| PTT fiber would be used as shape memory products because it has unique molecular structure and high elastic recovery properties, so that PTT fiber has the stationary phase and reversible phase that required as shape memory polymer and a lower reversible phase transition temperature (45℃).In this paper, the condition of performacing PTT fiber's shape memory characteristics through torsional deformation and the main factor affecting shape memory characteristics were studied. Meanwhile, the process of simulating the fiber shape memory was established. On the basis of the experiments, the condition of achieve PTT filament yarn shape memory function was studied and the reasonable process parameters were determined, providing a reference for company to develop the shape memory products based on PTT filament yarns.The length variation of PTT filament yarn was analyzed after the first deformation by twisting, and the length difference between the true value and theoretical value was measured too. The result showed with the deformation increasing, PTT filament yarn twist shrinkage rate gradually increased, the differences between measured twist shrinkage value and theoretical value became larger. PTT filament deformation obviously increased while twist shrinkage rate was significantly increased in the high-twist zone. When the twist factor exceeded 693 tex1/2twist/10cm, the yarn formed pigtail due to contraction. In order to prevent the "braided knot" phenomenon caused by hard twist, the PTT filament yarn deformation should be controlled below the twist factor of 693 tex1/2 twist /10cm.The twisted PTT filament yarns were shaped by means of dry heat-setting method, namely, "the first deformed shape". The effect of a deformed shape was evaluated by testing the residual torque. The results shows:PTT filament yarns'shape effect achieveed better results with shaping temperature range from 160℃to 180℃and the shaping time was 60min.The shaping time of 60min had less impact on PTT filament yarn with smaller deformation.Mechanical properties of the first deformed shape PTT filament yarn was studied. The results shows: when the twist factor was 577tex1/2twist/10cm,the loss rate of strength and elongation of PTT filament yarn was smaller; when the shaping time was 30min and the twist factor was 577tex1/2twist/10cm, the strength,elongation and elastic property of the PTT filament yarn reached the maximum.Extract the first deformed shape twist of PTT filament yarn in the hot water bath, that is, simulat the secondary deformation of PTT filament yarn through "deformation reply" method. The change of the size and flexibility of secondary deformation samples were measured, in order to study the influence on the PTT filament yarns's shape memory characteristics caused by deformation, shaping temperature and time, while the main factors affecting the shape memory were determined using regression analysis with SPSS. The results shows: when shaping temperature was 160℃, shaping time was 30min, and the twist factor was 577 tex1/2twist/10cm, the PTT filament yarns with the secondary deformation had the better the shape recovery capability and were able to maintain a good shape memory characteristics.The obvious "wrinkle" phenomenon of PTT filament yarns with the secondary deformation was observed by microscope, this mainly because the gap between PTT fibers became larger after the secondary deformation. the average diameter of the the secondary deformation is larger than the first deformation yarns .Birefractive index results showed: After the first deformation process, with the heat-setting temperature increasing, PTT fiber birefractive index increased, when the heat-setting temperature was 160℃, the fiber birefractive index reached the maximum, afterwards the fiber birefractive index tended to decrease; With the deformation increased, the fiber birefractive index increased, while the deformation increased twist factor of 577 tex1/2twist /10cm,the change of the fiber birefractive index was little; the fiber birefractive index showed a downward trend after the secondary deformation.The X-ray diffraction experiments results showed: In the first deformation process, with the heat-setting temperature increasing, PTT fiber's crystallinity increased gradually, when the heat-setting temperature exceeded 160℃, the fiber crystallinity increased slowly and stabilized. The crystallinity of PTT fiber with shaping time of 60min was higher than that of shaping time of 30min. With the increase of the deformation, PTT fiber's crystallinity increased; PTT fiber's crystallinity tended to decrease after the secondary deformation.The differential thermal analysis (DSC) results showed:There were not obvious changes in DSC curves of PTT fiber afer the first deformed shape,indicating that the thermal properties of the sample has not changed significantly.With the shaping temperature incraesed, the glass transition temperature increased, The glass transition temperature of PTT fiber with shaping time of 60min was higher than that shaping time of 30min.The infrared spectroscopy results revealed there were some clear absorption peaks around characteristic bands such as 734cm-1, 830cm-1, 1130cm-1, 1260cm-1, 1730cm-1 and other places; a weak peak appeared in the vicinity of 854cm-1 bands with the heat-setting temperature temperature increasing, which proved that PTT fibers'crystallinity increased after heat-setting.
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