Oxidised cellulose

The author is unaware of any commerical polymers that are specifically designed to degrade oxidatively, although oxidation may be involved in association with hydrolytic and biological degradation. It may be of interest to note that before World War II products known as rubbones were produced by degrading natural rubber with cobalt linoleate in the presence of cellulosic materials to produce low molecular weight, fluid oxidised natural rubber (Section 30.4). 

Oridation. This is caused by contact with oxidising acids, exposure to u-v, prolonged application of excessive heat, or exposure to weathering. It results in a deterioration of mechanical properties (embrittlement and possibly stress cracking), increase in power factor, and loss of clarity. It affects most thermoplastics to varying degrees, in particular polyolefins, PVC, nylons, and cellulose derivatives. 

Figure 10.30 Functional groups formed by oxidising cotton cellulose with sodium hypochlorite over the pH range 5-10 [235]...

During preparation of an oxidising agent on a larger scale than described [1], addition of warm sodium hydroxide solution to warm ammoniacal silver nitrate with stirring caused immediate precipitation of black silver nitride which exploded [2], Similar incidents had been reported previously [3], including one where explosion appeared to be initiated by addition of Devarda s alloy (Al—Cu—Zn) [4], The explosive species separates at pH values above 12.9, only produced when alkali is added to ammoniacal silver solutions, or when silver oxide is dissolved with ammonia [5], The Sommer Market reagent mixture used to identify cellulose derivatives led to a severe explosion [6],... 

Fibrous organic material (jute storage bags) is oxidised in contact with sodium nitrate above 160°C and will ignite below 220°C [1]. Wood and similar cellulosic materials are rendered highly combustible by nitrate impregnation [2],... 

The solid oxide, or its concentrated solutions or vapour, tends to oxidise ethanol, cellulose fibres, etc., explosively [1,2]. Ethanol also gives an explosive by-product, probably an organoruthenium derivative [1]. 

Scheme 11 The mechanism of the formation of acid sites in oxidised cellulose.

Complex pyrolysis chemistry takes place in the conversion system of any conventional solid-fuel combustion system. The pyrolytic properties of biomass are controlled by the chemical composition of its major components, namely cellulose, hemicellulose, and lignin. Pyrolysis of these biopolymers proceeds through a series of complex, concurrent and consecutive reactions and provides a variety of products which can be divided into char, volatile (non-condensible) organic compounds (VOC), condensible organic compounds (tar), and permanent gases (water vapour, nitrogen oxides, carbon dioxide). The pyrolysis products should finally be completely oxidised in the combustion system (Figure 14). Emission problems arise as a consequence of bad control over the combustion system. 

Oxidation of kraft pulp cellulose by aq. RUCI3 or RuO /aq. Na(ClO) or aq. 0.02 M H SOj gave oxycellulose containing carbonyl and carboxylate gronps RuO itself is also effective and is likely to be the principal catalyst [348]. The system RuClj/ Na(Br03)/aq. Na2(C03) pH 9.8 oxidised varions forms of cellnlose [349]. 

Powerful oxidants are particularly dangerous when mixed with easily oxidised organic substances such as simple alcohols, polyhydric alcohols, carbohydrates and cellulose-containing materials such as paper, cloth or wood. They are also dangerous when mixed with elements such as sulphur and phosphorus, and with finely divided metals such as magnesium powder. The following are common examples ... 

B. Lindberg and O. Theander, The occurrence of 3-oxoglucose units in oxidised cellulose, Acta Chem. Scand., 11 (1957) 1355-1358. 

Abstract Pressure-sensitive paint (PSP) is applied to the areodynamics measurement. PSP is optical sensor based on the luminescence of dye probe molecules quenching by oxygen gas. Many PSPs are composed of probe dye molecules, such as polycyclic aromatic hydrocarbons (pyrene, pyrene derivative etc.), transition metal complexes (ruthenium(II), osumium(II), iridium(III) etc.), and metalloporphyrins (platinum (II), palladium(II), etc.) immobilized in oxygen permeable polymer (silicone, polystyrene, fluorinated polymer, cellulose derivative, etc.) film. Dye probe molecules adsorbed layer based PSPs such as pyrene derivative and porphyrins directly adsorbed onto anodic oxidised aluminium plat substrate also developed. In this section the properties of various oxygen permeable polymer for matrix and various dye probes for PSP are described. 

Figure 6. Both hydrolytic and oxidative enzymes participate in cellulose decomposition by the white-rot fungus Phanerochaete chrysosporium Burds. Hydrolytic enzymes i, endo-1 - - I ucanases 2, exo-1,4- -glucanase and 3, -glucosidase. Oxidative enzymes 4, glucose oxidase, 5, cMlobiose oxidise and 6, cellobiose quinone oxidoreductase. Adapted from Reference 23,...

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