Polyester, especially spandex-containing fabrics, generally have to be pre-formed by grey fabrics to ensure the smoothness of the fabric surface and the stability of specifications, and the setting conditions of grey fabrics (temperature, speed, air volume) will directly affect the subsequent dyeing. The coloring of dyes Depth and shade, which are caused by the distribution of crystalline and amorphous regions of polyester and the degree of movement of molecular chains with the change of blank setting temperature.
With different blank setting temperatures, the dye absorption rate of the same formula is very large, which will inevitably cause differences in color depth and shade. When the setting temperature of the grey fabric is lower than 180℃, the dye absorption rate decreases with the increase of temperature. When the temperature is higher than 180℃, the dye absorption rate increases with the increase of temperature, which is mainly related to the crystalline properties of polyester. At 180°C, the crystallization speed of polyester increases with the increase of the setting temperature. Due to the formation of more crystals, the dye dyeing is less; and when the temperature is further increased, the degree of macromolecular orientation may decrease, so the absorption of dyes increases again. . When the heating is continued to 230-240℃, the softening point of polyester is reached, the molecular chain movement in the amorphous area of polyester is intensified, and the forces of intermolecular interactions are disassembled. The piece has not been disassembled, so the fiber is only softened, not melted, but the use value of the fiber has been lost at this time, so it is not allowed to exceed this temperature in the printing and dyeing process. Therefore, the cloth used in the laboratory for recoloring must be made of large blanks to ensure the stability of yarn, weaving and blank setting conditions, and this can improve the reproducibility of dyeing.