GATE Textile Engineering Chemical Processing Syllabus

Chemical Processing syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Chemical Processing in GATE Textile Engineering, not a summary of it.

1. 1

   Impurities in Natural Fibre

   1 topic

   • Singeing
2. 2

   Preparatory Processes for Cotton

   1 topic

   • Chemistry and Practice
3. 3

   Preparatory Processing of Wool and Silk

   overview

   Examined as a single unit within Chemical Processing — no further topic split in the official outline.

4. 4

   Mercerization of Cotton

   overview

   Examined as a single unit within Chemical Processing — no further topic split in the official outline.

5. 5

   Preparatory Processes for Manmade Fibres and Their Blends

   overview

   Examined as a single unit within Chemical Processing — no further topic split in the official outline.

6. 6

   Optical Brightening Agent

   overview

   Examined as a single unit within Chemical Processing — no further topic split in the official outline.

7. 7

   Classification of Dyes

   1 topic

   • Dyeing of Cotton
8. 8

   Dyeing of Wool, Silk, Polyester, Nylon, and Acrylic

   overview

   Examined as a single unit within Chemical Processing — no further topic split in the official outline.

9. 9

   Dyeing of Polyester/Cotton and Polyester/Wool Blends

   overview

   Examined as a single unit within Chemical Processing — no further topic split in the official outline.

10. 10

    Dyeing Machines

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

11. 11

    Dyeing Processes and Machines for Cotton Knitted Fabrics

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

12. 12

    Dye-Fibre Interaction

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

13. 13

    Introduction to Thermodynamics and Kinetics of Dyeing

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

14. 14

    Relation Between Colour and Chemical Constitution

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

15. 15

    Beer-Lambert’s Law

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

16. 16

    Kubelka-Munk Theory and Its Application in Colour Measurement

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

17. 17

    Methods for Determination of Wash, Light, and Rubbing Fastness

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

18. 18

    Methods of Printing

    1 topic

    • Roller Printing
19. 19

    Screen Printing

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

20. 20

    Preparation of Printing Paste

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

21. 21

    Various Types of Thickeners

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

22. 22

    Printing Auxiliaries

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

23. 23

    Direct Styles of Printing

    3 topics

    • Cotton with Reactive Dyes
    • Wool, Silk, Nylon with Acid and Metal Complex Dyes
    • Polyester with Disperse Dyes
24. 24

    Resist and Discharge Printing

    1 topic

    • Cotton, Silk, Polyester
25. 25

    Pigment Printing

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

26. 26

    Transfer Printing of Polyester

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

27. 27

    Inkjet Printing

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

28. 28

    Printing Faults

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

29. 29

    Mechanical Finishing of Cotton

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

30. 30

    Stiff, Soft, Wrinkle Resistant, Water Repellent, Flame Retardant, and Enzyme (Bio-Polishing) Finishing of Cotton

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

31. 31

    Milling, Decatizing, and Shrink Resistant Finishing of Wool

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

32. 32

    Antistatic and Soil Release Finishing

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

33. 33

    Heat Setting of Synthetic Fabrics

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

34. 34

    Minimum Application Techniques

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

35. 35

    Pollution Control and Treatment of Effluents

    overview

    Examined as a single unit within Chemical Processing — no further topic split in the official outline.

Chemical Processing flashcards for GATE Textile Engineering

19 of 51 cards from the Chemical Processing deck — real questions with worked answers.

1. What is singeing in textile chemical processing?

   Singeing is a preparatory process in which protruding fibres on the surface of yarn or fabric are burnt off by passing the material rapidly over a gas flame or a heated plate, producing a smooth, clean surface, better lustre, and improved suitability for dyeing and printing.

2. Why is singeing carried out before dyeing and printing rather than after?

   Singeing removes surface hairiness that would otherwise cause uneven dye uptake, frosting, and poor print sharpness. Done early in preparation, it ensures a smooth surface so subsequent dyeing/printing gives clear, level, defect-free results.

3. Name the main types of singeing machines used industrially.

   The main types are gas (flame) singeing machines, plate singeing machines (fabric passes over a heated curved copper plate), and rotary-cylinder singeing machines (fabric contacts a heated rotating roller). Gas singeing is the most common for woven cotton goods.

4. What process immediately follows singeing to extinguish sparks, and why is it needed?

   Desizing (often after a quench/water bath or steam) follows singeing; the fabric is passed through water or a desizing liquor immediately to extinguish any afterglow or sparks that could burn holes, and to begin removing size from the warp yarns.

5. What is the purpose of the desizing step in cotton preparation?

   Desizing removes sizing agents (typically starch) applied to warp yarns for weaving. Removal is necessary because size is hydrophobic/insoluble and would resist scouring, bleaching, dyeing, and finishing, causing uneven absorbency and dye uptake.

