Synthesis of fibers

Used industrially in synthesis of fiber-reactive dyestuffs. 

Stinton, D.P., A.J. Caputo, and R.A. Lowden. 1986. Synthesis of fiber-reinforced SiC composites by chemical vapor infiltration. American Ceramic Society Bulletin 65(2) 347-350. ... 

In the Lanxide process for the synthesis of fiber-reinforced ceramic composites a liquid alloy (A1 based), impregnated in a whisker felt or fiber preform, is gradually oxidized in air to form an oxide matrix. 

Synthesis of fiber-forming aromatic polyamides and their properties. Aromatic polyamides do not melt totally below their decomposition temperature. For this reason, in contrast to aliphatic polyamides, they cannot be synthesized... 

The immediate future of the textile industiy belongs to biotechnology. Even today suggestions on the synthesis of various polysaccharides using microbiological methods are present. These methods may be applied to synthesis of fiber-forming monomers and polymers. 

Stinton, D.P., Caputo, A.J. and Lowden, R.A., Synthesis of Fiber-Reinforced SiC Composites by Chemical Vapor Infiltration. Amer. Ceram. Soc. Bull. 65 [2] 347-350 (1986). 

The first reported synthesis of acrylonitrile [107-13-1] (qv) and polyacrylonitrile [25014-41-9] (PAN) was in 1894. The polymer received Htde attention for a number of years, until shortly before World War II, because there were no known solvents and the polymer decomposes before reaching its melting point. The first breakthrough in developing solvents for PAN occurred at I. G. Farbenindustrie where fibers made from the polymer were dissolved in aqueous solutions of quaternary ammonium compounds, such as ben2ylpyridinium chloride, or of metal salts, such as lithium bromide, sodium thiocyanate, and aluminum perchlorate. Early interest in acrylonitrile polymers (qv), however, was based primarily on its use in synthetic mbber (see Elastomers, synthetic). 

Mechanism of Action. P-Agonists stimulate skeletal muscle growth by accelerating rates of fiber hypertrophy and protein synthesis, but generally do not alter muscle DNA content in parallel with the increases in protein accretion (133—135). This is in contrast to the effects of anaboHc steroids and ST on skeletal muscle growth. Both of the latter stimulate fiber hypertrophy and muscle protein synthesis, but also increase muscle DNA content coincident with increased protein accretion. Whether the P-agonists decrease muscle protein degradation is equivocal. 

Most Kaminsky catalysts contain only one type of active center. They produce ethylene—a-olefin copolymers with uniform compositional distributions and quite narrow MWDs which, at their limit, can be characterized by M.Jratios of about 2.0 and MFR of about 15. These features of the catalysts determine their first appHcations in the specialty resin area, to be used in the synthesis of either uniformly branched VLDPE resins or completely amorphous PE plastomers. Kaminsky catalysts have been gradually replacing Ziegler catalysts in the manufacture of certain commodity LLDPE products. They also faciUtate the copolymerization of ethylene with cycHc dienes such as cyclopentene and norhornene (33,34). These copolymers are compositionaHy uniform and can be used as LLDPE resins with special properties. Ethylene—norhornene copolymers are resistant to chemicals and heat, have high glass transitions, and very high transparency which makes them suitable for polymer optical fibers (34). 

The expiration of Phillips basic PPS patent in 1984 ushered in a large interest from the industrial sector. Companies, based largely in Europe and Japan, began acquiring patents worldwide for both the synthesis of PPS and a wide variety of appHcations, including compounds, blends, alloys, fiber, film, advanced composite materials, as well as end use products. 

Polymer Plasticizer. Nylon, cellulose, and cellulose esters can be plasticized using sulfolane to improve flexibiUty and to increase elongation of the polymer (130,131). More importantly, sulfolane is a preferred plasticizer for the synthesis of cellulose hoUow fibers, which are used as permeabiUty membranes in reverse osmosis (qv) cells (131—133) (see Hollow-FIBERMEMBRANEs). In the preparation of the hoUow fibers, a molten mixture of sulfolane and cellulose triacetate is extmded through a die to form the hoUow fiber. The sulfolane is subsequently extracted from the fiber with water to give a permeable, plasticizer-free, hoUow fiber. 

The synthesis of his[3-(2-a11y1phenoxy)phtha1imides] and their copolymer properties with BMI have been reported (43). These allylphenoxyimide—BMI copolymers provide toughness and temperature resistance when used in carbon fiber laminates (44). 

Synthetic polymers have become extremely important as materials over the past 50 years and have replaced other materials because they possess high strength-to-weight ratios, easy processabiUty, and other desirable features. Used in appHcations previously dominated by metals, ceramics, and natural fibers, polymers make up much of the sales in the automotive, durables, and clothing markets. In these appHcations, polymers possess desired attributes, often at a much lower cost than the materials they replace. The emphasis in research has shifted from developing new synthetic macromolecules toward preparation of cost-effective multicomponent systems (ie, copolymers, polymer blends, and composites) rather than preparation of new and frequendy more expensive homopolymers. These multicomponent systems can be "tuned" to achieve the desired properties (within limits, of course) much easier than through the total synthesis of new macromolecules. 

