Application of natural dyes by padding technique on textiles

This thesis presents the findings from investigations into adapting the padding process for dyeing cotton and wool using natural dyes. The aim was to apply traditional dyes employing current and emerging technologies of textile colouration. This synergistic amalgamation led to a cleaner production process with low environmental impact. Mordant dyes (derived from Acacia catechu and Acacia nilotica) and vat dyes (Indigofera tinctoria) were evaluated. The work on mordant dyes focused on determining optimal process parameters (padding sequence, mordanting method and mordant concentration). Post-mordanting with copper (II) sulfate or iron (II) sulphate yielded the darkest shades for both dyes. Ideal process sequence for copper (II) sulfate was pad (dye) → dry → steam followed by pad (mordant) → steam → dry while for iron (II) sulfate it was pad (dye) → steam → dry followed by pad (mordant) → steam → dry for both dyes. Similarly, use of the first mordant yielded a beige shade while a yellow-grey shade was obtained with the second. Optimum mordant concentration for 10 g/l dye was 15 g/l copper (II) sulfate or 5 g/l iron (II) sulphate for both dyes. These were lower than those recommended for exhaust dyeing (5% OWM) and padding (60 g/l) reported in the literature. Atomic absorption spectroscopy revealed higher amount of metal in the dyed fabric compared to identically mordanted fabric, confirming the formation of a dye-metal-textile complex. FTIR spectra were distinctly different for the two dyes investigated. However, the spectra for dyed samples, coloured using the above dyes in combination with the same mordant, exhibited minimal differences. This indicated that metal plays a major role in defining the bonds created during dye-metal-textile complex formation causing a similarity in shade. Darker shades were obtained by atmospheric pressure plasma pretreatment of the textile, or including chitosan in the pad liquor. Pure helium and a 95/5 helium/nitrogen mixture were evaluated as the plasma gas. Exposure to either plasma improved the wettability of wool. Wool treated in pure helium plasma for 14 seconds exhibited a 30% increase in the depth of shade. A tone-on-tone pattern was created in a single padding operation by selective plasma pretreatment. Incorporation of 0.05% chitosan in the pad liquor resulted in a 20% darker shade while imparting antimicrobial properties to the dyed fabric. Indigo was applied on cotton by the vat dyeing process of pad (dye) → dry → pad (reducing chemicals) → steam. In this process, sodium dithionite and sodium hydroxide, the common reducing agent and alkali in exhaust dyeing of indigo, were replaced by thiourea dioxide and sodium carbonate respectively. Although equivalent shades were obtained, the use of sodium carbonate required comparatively longer steaming time. Natural indigo produced a darker shade when reduced using the alternative chemicals perhaps due to its higher reactivity resulting from its lower crystallinity as compared to synthetic indigo. However, printing with synthetic indigo resulted in darker shades. The discrepancy between printing and dyeing may be attributed to interference by the print paste thickener on diffusion of reduced indigo into the fabric

Care and maintenance of textile products including apparel and protective clothing

Proper care and maintenance of textile materials is essential in prolonging their durability and appearance. This books describes methods of care and maintenance for textile products, focusing on types of laundering and dry-cleaning processes, chemicals, and equipment, while considering the environmental impacts of these procedures and green cleaning approaches. It details care labelling of garments, including electronic care labelling and instructions for different specialty textiles. Factors such as pilling, abrasion, snagging, color fading, and dimensional change are discussed. This book also emphasizes care and maintenance of textiles used for protection from fire, bullets, cold weather, and chemicals

Application of acacia natural dyes on cotton by pad dyeing

Coloration of textiles, traditionally achieved using natural dyes, commonly employs synthetic dyes at the industrial level. A revival of commercial interest in natural dyes has opened several research avenues. This paper investigates the application by padding of cotton fabric with 10 g/l of two natural dyes derived from the Acacia plant family. Three mordanting techniques were studied; of which post-mordanting produced the most even shade. Among the two mordants investigated, the use of copper sulfate resulted in a level beige shade at 15 g/l concentration while ferrous sulfate performed best at 5 g/l yielding a yellow-grey shade. An optimum process-sequence for the copper sulfate mordant was "pad (dye)¨dry¨steam followed by pad (mordant)¨steam¨dry", and for ferrous sulfite it was "pad (dye)¨steam¨dry followed by pad (mordant)¨steam¨dry". Typically a change in mordant resulted in a different shade with the same dye. The study concluded that padding is a readily adaptable process for the dyeing of cotton using natural dyes and acceptable fastness in shades can be obtained

Sustainable colouration of cotton fabrics utilising chitosan and natural dyes

Responding to the current industrial scenario, where process and manufacturing demand emphasise the importance of recyclability and sustainability, the textile manufacturing industry is proactive to embrace the same. Development of organic and renewable processes are being encouraged and readily accepted when they mitigate environmental pollution. The chemical processing industry in textiles has prompted research into use of dyes from renewable and organic sow-ces. Synthetic dyes and dyeing auxiliaries such as salt and alkali, which are detrimental to the environment, are being replaced by natural dyes and colourants. In this study, chitosan, an ceo-material abundantly found in the exoskeleton of crustaceans (crabs, shrimps, lobsters etc.), has been investigated for its application in pad-dyeing of cotton fabric. Padding, an established continuous dyeing technique, is known for its efficient use of water, time and energy. The cmTenl study explores u:;e of natural dyes in combination with chitosan for colouration of 100% cotton fabric. The study focused on the effects of chitosan for obtaining consistent and improved. shades using dyes derived from plants belonging to Acacia family. Up to 20% enhancement in dye uptake was observed when chi to san was incorporated in the. padding technique. Consequently, chi to san could promote a cleaner production by reducing the amount of dye used and the effluent released to obtain the required shade. Key performance parameters such as fastness of dyed fabric to washing, rubbing and light were evaluated and found to be satisfactory. This research concludes that, pad-dyeing of cotton with an innovative combination of natm·al dyes and chitosan can noticeably improve dye uptake making this process sustainable

