Textile fabric's and dyes

Chemical agents are generally liquids, often aerosolized, and most have immediate effects or are delayed for a few hours. Many chemical agents have a unique odor and color. The effects of toxins, such as botulinum toxin, occur typically in less than a day. There are many different potential chemical agents that a terrorist could use as a weapon, but we can make the following broad generalizations. Buyers in the Europe markets frequently ask for certification of common eco-labels. Eco-labels are basically of two categories, those which are Government administrated and other which are commercially introduced. Some of these labels are given below. Some labels have special requirements that the processor will need to understand what the customer/buyer needs before deciding processes, process parameters and dyes & chemicals that should be used. Dyeing is the process of give color to fibers, yarn, or fabrics by using natural or synthetic dye . In this process it have involving three principle process, that are retardation, migration and diffusion which all this are chemical process. There are many type of dyeing that using in textile wet processing such as cross dyeing, union dyeing and gel dyeing. All of then has there own process to make the dyeing process smoothly and produce a good quality of dyeing. As per this article will confirm that standard and achieve new trend of advances for textile chemical industry with special reference of Dyeing process. Keyword: Dyeing process, Chemical agents, Dyeing parameters, Principle process

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Textile materials (natural and synthetic) used to be coloured for value addition, look and desire of the customers. Anciently, this purpose of colouring textile was initiated using colours of natural source, untill synthetic colours/dyes were invented and commercialized. For ready availability of pure synthetic dyes of different types/classes and its cost advantages, most of textile dyers/ manufacturers shifted towards use of synthetic colourant. Almost all the synthetic colourants being synthesized from petrochemical sources through hazardous chemical processes poses threat towards its eco-friendliness. Hence, worldwide, growing consciousness about organic value of eco-friendly products has generated renewed interest of consumers towards use of textiles (preferably natural fibre product) dyed with eco-friendly natural dyes. Natural dyes are known for their use in colouring of food substrate, leather as well as natural fibres like wool, silk and cotton as major areas of application since prehistoric times. Although this ancient art of dyeing textiles with natural dyes withstood the ravages of time, but due to the wide availability of synthetic dyes at an economical price, a rapid decline in natural dyeing continued. However, even after a century, the uses of natural dyes never erode completely and they are being still used in different places of the world. Thus, natural dyeing of different textiles and leathers has been continued mainly in the decentralized sector for specialty products besides the use of synthetic dyes in the large scale sector for general textiles/apparels. Recently, most of the commercial dyers and textile export houses have started re-looking to the maximum possibilities of using natural dyes for dyeing and printing of different textiles for targeting niche market. Natural dyes produce very uncommon, soothing and soft shades as compared to synthetic dyes. On the other hand, synthetic dyes, which are widely available at an economical price and produce a wide variety of colours, sometimes causes skin allergy and other harmfulness to human body, produces toxicity/chemical hazards during its synthesis, releases undesirable/hazardous/toxic chemicals etc. For successful commercial use of natural dyes for any particular fibres, the appropriate and standardized techniques for dyeing for that particular fibre-natural dye system need to be adopted. Therefore to obtain newer shade with acceptable colour fastness behaviour and reproducible colour yield, appropriate scientific dyeing techniques/procedures are to be derived. Thus, relevant scientific studies and its output on standardization of dyeing www.intechopen.com Natural Dyes 30 methods, dyeing process variables, dyeing kinetics and test of compatibility of selective natural dyes have become very important, however the information on which is insufficient. That is why, this chapter is very much relevant to the current need of the textile dyers. An attempt has been made here to give scientific overview on dyeing of textiles with natural dyes and related issues. 