Evaluating Single Fiber Tenacity Degradation Driven by Microfibril Angle Widening
Widened microfibril angles reduce single fiber tenacity by increasing matrix shear stress, requiring X-ray diffraction checks to prevent yarn breakage.
Fiber Bundle Drafting
Drawing Process
Mechanical attenuation is the progressive reduction of the linear density of a strand of fibers as it passes through a series of rollers running at different surface speeds. In wet spinning of flax, fiber bundle drafting relies on the differences in rotational speed between the feed roller and the drawing roller to slide the long, combed fibers past one another. The hot water bath situated before the drafting zone softens the pectins that glue the individual fiber bundles together.
This softening permits a controlled slipping action, preventing the bundles from breaking and ensuring the production of a fine, uniform strand of yarn.
Mechanical Parameter
The distance between the pair of rollers is known as the ratch, and its setting is determined by the length of the fibers being processed. Setting this distance too wide leads to uncontrolled drafting and produces uneven yarn with thick and thin regions. If the ratch is shorter than the average fiber length, the fibers will be gripped by both rollers simultaneously, causing fiber breakage or machine jams.
Tension is maintained continuously during this step to prevent loops.
Quality Effect
Inconsistent sliver density reduces yarn strength. Since fiber bundle drafting establishes the final mass per unit length of the spun yarn, any fluctuation in drafting force results in a direct loss of product uniformity. This variation can cause warp breakages during the subsequent weaving stage.
Poorly drafted yarn also exhibits uneven dye uptake due to localized density variations.