The factors that affect the strength and elongation of yarn are mainly the fiber properties and yarn structure of the yarn. The strength and elongation of blended yarn are also closely related to the property differences and blending ratio of blended fibers. The effects of external factors such as temperature, humidity and strength testing conditions on yarn strength and elongation are basically the same as those of fibers.
1. Fiber properties
Fiber length, linear density:
Longer fiber length, smaller fiber When it is thin, the friction resistance between the fibers in the yarn is greater and it is not easy to slip, so the strength of the yarn is higher
When the fiber length uniformity is good and the fibers are thin and uniform, the yarn will be even and the weak rings will be few and not obvious, which is conducive to improving the strength of the yarn.
Fiber strength:
When the fiber is strong and stretchy, the yarn will be strong and stretchy. Large; the fiber is strong and the elongation unevenness is small, the yarn strength is high.
Surface friction properties of fiber:
when The fiber surface friction coefficient μ increases, the sliding resistance between fibers is large, the slippage length lc decreases, the proportion of the number of slippery fibers decreases, and the yarn strength increases. Increasing the crimp number of fibers can increase the sliding resistance between fibers.
2. Yarn structure
(1) The influence of short fiber yarn structure on its strength and elongation, Mainly reflected in the twist
When the twist coefficient increases, the frictional resistance between wood fibers increases and they are less likely to slip off. This is a positive side for the strength of short fiber yarns. However, when the twist coefficient increases, the tilt of the fibers increases. The larger the value, the effective component of fiber strength in the yarn axis is reduced, the fiber breakage in the yarn is aggravated, and the yarn diameter increases when the fiber is tilted, which are all unfavorable factors for the relative strength of the yarn.
(2) The impact of joint stock
The combination of single yarns makes the plyyarn uniform, and there is contact between the single yarns, which increases the cohesion between the outer fibers of the single yarns; the strength of the plyyarn is greater than the sum of the strength of each single yarn .
(3) The arrangement of fibers in staple fiber yarn
The strength of rotor yarn is lower than that of ring-spun yarn: In rotor yarn, there are more irregularly arranged fibers such as folding, curling, and looping, and less normal fiber transfer, resulting in fiber and The fiber cohesion and contact are poor, and more fibers slip out during stretching.
(4) Textured yarn
The tensile breaking strength of bulked yarn is smaller than that of traditional yarn, while the breaking elongation is larger.
Structural characteristics: Two fibers with very different thermal shrinkage are blended and then subjected to heat shrinkage treatment, so that the highly shrinkable fibers in the yarn are fully retracted, and at the same time, the normal fibers with small thermal shrinkage are forced to move along the yarn axis. It curls toward compression and exhibits bulk characteristics.
Stretch fracture process: When the bulked yarn is stretched, the number of fibers that bear the external force is small, and the tension of each fiber is uneven. When it starts to be stretched, only a small part of the fibers bear the external force, and the other fibers bear the external force. The fibers are wrinkled and relaxed. After the former fiber is pulled apart, the latter fiber straightens and bears the tensile force until the entire fiber breaks. -width: 100%; clear: both; min-height: 1em; color: rgb(62, 62, 62); font-family: 宋体; font-size: 14px; line-height: 24px; background-color: rgb(245, 248, 253 ); box-sizing: border-box !important; word-wrap: break-word !important;”>(5) Textured yarn and elastic yarn
Relying on various shaping methods, each fiber is made into a spiral spring-like or curl-like directional wrinkle curve.
During a considerable period of the initial stretching process, the fiber is actually gradually straightened under the condition that the tensile force increases very little, and it has a high breaking elongation.
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