2. Definition of natural dyes/colouants The word 'natural dye' covers all the dyes derived from the natural sources like plants, animal and minerals. Natural dyes are mostly non-substantive and must be applied on textiles by the help of mordants, usually a metallic salt, having an affinity for both the colouring matter and the fibre. Transition metal ions usually have strong coordinating power and/or capable of forming week to medium attraction/interaction forces and thus can act as bridging material to create substantivity of natural dyes/colourants when a textile material being impregnated with such metallic salt (i.e. mordanted) is subjected to dyeing with different natural dyes, usually having some mordantable groups facilitating fixation of such dye/colourant. These metallic mordants after combining with dye in the fibre, it forms an insoluble precipitate or lake and thus both the dye and mordant get fixed to become wash fast to a reasonable level. 3. Advantages and disadvantages of natural dyes/ colouants In the recent years, there has been a trend to revive the art of natural dyeing. This is mainly because in some aspects natural colourants are advantageous against synthetic dyes. Some of these advantages along with some limitations (disadvantages) are listed below: 3.1 Advantages of natural dyes/ colouants i. The shades produced by natural dyes/colourants are usually soft, lustrous and soothing to the human eye. ii. Natural dyestuff can produce a wide range of colours by mix and match system. A small variation in the dyeing technique or the use of different mordants with the same dye (polygenetic type natural dye) can shift the colours to a wide range or create totally new colours, which are not easily possible with synthetic dyestuffs. iii. Natural dyestuffs produce rare colour ideas and are automatically harmonizing. iv. Unlike non-renewable basic raw materials for synthetic dyes, the natural dyes are usually renewable, being agro-renewable/vegetable based and at the same time biodegradable. v. In some cases like harda, indigo etc., the waste in the process becomes an ideal fertilizer for use in agricultural fields. Therefore, no disposal problem of this natural waste. vi. Many plants thrive on wastelands. Thus, wasteland utilization is an added merit of the natural dyes. Dyes like madder grow as host in tea gardens. So there is no additional cost or effort required to grow it. vii. This is a labour intensive industry, thereby providing job opportunities for all those engaged in cultivation, extraction and application of these dyes on textile/food/leather etc. viii. Application of natural dyes has potential to earn carbon credit by reducing consumption of fossil fuel (petroleum) based synthetic dyes. www.intechopen.com Dyeing of Textiles with Natural Dyes 31 ix. Some of its constituents are anti-allergens, hence prove safe for skin contact and are mostly non-hazardous to human health. x. Some of the natural dyes are enhanced with age, while synthetic dyes fade with time. xi. Natural dyes bleed but do not stain other fabrics, turmeric being an exception. xii. Natural dyes are usually moth proof and can replace synthetic dyes in kids garments and foodstuffs for safety. Despite these advantages, natural dyes do carry some inherent disadvantages, which are responsible for the decline of this ancient art of dyeing textiles. 3.2 Limitation/ disadvantages of natural dyes/ colouants i. It is difficult to reproduce shades by using natural dyes/colourants, as these agroproducts vary from one crop season to another crop season, place to place and species to species, maturity period etc. ii. It is difficult to standardize a recipe for the use of natural dyes, as the natural dyeing process and its colour development depends not only on colour component but also on materials. iii. Natural dyeing requires skilled workmanship and is therefore expensive. Low colour yield of source natural dyes thus necessitates the use of more dyestuffs, larger dyeing time and excess cost for mordants and mordanting. iv. Scientific backup of a large part of the science involved in natural dyeing is still need to be explored. v. Lack of availability of precise technical knowledge on extraction and dyeing techniques. vi. The dyed textile may change colour when exposed to the sun, sweat and air. vii. Nearly all-natural dyes with a few exceptions require the use of mordants to fix them on to the textile substrate. While dyeing, a substantial portion of the mordant remains unexhausted in the residual dye bath and may pose serious effluent disposal problem. viii. With a few exceptions, most of the natural dyes are fugitive even when applied in conjunction with a mordant. Therefore, sometimes their colour fastness performance ratings are inadequate for modern textile usage.

Dyeing is a complex, specialized science. Nearly all dye stuffs are now producing from synthetic compounds. This means that costs have been greatly reduced and certain application and wear characteristics have been greatly enhanced. But many practitioners of the craft of natural dyeing (i.e. using naturally occurring sources of dye) maintain that natural dyes have a far superior aesthetic quality which is much more pleasing to the eye. On the other hand, many commercial practitioners feel the natural dyes are non-viable on grounds of both quality and economics. In the west, natural dyeing is now practiced only as a handcraft, synthetic dye being used in all commercial applications. Some craft, weavers and knitters use natural dye as a particular feature of their work.

