Standard Linen Yarn Tensile Specifications for Weaving Preparation
Wet-spun linen warps demand a minimum tenacity of 18.5 cN/tex with under 1.2% beaming stretch to maintain loom stop rates below 1.5 per 100,000 picks.
Constant Rate Extension
Tensile Evaluation
Testing apparatuses for determining yarn and fabric strength operate by applying a controlled mechanical pull to a clamped specimen. In a constant rate extension tester, the pulling clamp moves at a uniform displacement speed while the load-measuring clamp remains virtually stationary. This method represents the standard approach for assessing the breaking force and elongation of linen yarns and woven flax fabrics.
Calibration Standard
Mechanical settings on the apparatus require precise adjustment of the gripping force to prevent the specimen from slipping during the test. For linen yarns, which possess high stiffness and low elasticity, any slippage in the clamps generates false elongation data. The constant rate extension method overcomes this by utilizing pneumatic grips that maintain a constant pressure throughout the pull.
Technicians calibrate the extension speed, typically set at hundreds of millimetres per minute, to match the guidelines of international standards like iso 2062.
Quality Control
Spinning mills analyze the load-extension curves to identify the elasticity limits of the processed flax fibre. Low tensile strength indicates weak points that will cause yarn breaks during high-speed weaving operations. Applying constant rate extension ensures that yarn shipments meet the mechanical performance levels required by commercial weaving mills.