Cellulose Degradation, alkaline

The end group which is produced contains a carboxylic acid functionality which has an influence on the anionicity of pulp fibres (Chapter 6) but, in this form, it is resistant to further alkaline degradation. The hemicelluloses are also able to undergo the same type of peeling reaction but at different rates from each other and from cellulose. The /3-1,4-xylans, for example, are more stable to alkaline degradation than the glucomannans. 

Golova and Nosova (22) have reviewed the alkaline degradation of cellulose and of oxidized celluloses ... 

The main processes occuring in the alkaline degradation of cellulose are the so called degradation of cellulose from the reducing end of the molecule and the alkaline hydrolysis of glycosidic bonds. The former process is observed almost exclusively at temperatures up to 150°C. 

Overall Process. Figure 7 illustrates the alkaline degradation of cellulose at elevated temperatures [102,106]. The existing reducing endgroups will... 

Figure 7 Alkaline degradation of cellulose at elevated temperature. (From Ref. 106.)...

Alkaline degradation reactions are largely controlled by the carbonyl content of cellulose (27-29). Because the carbonyl levels go up as natural aging proceeds, one should expect that an 800-year-old textile would be much more likely to be adversely affected by alkali than would new, unoxidized cellulose. The vast majority of the conservation... 

These alkaline degradations can cause a loss of up to 25% (usually 10-20 %) of aZp/to-cellulose during alkaline refining of pulps. 

Alkaline degradation of cellulose is important during alkaline pulping it produces non-volatile acids > which are, for the most part, D-gluco-isosaccharinates. " ... 

No dialdehyde groups are detectable in modified celluloses obtained by oxidation of cellulose with persulfate, hypobromite, hypochlorite, permanganate, nitric acid, or dichromate. " Alkaline-hypochlorite oxidized starches, which have already been partially degraded by alkali, are more resistant to alkaline degradation than are unmodified starches, and the alkali-lability slowly decreases with increasing oxidation because of the resulting oxidation of reducing ends."... 

Polysaccharides. See also. Carbohydrates, Cellulose, Dextran, Dextrins, Fructans, Glycogen, Glycosiduro-nic acids (poly-), Pectin materials, Starch, and Xylan, alkaline degradation of, 13,289-329 associated with wood cellulose, 10, 283-333... 

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