Dynamic Friction Limits in Fine Wet Spun Linen Warps
Dynamic friction limits in fine wet spun linen warps demand starch lubricant optimization and speed adjustments to prevent fibril breakage and machine downtime.
Yarn Friction Coefficient
Slippage Index
Mathematical ratio of the tension of a yarn after it passes over a guide surface to the tension before it makes contact represents the friction of that yarn. The yarn friction coefficient of flax determines the mechanical resistance and surface wear that occur during high-speed spinning and winding. This dimensionless value is influenced by yarn hairiness and surface wax content.
Maintaining a low and consistent friction coefficient is essential to prevent yarn damage and ensure uniform tension during downstream processing.
Mechanical Impact
Tensile forces during winding increase exponentially with the friction between the yarn and the guide rollers. When the yarn friction coefficient is high, it causes excessive tension spikes that can lead to yarn breakage or uneven package density. High friction also causes the natural fibers to rub off, generating lint that clogs tension disks and guides.
Applying a uniform layer of wax during winding reduces this friction coefficient, protecting the yarn and the machine parts from premature wear. This protection is especially important for natural fibers like linen, which are less elastic and more vulnerable to tension spikes than synthetic yarns.
Testing Standard
Standard friction testers measure this property by pulling yarn at a controlled speed across a chrome-plated steel pin. The input tension is set to a constant value, and the output tension is continuously recorded by a high-precision load cell. Calculating the natural logarithm of the tension ratio and dividing it by the angle of wrap yields the coefficient of friction for the yarn under test.