Microwave Assisted Dyeing of Enzyme Treated Wool – A Comparative Study

Gavhane, Pooja and Karnad, Vishaka

The scaly structure of wool is responsible, to a great extent, for the tendency of wool to felt and shrink and its unique properties. Chlorination is a commonly used process to modify the scales of wool fibers with the purpose of providing resistance to felting and shrinkage but this process shows a number of drawbacks leading to the quest of ecologically clean alternatives. Enzyme processing is one such process. Conventional dyeing methods for wool require long dyeing periods of forty-five minutes and high energy consumption. Microwave assisted dyeing is an alternative dyeing method for wool fabrics saving on time, energy and cost. In the present study, an attempt was made to treat wool fabric with acid and alkaline protease enzyme. Enzyme treatment followed by microwave dyeing and their effects on physical properties including handle, weight,  scanning electron microscope (SEM) imaging, tensile strength and color fastness (washing, rubbing, light and perspiration) properties of treated and untreated wool in comparison with conventionally dyed wool was under study. Untreated wool fiber showed fair handle, rough and sharp scales on the surface of fiber, however acid and alkaline enzyme treatment of the wool fabric showed improvement in softness, change in fabric weight, smoother surface scales. The broad conclusion of the research study is that alkaline enzyme treatment gave optimum results when compared to acid enzyme treated samples. On overall comparison, the fastness properties of both conventionally dyed and microwave-assisted dyed samples showed similar results, though it may be noted that the time for dyeing is lesser in microwave assisted dyeing. Thus, microwave assisted dyeing may be suggested as an alternative energy conserving method of dyeing but may find limited commercial viability.

Keywords: Wool | Acid and Alkaline Enzyme Treatment | Microwave Assisted Acid Dyeing | Physical and Colorfastness Properties


Origin of the research problem: Environment and ecology occupy the most important place amongst the key focal issues faced by the world today. Natural fibers are eco-friendly and bio-degradable. Wool is a natural proteinic fiber that is obtained comes from the fleece of domesticated sheep. It is a natural, protein and a multi-cellular staple fiber. Wool consists of three major morphological parts: the cuticle, the cortex and medulla. The fiber form is composed of overlapping cells (scales) that surround the latter. This scaly structure is responsible for difficulty in dyeing of wool fibers and for its tendency to felt and shrink. This complex structure makes it difficult for the dye molecules to permeate into the fibers, resulting in low levels of dye exhaustion. A number of studies have featured in the literature that aims at improving the dye ability of wool by modifying the wool fiber. In recent years, modification and dyeing some of materials have been conducted under microwave assisted dyeing conditions http://www.hrpub.org
Microwave-assisted dyeing is one of the powerful techniques of non-heating contact. It is an alternative to conventional heating that is more rapid, uniform and efficient. It has been assumed that the microwave irradiation could affect dye ability of wool fabric. www.virginiafarm woolworks.com.au. Chlorination is one of the most common methods used to modify the scaly structure of wool fibers towards enhancing its texture. In today’s times, chlorination process shows many drawbacks like: limited durability, poor handle, yellowing of wool most importantly its environmental impact. Thus, enzymatic treatment is gaining importance in textile technology. The bio-enzymatic process reduces the cost of processing and effluent treatment as compared to the chlorine process. www.patagonia.com/chlorine_free_wool.
Enzymes are natural protein molecules that act as highly efficient catalysts in biochemical reactions. Enzymes not only work efficiently and rapidly, but they are also biodegradable and eco-friendly. Thus, in this study the bio-protease enzymes treatment was used to modify the properties on wool fabric. Modification and enzyme treatment of wool alters the dyeability and changes the properties of wool due to the reduction in the number of scales.
Microwave assisted dyeing has shown to have enhanced the dyeability of wool reducing the dyeing and contact time of the substrate with the treating chemicals. The present study therefore aims at exploring microwave assisted dyeing of enzyme treated wool in comparison to conventional dyeing of untreated wool. The study involves examining the physical properties of wool fabric after enzyme treatment and its effect on dyeing with regards to dye-uptake and colorfastness.

Download PDF