Pigmentation

1. PIGMENTS

2. INTRODUCTION
Pigment is derived from word “pigmentum” means coloring matter. DEFINE:
In terms of physics:
“A material that changes the colour of reflected or transmitted
light as a result of wavelength selective absorption”.
In terms of chemistry:
“Pigment means a substance consisting of small particles that
is practically insoluble in the applied medium and is used on
account of its coloring, protective, or magnetic properties”.

3. PIGMENTS
International Definition
by CPMA
Pigments are colored, black, white or fluorescent particulate organic
or inorganic solids which usually are insoluble in, and essentially
physically and chemically unaffected by, the vehicle or substrate in
which they are incorporated.
They alter appearance by selective absorption and/or by scattering
of light.
Pigments are usually dispersed in vehicles or substrates for
application, as for instance in the manufacture or inks, paints, plastics
or other polymeric materials.
Pigments retain a crystal or particulate structure throughout the
coloration process.

4. Dyes are intensely colored or fluorescent organic substances
only, which impart color to a substrate by selective absorption of
light.
They are soluble and/or go through an application process
which, at least temporarily, destroys any crystal structure by
absorption, solution, and mechanical retention, or by ionic or
covalent chemical bonds.
(defined by ETAD The Ecological and Toxicological Association of Dyes
and Organic Pigment Manufacturers)

5. Both pigments and dyes are included in the general term “coloring
materials”, which denotes all materials used for their coloring properties.
The characteristic that distinguishes pigments from soluble organic
dyes is their low solubility in solvents and binders.

6. Classification of pigments
1. Classified by Chemical Structure

8. Organic pigments Inorganic pigments
Azo pigments Titanium dioxide white
Monoazo yellow and orange Carbon and vegetable black
Diazo Iron oxide
Naphthol Cadmium
Naphthol AS Lead chromate
Azo lakes Chromium oxide green
Diazo condensation Ultramarine blue
Metal complex Iron blue
Anthraquinone Chrome green
Polycyclic pigments Phthalo chrome green
Thioindigo Mixed metal oxide
Dioxazine pigments Bi-vanadate
Triayl carbonium pigments Manganese oxide (MnO)

9. Inorganic pigments Organic pigments
Varieties of chromatography Less variety, narrow spectrum More varieties, wider spectrum
Color characteristics lower brightness, dark Higher Brightness
Tinting strength low color strength High color strength
Special dosage forms less
A variety of commercial
formulations
Heat resistance Most are higher
Generallylow, high-
performance varieties have
excellent heat resistance
Durability (light and weather
resistance)
Most varieties are higher
High-performancevarieties
excellent durability
Acid and alkali resistance
Some species discoloration
decomposition
Preferably, excellent
Solvent resistance excellent Medium to fine
Toxicity (heavy metals)
Some varieties of high toxicity
(lead, chromium, mercury, etc.)
Non-toxic, low toxicity
Cost Lower Higher
Comparison
of
organic
and
inorganic
pigments

10. 2. Classified by Chromatography
Pigment can be divided into red, yellow, blue, green, orange,
violet, white, black, brown pigment, they are not all independent of
each other.
There is a certain internal relationship between colors, a color
is determined by three parameters, which are hue, chroma, value.
Dimension Definition
Hue Name of a color family
Value Lightness or darkness of a color
Chroma Strength or intensity of a color

11. Here the Hue is purple.
There are 60+ colors here, but all of them are
purple-hued colors.
Chroma changes from left-to-right
Low chroma colors are on the left... mid-
chroma colors near the center...
high chroma colors on the right.
Value changes from bottom-to-top:
Low values (shades) near the bottom
High values (tints) near the top.

12. 3. Classified by Application
Pigment can be divided into ink, paint, plastic and other pigments.
4. Classified by Color Index
The famous “Color Index” Color Index is a color classification method, pigment is classified
into pigment yellow (PY), pigment orange (PO), pigment red (PR), pigment violet (PV),
Pigment Green (PG), Pigment Brown (PBr), Pigment Black (PBk), Pigment White (PW), Metal
Pigment (PM) according to Color Index.

14. Classification of inorganic pigments.
White pigments:
The optical effect is caused by nonselective light scattering (examples: titanium dioxide and zinc
sulfide pigments, lithopone, zinc white).
Colored pigments:
The optical effect is caused by selective light absorption and also to a large extent by selective
light scattering (examples:iron oxide red and yellow, cadmium pigments, ultramarine pigments,
chrome yellow, cobalt blue)
Black pigments:
The optical effect is caused by nonselective light absorption (examples: carbon black pigment,
iron oxide black)
Effect pigments:
The optical effect is caused by regular reflection or interference.

15. Metal effect pigment:
Regular reflection takes place on mainly flat and parallel metallic pigments particles e.g. aluminum flakes)
Pearl luster pigment:
Regular reflection takes place on highly refractive parallel pigment platelets e.g. titanium dioxide on mica)
Interference:
The optical effect of colored luster pigments is caused wholly or mainly by the phenomenon of interference
(e.g. iron oxide on mica)
Luminescent Pigments :
The optical effect is caused by the capacity to absorb radiation and to emit it as light of a longer
wavelength.
Fluorescent :
The light of longer wavelength is emitted after excitation without a delay (e.g. silver-doped zinc sulfide).
Phosphorescent pigments:
The light of longer wavelength is emitted within several hours after excitation (e.g. copper-doped zinc
sulfide)

18. SELECTION OF A PIGMENT
In general the following properties of the pigments are important in selecting a
pigment for any particular product.
a) Hiding power
b) Tinting strength
c) Refractive index
d) Light fastness
e) Bleeding Characteristics
f) Particle size and shape

24. Applications of pigments:
There are many applications of pigments.
 Pigments are used for coloring of leather, building materials, paper, floor
covering and ceramic glazes.
 Pigments are used for coloring paint, ink, plastic, fabric, cosmetics, food and
other materials.
 Most pigments used in manufacturing and the visual arts are dry colorants,
usually ground into a fine powder. This powder is added to a vehicle (or
binder), a relatively neutral or colorless material that suspends the pigment
and gives the paint its adhesion.

25. Chemical engineering aspects of pigments and dyes synthesis made essential
part in development applied in chemical technology operations and constructions of
specialist apparatuses.
Besides their traditional use in textile, leather, paper, as well as the paint and
varnish industries, dyes and pigments have become indispensable in other fields
such as microelectronics, medical diagnostics and information recording techniques
and they continue to be intensively developed.