Main Factors Affecting Yarn Strength and Elongation

The factors affecting yarn tenacity and elongation mainly fall into two categories: fiber properties that constitute the yarn and yarn structure. For blended yarns, their tenacity and elongation are also closely related to the property differences of blended fibers and the blending ratio. External factors such as temperature, humidity and tensile testing conditions affect yarn tenacity and elongation basically in the same way as they do fibers.

fiber properties

Fiber length and linear density：

When fibers are longer and finer, the frictional resistance between fibers in the formed yarn increases, making fibers less prone to slipping, thus resulting in higher yarn strength.

With better fiber length uniformity and fine, uniform fibers, the yarn exhibits even yarn evenness with fewer and less obvious weak places, which is conducive to the improvement of yarn tenacity.

Fiber strength：

When the fiber has high tenacity and elongation, the resulting yarn also possesses high tenacity and elongation;when the unevenness of fiber tenacity and elongation is low, the yarn strength is higher.

Fiber surface friction properties：

When the fiber surface friction coefficient μ increases, the sliding resistance between fibers becomes greater, the slip length lc decreases, the proportion of slipping fibers reduces, and the yarn strength increases.Increasing the fiber crimp count can enhance the sliding resistance between fibers.

Yarn structure

(1) The influence of staple yarn structure on its tenacity and elongation is mainly reflected in twist.

When the twist coefficient increases, the frictional resistance between wood fibers rises, making the fibers less prone to slipping, which acts as a positive factor for the strength of staple yarn.
However, as the twist coefficient increases, the inclination angle of fibers becomes progressively larger, the effective component of fiber strength along the yarn axial direction decreases, and the asynchronism of fiber breakage in the yarn intensifies.Meanwhile, the increase in yarn diameter caused by fiber inclination are all adverse factors for the relative strength of the yarn.

(2) Effect of Plying

The doubling of single yarns makes the ply yarn have even yarn evenness. Meanwhile, the contact between single yarns enhances the cohesion among outer-layer fibers of individual single yarns; the tenacity of ply yarn is greater than the sum of the tenacities of each single yarn.

(3) Arrangement Morphology of Fibers in Staple Yarn

The strength of rotor-spun yarn is lower than that of ring-spun yarn.In rotor-spun yarn, there are a large number of irregularly arranged fibers such as folded, crimped and looped fibers, while normally transferred fibers are fewer. This results in poor cohesion and contact between fibers, leading to a greater number of slipping fibers under tensile load.