6. What is mercerization and what are its main benefits to cotton?

   Mercerization is treatment of cotton with strong cold caustic soda ($\ce{NaOH}$, ~18–26%) under tension. It causes fibre swelling and deconvolution, giving increased lustre, higher tensile strength, greater dye uptake, and improved dimensional stability.

7. Define substantivity (direct affinity) of a dye for a fibre.

   Substantivity is the inherent attraction or affinity a dye has for a fibre from solution, i.e. the tendency of the dye to leave the dyebath and be taken up (exhausted) by the fibre under given conditions without the help of fixing chemicals.

8. What is meant by the exhaustion of a dyebath, and how is it expressed?

   Exhaustion is the fraction of dye transferred from the dyebath onto the fibre. It is expressed as $$E = \frac{C_{0} - C_{t}}{C_{0}} \times 100\%$$ where $C_{0}$ is the initial dye concentration and $C_{t}$ the concentration remaining in the bath at time $t$.

9. Define the material-to-liquor ratio (MLR) in dyeing.

   The material-to-liquor ratio is the ratio of the mass of textile material to the mass (or volume) of dye liquor in the bath, e.g. $1:20$ means 1 kg of fabric in 20 L of liquor. A lower (shorter) liquor ratio improves exhaustion and saves water/energy.

10. Which class of dyes is the principal class used for dyeing cotton with high wash-fastness through covalent bonding?

    Reactive dyes are the principal class; they form a covalent bond with the cellulose hydroxyl groups, giving high wash-fastness combined with bright shades.

11. What chemical bond forms between a reactive dye and cotton, and to which group of cellulose does it bond?

    A covalent bond forms between the reactive dye and the hydroxyl ($\ce{-OH}$) groups of cellulose. The cellulosate anion ($\ce{Cell-O^-}$), formed under alkaline conditions, attacks the reactive group of the dye.

12. What are the two main reaction mechanisms by which reactive dyes bond with cellulose?

    The two mechanisms are: (1) nucleophilic substitution (e.g. dichlorotriazine and other triazinyl dyes, where a chlorine is displaced), and (2) nucleophilic addition across a double bond (e.g. vinyl sulphone dyes formed from sulphatoethylsulphone groups).

13. Write the activation reaction of a vinyl sulphone reactive dye before it bonds with cellulose.

    Under alkali, the $\beta$-sulphatoethylsulphone group eliminates to form the reactive vinyl sulphone: $$\ce{Dye-SO2-CH2-CH2-OSO3Na ->[OH^-] Dye-SO2-CH=CH2 + NaHSO4}$$

14. What is the unwanted side reaction of reactive dyes in the dyebath, and what does it produce?

    Hydrolysis is the unwanted side reaction: water (as hydroxide) competes with cellulose for the reactive group, producing hydrolysed dye that cannot bond to the fibre. This lowers fixation efficiency and must be washed off, requiring extensive rinsing/soaping.

15. Why is salt (electrolyte) added when dyeing cotton with reactive dyes?

    Salt ($\ce{NaCl}$ or $\ce{Na2SO4}$) is added to suppress the negative surface (zeta) potential of cellulose, reducing dye-fibre electrostatic repulsion (since both are anionic) and promoting exhaustion/migration of the anionic dye onto the fibre.

16. Why is alkali (soda ash/caustic) added in reactive dyeing of cotton, and at what stage?

    Alkali is added after exhaustion, in the fixation stage. It ionizes cellulose to the more nucleophilic cellulosate anion and activates the dye, driving covalent bond formation (fixation) between dye and fibre.

17. Classify reactive dyes as 'cold brand' versus 'hot brand' based on reactivity.

    Cold-brand (high-reactivity) dyes, e.g. dichlorotriazine types, fix at low temperature (~30–40 °C) with mild alkali. Hot-brand (low-reactivity) dyes, e.g. monochlorotriazine types, require higher temperature (~80–90 °C) and stronger alkali for fixation.

18. What does the reactive dye fixation efficiency depend on, expressed as a ratio?

    Fixation efficiency is the proportion of applied dye covalently bonded to the fibre: $$F = \frac{\text{dye fixed on fibre}}{\text{total dye applied}} \times 100\%$$ It depends on the competition between the dye–cellulose reaction and dye hydrolysis.

19. What class of dye is most widely used for ordinary (economical) cotton dyeing with simple application but moderate wash-fastness?

    Direct (substantive) dyes are widely used; they are applied from a neutral or slightly alkaline bath with salt, are simple and economical, but have only moderate wash-fastness unless after-treated.

See more Chemical Processing flashcards →

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Chemical Processing (GATE Textile Engineering) FAQ