Fibres and Yarns
This domain covers fibre classification, essential fibre properties, yarn formation, yarn count and twist. The exam tests whether you can match a fibre to its source and behaviour, distinguish staple from filament yarns, and use count systems correctly.
Core concepts
- Natural fibres: cotton, wool, silk, jute. Manufactured fibres: viscose, polyester, nylon, acrylic and others.
- Staple fibres are short and must be twisted together; filament yarns are made from long continuous strands. Viscose can be produced as either staple or filament.
- Fibre properties include length, fineness, strength, elongation, moisture regain, elasticity and heat sensitivity.
- Yarn count expresses fineness. In the indirect cotton count (Ne), a higher number means a finer yarn. In direct systems such as tex, a higher value means a coarser yarn.
- Twist holds staple fibres together; direction is described as S or Z. More twist generally gives a stronger, leaner yarn up to a point, but excessive twist can cause snarling.
- Blending combines fibres to improve strength, comfort, appearance or cost.
Worked example
A cotton yarn is Ne 30. Convert it to tex using the approximate relation tex = 590.5 ÷ Ne. Thus tex = 590.5 ÷ 30 = 19.7 tex, meaning the yarn weighs about 19.7 g per 1,000 m. Reasoning: Ne is an indirect count, so a higher Ne is finer; tex is direct, so a lower tex is finer. The converted value must therefore be a relatively fine yarn.
Traps that cost marks
Do not assume every manufactured fibre is a filament. Do not confuse higher Ne with coarser yarn or higher denier with finer filament. Check whether a question uses cotton count, metric count, tex or denier before calculating. Do not describe twist direction without stating S or Z.
Key idea
Fibre source and length determine spinning route, yarn properties and appropriate end use.