5wt.% HNO3 for 1 h. Then the support is rinsed with distilled water, air-dried for 12h at room temperature and for 5h at 393 K. BET specific surface area of the ACF is 950m /g. 

Synapses between the autonomic postganglionic neuron and effector tissue — the neuroeffector junction — differ greatly from the neuron-to-neuron synapses discussed previously in Chapter 5 (see Table 9.1). The postganglionic fibers in the ANS do not terminate in a single swelling like the synaptic knob, nor do they synapse directly with the cells of a tissue. Instead, the axon terminals branch and contain multiple swellings called varicosities that lie across the surface of the tissue. When the neuron is stimulated, these varicosities release neurotransmitter over a large surface area of the effector tissue. This diffuse release of the neurotransmitter affects many tissue cells simultaneously. Furthermore, cardiac muscle and most smooth muscle have gap junctions between cells. These specialized intercellular communications... 

Fine fibers of PET usually appear white, even though the polymer chips that they are made from may appear grey in color. This is a consequence of the high amount of specular reflection of ambient light, emanating from the large surface area of the fibers. 

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