Fibre Science and Textile Fibres
This domain tests whether you can place any fibre in the correct class, name its chemical base, and connect measurable properties - fineness, length, tenacity, elongation, moisture regain, crimp - to how it spins, dyes and performs. Expect classification trees, definitions with units, fibre identification tests and small numerical items on regain or count conversion.
Classification rules
- Natural: vegetable (cotton, jute, linen), animal (wool, silk), mineral (asbestos). Manufactured: regenerated (viscose, modal, acetate) and synthetic (polyester, nylon 6, nylon 6.6, acrylic, polypropylene).
- Silk is the only natural filament; every manufactured fibre can be spun as filament or cut to staple.
- Cotton is roughly 90% cellulose with convolutions and a lumen; wool is keratin with cuticle scales and natural crimp; silk is fibroin held by sericin gum.
Properties that carry marks
- Tenacity is quoted in cN/tex; 1 gf/denier ≈ 0.882 cN/tex.
- Moisture regain is always based on oven-dry mass, not on the conditioned mass.
- Rising crystallinity and orientation raise strength and reduce extensibility and dye uptake.
- Degree of polymerisation (DP) governs chemical resistance: cotton about 2000–3000, viscose only about 250–350, so viscose loses strength easily in wet processing.
Worked example
A cotton sample weighs 12.0 g as received; after drying at 105 °C it weighs 10.0 g. Moisture content = water ÷ wet mass × 100 = 2.0 ÷ 12.0 × 100 = 16.7%. Moisture regain = water ÷ oven-dry mass × 100 = 2.0 ÷ 10.0 × 100 = 20.0%. The two figures differ; fibre property tables quote regain, so read the question wording carefully.
Traps that cost marks
- Reporting content when regain is asked (see above).
- Mixing g/denier with tex-based tenacity without conversion.
- Calling viscose or acetate a synthetic fibre - both are regenerated.
- Writing that all natural fibres are staple, forgetting silk.