18 Jul Introduction to yarn imperfections, yarn hairiness

Yarn hairiness is one of the imperfections found in the spinning of discontinuous yarns. It is not found in filament yarns due to the continuity of consumed fibers. All yarns of discontinued fibers have hairiness. Basically, one of the methods for detecting continuous yarns out of discontinuous ones is the existence of protruding of fibers out of the compact yarn body, however; if it is too much, it is referred as yarn imperfection.
Yarn hairiness occurs due to:
Some fiber ends protrude from the yarn body
Some looped fibers projected out from the yarn core.

Factors Affecting Hairiness of Yarn:

Properties of used fiber
characteristics of Produced Yarn
Production line properties
Technology of spinning system
Additional work done on the base yarn
Environmental factors
Each of these factors have some effects on the yarn’s hairiness, and a complete understanding of each of them is required to control the amount of hairiness.

Properties of used fiber

Those properties that affect the level of hairiness are:
Length, diameter, torsional rigidity, strength, cross-section shape, twisting, and compressive strength. In a mixture of fibers, if the degree of fineness is constant and the length of consumed fibers vary, the longer fibers tend to migrate to the center of yarn and shorter fibers tend to migrate to the yarn surface.

Hairiness of yarn with mixed fibers

Most yarns produced in spinning operations are made from fiber mixtures. Mixing the fibers is mainly done for the optimal use of the properties of the mixed fibers. When these mixed fibers have a difference in delicacy, the thicker fibers tend to migrate towards the surface of the yarn, and they are more likely to play role in hairiness of the yarn. This effect becomes greater when the length of this fiber is longer. On the other hand, when the fibers mixture includes thicker fibers, the yarn hairiness also increases.

The effect of yarns properties on the degree of hairiness

These features include:

• Yarn size
• Yarn twist

In general, the higher linear density of the yarn, that is the thicker yarn, increases the hairiness degree of the yarn. On the other hand, increment in the amount of twisting in the yarn reduces the hairiness. These two factors are essentially dependent to each other, therefore; in spinning process, in order to prevent hairiness, the thinner yarns must be twisted more than the thicker yarns.
Production lines factors, affecting on the yarn hairiness are:

• Stretching rate
• Unevenness due to tensional strength
• Spindle Speed
• Pawl Weight
• Two-roving feeding on the ring spinning system
• Parallelization of the fibers
• Stretching system type
• The amount of twisting in the roving
• The size of roving pack
• The presence of bobbin holder in the ring system
• The length of mixed cotton fibers
• Consistency of fiber
• Linear density of roving
• Swing speed of bobbins