OPTICAL WHITENING OF 50/50% PES/WOOL FABRICS

Abstract

If a high level of whiteness is required for wool and wool blends, it is normal to carry out a combined oxidative/reductive bleaching treatments. A higher whiteness can be achieved by the use of optical whitening agents. The aim of this experimental work was to whiten 50/50% PES/Wo woven fabrics. 50/50% PES/Wool fabrics were first bleached in acidic conditions by hydrogen peroxide, and then, the reduction washing processes were carried out by sodium hydrosulphite (Merck), thiourea dioxide (Merck) or sodium borohydride (DyStar). The optical whitening agents, Hostalux ETB Liq. and Leucophor BSB Liq. were later applied at four different concentrations either in a single bath or in two separate baths to the fabrics treated with one of these three chemicals. The processes were repeated twice to check the repeatability of the results. The optical whitening processes were carried out in a laboratory type HT machine (Roaches). The colour measurements were carried out by Datacolor SF600+ spectrophotometer. The Whiteness Indexes of the optically whitened samples were evaluated in accordance with CIE Whiteness Index. The optical whitening agent used for wool gave better results, and also the best results were obtained in single-bath treatments. The best whiteness value was obtained with hydrogen peroxide bleached and washed with sodium hydrosulphide samples which were later optically whitened with 0.8% Hostalux ETB Liq. and 2% Leucophor BSB Liq. at 95°C treatment.

Keywords

• optically whitening
• 50/50% polyester/wool blends
• reductive washing