Cellulose, regenerated development

Flammability Tests Burning wool smells like burnt horn, burning silk smells like burnt egg-white, and burning cellulose fiber smells like burnt paper. Polyamide and polyester fibers melt before they burn polyacrylonitrile fibers, upon burning, leave a residue of hard, black spherical particles. On heating the dry fibers in a test tube, wool, silk, and polyamides develop alkaline vapors, while cotton, bast fibers, and regenerated cellulose (rayon) develop acidic vapors (test with moistened universal indicator paper). 

Several processes have evolved for the preparation of regenerated cellulose. One, developed as far back as 1884, converts it first to a nitrate ester. The nitrated material is dissolved in a mixture of ethyl alcohol and diethyl ether and extruded into fibers. The fibers are then denitrated by treatment with ammonium hydrogen sulfide at about 40 °C. The product is called Chardonnet silk. It appears that this process is no longer practiced anywhere. 

Several processes evolved for preparation of regenerated cellulose. One, developed as far back as 1884, converts it first to a nitrate ester. The nitrated material is dissolved in a mixture of ethyl alcohol... 

The first form of regenerated cellulose was developed in 1884 by de Chardonnet. Cellulose was nitrated and dissolved in a mixture of ether and ethanol. The solution was extruded through a small orifice and the solvent evaporated to leave a fibre. The fibre (which was too inflammable for direct use) was then passed through aqueous ammonium hydrogen sulphide at about 40°C this treatment resulted in denitration. The product (often called Chardonnet s/ifc) was popular for many years but was gradually displaced by other synthetic fibres. Commercial production of the material ceased in 1949. 

To develop a continuous process, the immobilisation of aminoacylase of Aspergillus oryzae by a variety of methods was studied, for example ionic binding to DEAE-Sephadex, covalent binding to iodo-acetyl cellulose and entrapment in polyacrylamide gel. Ionic binding to DEAE-Sephadex was chosen because the method of preparation was easy, activity was high and stable, and regeneration was possible. 

Advanced development of ion-selective films has been attempted by radiation grafting of methacrylic acid on polyethylene films, and combination of this with cellophane are also being tested. Polyamide fleece impregnated with regenerated cellulose, is another option for zinc-silver oxide batteries. 

China. See also People s Republic of China acrylic fiber production in, 11.T89, 220 adhesive joint ventures, 1 526 advanced materials research, 1 696 aquaculture history, 3 183 aquaculture production, 3 189t ascorbic acid synthesis in, 25 754 demand for oil in, 23 530 nanocomposite development, 1 717 natural graphite in, 12 780 oil recovery program in, 23 534 olefin fiber production in, 11 243 production and consumption of regenerated cellulose fibers in,... 

Many membrane materials have been developed and are used for hemodialyzers. Today, these include regenerated cellulose, cellulose acetate, polyacrylonitrile, poly(methylmethacrylate), vinyl alcohol-ethylene copolymer, polysulfone, polyamide, and others. 

Study of the mechanism of this complex reduction-liquefaction suggests that part of the mechanism involves formate production from carbonate, dehydration of the vicinal hydroxyl groups in the cellulosic feed to carbonyl compounds via enols, reduction of the carbonyl group to an alcohol by formate and water, and regeneration of formate (46). In view of the complex nature of the reactants and products, it is likely that a complete understanding of all of the chemical reactions that occur will not be developed. However, the liquefaction mechanism probably involves catalytic hydrogenation because carbon monoxide would be expected to form at least some hydrogen by the water-gas shift reaction. 

The membrane separation processes described above represent the bulk of the industrial membrane separation industry. Another process, dialysis, is not used industrially but is used on a large scale in medicine to remove toxic metabolites from blood in patients suffering from kidney failure. The first successful artificial kidney was based on cellophane (regenerated cellulose) dialysis membranes and was developed in 1945. Over the past 50 years, many changes have been made. Currently, most artificial kidneys are based on hollow-fiber membranes formed into modules having a membrane area of about 1 m2 the process is illustrated in Figure 1.7. Blood is circulated through the center of the fiber, while isotonic... 

Membranes and composites from cellulose and cellulose esters are important domains in the development and application of these polymer materials. The most important segment by volume in the chemical processing of cellulose contains regenerated cellulose fibers, films, and membranes, hi the case of the cellulose esters mainly cellulose nitrate and cellulose acetate as well as novel high-performance materials created therefrom are widely used as laminates, composites, optical/photographic films and membranes, or other separation media, as reviewed in [1], The previously specified nanocelluloses from bacteria and wood tie in with these important potentials and open novel fields of application. 

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