Unit 3: Textile yarns and yarn manufacturing
Elements of Textiles notes · PTU syllabus (BSTD 101-20)
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Unit summary
Fibres become yarns by spinning, and yarn type affects every fabric. This unit covers yarn classification, ring and open-end spinning, yarn properties, yarn numbering, texturing, fancy yarns and sewing threads.
After this unit you can
- Classify yarns
- Compare ring and open-end spinning
- Calculate yarn count in direct and indirect systems
- Describe texturing, fancy yarns and sewing threads
PTU syllabus topics
- Yarn classification
- ring spinning and open-end spinning
- properties of yarns
- yarn numbering system
- yarn texturing
- fancy yarns
- sewing threads
Meaning
Length per unit weight
Weight per unit length
Higher number
Finer yarn
Coarser yarn
Examples
English cotton count (Ne), metric (Nm)
Tex, denier
Typical for
Cotton yarns
Filament and synthetic yarns
Topic 1
Classification of yarns
By fibre length
Spun (staple) yarns and filament yarns (mono- and multifilament)
By number of strands
Single, ply (two-ply, three-ply), cord or cable
By twist
S-twist and Z-twist; low twist (soft) to high twist (crepe)
By composition
Pure and blended (polyester–cotton, polyester–viscose)
By use
Weaving, knitting, sewing, embroidery, fancy yarns
Topic 2
Ring and open-end spinning
- 1
Blow room
Opening and cleaning
- 2
Carding
Individualises fibres; forms sliver
- 3
Combing (optional)
Removes short fibres for fine combed yarn
- 4
Drawing
Straightens and evens slivers
- 5
Roving (simplex)
Thinner strand with slight twist
- 6
Ring frame
Drafting and twisting into yarn
- 7
Winding
Onto cones
Process
Drafting and twist by traveller on a ring
Fibres separated and collected in a spinning rotor
Speed and cost
Slower; more steps
Much faster; skips roving and winding
Yarn
Stronger, finer, smoother
Weaker, coarser, bulkier, more even
Count range
Fine to coarse
Coarse to medium — denim, towels
- Other systems: compact spinning (less hairiness), air-jet (vortex) spinning.
Topic 3
Yarn properties
- Count (fineness), twist (turns per inch), strength and elongation, evenness, hairiness, imperfections (thin and thick places, neps), lustre and bulk.
Topic 4
Yarn numbering systems
Indirect (fixed weight)
Length per unit weight; higher number = finer yarn
English cotton count (Ne): number of 840-yard hanks per pound; metric (Nm): km per kg
Direct (fixed length)
Weight per unit length; higher number = coarser yarn
Tex: grams per 1,000 m; denier: grams per 9,000 m; decitex
Tex and Ne
Tex = 590.5 ÷ Ne
Denier and tex
Denier = 9 × tex
Nm and Ne
Nm = 1.693 × Ne
Example
A 30s cotton yarn (Ne 30): tex = 590.5 ÷ 30 ≈ 19.7 tex ≈ 177 denier. A 150-denier polyester filament = 16.7 tex.
Topic 5
Yarn texturing
- Texturing adds crimp, loops or bulk to smooth synthetic filaments, giving warmth, stretch and a natural feel.
- False twist
- Twist, heat-set, untwist — stretch yarns (most common)
- Air-jet
- Turbulent air forms loops — bulky, spun-like yarns
- Stuffer box
- Filaments crammed and heat-set — crimp for carpets
- Knit-de-knit
- Knitted, set, unravelled — crinkle effect
- Edge crimping
- Drawn over a sharp edge
Topic 6
Fancy yarns
- Slub
- Thick, soft places at intervals
- Bouclé
- Loops on the surface
- Chenille
- Velvety pile
- Nub and knop
- Small knots or bunches
- Spiral or corkscrew
- Two yarns twisted at different speeds
- Metallic
- Lurex and zari
- Core-spun
- Spandex or polyester core covered with cotton
Topic 7
Sewing threads
- Requirements: strength, even diameter, smoothness, elasticity, colour fastness, heat resistance for high-speed sewing.
Cotton (mercerised, glacé)
Spun cotton, polished
Cotton garments; dyeable with fabric
Spun polyester
Staple polyester
General purpose; strong
Core-spun (poly–cotton or poly–poly)
Filament core with spun cover
Industrial garments — denim, shirts
Nylon and polyester filament (bonded)
Continuous filament, sometimes bonded
Leather, footwear, upholstery
- Thread size: tex or ticket numbers; choose thread finer than the fabric yarns so seams fail before fabric tears.
Key terms
- Ply yarn
- Two or more singles twisted together
- Ring spinning
- Conventional spinning with ring and traveller
- English count (Ne)
- Number of 840-yard hanks per pound
- Tex
- Grams per kilometre of yarn
- Texturing
- Adding bulk and crimp to filament yarns
Quick revision
- Spun vs filament; single, ply, cord; S and Z twist; blends.
- Blow room → carding → combing → drawing → roving → ring frame; rotor spinning.
- Yarn properties.
- Indirect (Ne, Nm) vs direct (tex, denier); conversions.
- Texturing methods; fancy yarns; sewing threads.
Important exam questions
Practice questions written to the PTU exam pattern for this unit's syllabus: short answers (Section A style) and long answers (Sections B and C style).
Short-answer questions
- Q1.Distinguish spun and filament yarns.
- Q2.What is the purpose of carding?
- Q3.Give two advantages of rotor spinning.
- Q4.Convert Ne 40 to tex.
- Q5.What is a bouclé yarn?
- Q6.Why is core-spun thread used in industry?
Long-answer questions
- Q1.Describe the ring spinning process.
- Q2.Explain direct and indirect yarn numbering with conversions.
- Q3.Describe texturing methods and fancy yarns.
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