Fibres
Classification
Fibres are natural or manufactured. Natural: cotton, flax, jute (cellulosic); wool, silk (protein); asbestos (mineral). Manufactured: regenerated (viscose rayon, acetate, lyocell) from natural polymers; synthetic (polyester, nylon, acrylic, elastane) from petrochemicals; inorganic (glass, metallic). Staple fibres are short; filament fibres are continuous.
Properties that drive selection
- Cotton: absorbent, comfortable, good wet strength, poor elasticity, creases.
- Wool: crimp, warmth, elastic recovery, felts; weaker when wet.
- Silk: natural filament, lustre, drape, moderate strength; weaker wet.
- Viscose: absorbent and soft but low wet strength; not a synthetic fibre.
- Polyester: strong, hydrophobic, quick-drying, heat-settable; low absorbency.
- Nylon: high abrasion resistance; elastane: high stretch and recovery. Identification uses burn behaviour, solubility and microscopy, but property selection is the exam's usual application.
Worked example
Choose fibre for a bath towel and a competitive swimsuit. Towel: cotton, because it absorbs water and withstands repeated washing; a polyester towel would feel clammy. Swimsuit: polyester or nylon blended with elastane, because it resists water, dries fast and stretches/recover. Reasoning: match fibre property to end-use performance, not to cost alone.
Traps
Rayon is regenerated, not synthetic. Silk is a natural protein filament, not a manufactured fibre. Cotton's wet strength is higher than its dry strength; wool's is lower. Do not write that all natural fibres are absorbent - wool absorbs moisture but feels warm and has different hand.