Mechanism of Photoprotection of Wool With Formaldehyde and Thiol Derivatives (original) (raw)

Phototendering of wool sensitized by naturally occurring polyphenolic dyes

Journal of Photochemistry and Photobiology A: Chemistry, 2005

A number of naturally occurring polyphenolics have been used since antiquity to dye wool. These colourants, originally extracted from plants and insects, can be fixed to wool fibres by a metal ion mordant with the free carboxylic acid and sulphydryl groups present in wool protein providing the necessary metal ion binding sites. Wool undergoes a variety of chemical reactions induced by exposure to UV radiation which eventually manifest themselves as changes in the tensile strength and elasticity of the fibre (phototendering). It is expected that UV-absorbing dyes applied to wool fibres provide some photoprotection to the fibres by partially screening them from this damaging radiation. However, it was found that when mordanted by some metal ions, the natural polyphenolic dyes madder, alizarin and weld which contains the flavonoid, luteolin, exacerbate phototendering compared with undyed wool or fibres which had been treated with the mordant metal ions alone. Several metal ions used as mordants since antiquity such as ferric, cupric, stannic and aluminium have different effects on the rates of this phototendering of dyed wool fabric.

Protection against phototendering of wool by metal salts and mordanted dyes

Journal of the Society of Dyers and Colourists, 2008

Samples of treated and dyed wool have been irradiated with an artificial UV radiation source with a spectral distribution that matched the summer solar UV spectrum. The extent of phototendering was determined by measuring the loss of tensile strength of strips of wool fabric. Many of the dyes studied accelerated phototendering, although some metal-complex dyes prolonged the lifetime. Significant protection of wool against phototendering could be obtained by treatment with aluminium salts, or related salts, followed by dyeing with classical mordant dyes.

Yellow chromophores formed in wool during exposure to light

The structure of the yellow chromophores of wool which are formed during light exposure is not known. This study describes the analysis of the photodegradation products and the yellow chromophores formed during irradiation of model compounds, in particular amino acids and peptides or wool. It is assumed that the amino acid tryptophan contributes strongly to the yellowing of wool during light exposure. Thus, tryptophan was irradiated with UV-rich light and the degradation products were analysed by HPLC analysis. As major photodegradation products kynurenine, 3-hydroxykynurenine and N-formylkynurenine were detected. Similar degradation products were found in aqueous tryptophan solutions after the Fenton reaction with hydroxyl radicals as the active species.

Some possible pathways to the formation of the yellow chromophores of wool during irradiation

The structure of the yellow chromophores of wool which are formed during light exposure is not known. This study describes the analysis of the photodegradation products and the yellow chromophores formed during irradiation of model compounds, in particular amino acids and peptides or wool. It is assumed that the amino acid tryptophan contributes strongly to the yellowing of wool during light exposure. Thus, tryptophan was irradiated with UV-rich light and the degradation products were analysed by HPLC analysis. As major photodegradation products kynurenine, 3-hydroxykynurenine and N-formylkynurenine were detected. Similar degradation products were found in aqueous tryptophan solutions after the Fenton reaction with hydroxyl radicals as the active species.

New thiol-disulfide exchangers as anti-setting agents for wool fabric during dyeing

Fibers and Polymers, 2016

Setting of wool fabrics during dyeing is an acute industrial dilemma facing most of wool dyers. Therefore, wool fabrics were dyed with acid, basic, as well as mono-and bi-functional reactive dyes in the presence of selected aliphatic and aromatic anti-setting agents; namely 3,3-dithiodipropionic acid (DTDPA), dithiodiglycolic acid (DTDGA), 5,5-dithio-bis(2nitrobenzoic acid) (DTBNBA), dithiodibutyric acid (DTDBA), 2,2-dithiodisalicylic acid (DTDSA), and 6,6-dithiodinicotinic acid (DTDNA). The effect of incorporating the said thiol/disulfide-exchangers into the dyeing bath of wool on its dimensional stability was assessed. The influence of the proposed anti-setting agents on the dyeability of wool with the said reactive dyes was monitored. The alteration in the chemical composition of the dyed fabrics was monitored by determining their sulfur and nitrogen contents, cysteine content, and the solubility degree in alkaline solution. The used reagents were found to be effective in stabilization of wool during dyeing with reactive dyes to different extents depending on the nature of the used anti-setting agent. Limited change in the chemical composition of the dyed samples was monitored without affecting their dyeability with the said dyes. The mechanism of interaction of these reagents with wool fabrics during dyeing was proposed.

Photosensitization Studies in Selected Dyestuffs

E-Journal of Chemistry, 2009

There are various dyestuffs species to produce reactive oxygen such as singlet oxygen O2and super oxide radicals. Irradiation with sun lightin vitro, the dyestuff like benzanthrone, metanil yellow andp-aminodiphenylamine were found to produce reactive oxygen species such as singlet oxygen (1O2) and/or superoxide radicals (O2-). However benzanthrone produces detectable amount of1O2Although metanil yellow andp-aminodiphenylamine (p-ADPA) did not produce detectable amounts of1O2under similar conditions. The above dyestuffs are routinely used in textiles, cosmetics, detergents, leather industries as well as food additives. In view of the fact that workers exposed to some of these chemicals during manufacture, pulverization and storage develop edema and even skin cancers in the exposed areas of skin. We believe that activated oxygen species may play a major role in the development of these symptoms.

Applications of Ultraviolet Radiations in Dyeing Processes of Yarns and Fabrics

2014

Not dyed wool yarns and fabrics were treated by ultraviolet radiations, using a medium pressure Hg lamp, in order to obtain a modification onto fibre surface. As consequence, UV treated wool showed increase in metal ions absorption and hydrophilicity, together with improved kinetics of dye absorption under the same dyeing conditions as untreated wool. The surface modification of wool due to UV radiations was confirmed by FTIR-ATR analysis, nevertheless the fibre morphology by SEM analysis was unaffected. Experimental results showed that different kind of dyes are able to give differential dyeing after irradiation, but not all members of the same dyeing class have similar behaviour. Then, a selection of 1:1 metal-complex dyes was chosen to evidence the maximum of difference between irradiated and not irradiated areas. The main interests on wool fabrics were focused on two effects: a) one shade, double face with different depth, higher on treated side; b) two shades, double face with ...