Yarn Tenacity and Elongation
topic
Ring-spun yarn tenacity ranges from 12–22 cN/tex depending on fibre tenacity, yarn count, and twist level. Elongation at break is 4–8%. The tenacity–twist relationship shows an optimum at the critical twist multiplier (TM = 3.6–4.2 for cotton Ne 20–40), below which under-twisting causes fibre slippage and above which over-twisting causes helix angle inefficiency. Yarn strength CV% (coefficient of variation of breaking strength) should be <8% for weaving quality yarn.
Role
Yarn tenacity and its variability are the primary mechanical specifications in yarn purchase contracts and the key inputs to fabric engineering calculations (warp tension, weaving shed force balance). Understanding the tenacity-twist relationship allows engineers to optimise twist level for maximum strength, and CVT% testing identifies spindle positions producing weak yarn before the yarn reaches the customer.