-
8/14/2019 Dye and Dying
1/8
Dye And
Dyeing
-
8/14/2019 Dye and Dying
2/8
Compounds that absorb one or
more wavelengths of visible lightappear colored to the human
eye.White light possesses all
wavelenghts of visible light. Whena beam of white light strikes
acolored surface,certainwavelengths are absorbed and
others are reflected,we see what isreflected.
-
8/14/2019 Dye and Dying
3/8
what structural features cause anorganic molecule to
appearcolored?
The compound has a chromophoregroup ( a chemical group of
selectivelight absorption resulting in coloration of
certain organic compounds,also calledcolor radical)
There is an extensive network of
alternating single and double bonds(conjugation) of which the
chromophoreis a part.
-
8/14/2019 Dye and Dying
4/8
For a compound to be a dye,it must not onlyshow color,it must
also be able to adhere to afabric. Auxochrome is a chemical group
within
a dye molecule by which the dye is bound toreactive end group in
tissues. The auxochromeenhances the intensity of absorption.
-
8/14/2019 Dye and Dying
5/8
Classification of dyes
DIRECT DYES
Any of a class of coloured,water-soluble compounds
that have an affinity for fiber and are taken up directly,such
asthe benzidine derivatives. Direct dyes are usually cheap and
easily applied,and they can yield bright colours. Washfastnessis
poor but may be improved by after treatment. Silk andwool,can be
colored simply by being dipped in the dye (thedyes so used are
consequently called direct dyes).
-
8/14/2019 Dye and Dying
6/8
MORDANT DYES
Dyes which require a mordant in theirapplication and which upon
combination with
the mordant deposit insoluble color on thesubstrate. e.g.,dyes
with metal chelatinggroups. Mordants are substances of organic
orinorganic origin which combine with the
coloring matter and are used to fix the same inthe production of
the color. For the purpose ofthis class,such materials as oils and
sulfonatedoils, soaps, fats and higher acids,are notgenerally
considered as mordants.
-
8/14/2019 Dye and Dying
7/8
REACTIVE DYES
Fiber reactive dyes are textile dyes whichform a covalent bond
with the fibers of thetextile,resulting in a long lasting,bright
dye.
-clothing colored with reactive dyes will notbleed in washing or
fade.unless exposed tobright light.
INGRAIN DYE
A colourant which is formed in suit in thesubstrate by the
development and coupling ofone or more intermediate compounds.
-
8/14/2019 Dye and Dying
8/8
VAT DYE
Dyes such as indigo,that produces a fastcolor by impregnating
fiber with a reduced
soluble form that is then oxidized to aninsoluble form. Applied
by reducing the dye to abase-soluble form,applying the
dye,theregenerating the insoluble dye by oxidation in
he material,used for dyeing cotton using Vat orbuckets. It can
be performed whenever aliquid,even shade over the entire garment
isdesired.
