Stereotype: A process in the production of chemical fibers. The purpose is to obtain stress relaxation of the fiber after stretching, which is beneficial to improve the crystallinity of the fiber and the stability of various properties, and reduce the boiling water shrinkage. The method is to make the fiber under the condition of being heated for a certain period of time, so that the macromolecule constituting the fiber obtains sufficient activity energy, and adjusts the "position" of the segment, so that the energy of the fiber structure tends to be the lowest. The setting machine is a device that performs the above processes. Stereotypes need to pay attention to many aspects.
Here we talk about the three elements of the process of the stenter:
First, the temperature
Temperature is the most important factor affecting the quality of heat setting.
Because the fabric is heat-set, the degree of wrinkles that have been eliminated, the improvement of surface flatness, the thermal stability of the fabric and other performances are closely related to the heat setting temperature.
The setting time is another major process condition for heat setting. After the fabric enters the heating zone, the time required for heat setting can be divided into the following parts:
Heating time: The time required for the fabric surface to heat up to the setting temperature after it enters the heating zone.
Heat penetration time: After the surface of the fabric reaches the setting temperature, the fibers in the inner and outer parts of the fabric have the same heat penetration time required for the setting temperature.
Molecular adjustment time: The time required for the molecules in the fiber to be adjusted according to the setting conditions after the fabric reaches the setting temperature.
Cooling time: The time it takes for the fabric to exit the oven and fix the size of the fabric for cooling.
Usually referred to the type of time, often refers to the time required for the first three items, not including the fourth item. If the first item is regarded as a kind of preheating, then the setting time refers only to the time required for the second and third items, namely the time required for heat penetration and molecular adjustment.
The time required for heating and heat infiltration depends on the properties of the heat source, the weight per unit area of the fabric, the thermal conductivity of the fibers, and the moisture content of the fabric.
Third, the tension
The tension experienced by the fabric during the heat setting process has a certain influence on the setting quality, including the dimensional thermal stability, strength and elongation at break of the fabric.
The thermal stability of the warp direction increases with the increase of the warp overfeed during the setting, while the thermal stability of the weft dimension decreases as the degree of stretch of the web increases.
After sizing, the average single yarn strength of the fabric is slightly higher than that of the unshaped, and the latitudinal change is more obvious than the warp direction.
After the styling, the elongation at break of the fabric decreases, and the latitude decreases as the degree of stretching increases, while the warp direction increases as the overfeed increases.