Establishing Elastic Strain Limits for Hydrolyzed Polyvinyl Alcohol Films on Fine Linen Warps
Polyvinyl alcohol sizing on fine linen warps must maintain elastic strain capacity above dynamic shedding peak strain to prevent brittle coating breakdown.
Tensile Yield Strength
Elastic Limit
The maximum force a flax yarn can withstand before undergoing permanent plastic deformation defines its boundary between elastic and inelastic behaviour. This tensile yield strength is determined by pulling a single yarn until the linear relationship between force and elongation breaks down. Testing laboratories record this limit in the yarn strength certificate before the spinning lot is released for warping.
Spinning Optimization
Yarns with low limits will stretch permanently during high-tension warping and loom processing, causing tension variations and loose yarns in the loom. Proper sizing and spinning increase the load-bearing capacity of the yarn, allowing it to withstand the rigorous motions of modern rapier looms. This property is critical for producing heavy linen fabrics that meet international tension-bearing specifications.
Structural Characterization
Tensile testing machines equipped with pneumatic grips measure the force-displacement curve of twenty yarn samples from each production lot. The averaged load value at the yield point is registered in the mill’s laboratory ledger and compared with the buyer’s acceptance criteria. If the yield strength is below the specified value, the spinning lot is downgraded to coarser weft applications.
This yield measurement acts to control quality to ensure that the linen fabric remains dimensionally stable during subsequent dyeing, washing and finishing operations.