Wool Yarn Tensile Research

The relative lower count wool yarns were processed by the chemical pretreatment-mechanical stretching and heat setting.The metric count of the wool yams was 22.5; the wool yarns were treated by the optimized conditions of chemical pretreatment. Then they were stretched by mini-spinning frame, which had different stretching ratio. Under specific tension, the stretched yams were set under wet heat setting. Under the standard conditions (Temperature:20℃,Hurnidity:65%, Depositing for about one day), the main properties of the yarns were tested, such as yarn fineness, breaking strength, elongation rate and fiber fineness in the yarn. The data was analyzed by the methods of one-way analysis of variance and multiple comparisons. The yarns were knitted into fabrics. At the same time, the situation of knitting was observed, and the weight per square meter, abrasion resistance and bursting strength of the fabric were tested.Following key finders were found. The average diameter of wool fiber in the stretched wool yarns was 3 micron thinner than that in the original yarns, the yarn fineness decreased obviously. When the ratio of the stretching was 1.6, the fineness of the stretched yarns reached 26.1 Nm, while the fineness of the original yarns was 22.5 Nm; The microscope photos of the original and the stretched yarns show that the structure of the stretched yarns was more compact than that of the original yarns, and their hairiness were less and the crooked fibers in the stretched yarns were less; while the breaking strength decreased to some extent, the breaking strength decreased more obviously when the ratio of stretching was 1.5, it had no obvious change when the ratio was 1.25 and 1.4; the elongation rate decreased too, the elongation rate of the stretched yarns was half of the original yarns when the ratio was 1.5. The measured values of the mechanical properties were analyzed by the methods of analysis of variance and multiple comparisons; the optimum ratio of stretching was 1.4 under the current experiment conditions. The process of knitting with the stretched yarns was successful, and the surface of the fabrics were smoother, the weight per square meter was less than the fabrics knitted with original yarns, but the abrasion resistance was not changed obviously, the bursting strength of the fabrics showed a little bit lower.The conclusions were drawn by the above analysis; the wool yams could be stretched thinner and longer in a logical range by the technology of stretching wool yarn. Though the mechanical properties were decreased a little, the stretched yarns still meet the requirements of fabric knitting. The optimum ratio of stretching was 1.4 under the current experiment conditions.