The Study On Mechanical Properties Of PTT Fiber And Yarn

As a member of the terephthalic polyester family and a new textile material, PTT has good elasticity and other properties, which makes it has wide applying foreground. So far most study work has been emphasized on PTT fiber, such as its manufacturing craft and interior structure. Little work has been done on PTT yarns and other final products. In order to provide a theoretic basis to manufacturing craft and other theories, the article studied systemically the mechanical properties of PTT fiber and its yarns, in which the influence of heat treatment on it has also been analyzed. The conclusions are as follows:1. PTT fiber has lower breaking strength, lower initial modulus and higher breaking elongation than PET fiber, whose breaking elongation is similar to high shrinking PET fiber, and all these indicate that PTT fiber has good extensibility and softness. PTT fiber has also superiority on elastic recovery, especially for low elongation. Three-component-model had been well used to simulate the relaxing curve of fibers, the result indicates that PTT fiber has good elasticity.2. The hairiness and evenness of PTT yarns blended with cotton fibers are not good. Owing to the different properties between PTT fiber and PET fiber, many problems occur in spinning process, for example, the yarns break easily and it is difficult to control the spinning tension.3. The twist and structure have some weak effect on tensile property of PTT yarns. The tensile property of PTT yarns mainly depends on blending ratio and the properties of blended fibers. For blended yarns, along with the increasing of the blending ratio of PTT fiber the breaking tenacity firstly rises and later declines, but the breaking elongation always rises. Theoretical study indicates that the influence of twist on mechanical property is very weak, and the mechanical property of the yarn is mainly depended on the slippage and the mechanical property of the fiber. For there are a lot of weak areas in PTT yarns, the tensile property of PTT yarns is lower than that of PTT fiber. Due to large frictional coefficient, PTT fiber has also goodmigration trend in yarns.4. In blended yarns, the elastic recovery becomes larger with the increasing of the ratio of PTT fiber to cotton fiber, especially when the ratio exceeds 50/50. The elastic recovery of Sirospun yarns is also better than that of ring-spun yarns. The twist has little influence on the elastic recovery of PTT yarns. The elasticity recovery of the yarn especially under small elongation is mainly determined by the elasticity recovery of the fiber. Four-component-model can be well used to simulate the elongation curve of yarn under an invariable load, the result indicates that PTT yarns have good elasticity.5. After heat treatment in wet circumstance, the tensile property and elastic recovery of both PTT fiber and PET fiber decrease, and the change of PTT fiber is more obvious than that of PET fiber. This result indicates that the effect of temperature on PTT fiber is more obvious, and that is the thermal stability of PTT is not good.6. Heat treatment makes PTT yarns shrinked and lowers its breaking intensity and elasticity, however the last breaking elongation of PTT yarn increases after heat treatment for the thermal shrinkage. The effect of heat treatment in dry circumstance is also bigger than it in wet circumstance.6. Heat treatment made the PTT yarns to shrink. The higher the temperature is the greater the shrinkage is. The breaking strength of PTT yarns decreases after the heat treatment, but its breaking elongation increases for the shrinkage of yarns happened during the heat treatment process.