1. Dye: Colorant which is homogeneously dispersed in the dye medium
Usually soluble
Naturally occurring or synthetic organics

2. Pazyryk carpet (Siberia) 5th century BC
Peruvian textile B.C.

3. Medieval Guilds of Master Dyers
Formed in Germany in the 12th century
Apprentice system
Dye recipes were heavily guarded secrets

4. Development of Trade Routes
Textile trade
beginnings in 2,000 B.C.
the “Silk Road”
sea routes from the Americas (15th century)
East India Trading Company (17th century)
Exchange of not only textiles but also designs, ideas and dyestuffs
China Europe

5. Three Classes of Natural Dyes
Substantive dyes
Easiest to apply to fibers
No need to use other substances to enhance dyeing
Vat dyes
Involve chemical change of dye through “fermentation” or “chemical reduction” to make it soluble
Adjective dyes (Mordant dyes)
Require another chemical to develop color and “fix” it to the fiber

6. Dyes from Snails Tyrian Purple or “Royal Blue”
9000 snails to obtain 1 g of dye
Used primarily before 8th century A.D. to dye wool and silk
Chemically it is 6,6’-dibromoindigo

7. Dyes from Bugs Kermes — the most ancient dye in Europe
70,000 female oak beetles produce 1 pound dye
Cochineal — Mexico and Central America
Mexican cactus beetle

8. Kermes, Cochineal — Carmine
Chemically similar structure, light sensitive
Dyed wool and silk — “carmine red”

9. Dyes From Plants Indigo — used since 2000 B.C. Woad
Extracted from Indigofera tinctoria
“Navy Blue” of English sailors
Blue jeans
Insoluble in water
Must be chemical reduced to soluble leucoindigo to use as dye
Woad
Member of the mustard family
A common weed in temperate climates
Leaves contain same chemical as indigo but in lower amounts
Celtic war paint and tattoos
Braveheart
Blue robes of priests

10. More Dyes From Plants Madder — “Turkey Red”
Root of madder plant found in Europe and Asia
Prepared as a “lake” with Al(OH)3
British “Redcoats”
Alexander the Great used it to simulate blood
Chemically — Alizarin and Pupurin
Synthetic alizarin prepared in 1875

11. Methods of Application
Dye and Substrate can interact through ionic forces 2. hydrogen bonding 3. van der Waals forces 4. covalent bonds
Dye
Substrate

12. Types of Dyes by Application
Acid Dyes
Basic Dyes
Mordant Dyes
Direct Dyes
Fiber-reactive Dyes
Vat Dyes

13. Functional groups for acidic and basic dyes
-ROOH acid sulfonic acid, carboxylic acid
-NH2 amine base
Acid + base = salt
(+) (-)
-NH OOH  NH ROO–
from base from acid

14. Acid Dyes Fiber DYE SO3- Sulfonic acid group NH3+ Basic amine group
Acidic dye (-) (+) Basic fiber
DYE
SO3-
Sulfonic acid group
Fiber
NH3+
Basic amine group
Wool, silk, nylon have amine groups

15. Basic Dyes Fiber Basic Dye (+) (-) Acidic Fiber DYE NH3+
Basic amine group
Fiber
-OOC
Carboxylic acid group
Wool, silk, leather, acrylic fibers have carboxylic acid groups

16. Mordant Dyes Have no natural affinity for fiber
Must use a “mordant” to link dye and fiber
Dye
Fiber
Mordant
salts of Fe2+, Sn2+, Cr3+, and Cu2+
hydroxides of Al, Mg, Ca, and Ba
tannic acid

17. Direct Dyes Fiber Polar dye Polar Fibers
Dye applied from a hot water solution
DYE N
Fiber HO H
Polar group
Hydrogen Bond
Cotton and cellulose-based fibers
Synthetic dyes

18. Fiber-Reactive Dyes Covalently bonded to fibers R—C—O—fiber
R—C—S—fiber
R—C—NH—fiber
Developed in 1950’s
Used primarily on cellulosic and protein fibers

19. Color Centers in Organic Dyes
CHROMOPHORES — “color bearer” structural part of colored molecule which is responsible for its color
Conjugated double bond systems
Aromatic rings
Azo groups —N=N—
Carbonyl groups —C=O
Quinoid rings

20. AUXOCHROMES —NH2 —OH —OR “color augmenting” groups
functional group with non-bonded electrons which acts to strengthen or deepen the color and hue
—NH2 —OH —OR

21. AZO Dyes first prepared in 1863 R—N = N—R
Have widest range of colors of all dyes
Contain the AZO Chromophore
Generally lightfast
R—N = N—R
Azo group
Brilliant colors ranging from reds to blues
Methyl orange, Orange II, etc.

22. Orange II and Methyl Orange
Both are azo dyes
Azo Group HO HO 3 S
N=N
(CH 3 ) 2 N
N=N SO 3 - Na +
Orange II
Methyl Orange

23. FD & C Food Colors Yellow No. 6 Red No. 40 FD&C Red No. 40 Allura RedNa +- O 3 S
OCH CH
N = N HO SO - +
FD&C Red No. 40
Allura Red

24. CARBONYL Dyes Anthroquinone Dyes Originate from plants
Contain several —C =O groups
Multiple aromatic rings
Originate from plants
Coloring agents in flowers, fruits, vegetables

25. QUINOIDS
Naphthaquinone
Anthraquinone
Red plant dyes and insect dyes

26. Alizarin, Cochineal, Kermes
All are anthraquinone-based carbonyl dyes O OH CH 3 CO 2 H HO
Cochineal
Kermes
Alizarin

27. FLAVONOIDS Structure of yellow plant dyes
Luteolin (weld or Dyers Weed) OH HO O OH
Quercitin (Oak bark) OH OH O

28. Indigo — a Carbonyl Vat Dye
Indigo is insoluble in water
Must be chemical reduced to leucoindigo
Leucoindigo is soluble
Used to dye cellulose fibers

29. TRIPHENYLENE Dyes
Three aromatic rings attached to the same carbon atom C
FD&C Blue 2

30. Fiber-Reactive Dye Structure
Chromophore
Reactive group
Leaving group
Mono chlorotriazinyl dye
Procion Scarlet H-R, Cibacron Scarlet RP, Chlorine Reactive Red 3

31. Dichlorotriazinyl Dye
Higher reactivity than monochloro dyes
Procion Brillian Yellow M-6G, CI Reactive Yellow 1

32. Fastness in Dyes Stability of dyes towards light
Dyes vary greatly in their lightfastness and colorfastness
Undergo photo-oxidation and photo-reduction by light — dyes fade and degrade

33. Effects of Chemicals on Dyes
H2O HCl NaOH CaCl2 Chlorox Na2S2O4
Madder
Cochineal
Orange II
Methyl orange

34. Mauvine