Drafting Parameter
Physical parameter that determines the force required for flax fibres to slide past one another during drafting. Inter-fibre shear resistance arises from the surface friction and the physical entanglement of the bundles. Frictional drag acts as the primary opposing force to the tension applied by the rollers.
Surface Interaction
Surface characteristics of the linen fibres, including the presence of residual waxes, gums, oils and pectins, influence this friction. High inter-fibre shear resistance often results from insufficient degumming or low moisture content, making the fibres stick together. This stickiness prevents the smooth attenuation of the fibre mass during the drawing process.
Mill operators apply lubricants or softening agents to modulate these forces. Reducing the resistance allows for the production of finer, more consistent yarns by enabling more precise control over the fibre movement.
Operational Impact
Control of this property is essential for maintaining the stability of the wet spinning process. If the inter-fibre shear resistance is too low, the roving may pull apart under its own weight or during the transition between rollers. Conversely, excessive resistance leads to the formation of thick and thin places in the yarn.
Laboratory tests using a coherence meter measure the force needed to draft the sliver at a constant speed. Results from these tests guide the setting of the nip pressure and the distance between drafting rollers.
