Dyes and pigments

Dyes are colored organic compounds that are used to impart color to various substrates, including paper, leather, fur, hair, drugs, cosmetics, waxes, greases, plastics and textile materials.
whereas pigments are organic and inorganic materials which are practically insoluble in medium in which they are incorporated.

1. 1 Dyes & Pigments Ihsan Ali Wassan Chemical Engineering Department Presented By: Quaid-e- Awam University of Engineering, Science & Technology, Nawabshah, Sindh, Pakistan

2. 2 Presentation Outlines Introduction Classification Properties Comparison Applications Dyes & Pigments

3. 3 Dyes

4. Dyes are colored organic compounds that are used to impart color to various substrates, including paper , leather , fur , hair , drugs , cosmetics , waxes , greases , plastics and textile materials . A Dye is a colored compound, normally used in solution, which is capable of being fixed to a fabric . The dye has a colour due to the presence of chromophore and its fixed property to the acid or basic groups such as OH,SO 3 H, NH 2 , NR 2 , etc . The polar auxochrome makes the dye water-soluble and binds the dye to the fabric by interaction with the oppositely charged groups of fabric structure. 4 Introduction

5. Properties of Dye To be of use, dyes must possess the following four properties: 1 .  Colour 2.  Solubility in water 3. Ability to be absorbed and retained by fibre (substantivity) or to  be chemically  combined with it (reactivity).  4.  Ability to withstand washing, dry  cleaning  and exposure to  light . 5

6. Classification of Dye There are several ways for classification of dyes. Some of the prominent ways of classification are: Classification based on the source of materials classification of the Dyes- Based on the nature of their respective chromophores. 6

7. Classification based on the source of materials A very common classification of the dyestuff is based on the source from which it is made. Accordingly the classification could be:  Natural Dyes  Synthetic Dyes 7

8. Natural Dye Natural dyes are dyes or colorants derived from plants, invertebrates, or minerals. The majority of natural dyes are vegetable dyes from plant sources. E.g. roots, berries, bark, leaves, and wood. Other organic sources include fungi and lichens. 8

9. Synthetic Dyes Almost all the colors that you see today are Synthetic dyes. Synthetic dyes are used everywhere in everything from clothes to paper, from food to wood. This is because  they are cheaper to produce, brighter, more color-fast, and easy to apply to fabric. E.g. Acid Dyes, Azo Dyes, Basic Dyes, Mordant Dyes, etc 9

10. Classification based on the Chromophore present Dyes may be classified according to the type of chromophores present in their structures. Nitro and Nitroso Dyes Azo Dyes Anthraquinone Dyes Indigo dyes 10

11. Nitro and Nitroso Dyes These dyes contain nitro or nitroso groups as the chromophores and – OH  as auxochrome. A few examples are: 11 Naphthol yellow S Mordant green 4

12. Azo Dyes Azo dye is a large class of synthetic organic dyes that contain nitrogen as the azo group −N=N− as primary chromophore their molecular structures. These dyes are highly coloured and are prepared by diazotizing an aromatic amine and coupling with suitable aromatic compound . Azo dyes account for approximately 60-70% of all dyes used in food and textile manufacture.  12 Para Red Methyl Orange

13. Anthraquinone Dyes Anthraquinone dye,   any of a group of organic dyes having molecular structures based upon that of anthraquinone.  Alizarin is the main ingredient for the manufacture of the madder lake pigments known to painters as Rose madder and Alizarin crimson. Alizarin is also used commercially as a red textile dye. 13 Alizarin

14. Indigo Dyes Indigo dye is an organic compound with a distinctive blue color Historically, indigo was a natural dye extracted from plants. But today nearly all indigo dye is produced synthetically. It contains carbonyl chromophore . The primary use for indigo is as a dye for cotton yarn, which is mainly for the production of denim cloth for blue jeans  Small amounts are used for dyeing  wool  and silk. 14 Indigo

15. 15 Pigments

16. Pigment is derived from word “ pigmentum ” means coloring matter . Pigments are organic and inorganic materials which are practically insoluble in medium in which they are incorporated. Pigments are used almost 30,000 years ago . About 2000 BC natural ocher was burnt sometime in mixture with manganese ore to produce red, violet and black pigments for pottery. 16 Introduction The first synthetic pigment was Prussian blue which was synthesized in 1704.

17. Classification of Pigments 17

18. Organic pigments are based on carbon chains and carbon rings . However, they can also contain metallic (inorganic) elements that help stabilize the properties of the organic component.  Examples: Azo pigments Polycyclic pigments Anthraquinone pigments Triayl carbonium pigments 18 Organic Pigments

19. Inorganic pigments, chemical compounds not based on carbon, are usually metallic salts precipitated from solutions.  19 Inorganic Pigments Examples: White pigments Black pigments Special pigments Color pigments

20. 20 Ultramine Pigments

21. 21 Iron Oxide Pigments

22. 22 Cadmium Pigments

23. Difference between Organic & Inorganic Pigments No. Organic pigments  Inorganic pigments  1 These are natural pigments like the Cadmiums, Cobalts, Earth Colors, etc. These are pigments created in the laboratory and include the Pthalocyanines , Quinacidrones , Dioxazenes , Napthols , etc. 2 The main source of organic pigments are plants and plant products The inorganic pigments are manufactured from topical cosmetic and also from dirt . 3 Carbon chains or carbon rings are always present in the molecules of the Organic Pigments. In the molecules of the Inorganic Pigments, the cat-ions of metal are found in an array form with the non-metallic anions. This arrangement doesn't allow these pigments to dissolve in the solvent and plastic 4 have a high refractive index have much lower values 5 most inorganic pigments are opaque organic pigments are transparent 23

24. A ttributes of Pigments Lightfastness and sensitivity for damage from ultra violet light. Heat stability. Toxicity. Tinting strength. Staining. Dispersion. Opacity or transparency. 24

25. No auxochrome group. No direct affinity towards textile materials. Binder is required for fixation. Applicable to all kinds of fibers or textile materials. Rubbing fastness is poor. Water, wash and light fastness is very good . Insoluble in water & other solvents like white spirit, per chloroethylene, trichloroethylene, CCl4 etc. Most of the pigments are azoic compounds. Besides that it may be inorganic oxide, inorganic salt phthalocyanine metal compounds etc. Pigments are toxic. Some are oral toxic, some are dermal toxic, some causes eye irritation etc. Properties of Pigments Particle size : 0.2-0.4 µ Specific gravity : 1.14-1.37 Boiling points : 190- 345℃ Melting points : 110-175 ℃ 25

26. Pigments are used for coloring of leather , building materials , paper , floor covering , ceramic glazes , paint , ink , plastic , fabric , cosmetics , food , and other materials.     26 Applications of Pigments

27. DYES PIGMENTS 1. Water solubility is 70% 1. 100% water insoluble 2. Dyes have direct affinity to textile material 2. They have no direct affinity to textile materials 3. Auxochrome groups are present 3. Auxochrome groups are absent 4. Most of the dyes are organic 4. Most of dyes are inorganic 5. Costly 5. Cheap 6. No binding agent is required 6. Binding agent is required 7. Dye diffusions in the fabric 7. Pigment diffusions on the fabric Difference between Dyes & Inorganic Pigments 27

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29. 29 Thanks