Green fiber

Poly[5-(alkylamino)borazines] 7-10 exhibited suitable viscoelastic and thermal stabilities to be extruded in the molten state through the monohole spinneret of a lab-scale melt-spinning apparatus. Thus, an extruded filament (diameter, 200 gm) was drawn with a windup unit, that is, a graphite spool. This provided green fibers with a wide range of diameters (16 =s (f> =s 50 gm Table 2), depending on polymer architecture. 

The spun polysilane fibers are cured by oxidation in air at a temperature of 160 - 200°C. The curing process is necessary to permit the conversion of the green fiber to the ceramic fiber without softening during pyrolysis. It is presumed that the oxidation mechanism results in the formation of Si-O-C and Si-O-Si bonds by the reaction of Si-CH3 and Si-Si in the polysilane. 

As previously mentioned, FMs were first fabricated by hybrid extrusion and dip-coating [4-6], Firstly, highly concentrated, viscous slurries are extruded and then dried to form a green fiber. The resulting green fibers are dip-coated... 

In the last 10 years, significant advances in fibrous monolithic ceramics have been achieved. A variety of materials in the form of either oxide or nonoxide ceramic for cell and cell boundary have been investigated [1], As a result of these efforts, FMs are now commercially available from the ACR company [28], These FMs are fabricated by a coextrusion process. In addition, the green fiber composite can then be wound, woven, or braided into the shape of the desired component. The applications of these FMs involve solid hot gas containment tubes, rocket nozzles, body armor plates, and so forth. Such commercialization of FMs itself proves that these ceramic composites are the most promising structural components at elevated temperatures. 

Besides the desired dehydrocoupling, Si-N bond cleavage of HPZ and formation of DEB-NHSiMej occurred. Nevertheless, the polymeric precursor had an ideal glass-transition temperature for melt spinning and stable melt viscosity. Melt spun Si-B-C-N-H green fibers were subsequently transformed into ceramic fibers by thermolysis at 1400°C. 

X-Ray diffraction (XRD) of the green material from side B of the halberd produced the powder pattern characteristic of malachite as well as another pattern that was attributed to some aluminum oxide or hydroxide. The exact form of the aluminum material could not be determined conclusively from the data available. XRD analysis of mixtures is difficult and involves more speculation than that of a pure material, particularly in ancient alloys (JO). Although the diffraction powder pattern of the green fiber pseudomorphs from side A was not as clear as that of the green nodule from side B, all of the lines apparent in the pattern could be correlated with those of the green nodule. The two must contain the same material, that is, malachite and some aluminum oxide or hydroxide. 

Cotton strains and species with green fiber have lamellar layers (up to 26) of suberin and wax deposited alternately with cellulose during formation of secondary walls in the epidermal cells, including fiber cells, of the seed coat. Seeds of cotton with green lint are less permeable to water than those with white lint, indicating that suberin may be involved in regulating water uptake by seeds. 

Fig. 6 Conversion of butyric acid in butyl butyrate synthesis catalyzed by immobilized lipase B of Candida antarctica on coconut green fiber (closed circle) and Novozyme 435 (closed square)...

Figure 2.7 Schematic illustration of the formation and aggregation of PAN particles. The green fibers and purple dots represent PANI particles that result from homogeneous and heterogeneous nucleation, respectively. (Reprinted with permission from the Journal of the American Chemical Society, Shape and Aggregation Control of nanoparticles Not shaken, not stirred by D. Li and R. B. Kaner, 128, 968-975. Copyright (2006) American Chemical Society)...

Step 2. Spinning. The slurry is extruded through a spinnerette into green fibers and dried. A similar process produces polymer fibers, such as nylon. 

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