We investigated whether the fastness properties of wool textiles could be enhanced by modifying the dyeing and post-dyeing procedures in ways designed to increase the crystallinity of dyes in the wool. In one approach, the dyebath was maintained at 98°C for three hours, in another, dyed fabric was rapidly cooled. In a third approach, dyed fabric was alternately held in solutions of 80°C and 40°C. Commercial acid levelling and acid milling dyes were used. Fastness to light and washing were assessed by standard methods, and samples were exposed to sunlight behind glass for 12 months. The crystallinity of the dyes in the wool was assessed by x-ray diffraction. Small increases in lightfastness and crystallinity occurred, with the two classes of dyes behaving differently. This preliminary study demonstrated that the concept of increasing the crystallinity of dyes in wool to improve lightfastness warrants further investigation.
It is well known that wool carpets and upholstery permanently remove many gaseous pollutants from the air, thus improving indoor air quality, and peoples’ wellbeing. The aim of the work reported here was to develop wool-based filters that could be used in homes and offices to improve indoor air quality. The abilities of wool, jute, and some other materials used in building interiors, to absorb common indoor air pollutants, formaldehyde, sulphur dioxide and nitrogen oxides were compared. Testing was conducted in a chamber that reproduced the conditions found in a typical room. Wool and jute were found to give high levels of absorption and the results were used to design six types of wool-based filters that were intended to be compact, with high rates and capacities of absorption. The filters were passive, relying on high surface areas and diffusion, rather than forced air circulation, thus minimising their net environmental impact. Filters based on wool yarn, roving, balls and unbacked carpet, were all very effective, absorbing between 94 and 96% of the air pollutants over six hours. This study has shown that wool-based passive filters can significantly improve indoor air quality, and represent a new use for wool.
Disperse dyes are not currently applied to wool commercially, in large part because of inadequate wash fastness, but they do have potential, especially for wool-polyester blends. In this study, for the first time hydrogen peroxide was investigated to increase the wash fastness of disperse dyes on wool. In the absence of oxidants, 10 disperse dyes from seven classes imparted colours with a range of depths (K/S 2-26) with wash fastness (grey scale ratings for colour change) grades of 3 to 4-5. Hydrogen peroxide had only small effects on colours and gave only small enhancements to wash fastness, which were limited to anthraquinone, nitrodiphenylamine, disazo and coumarin dyes. The bleach activators Prestogen W and citric acid enhanced the bleaching effect of hydrogen peroxide but did not assist with raising wash fastness.Hydrogen peroxide in post-dyeing scouring made the dyeings brighter but did not significantly enhance wash fastness. Ammonium persulphate, which was included for benchmarking with earlier studies, yellowed the wool and decomposed some dyes. This study extends the range of dye classes whose wash fastness on wool can be improved by ammonium persulphate to now include diazo, coumarin and methine, and confirms that oxidants/free radical initiators have potential for enabling the disperse dyeing of wool.All dyeings were performed in a Turbomat dyeing machine (Ahiba) with a 30:1 liquor-to-wool ratio and 600 mL SUPPORTING INFORMATIONAdditional supporting information may be found online in the Supporting Information section. How to cite this article:McNeil SJ, Zaitseva LI. Enhancing the wash fastness of disperse dyes on wool with oxidants. Coloration Technol. 2020;136:231-243. https ://doi.
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