Dyes & Pigments
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Presentation Outlines
Dyes & Pigments

Introduction

Classification

Properties

Comparison

Applications
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Dyes
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Introduction
 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,SO3H, NH2, NR2, 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.
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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.
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Classification of Dye
There are several ways for classification of dyes. Some of the prominent ways of
classification are:
1.
Classification based on the source of materials
2.
classification of the Dyes- Based on the nature of their respective chromophores.
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Classification based on the source ofmaterials
 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
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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.
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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
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Classification based on the Chromophore present
 Dyes may be classified according to the type of chromophores present in their
structures.
1. Nitro and Nitroso Dyes
2. Azo Dyes
3. Anthraquinone Dyes
4. Indigo dyes
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Nitro and Nitroso Dyes
 These dyes contain nitro or nitroso groups as the chromophores and –OH as
auxochrome.
 A few examples are:
Naphthol yellow
S
Mordant green
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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.
Para Red
Methyl
Orange
 Azo dyes account for approximately 60-70% of all dyes used in food and textile
manufacture.
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Anthraquinone Dyes
 Anthraquinone dye, any of a group of organic dyes having molecular structures based
upon that of anthraquinone.
Alizari
n
 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.
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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.
Indig
o
•
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.
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Pigments
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Introduction
 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.
The first synthetic pigment was Prussian blue which was
synthesized in 1704.
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Classification of Pigments
Pigment
Organic Pigments
Polycyclic
pigments
Azo
Pigments
Anthraquinone
pigments
Inorganic Pigments
Triayl carbonium
pigments
White Pigments
Ultramine
Coloured
Pigments
Cadmium
Iron oxide
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Organic Pigments
 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
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Inorganic Pigments
 Inorganic pigments, chemical compounds not based on carbon, are usually metallic salts
precipitated
from solutions.
Examples:
 White pigments
 Black pigments
 Special pigments
 Color pigments
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Ultramine Pigments
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Iron Oxide Pigments
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Cadmium Pigments
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Attributes of Pigments

Lightfastness and sensitivity for damage from ultra violet
light.

Heat stability.

Toxicity.

Tinting strength.

Staining.

Dispersion.

Opacity or transparency.
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Properties of Pigments
 No auxochrome group.
 No direct affinity towards textile materials.
 Binder is required for fixation.
 Applicable to all kinds of fibers or textile
materials.
 Particle size
: 0.2-0.4 µ
 Specific gravity : 1.14-1.37
 Boiling points : 190- 345℃
Melting points :110-175℃
 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.
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Applications of Pigments
Pigments are used for coloring of leather, building materials, paper, floor covering,
ceramic
glazes, paint, ink, plastic, fabric, cosmetics, food, and other materials.
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Difference between Dyes & InorganicPigments
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
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