Degradation of Wool

As the formation of disulfide bridges between proximate cysteine residues plays a particularly important role in physical properties of wool, any reagents or conditions that interfere with these bonds will have a significant effect on the fibres. A particular and related problem associated with the deterioration of wool fibres is the release of volatile sulfur compounds, which may then attack adjacent materials many of the silver-containing metal threads found on the Tree of Jesse tapestry show signs of surface corrosion, in the form of silver sulfide. 

Biological Degradation. Wool may be targeted by a variety of keratinophilic bacteria and fungi, which break down the component proteins via enzymatic oxidation, reduction or hydrolysis this type of attack predominantly tends to occur in the amorphous regions, particularly in the cuticle. Wool fibres are also susceptible to attack by several species of moths and beetles. 

Electron microscopy can provide valuable information about morphological changes in the fibres, and can potentially give an indication of the nature and cause of degradation, such as photolytic damage, swelling, desiccation or abrasion. The appearance of fracture surfaces is a particularly useful source of information. 

Chromatographic techniques may also reveal a range of important data. End-group analysis will give an indication of the breakdown of the peptide chain, and the measurement of extracted soluble protein will similarly indicate the extent to which the polymer has deteriorated. These techniques, alongside mass spectroscopy, can also reveal the presence of dyes and other treatments. 

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The information available so far on the photochemical degradation of wool presents a very complex picture. Tryptophan, tyrosine, and cystine... 

The wool burrs contain hemi-cellulose and lignin apart from cellulose. The lignin is not effected by carbonising process on acid hydrolysis, but can be split oxidatively. Salt of persulphuric acid accelerates degradation of wool burrs which enable shortening the time of reaction [51]. 

Sweetman, B.J. 1967. The hygrothermal degradation of wool keratin. Part n Chemical changes associated with the treatment of wool with water or steam at temperatures above 100°C, Text. Res. J., 37 844-851. 

ChristeUer, J.T. (1996), Degradation of wool by Hofmannophila pseudospretella (Lepidoptera Oecophoridae) larval midgnt extracts nnder conditions simnlating the midgnt environment . Arch. Insect Biochem. Physiol. 32 (2), 99-119. 

Sweetman, B.J. 1967. The hygrothermal degradation of wool keratin. Part n Chemical changes associated with... 

During photo-oxidative degradation of wool several amino acids are formed, and the main photocleavage occurs between the side amino acid groups and the main chain [153, 965, 1469, 1470, 1578]. Determination of the free radicals so formed by ESR spectroscopy is difficult, due to a lack of distinct hyperfine structure in the resulting spectra [1684-1686,1886]. 

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