Cellulose with hydrogen peroxide

Other Cellulosics. Rayon is bleached similarly to cotton but under milder conditions since the fibers are more easily damaged and since there is less colored material to bleach. Cellulose acetate and triacetate are not usually bleached. They can be bleached like rayon, except a slightly lower pH is used to prevent hydrolysis. The above fibers are most commonly bleached with hydrogen peroxide. Linen, dax, and jute requite more bleaching and mil der conditions than cotton, so multiple steps are usually used. Commonly an acidic or neutral hypochlorite solution is followed by alkaline hypochlorite, peroxide, chlorite, or permanganate, or a chlorite step is done between two peroxide steps. A one-step process with sodium chlorite and hydrogen peroxide is also used. 

The xanthate method [62] is considered as one of the most promising methods for industrial chemical modification. The principal involved in the xanthate method of grafting is that cellulosic xanthate either ferrated or in acidic conditions reacts with hydrogen peroxide to produce macroradicals. The following reaction mechanism has been proposed ... 

Oxidative bleaching of wool is invariably carried out with hydrogen peroxide. The active species involved is likely to be the same as on cellulosic substrates but specific reactions with wool amino acid residues must be considered. The primary reaction is oxidation of cystine disulphide bonds leading to the formation of cysteic acid residues (Scheme 10.41). The rupture of disulphide crosslinks, with attendant increase in urea-bisulphite and alkali solubility values, adversely affects fibre properties. As the severity of bleaching conditions increases, the urea-bisulphite solubility remains little changed but the relationships between alkali solubility and cysteic acid (Figure 10.36) and between cystine and cysteic acid (Figure... 

A method of grafting vinyl monomers to substrates of cellulose xanthate was invented by Faessinger and Conte-. The initiation is a reaction of ferrated (12) or acidic (13) cellulose xanthate with hydrogen peroxide according to the following scheme (HO-OH and Fe + give HO- radicals) ... 

Figure 6.10 Xanthation of cellulose followed by reaction with hydrogen peroxide to generate a radical.

Nonabsorbable Natural Sutures. Cotton and silk are the only nonabsorbable sutures made from natural fibers that are still available in the United States. Cotton suture is made from fibers harvested from various species of plants belonging to the genus Gossipium. The fiber is composed principally of cellulose. The seeds are separated from the cotton bolls, which are carded, combed, and spun into yams that are then braided or twisted to form sutures in a range of sizes (Table 4). The suture is bleached with hydrogen peroxide and subsequendy coated (finished or glaced) with starch and wax. The suture may be white or dyed blue with D C Blue No. 9. 

From such considerations, the technique that has emerged is to expose the cellulose first to a solution of ferrous salt. The ferrous ions are absorbed by the cellulose, and in subsequent contact with hydrogen peroxide and monomer the initiation will take place in close proximity to the cellulose molecules and under conditions where the concentration of the latter is high. An advantage of this technique already recognized by Lipson and Speakman (31) is that polymerization mostly occurs inside the fibers and only small amounts of homopolymer are formed. 

The cyanide method is presently the only method for the determination of ketone groups in the polymers and was highly instrumental in the chemical characterization of degraded and oxidized celluloses. The use of this method enabled the development of the first two systems for the preparation of keto-cellulose, namely by mild oxidation with aqueous bromine at low pH values at room temperature [441,442] and by mild oxidation with hydrogen peroxide at pH 10 and 80°C [420,443]. 

OSHA PEL CL 5 mg(Mn)/m3 ACGIH TLV TWA 0.03 mg(Mn)/m3 DOT CLASSIFICATION 5.1 Label Oxidizer SAFETY PROFILE Poison by intravenous route. See also CALCIUM COMPOUNDS, MANGANESE COMPOUNDS, and PERMANGANATES. A strong oxidant. May explode on contact with acetic acid or acetic anhydride. Ignites on contact with cellulose. Incompatible with hydrogen peroxide. 

Cyclic disulfide libraries have primarily been generated through sohd-phase oxidation of support-bound peptide libraries, either on resin beads l or on a cellulose membrane support.P A study comparing several methods for solid-phase and solution cyclizationt found oxidation with hydrogen peroxide (1.5 equiv at a peptide concentration of 0.5g L i) to be best suited for the generation of cyclic disulfide peptide hbraries in solution. 

N sodium hydroxide for 3 hr. at 25°, (52) could be isolated in a yield of 3.7%. The isolation procedure involved deionization and chromatography on a cellulose column. Except for characterization by elemental analysis and the preparation of the (2,4-dinitrophenyl)osazone (identical with that synthesized) and its triacetate, the proof of structure depended upon the identification of formic acid and 2-deoxy-n- ribonic acid, obtained after oxidation with hydrogen peroxide at pH 8. 

Solubilised vat dyes (Figure 7.7) are a group of water-soluble, prereduced forms of vat dyes, stabilised as the sodium salts of sulfate esters, which are prepared via the leuco form by chlorosulfonation. These dyes may be applied directly to the cellulosic fibres and subsequently generate the vat dye within the fibres by acid hydrolysis and oxidation with hydrogen peroxide. 

Reicher J (1992), Decomposition kinetics of the oxidizing agent and damage to cotton cellulose during metal-catalyzed bleaching with hydrogen peroxide , Melliand... 

Treatment with hydrogen peroxide has attracted the attention of many researchers because it is relatively simple and provides an improvement in the fiber mechanical properties [44]. During the treatment the organic peroxides tend to decompose into free radicals that react with the hydroxyl groups of the cellulose, according to the scheme of Figure 13.6. 

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