Cotton Fibre Structure and Morphology
category
Cotton fibre is a single elongated seed hair cell (trichome) developing from the outer integument of the cotton ovule, reaching mature length of 10–60 mm over 25–30 days post-anthesis. The fibre cross-section is kidney-shaped with a collapsed lumen in mature fibres, outer diameter of 12–20 µm, and cell wall thickness of 4–8 µm. Fibre structure consists of cuticle (wax layer, 0.5–1.0 µm), primary wall (cellulose microfibrils at 70° to fibre axis, 0.1–0.2 µm), secondary wall S1, S2, S3 layers (cellulose microfibrils at 20–30° to fibre axis), and central lumen (collapsed in mature fibre). Secondary wall crystallinity is 70–80% (cellulose I polymorph) measured by X-ray diffraction. Degree of polymerisation (DP) of native cotton cellulose is 10,000–15,000.
Role
Fundamental structural knowledge of cotton fibre architecture governs all downstream processing decisions from ginning and opening through spinning, dyeing, and finishing, as fibre morphology directly determines yarn quality, fabric performance, and chemical reactivity.