Current Trends in Fashion Technology & Textile Engineering

A review of the literature on the chemical structure of the textile dyes. This review discusses characteristics associated with the production and use of textile dyes throughout the world. In addition, the data discussed mainly concerns the in terms of their chemical structure (Azo dyes, Nitro dyes, application of these dyes in the textile industry. Keywords: Chemical structure of the textile dye and use of textile dyes.

The textiles exports consists of fabrics, ready-made garments, cotton textiles, textiles made from man-made fiber, wool and woolen goods, silk, handicrafts etc. Out of which man-made textiles and silk are showing the highest growth rate. Textiles, namely protein fibers, in continental part of central Europe have been traditionally dyed by natural dyes. Increasing the contribution of small and medium enterprises of textile, chemical & Pharmaceutical in total exports of India is vital to India's future economic growth. In this century, a global awareness is already in place favoring the use of natural resources for protecting the environment and earth from pollution and ecological imbalances. The present scenario is focused more towards the utilization of the vast diversity of natural resources of color pigments for their use in food materials, pharmaceuticals and textiles, in place of their synthetic counterparts. This trend is aimed at safeguarding human health as well as protecting and prolonging life on earth. Detailed scientific studies with natural dyes have established that in most cases their properties are comparable to those of synthetic dyes. Therefore, if natural dyes have to be commercialized, they need to conform to the same stringent standards of performance that are applied to synthetic dyes. It thus follows that much more research and developmental effort needs to go in this area. The traditional practices may have to be substituted by modern, more scientific practices in order to overcome some of the so-called disadvantages of this dye. In this article, we are illustrating various natural dye materials available for textile industries. Good fastness to processes of textile washing and care implicate to the stability of formed metal complexes.

The use of natural dyes for textile dyeing purpose decreased to a large extent after the discovery of synthetic dyes in 1856. As a result with a distinct lowering in synthetic dyestuff costs, the natural dyes were virtually neglected at the beginning of twentieth century presently there is an excessive use of synthetic dyes estimated at around 10,000,000.00 tons per annum, the production and application of which releases large amount of wastes and unfixed colorants to the environment thereby causing serious health hazards and disturbing the eco-balance of nature. Due to the current economic and environmental consciousness, research in this front should be titled towards the use of natural dyes for dyeing textile materials. This article gives an in depth review and analysis on the categories of textile materials suitable for dyeing with natural dyes, equipments for home and small scale commercial natural dyeing of textile, extraction and mordents used in dyeing textile with natural dyes, conventional and non-conventional method of natural dyeing of textile as well as colour fastness properties of natural dyes. This could help in explaining the merits associated with the use of natural dyes other than synthetic dyes in textile dyeing to overcome the challenges of using synthetic dyes in textile dyeing and as well portray the benefits of using natural dyes

2014

Dyes are coloured substances which can adhere to the surface of material and are used to give colour to paper, food stuffs and various textiles such as cotton, wool, synthetic fibre, silk etc. Dyeing of textiles has been practiced for thousands of years. The present work focuses on dyeing of cotton and wool by dyes like malachite green and vasantha colour. Also the dyeing properties of cotton without using the mordant is also analysed.

2009

This paper reports the studies available on the characterization and chemical/biochemical analysis of natural dyes; extraction of colorants from different natural sources; effects of different mordants and mordanting methods; conventional and non-conventional methods of natural dyeing; physico-chemical studies on dyeing process variables and dyeing kinetics; development of newer shades and analysis of colour parameters for textiles dyed with natural dyes; and test of compatibility for application of binary mixture of natural dyes. The chemical modification of textile substrate for improving dyeability, attempts for improvement in overall colour fastness properties and survey of some traditional processes of natural dyeing in different parts of India have also been discussed.

Eco-Friendly Textile Dyeing and Finishing, 2013