Bleaching tests were conducted to study the efficacy of peracetic acid as a replacement of hydrogen peroxide in bleaching processes of 100% cotton fabric. The criteria chosen for assessing bleaching performances of peracetic acid and hydrogen peroxide were whiteness index, tensile strength, absorbency and fluidity values. The CIE whiteness index value of fabrics was measured by a spectrophotometer using appropriate computer software. Universal Strength Tester (Titan) was used to measure tensile strength. Ostwald-Fenske Cuen viscosimeter was used to determine chemical degradation of cotton fabric by measurement of its fluidity and embroidery hoop was used to determine absorbency. The results of this research showed that the peracetic acid is more effective as a bleaching agent than hydrogen peroxide. An acceptable degree of whiteness (CIE whiteness index 80) can be obtained with minimum loss of tensile strength. This study has also provided valuable information for industrial application of the developed bleaching systems.
Key words: Cotton, Bleaching, Peracetic acid, Hydrogen peroxide
The art of bleaching has been practiced since beginning of civilization. Bleaching is the process of removing colored impurities from the griege fabric as efficiently as possible, with minimum or no damage to the fiber and leaving in a perfect white state.
Nowadays, consumers increasingly demand more environmentally friendly products. This also effect the textile industry, and thus, aspects such as control of water, energy and chemicals consumption should be taken into account in wet textile processes. Hydrogen peroxide (H2O2) is the most widely used bleaching agent for textiles and came into use around 1878. Hydrogen peroxide is suitable for most fibers and it can be used in a wide range of machines under different conditions. Reaction products are non-toxic and non-dangerous but hydrogen peroxide is a highly corrosive compound and degrades to oxygen and water. Hydrogen peroxide is however, damaging to fiber, because it is applicable in strongly alkaline medium and it requires a high temperature to give the most effective bleaching.
Paracetic Acid (PAA) as a bleaching agent has many advantages compared to hydrogen peroxide. It does not produce any toxic by product in bleach reaction, it is less corrosive, it is biologically totally degradable and it causes no AOX (absorbable halogenated organic compounds) load in the waste water.
The author is associated with the Department of Textile Science, Textile Institute of Pakistan, Karachi