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100% polyester dyed spun yarn

What are the disadvantages of dyeing polyester at normal temperature and pressure? Why must it be baked after dyeing?

What are the disadvantages of boiling temperature and atmospheric pressure dyeing of polyester? Why must it be baked after dyeing?

(1) Disadvantages of boiling temperature and atmospheric pressure dyeing. Boiling temperature and atmospheric pressure dyeing method is to dye at 100 ℃ without carrier. Therefore, it is different from boiling temperature carrier dyeing method.

It is well known that the glass transition temperature (TG) of polyester is high. The TG value of unshaped polyester is 67 ~ 81 ℃. The actual TG value of pet treated at 195 ~ 210 ℃ should be above 100 ℃.

Because of this, the boiling temperature and atmospheric pressure dyeing method has two disadvantages

(2) The reason for baking treatment after dyeing: after high temperature dry heat treatment, the polyester fiber dyed by boiling temperature and atmospheric pressure changes from ring dyeing to through dyeing, and the light absorption property of the fiber (dye) changes (Fig. 4-8). A kind of

A kind of

When the light is incident from above, part of the light is reflected on the surface of the fiber, showing white light. Part of the light is refracted into the fiber. Among them, part of the light is partially absorbed by the dye and becomes transmitted light, which appears as colored light. The remaining light diffuses and refracts repeatedly in the fiber and is dyed and absorbed continuously.

According to the principle of color generation, the more the incident light is absorbed by the material (dye), the darker the color will be. The dye is evenly distributed in the fiber, the absorption of incident light is more, and the color is deeper. However, for the ring dyed fiber, the dye is limited to the surface of the fiber, and the absorption of incident light is relatively small, so the color of the fiber is relatively shallow.

It is based on this principle that the polyester fiber dyed at boiling temperature and atmospheric pressure should be baked at high temperature (180 ℃, 30s) on the setting machine. According to experience, after baking, the "ring dyeing" state of polyester fiber will change into "through dyeing" state. Not only the color can be greatly deepened, but also the color fastness (especially ironing fastness) can be fundamentally improved. Especially when dyeing with high temperature disperse dyes.

However, according to practical production experience, the baking conditions must be sufficient and stable. If the baking conditions are different, especially the baking temperature is low or the baking time is short, it is easy to produce obvious or even serious batch difference, cylinder difference, head and tail color difference, left, middle and right color difference due to the different coloring degree of dyes. ,

At present, our domestic dyeing process of polyester is quite mature.