Rayon carbonized

Used industrially as a chemical intermediate in the production of rayon, carbon tetrachloride, xanthogenates, flotation agents, and pesticides used in the cold vulcanization of vulcanized rubber, in adhesive compositions for food packaging as a solvent for phosphorus, sulfur, selenium, bromine, iodine, fats, resins, rubbers, waxes, lacquers, camphor, resins and in the production of optical glass, paints, enamels, varnishes, paint removers, tallow, putty preservatives, rubber cement, soil disinfectants, explosives, rocket fuel, and electronic vacuum tubes. 

Carbon disulfide is used to produce intermediates in the manufacture of rubber vulcanization accelerators, rayon, carbon tetrachloride, cellophane, and agricultural and pharmaceutical chemicals. The end products for the U.S. production of carbon disulfide are given in Table 4.3 [129], Production of carbon disulfide is heavily related to rayon and cellophane which accounts for about 55—65% of its usage [130]. 

Carbon disulfide is widely used in production of rayon, carbon tetrachloride, rubber chemicals and cellulose film, and is a by-product of widely used dithiocarbamate pesticides. Chronic low level and long term exposure to CS2 can cause eye, ear, cardiovascular, nervous system and reproductive effects (Tan et al., 2001), (WHO Criteria 10, 1979), (Kaloyanova, 1981). There are scientific reports that the long term exposure to low concentrations of CS2 is related to endocrine disturbances as well (Lancranian I. et al., 1972) (Lyubomirova K. et al., 2006). Carbon disulfide is mostly used in viscose industry to yield sodium cellulose xanthate from alkali cellulose. (Tan et al., 2001). 

USk In the manuf of rayon, carbon tetrachloride, xantho-gosles, soil disinfectants, electronic vacuum tubes. Solvent for phosphorus, sulfur, selenium, bromine, iodine, fats, result, rubbers. 

OTHER COMMENTS used in the manufacture of rayon, carbon tetrachloride, soil disinfectants, and electronic vacuum tubes used as a solvent for phosphorus, selenium, sulfur, bromine, and iodine. 

Whereas carbon fibers with a low carbon content are formed predominantly from aliphatic raw materials (rayon), carbon fibers with a high carbon content are produced from aromatic feedstocks or easy-to-aromatize base materials. The most important raw materials for the manufacture of high-carbon fibers are polyacrylonitrile and mesophase pitch. 

Figure 20.29 Grayon (carbonized rayon) carbon fiber weight loss t/s temperature in air. Source Reprinted from RK Carbon Fibre s technical literature.

Koo et al. [71] compared the ablative properties of carbon phenolic composite (MX-4926) to laboratory produced carbon nanofibers (CNFs)/phenolic nanocomposites (CNF-NRAMs). Three CNF loadings, namely 20 %, 24 % and 28 wt% were dispersed in the phenolic matrix without rayon-carbon fiber reinforcement. A subscale rocket motor (heat flux 1140 W/cm ) was used to study the ablation and insulation characteristics of the ablatives. According to the experimental results, when compared to the MX-4926, all the CNF-NRAMs exhibited lower ablation rates and the lower maximum backside heat-soaked temperature increase. Peak... 

Rayon High modulus rayon-carbon fiber. U.S.A. [9] Sparked high performance cf industry in U.S.A. 

Figure 5.45. The distribution of narrow microporosity, wider microporosity and mesoporosity in viscous rayon carbons.

Union Carbide, and now Amoco, are producing pitch carbon-fibres as continuous filament yarn and as fibre mat. The two forms are primarily differentiated by the spinning technique but differ significantly in appearance, properties and cost potential. The continuous fibres (Thornel P Series) are round and have a diameter of about 7.8 pm and a density of 1.958 gcm . They have mechanical properties comparable to PAN in rayon carbon-fibres, their strength being somewhat lower. But they have very good electrical properties which can be further enhanced by intercalation. 

On standing, gelatinous aluminium hydroxide, which may initially have even more water occluded than indicated above, is converted into a form insoluble in both acids and alkalis, which is probably a hydrated form of the oxide AI2O3. Both forms, however, have strong adsorptive power and will adsorb dyes, a property long used by the textile trade to dye rayon. The cloth is first impregnated with an aluminium salt (for example sulphate or acetate) when addition of a little alkali, such as sodium carbonate, causes aluminium hydroxide to deposit in the pores of the material. The presence of this aluminium hydroxide in the cloth helps the dye to bite by ad sorbing it—hence the name mordant (Latin mordere = to bite) dye process. 

Rayon. Viscose rayon is obtained by reacting the hydroxy groups of cellulose with carbon disulfide in the presence of alkali to give xanthates. When this solution is poured (spun) into an acid medium, the reaction is reversed and the cellulose is regenerated (coagulated). 

For nosetip materials 3-directional-reinforced (3D) carbon preforms are formed using small cell sizes for uniform ablation and small pore size. Figure 5 shows typical unit cell dimensions for two of the most common 3D nosetip materials. Carbon-carbon woven preforms have been made with a variety of cell dimensions for different appHcations (27—33). Fibers common to these composites include rayon, polyacrylonitrile, and pitch precursor carbon fibers. Strength of these fibers ranges from 1 to 5 GPa (145,000—725,000 psi) and modulus ranges from 300 to 800 GPa. 