Poly(arylene vinylenes). The use of the soluble precursor route has been successful in the case of poly(arylene vinylenes), both those containing ben2enoid and heteroaromatic species as the aryl groups. The simplest member of this family is poly(p-phenylene vinylene) [26009-24-5] (PPV). High molecular weight PPV is prepared via a soluble precursor route (99—105). The method involves the synthesis of the bis-sulfonium salt from /)-dichloromethylbenzene, followed by a sodium hydroxide elimination polymerization reaction at 0°C to produce an aqueous solution of a polyelectrolyte precursor polymer (11). This polyelectrolyte is then processed into films, foams, and fibers, and converted to PPV thermally (eq. 8). 

Early diffraction photographs of such DNA fibers taken by Rosalind Franklin and Maurice Wilkins in London and interpreted by James Watson and Francis Crick in Cambridge revealed two types of DNA structures A-DNA and B-DNA. The B-DNA form is obtained when DNA is fully hydrated as it is in vivo. A-DNA is obtained under dehydrated nonphysiological conditions. Improvements in the methods for the chemical synthesis of DNA have recently made it possible to study crystals of short DNA molecules of any selected sequence. These studies have essentially confirmed the refined fiber diffraction models for A- and B-DNA and in addition have given details of small structural variations for different DNA sequences. Furthermore, a new structural form of DNA, called Z-DNA, has been discovered. 

Regarding a historical perspective on carbon nanotubes, very small diameter (less than 10 nm) carbon filaments were observed in the 1970 s through synthesis of vapor grown carbon fibers prepared by the decomposition of benzene at 1100°C in the presence of Fe catalyst particles of 10 nm diameter [11, 12]. However, no detailed systematic studies of such very thin filaments were reported in these early years, and it was not until lijima s observation of carbon nanotubes by high resolution transmission electron microscopy (HRTEM) that the carbon nanotube field was seriously launched. A direct stimulus to the systematic study of carbon filaments of very small diameters came from the discovery of fullerenes by Kroto, Smalley, and coworkers [1], The realization that the terminations of the carbon nanotubes were fullerene-like caps or hemispheres explained why the smallest diameter carbon nanotube observed would be the same as the diameter of the Ceo molecule, though theoretical predictions suggest that nanotubes arc more stable than fullerenes of the same radius [13]. The lijima observation heralded the entry of many scientists into the field of carbon nanotubes, stimulated especially by the un-... 

Composites fabricated with the smaller floating catalyst fiber are most likely to be used for applications where near-isotropic orientation is favored. Such isotropic properties would be acceptable in carbon/carbon composites for pistons, brake pads, and heat sink applications, and the low cost of fiber synthesis could permit these price-sensitive apphcations to be developed economically. A random orientation of fibers will give a balance of thermal properties in all axes, which can be important in brake and electronic heat sink applications. 

For rayon fiber based eomposites (Seetions 3 and 4) the fiber and powdered resins were mixed in a water slurry in approximately equal parts by mass. The isotropie piteh earbon fiber eomposites (Seetion 5) were manufaetured with less binder, typically a 4 1 mass ratio of fiber to binder being utilized. The slurry was transferred to a molding tank and the water drawn through a porous sereen under vacuum. In previous studies [2] it was established that a head of water must be maintained over the mold screen in order to prevent the formation of large voids, and thus to assure uniform properties. The fabrieation proeess allows the manufaeture of slab or tubular forms. In the latter case, the cylinders were molded over a perforated tubular mandrel covered with a fine mesh or screen. Moreover, it is possible to mold eontoured plates, and tubes, to near net shape via this synthesis route. 

Hydrogen cyanide (hydrocyanic acid) is a colorless liquid (b.p. 25.6°C) that is miscible with water, producing a weakly acidic solution. It is a highly toxic compound, but a very useful chemical intermediate with high reactivity. It is used in the synthesis of acrylonitrile and adiponitrile, which are important monomers for plastic and synthetic fiber production. 

Uses of Methylamines. Dimethylamine is the most widely used of the three amines. Excess methanol and recycling monomethylamine increases the yield of dimethylamine. The main use of dimethylamine is the synthesis of dimethylformamide and dimethylacetamide, which are solvents for acrylic and polyurethane fibers. 

Oxidation of n-hutane to maleic anhydride is becoming a major source for this important chemical. Maleic anhydride could also be produced by the catalytic oxidation of n-butenes (Chapter 9) and benzene (Chapter 10). The principal use of maleic anhydride is in the synthesis of unsaturated polyester resins. These resins are used to fabricate glass-fiber reinforced materials. Other uses include fumaric acid, alkyd resins, and pesticides. Maleic acid esters are important plasticizers and lubricants. Maleic anhydride could also be a precursor for 1,4-butanediol (Chapter 9). 

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