Fiber Yield

Although PAN loses constituents in oxidation, there is also an uptake of O2, providing an overall loss in weight of about 3% during oxidation. Although tar removal might be expected to contribute most of the weight loss in the carbonization process, in reality, the loss up to about 700°C based on the dry oxidized fiber, is about 25%, whilst a further 20% is lost in the furnace up to 1350°C. Yields depend on the composition of the precursor and a typical carbon fiber yield for Courtelle would be of the order of 50-55%. 

A well stabilized fiber will have a better yield than a fiber with inadequate stabihza-tion [135], 

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Halogenation of sulfoxylated fibers yields materials with excellent dame-retardant properties (32). 

The F-actin helix has 13 molecules of G-actin in six turns of the helix, repeating every 360 A. Oriented gels of actin fibers yield x-ray fiber diffraction patterns to about 6 A resolution. Knowing the atomic structure of G-actin it was possible for the group of Ken Holmes to determine its orientation in the F-actin fiber, and thus arrive at an atomic model of the actin filament that best accounted for the fiber diffraction pattern. 

Faser-gehalti m. fiber content (Paper) fiber yield, -gewebe, n. fibrous tissue fibrous texture, -gips, m. fibrous gypsum, -haut,/. (Anat.) fibrous membrane, faserig, a. fibrous, fibery, fillamentous, stringy. 

Chemical chemical and mechanical treatments Chemicals and heat properties (some unique properties) Long, strong, stable fibers yield sulfite Kraft, sulfite, soda 84... 

Commercial Masonite and Asplund boards and the asphalt-impregnated insulation board were sampled before any commercial heat treatment. The corresponding "thermomechanical" pulps had been produced by pressurized refining of steamed chips. The higher pre-steaming temperature used in the Masonite process resulted In a yield of about 85% as compared to a fiber yield of about 94% of the Asplund pulps, the remainder being dissolved. 

Wahjudi, J., Xu, L., Wang, P., Singh, V., Buriak, P., Rausch, K.D., McAloon, A.J., Tumbleson, M.E., and Eckhoff, S.R. 2000. Quick fiber process Effect of mash temperature, dry solids and residual germ on fiber yield and purity. Cereal Chem. Tl, 640-644. 

Fully Plastic Section Extreme Fiber Yielding... 

Not all fibers yield fibers on comminution. Fibrous varieties of quartz (Si02), for example, are formed from tightly bonded, aligned helical fibers that cannot be separated mechanically (Frondel, 1978). Fibrous calcite (CaCOa), when crushed or ground, breaks into equant grains of rhombic shape. The fragments reflect the cleavage characteristics of the mineral. 

In the case of ITPP, Ferro and BrCickner (28) showed that unrestrained minimization of the total energy for a microcrystal corresponding to unstretched fibers yields a structure in very close agreement to the crystallographically refined one. This was in contrast to the earlier results with less accurate calculations. Furthermore, their calculations, which used slightly modified MM2 potentials and a modest restraint on the cartesian coordinates, provided a stereochemically acceptable model that reproduces the powder diffraction profile as accurately as the least-squares fitted model. 

Polyacrylonitrile (PAN) precursor fibers are more expensive than rayon. Nevertheless, PAN is more commonly used because the carbon fiber yield is about double that from rayon. Pitch-based carbon fibers are also important, because, potentially pitch is perhaps the cheapest raw material. Table 8.2 shows that carbon yield is highest from the mesophase pitch. The reader is cautioned that this is true only if we exclude the losses during the mesophase conversion step. If, however, one compares the overall carbon fiber yield from raw pitch to that from PAN, then the yield from PAN is higher. In any event, the carbon fiber yield or precursor weight loss is a very important factor in the economics of processing. 

Table 8.2 Some commerciaUy important precursors, their chemical structure, and the carbon fiber yield (after Riggs, 1985).

If the melt viscosities of polypropylene and poly(ethylene terephthalate) polymers are reasonably matched under extrusion conditions, a finely dispersed blend may be produced in fiber form. Orientation of such fibers yields strong filaments in which microfibrils of the two partially crystallized polymers are intertwined and unable to separate. Similar fibers with a sheath of one polymer surrounding a core of the other have no mechanical integrity [27]. 

A typical corn fiber sample contains approximately 20% starch, 14% cellulose, and 35 % hemicellulose. The composition is shown in Table 3. Upon hydrolysis, corn fiber yields glucose, xylose and arabinose as the major carbohydrates. 

A restricted (<, ifi) region for Gly in the Ramachandran map (-180° > 0°, 0° > i/r> 180°) was obtained as the overlap of each region obtained experimentally from the NH, NC, CN, and CO bond orientations as described above. The quadrupole echo spectrum of the oriented [2,2- HaJGly labeled silk fibroin fiber yields an angle, 0 = 90 2°, for the C H2 bond vector of Gly residue relative to the fiber axis. A further narrow... 

Elemental sulfur is altered by chemical, allotropic, or me-chanical means. Of the chemical modifiers the Thiokol family of additives are some of the most effective modifiers available. By control of the time-temperature history of sulfur in the liquid and solid phases, it is possible to control the allotropic modification of sulfur and its mechanical properties. Mechanical modification of sulfur with non-chemically reactive filler materials such as aggregates and fibers yields materials with properties different from those of the parent materials. 

The cellulose molecules are highly oriented in the secondary cell walls. Fibers can be relatively easily obtained from the secondary cell walls of cellulose-rich plants, and mankind has done this from antiquity. Especially cotton, flax, hemp, ramie, jute, esparto grass, and kapok have been used as fiber-yielding plants. 

Determination of the crystal lattice strain along the c-axis by x-ray diffraction for a PBT fiber yielded a modulus of 395 G Nm and for PBO fiber 460 G Nm Theoretical calculations of the chain moduli resulted in much larger values, viz. 615 and 730 G Nm , respectively [184]. 

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