Single End Tensile Testing of Yarn
topic
Single end tensile testing (ISO 2062, CRE principle, Textechno Statimat 4U or SDL Atlas Tensorapid 4) clamps individual yarn ends between fixed (load cell) and moving (linear actuator) jaws at 500 mm gauge for staple yarn, applies extension at 500 mm/min, records force-extension curve to break, and calculates tenacity (cN/tex), elongation (%), initial modulus (cN/tex), and work to break (cN·cm/tex). Jaw design: pneumatic flat rubber jaws (50 mm width, 25 mm contact, jaw pressure 3–5 bar) for staple yarn; V-groove metal jaws with rubber insert for monofilament; twisting jaws (±180° rotation) for elastic covered yarn preventing jaw slip. Statistical requirements: minimum 20 tests for mean and CV%, with jaw break exclusion (breaks within 10% of gauge length from jaw = jaw break, excluded if >15% of total tests — >15% jaw breaks invalidates test series indicating jaw damage or yarn surface damage). USTER Tensorapid 4/5 (automated high-speed tensile tester, 400–5,000 tests/hour from cheese package, bobbin, or cop): 50 mm gauge, 5,000 mm/min speed, force range 0–500 cN, elongation 0–150% — used for mill quality control where 200+ tests per lot provides full tenacity distribution rather than single 20-test mean. Ring yarn Ne 30 specification limits: tenacity minimum 18 cN/tex mean and CV% < 8%; elongation minimum 5.5% mean — yarn below these limits rejected for warp weaving application with typical penalty pricing −10 to −25% versus specification-compliant lots. Lea strength test (ISO 10254, 80-turn hank on 1.5 m circumference reel = 120 m hanks, break in Pressley-type tester): lea strength result in lbf/hank × count (Ne) = CSP (count strength product) — CSP > 2,200 for Ne 30 export warp cotton quality threshold, CSP < 1,800 = rejected quality.
Role
Single end tensile testing provides the definitive mechanical performance data for yarn warp acceptance testing — the minimum tenacity specification is the commercially contractual quality threshold between spinning mills and weaving customers, with below-specification lots subject to price penalty or rejection that creates direct financial consequences for spinning mill revenue management.