Neste patented an industrial route to a cellulose carbamate pulp (90) which was stable enough to be shipped into rayon plants for dissolution as if it were xanthate. The carbamate solution could be spun into sulfuric acid or sodium carbonate solutions, to give fibers which when completely regenerated had similar properties to viscose rayon. When incompletely regenerated they were sufficientiy self-bonding for use in papermaking. The process was said to be cheaper than the viscose route and to have a lower environmental impact (91). It has not been commercialized, so no confirmation of its potential is yet available. 

Rayon is unique among the mass produced man-made fibers because it is the only one to use a natural polymer (cellulose) directly. Polyesters, nylons, polyolefins, and acryflcs all come indirectly from vegetation they come from the polymerization of monomers obtained from reserves of fossil fuels, which in turn were formed by the incomplete biodegradation of vegetation that grew millions of years ago. The extraction of these nonrenewable reserves and the resulting return to the atmosphere of the carbon dioxide from which they were made is one of the most important environmental issues of current times. CeUulosic fibers therefore have much to recommend them provided that the processes used to make them have minimal environmental impact. 

In the calendering method, a PVC compound which contains plasticizers (qv) (60—120 phr), pigments (qv) (0—10 phr), fillers (qv) (20—60 phr), stabilizers (10—30 phr), and other additives, is kneaded with calender roUs at 150—200°C, followed by extmsion between clearance-adjusted roUs for bonding onto the substrate. This method is employed for products with thick PVC layers, ie, of 0.05—0.75 mm thickness. The main plasticizer used is di-2-ethylhexyl phthalate (DOP). For filler to reduce cost, calcium carbonate is mainly used. A woven or knit fabric made of cotton, rayon, nylon, polyester, and their blend fiber is used as substrate. For foamed vinyl-coated fabrics, the bonded materials are heated in an oven to decompose the foam-blowing... 

Plastics and Other Synthetic Products. Sulfur is used in the production of a wide range of synthetics, including cellulose acetate, cellophane, rayon, viscose products, fibers, and textiles. These uses may account for 2% of sulfur demand in developed countries. Sulfur intermediates for these manufacturing processes are equally divided between carbon disulfide and sulfuric acid. 

Several cellulose esters (qv) are prepared commercially. Cellulose xanthate [9032-37-5] is made by reaction of cellulose swollen in 8.5—12% sodium hydroxide solution (alkaU cellulose [9081-58-7J) with carbon disulfide and is soluble in the alkaline solution in which it is made. When such a solution, termed viscose, is introduced into an acid bath, the cellulose xanthate decomposes to regenerate cellulose as rayon fibers or cellophane sheets (see Fibers, REGENERATED CELLULOSICS). 

Carbon fibers are generally typed by precursor such as PAN, pitch, or rayon and classified by tensile modulus and strength. Tensile modulus classes range from low (<240 GPa), to standard (240 GPa), intermediate (280—300 GPa), high (350—500 GPa), and ultrahigh (500—1000 GPa). Typical mechanical and physical properties of commercially available carbon fibers are presented in Table 1. 

Producers of PAN-based carbon fiber include Toray, Toho Beslon, Mitsubishi Rayon, and Asahi Kasai Carbon in Japan Hercules, Amoco Performance Products, BASE Stmctural Materials, Eortafil (Akzo), and Mitsubishi Rayon in the United States and Akzo, Sigri, and Soficar in Europe. Primary suppHers of high performance pitch-based carbon fibers include Amoco Performance Products, Mitsubishi Kasai, and Tonen Corp. 

CeUulose is subsequendy regenerated from the viscose solution in sulfuric acid and carbon disulfide is Hberated. These are the basic steps in manufacturing viscose rayon. The production of regenerated ceUulose is estimated to account for mote than 75% of the total carbon disulfide consumption woddwide... 

United States consumption of carbon disulfide totaled about 108,000 t in 1990 according to SRI International, with the following distribution by end use appHcation 46,000 tons for rayon 33,000 tons for carbon tetrachloride 12,000 tons for mbber 5,000 tons for cellophane and 12,000 tons for agricultural and miscellaneous uses (129). During 1991 the carbon tetrachloride appHcation disappeared entirely thereby reducing the aimuali2ed carbon disulfide usage to an estimated 75,000 tons. Net exports are around 6,000 tons, and are expected to increase in the future. 

Type of dryer tions, extracts, milk, blood, waste liquors, rubber latex, etc. gents, calcium carbonate, bentonite, clay sbp, lead concentrates, etc. trifuged sobds, starch, etc. dry. Examples centrifuged precipitates, pigments, clay, cement. ores, potato strips, synthetic rubber. objects, rayon skeins, lumber. sheets. her sheets. 

Cellulose acetate Silica gel Scoured wool Sawdust Rayon waste Fluorspar Tapioca Breakfast food Asbestos fiber Cotton linters Rayon staple Starch Aluminum hydrate Kaolin Cryolite Lead arsenate Cornstarch Cellulose acetate Dye intermediates Calcium carbonate White lead Lithopone Titanium dioxide Magnesium carbonate Aluminum stearate Zinc stearate Lithopone Zinc yellow Calcium carbonate Magnesium carbonate Soap flakes Soda ash Cornstarch Synthetic rubber... 

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