DYEING OF COTTON MATERIALS AFTER BIOSCOURING AND ENZYMATIC BLEACHING TREATMENTS

Abstract

The research aim was to determine the pretreatment (scouring and bleaching) method's influence on 100 % cotton materials dyeing. Before bleaching treatments, the fabrics' non-cellulosic attendants were removed during a pectinolytic treatment and classic alkaline treatment. The general idea of the investigation was maintained in all stages approached, so in addition to the alkaline treatment, an enzymatic treatment was performed (bioscouring) where the classical chelating agent, EDTA, was replaced with sodium citrate. Further, the fabrics were bleached using hydrogen peroxide or a green one, enzymatic, with laccase. A commercial reactive dye was used to colour the cotton samples. The efficiency of the treatment was determined by following the dye fixation degree through soaping. The weight loss, hydrophilicity, tensile strength, elongation at break and colorimetric measurements were used to analyse the treated samples. The higher weight loss values of ~ 5% were found for the alkaline scoured sample and alkaline scoured sample followed by hydrogen peroxide bleaching which also showed the lowest value for tensile strength (259.90 N). Hydrophilicity was less than 3 seconds for all treatments. The 100% dye fixation degree was obtained for the bioscoured sample and bleached with H2O2. Even if the eco-friendly treatments proposed as an alternative for classical scouring and bleaching lead to similar or lower results, some of their advantages should be considered: environmentally friendly, lower costs, a lower fibre damage degree, etc. All these procedures use a lower temperature, respectively, fewer quantities of reagents and are not significantly aggressive with the environment

Keywords

• eco-friendly treatments
• laccase
• dyed cotton fabrics
• colorimetric measurements
• dye fixation