1) fiber characteristics
The higher the fiber strength, the smaller the linear density and the longer the length, and the higher the yarn strength. The natural twist of cotton fiber and the curl of wool and chemical fiber will increase the cohesion between fibers under the condition of small twist of yarn, thus improving the strength of yarn. Short fiber content has a great influence on yarn strength. In cotton yarn, the short fiber rate below 16 mm increases 1%, and the strength of cotton yarn decreases 1% ~ 2%.
2) Yarn structure
When the fibers are transferred radially inside and outside the yarn and the structure is uniform, the yarn strength can be improved. When the fibers are arranged in layers, folded and hooked, the yarn strength decreases; Below the critical twist, the yarn strength increases with the increase of twist, and after exceeding the critical twist, it decreases with the increase of twist, and pure cotton yarn is easy to break in details and big neps. Polyester cotton yarn is easy to break at the inflection point of thick details.
3) Spinning method
The yarns spun by different spinning methods have obvious differences in strength due to different structures. The strength of coarse gauge air-spun yarn is about 5% ~ 10% lower than that of ring-spun yarn of the same specification, but the density of air-spun yarn is uniform and the Z weakness is not lower than that of ring-spun yarn. The strength of electrostatic spinning is similar to that of air spinning. Because of the untwisted area on the yarn, the strength of in-phase self-twisted yarn is very low; The strength of out-of-phase self-twisted yarn is improved by interlacing the untwisted areas on the yarn. Due to the reasonable twist distribution, the strength of twisted self-twisted yarn is further improved.
4) mixing ratio
In bicomponent blended yarn, when the blending ratio of one component increases gradually from zero, the strength of blended yarn will generally decrease gradually, and if the proportion of this component continues to increase after reaching a low value, the strength of spun yarn will increase gradually. The greater the difference in elongation at break between the two blended fibers, the more obvious this low strength phenomenon is.
5) Atmospheric temperature and humidity
With the increase of temperature, the yarn strength decreases; With the increase of relative humidity, the moisture regain of yarn increases, the strength of cotton and linen yarn increases, and the strength of wool and rayon yarn decreases. Therefore, the strength test should be carried out in the standard state (temperature is 20℃, relative temperature is 65%) after the balance, otherwise the measured strength should be corrected by temperature and moisture regain.