Textile Fibres and Yarn Fundamentals
This domain tests how fibre properties become yarn properties and how count, twist, strength and evenness are expressed, converted and judged against weaving requirements.
Core rules
- Tex is direct: grams per 1000 m. Ne is indirect: 840 yd per lb. Nm is indirect: metres per gram. Denier is direct: grams per 9000 m.
- Cotton conversion: Tex = 590.5 / Ne. Also Tex = 1000 / Nm and Tex = denier / 9.
- Fibre length, fineness, maturity, crimp and strength drive yarn tenacity, elongation, hairiness and unevenness. Longer, finer, uniform cotton gives fewer thick and thin places and lower CV%.
- Twist multiplier TM = turns per inch / square root of Ne. Strength rises with twist to an optimum, then falls; excessive twist increases liveliness and snarling.
- Moisture regain changes conditioned mass. Cotton is commonly conditioned at 8.5% regain for count and contract purposes.
- Yarn faults such as neps, slubs and thick or thin places are reported as IPI at defined sensitivity. Warp yarn usually needs higher strength and lower fault levels than weft.
Worked example
A cotton yarn is 30 Ne. Convert to Tex: 590.5 / 30 = 19.68 tex. With TM 4.0, twist = 4.0 × square root of 30 = 21.9 turns per inch. If tenacity is 18 cN/tex, breaking load = 18 × 19.68 = 354 cN, or 3.54 N.
Traps
- Using 1000 / Ne instead of 590.5 / Ne for cotton.
- Treating Ne and Tex as interchangeable without conversion.
- Reporting count without a regain basis.
- Confusing twist multiplier with turns per inch.
- Assuming a finer yarn is always stronger; fine fibres help, but unevenness and twist matter.