Chemistry Investigatory Project On Dyeing Of Fabrics
Name: Anna Wilson Class: XII- A School: International Indian School Al- Jubail Academic Year: 20142015
Acknowledgement I would like to express a deep sense of thanks and gratitude to my chemistry teachers Mrs. Mandakrantha Basu and Mrs. Ayesha Tasneem for guiding me immensely through the course of my project. Their constructive advice and constant motivation have been responsible for the successful completion of my project. My sincere thanks to my parents for their motivation and support. I must thank my classmates for their timely help and support for compilation of this project.
Contents
1. Introduction 2. Objective 3. Requirements 4. Procedure 5. Conclusion 6. Bibliography
INTRODUCTION Dyes are colored substances which can adhere to the surface of materials and are used to give color to paper, foodstuffs, and various textiles such as cotton, wool, synthetic fibres, silk etc. For example, alizarin, indigo, congo red, etc. Chemically, a dye contains: i.
Some group (such as azo, indigoid, triphenylmethyl, anthraquinone, etc.) which is responsible for the color of the dye.
ii.
Some groups (such as –NH2, -SO3H, -COOH, etc) which makes the dye
stick to the fabric by formation of some salt.
Dyeing is the process of adding color to textile products like fibres, yarn and fabrics. The temperature and time controlling are two key factors in dyeing. The primary source of dye, historically has been nature, with the dyes being extracted from plants and animals. Since the 18th century, humans produced artificial dyes to achieve a broader range of colors and to render the dyes more stable to resist washing and general use. The dyed fabrics appear to be colored because a particular dye absorbs radiations of some specific wavelengths from the visible region of electromagnetic radiations which fall
on the surface. The remaining radiations (complementary colors) of light are reflected. The color which we observe is due to the reflected light. For example, if a dye absorbs the light in the wavelength region corresponding to red, then it would appear green, which is the complementary color of red. Similarly, if a dye absorbs blue color, it would appear orange.
Methods to apply dye Dyes are applied to textile goods by dyeing from dye solutions and by printing from dye pastes. Methods include: 1. Direct application 2. Yarn dyeing
Characteristics of a dye 1. 2.
It must have a suitable color. It must be capable of being fixed to the material.
3.
When fixed it must be fast to detergents, soaps, water, drycleaning solvents, light and dilute acids.
Types of dye The dyes are classified by dye manufacturers for marketing into the following types: 1. Acid dyes: These are azo dyes and are characterized by the presence of acidic groups. The presence of soluble and serves as the reactive points for fixing the dye to the fibre. They are chiefly used for dyeing wool, silk and nylon. For example, Orange I and Orange II. 2. Basic dyes: These dyes contain NH2 or NR2. In acidic solutions, these
form water soluble cations and use the anionic sites on the fabric to
get used for dyeing wool, silk and nylon. For example, aniline yellow, butter yellow. 3. Direct dyes: These are also azo dyes and are used to dye fabrics directly by placing in aqueous solution of the dye. These dyes attach to the fabrics by means of hydrogen bonding. 4. Disperse dyes: These dyes are applied in the form of dispersion of minute particles of the dye in a soap solution in the presence of phenol or benzoic acid. These dyes are used to dye rayons, Dacron, nylon, polyesters etc. For example, celliton fast pink B and celliton fast blue B.
5. Fibre ractive dyes: These dyes are linked to the fibre by –OH or –NH2 group present on the fibre. These dyes induce fast color on fabrics which is retained for a longer time. These dyes are used for dyeing cotton, wool and silk. 6. Insoluble dyes: These dyes are directly synthesized on the fibre. The fabric to be colored is soaked in an alkaline solution of phenol and then treated with a solution of diazotized amine to produce azo dye. The color induced by such dyes is not so fast. These dyes are used for dyeing of cotton, silk, polyester nylon, etc. For example, nitroaniline red.
7. Vat dyes: These dyes are waterinsoluble and before dyeing these are reduced to colorless compounds in wooden vats by alkaline reducing agents. The fibre is then soaked in the solution of the dye. Fibre is then exposed to air or an oxidizing agent. By doing so the colorless compound gets reoxidized to colored dye on the fabric. For example, indigo. 8. Mordant dyes: These dyes are applied after treating the fabric with precipitates of certain substances (mordant material) which then combines with the dye to form a colored complex called lake. Some of the mordants are
salts of aluminium, iron and tannic acids. Depending on the mordant used, the same mordant dye can give different colors and shades. For example, alizarin gives red color with aluminium and black violet with iron mordant. Mordant dyes are used for dyeing of wool, silk and cotton.
OBJECTIVE To dye wool and cotton with malachite green.
REQUIREMENTS 500 ml beakers, tripod stand, wire gauze, glass rod, spatula, wool cloth and cotton cloth. Chemicals required: Sodium carbonate, tannic acid, tartaremetic acid, and malachite green dye.
PROCEDURE 1. Preparation of sodium carbonate solution: Take about 0.5 g of solid sodium carbonate and dissolve it in 250 ml of water. 2. Preparation of tartaremetic solution: Take about 0.2 g of tartaremetic and dissolve it in 100 ml of water by stirring with the help of glass rod. 3. Preparation of tannic acid solution: Take 100 ml of water in a beaker and add about 1.0 g of tannic acid to it. Heat the solution. On heating a clear solution of tannic acid is obtained. 4. Preparation of dye solution: Take about 0.1 g of malachite green dye
and add to it 4oo ml of water. On warming a clear solution of the dye results. 5. Dyeing of wool: Take about 200 ml of dye solution and dip it in the woolen cloth to be dyed. Boil the solution for about 2 minutes. After that remove the cloth and wash it with hot water 3-4 times, squeeze and keep it for drying. 6. Dyeing of cotton: Cotton does not absorb malachite green readily, therefore it requires the use of a mordant. For dyeing a cotton cloth dip it in sodium carbonate solution for about 10 minutes and then rinse with water. Then put the cloth in hot tannic acid solution for about 5
minutes. Now take out the cloth from tannic acid solution and keep it in tartaremetic solution for about 5 minutes. Remove the cloth and squeeze it with spatula to remove most of the solution. Now place the cloth in boiling solution of the dye for about 2 minutes. Remove and wash the dyed cloth thoroughly with water, squeeze and keep it for drying. 7. Dyeing of cotton directly: Take another piece of cotton cloth and pit it directly into boiling solution of the dye. Keep it dipped for about 2 minutes. Remove the cloth, wash with water, squeeze and keep it for drying.
Compare the color of this cloth with that dyed by using mordant.
OBSERVATIONS 1. The color of wool cloth dyed directly by dipping in hot solution of malachite green dye is fast. 2. The color of cotton dyed cloth directly (without using mordant) by dipping in hot solution of malachite green is not so fast to washing and is of low intensity. 3. The color of cotton cloth dyed indirectly by using mordant and then by dipping in hot solution of malachite green is fast to washing and is of high intensity.
BIBLIOGRAPHY 1. Comprehensive practical chemistry (class 12) 2. www.wikipedia.org/wiki/Dyeing 3. www.idocpub.com