Textiles Technology — Exercise Solutions
Key Concepts Quick Recap
| Process | Description | Input/Output |
|---|
| Ginning | Separation of cotton lint from seed | Seed cotton → lint + seeds |
| Carding | Aligns fibres, removes short fibres, neps | Lap → Card sliver |
| Combing | Removes short fibres, produces parallel fibres | Card sliver → Combed sliver |
| Drawing | Attenuates and blends slivers | Multiple slivers → One drawn sliver |
| Spinning | Drafts and twists roving → yarn | Roving → Yarn |
| Weaving | Interlaces warp and weft yarns | Yarns → Fabric |
| Knitting | Interlooping yarns | Yarn → Knit fabric |
| Dyeing | Colouring fibres/yarn/fabric | Colourless → Coloured |
| Finishing | Final treatments (softening, anti-wrinkle) | Grey fabric → Finished fabric |
I. Choose the Best Answer (MCQs)
1. The process of separating cotton fibre from its seed is called: (a) Carding (b) Ginning (c) Combing (d) Drawing
Answer(b) Ginning Cotton ginning: carried out at cotton gin. Whitney's gin (1793) mechanised ginning. Output: lint (seed cotton) and seeds (used for cottonseed oil).
2. Carding produces: (a) Yarn (b) Card sliver (c) Roving (d) Finished fabric
Answer(b) Card sliver Carding: fibres opened and disentangled by wire-covered rollers → removes short fibres, neps (fibre knots) → card sliver (loose rope of parallel fibres).
3. In the ring spinning system, the twist in yarn is imparted by: (a) Carding cylinder (b) Ring and traveller (c) Drafting rollers (d) Bobbin winder
Answer(b) Ring and traveller Ring spinning: roving fed through drafting rollers → twisted and wound onto bobbin by ring-and-traveller system. Traveller rotates on the ring → each revolution = one twist.
4. The warp yarns in a woven fabric run: (a) Horizontally (crosswise) (b) Vertically (lengthwise, parallel to selvage) (c) Diagonally (d) In loops
Answer(b) Vertically (lengthwise, parallel to selvage) Warp: lengthwise yarns, parallel to selvage (finished edge of fabric). Weft: crosswise yarns, perpendicular to selvage. Memory aid: warp = vertical → "warp" rhymes with "length."
5. Reactive dyes are most suitable for: (a) Polyester (b) Nylon (c) Cotton and other cellulosic fibres (d) Wool
Answer(c) Cotton and other cellulosic fibres Reactive dyes: form covalent bonds with cotton fibre → excellent wash-fastness. Used for: cotton, linen, viscose rayon. Disperse dyes: polyester. Acid dyes: wool, silk, nylon.
6. Mercerisation is a finishing process applied to: (a) Wool (b) Silk (c) Cotton (d) Polyester
Answer(c) Cotton Mercerisation (John Mercer, 1844): cotton treated with caustic soda (NaOH) under tension → fibre swells → becomes more lustrous, stronger, and more dye-absorbent. Mercerised cotton: shinier, silky appearance.
7. The tensile strength of a yarn is measured in: (a) g/denier or N/tex (b) cm/gram (c) Twist per meter only (d) Micronaire value
Answer(a) g/denier or N/tex Tenacity (tensile strength per unit linear density): g/denier or cN/tex. Higher value = stronger yarn for its weight. Used for specification and quality control.
II. Short Answer Questions
Q1. Describe the cotton spinning process from opening to yarn.
Answer
The short-staple spinning sequence:
1. Blow room: Raw cotton (with seeds, dust, leaves) → opened, cleaned. Output: lap (sheet of fibres).
2. Carding: Lap fed to carding machine → wire-covered cylinders disentangle fibres → removes short fibres (<12mm) and neps → card sliver.
3. Combing (for combed yarn): Further removes short fibres (noils) and straightens fibres → combed sliver with superior parallelism. Combed yarn: finer, smoother, stronger.
4. Drawing: 6-8 slivers doubled and drawn (attenuated) to one → blending and straightening.
5. Roving: Drawn sliver → slightly twisted, wound on bobbin.
6. Ring spinning: Roving drafted further → twisted and wound on cop. Ring and traveller impart twist.
7. Winding: Yarn wound from cop to cone for further processing.
Q2. What are the types of fabric weaves?
Answer
1. Plain weave: Each weft yarn passes over one warp, then under one warp, alternating. Simplest, most common. Examples: muslin, organdie, taffeta. Firm but not very strong.
2. Twill weave: Weft passes over 2-3 warp yarns, creating diagonal ribbing (twill line). Strong, heavy. Examples: denim, gabardine, drill, khaki.
3. Satin weave: 4-8 warp yarns float over weft. Lustrous surface (minimises intersections). Smooth but less durable. Examples: satin, sateen.
4. Dobby weave: Small, geometric patterns woven by dobby mechanism.
5. Jacquard weave: Complex patterns controlled by jacquard mechanism; each warp controlled individually. Examples: brocade, damask, tapestry.
Exam Checklist
- Ginning → carding → (combing) → drawing → roving → ring spinning → winding.
- Carding: removes short fibres, produces sliver. Combing: finer, removes noils.
- Warp: lengthwise (parallel to selvage); Weft: crosswise.
- Plain weave: over-under (simplest); Twill: diagonal (denim); Satin: lustrous (floats).
- Reactive dyes: cotton (covalent bond, wash-fast). Disperse: polyester. Acid: wool/silk.
- Mercerisation: NaOH treatment of cotton → lustre + strength.
- India: one of world's largest textile producers and exporters.