An innovative approach to indigo dyeing

Indigo, originally derived from plants, is the dye used to produce the colour of denim. The textile industry widely employs sodium hydroxide and sodium hydrosulphite to effect indigo dyeing. Commercial efforts are concentrated in reducing waste, effluent load and consumables so as to apply indigo in a sustainable manner. This and the growing global market for denim dyed using natural indigo fosters current academic research. This paper reports the possible use of benign auxiliaries (thiourea dioxide and sodium carbonate) and evaluates the pad-steam process for dyeing with indigo. Ideal dyeing parameters are outlined. The study concludes that indigo dyeing can be achieved using methods that have a reduced impact on the environment as compared to existing industrial processe

Effect of atmospheric plasma on pad-dyeing natural dyes on wool

Plasma treatment is an emerging surface modification technique that alters dye uptake of wool without using chemicals or water for pre-treatment. Padding is an established continuous dyeing technique known for its efficient use of water, time and energy. This study combined these two techniques for colouration of wool fabric using two natural dyes derived from the Acacia family. The investigation focused on the effects of plasma treatment and obtaining unique patterning effects. Helium (100%) and a mixture of helium and nitrogen (95% / 5%) were used as the plasma gases under atmospheric conditions. Plasma treated wool fabric was padded with the above natural dyes. Copper sulphate and ferrous sulphate were applied on the dyed fabric as mordant yielding neutral shades of beige and grey respectively. Up to a 30% enhancement of dye adsorption on plasma treated wool substrate was observed as compared to untreated sample for both gases used. This higher adsorption indicates the hydrophilic character of the natural dyes used. Key performance parameters such as fastness to washing, rubbing and light were tested and found to be satisfactory. A single process tone-on-tone pattern was achieved by controlling the plasma exposure to treated area. This study concludes that a merger of natural dyes with modern plasma treatment and padding techniques is feasible

Evaluation of comfort properties of coated kevlar/wool ballistic fabric

Multiple layers of ballistic fabrics are extensively used in the production of soft body armour. The importance of comfort and hence its evaluation for these fabrics is gaining significance among present day researchers. This research compares 100% Kevlar ballistic fabric and Kevlar/wool ballistic fabric focussing on two aspects of comfort, namely the evaluation of surface roughness and the ability to transport moisture. A water repellent treatment was applied to the ballistic Kevlar/wool fabric. The effects of the treatment on the Kevlar/wool fabric were examined as well

Colouration of cotton by combining natural colourants and bio-polysaccharide

A sustainable alternative to some synthetic dyes and dyeing auxiliaries could be substitution by their corresponding natural counterparts. This is in response to a growing premium market for goods with the natural tag brought about by the increasing consumer awareness about conserving and preserving the environment. Currently, natural dyes are used only by hobbyists and craftsmen in a small scale of operation. The present market trend prompts investigations into all aspects of large-scale application of natural dyes. This may encompass the social, economic and technical aspects. A critical technical consideration is the means of increasing colour yield during dyeing. In achieving this, the use of by-products or consequent acquisition of functionality will be an added benefit. In this study, chitosan, a bio-polysaccharide derived from the exoskeleton of crustaceans, has been investigated for enhancing dye uptake while imparting antimicrobial attribute to cotton fabric. Pad-dyeing of natural dyes, from the Acacia family, in the presence of a controlled amount of chitosan resulted in darker shades by approximately 20% as compared to without chitosan. Key performance parameters such as fastness of dyed fabric to washing, rubbing and light were evaluated and found to be satisfactory. In addition, chitosan imparted excellent antibacterial properties to the cotton fabric

Sustainable developments in printing cotton fabric with indigo

Indigo is insoluble in water and most dyeing solvents. Hence, its use in textile coloration is achieved by alkaline reduction to a soluble leuco-compound and then applying this solution followed by oxidation. Printing with indigo on cotton commonly employs sodium hydroxide (caustic soda) as the alkali and sodium hydrosulphite (hydros) as the reducing agent. Caustic soda poses effluent disposal problems. Hydros rapidly loses potency by reacting with atmospheric oxygen during the printing / padding process. This causes premature oxidation of print paste and necessitates constant monitoring. Further, the degradation products of hydros pose effluent hazards. Hence, there is a constant search to find better alternatives in terms of chemical stability and effluent management. In the above context, the present research used thiourea dioxide (TUD) as a more stable reducing agent and sodium carbonate as a milder alkali. The resulting effect on printing cotton fabric with both natural and synthetic indigo has been evaluated. The shades obtained using synthetic indigo were about 20% darker than those obtained using natural indigo. When caustic soda was used as the alkali, a steaming time of 60 seconds was found to be ideal, for both natural and synthetic indigo. However, when sodium carbonate was used darkest shades were obtained at steaming times of 2 and 6 minutes for natural and synthetic indigo respectively. The printed samples showed good colour fastness ratings when evaluated according to Australian standards. The study concludes that indigo can be printed on cotton fabric using chemicals with a lesser environmental impac