The factors affecting the strength and elongation of the yarn are mainly the two aspects of the fiber properties and yarn structure of the yarn. The strength and elongation of the blended yarn are closely related to the difference in the properties of the blended fiber and the blending ratio. Temperature and humidity The external factors such as the strong test conditions have the same effect on the strength and elongation of the yarn as the fiber.
1, fiber properties
Fiber length, linear density:
When the fiber length is long and the fiber is fine, the frictional resistance between the fibers in the yarn is large, and it is not easy to slip off, so the yarn strength is high.
When the fiber length is good and the fiber is fine and uniform, the yarn is evenly dried, and the weak ring is less and not significant, which is beneficial to the improvement of the yarn strength.
Fiber strength:
When the strength and elongation of the fiber are large, the strength and elongation of the yarn are also large; the fiber strength and the unevenness of the elongation are small, and the yarn strength is high.
Surface friction properties of the fiber:
When the friction coefficient μ of the fiber surface increases, the sliding resistance between the fibers is large, the slip length lc is decreased, the proportion of the number of slip fibers is decreased, and the yarn forming strength is increased. Increasing the number of crimps of the fibers increases the sliding resistance between the fibers.
2, yarn structure
(1) The influence of the structure of the short fiber yarn on its strength and elongation is mainly reflected in the twist.
When the twist coefficient increases, the frictional resistance between the wood fibers increases, which is not easy to slip off. This is a strong positive side for the strength of the short fiber yarn, but as the twist coefficient increases, the fiber tends to become larger and larger, and the fiber strength increases. The effective component force in the axial direction of the yarn is reduced, and the fiber breakage in the yarn is not uniform at the same time, and the increase in the yarn diameter when the fiber is inclined is an unfavorable factor for the relative strength of the yarn.
(2) The impact of the joint stock
The combination of the single yarns makes the plyyarn strips evenly distributed, and there is contact between the single yarns, so that the cohesion between the outer fibers of the single yarns is increased; the strength of the strands is greater than the sum of the strengths of the individual yarns.
(3) Arrangement of fibers in spun yarn
The strength of the rotor yarn is lower than that of the ring yarn: in the rotor yarn, there are more irregularly arranged fibers, such as folding, curling, and ringing, and there are fewer normal transfer fibers, resulting in poor fiber and fiber cohesion, and more slipping fibers during stretching. .
(4) bulked yarn
The tensile breaking strength of the bulked yarn is smaller than that of the conventional yarn, and the elongation at break is large.
Structural characteristics: heat-shrinking treatment is carried out by mixing two fibers having a large difference in heat shrinkability, so that the high-shrinkage fibers in the sliver are sufficiently retracted, and the normal fibers having low heat shrinkage are forced to compress and wrinkle along the yarn axis. Showing bulk properties.
Stretching and breaking process: The number of fibers that bear the external force when the bulked yarn is stretched is small, and the tension of each fiber is not uniform. When starting to be stretched, only a small portion of the fiber bears the external force, and the other fibers are wrinkled and relaxed. After the current fiber is broken, the latter fiber is stretched and bears the tensile force until it breaks.
(5) textured yarn and elastic yarn
Each fiber is subjected to a coil spring-like or curled oriented buckling curve by various shaping methods.
In the course of the beginning of the stretching, the fiber is actually gradually straightened under the condition that the tensile force is increased little, and it has a high elongation at break.