Views: 1000 Author: Site Editor Publish Time: 2022-01-12 Origin: Site
Fabric heat setting is usually a process of keeping the fabric in a certain size, heating it for a certain period of time and then cooling it under a certain temperature and humidity conditions. Therefore, the main process conditions of heat setting are nothing more than temperature, time, tension and swelling agent.
Temperature is the most important factor affecting the quality of heat setting. Because after the fabric is heat-set, the extent to which the existing wrinkles are eliminated, the surface smoothness is improved, the dimensional thermal stability of the fabric and other wearing properties are closely related to the heat-setting temperature.
Setting time is another major process condition for heat setting. After the fabric enters the heating zone, the time required for heating and setting can be roughly divided into the following parts:
①After the fabric enters the heating zone, the time required to heat the surface of the fabric to the setting temperature, or the heating time.
②After the surface of the fabric reaches the setting temperature, make the fibers inside and outside the fabric have the same heat penetration time required for the setting temperature.
③ After the fabric reaches the setting temperature, the time required for the molecules in the fiber to be adjusted according to the setting conditions, or called the molecular adjustment time.
④ The time required for the fabric to leave the drying room and the size of the fabric to be fixed for cooling, or called cooling time.
Usually referred to the stereotype time, often refers to the time required for the first three items, excluding the fourth item. If the first item is regarded as a preheating effect, then the setting time only refers to the time required for the second and third items, that is, the time required for thermal penetration and molecular adjustment. The time required for heating and heat penetration depends on the performance of the heat source, the weight of the fabric unit area, the thermal conductivity of the fiber and the moisture content of the fabric.
The tension on 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 warp dimensional thermal stability increases with the increase of warp overfeed during shaping, while the weft dimensional thermal stability decreases with the increase of the door width.
The average single-yarn tenacity of the fabric after setting is slightly higher than that of the unshaped fabric, and the change in the weft direction is more obvious than that in the warp direction. The elongation at break of the fabric after setting, the weft direction decreases with the increase of the stretch degree, while the warp direction increases with the increase of the overfeed.
Therefore, in order to obtain good dimensional thermal stability of the fabric and improve the wearing performance of the fabric, the warp direction should be properly over-fed during heat setting, and the weft stretch should not be too high. For this reason, it is required not to use a large warp tension in the pretreatment, so as to avoid excessive elongation and force a large shrinkage in the weft direction, so that a large extension is required at the end.
1. The number of molecular chain refolding increases with the increase of heat treatment temperature:
2. Tension hinders the refolding of the molecular chain;
3. At high temperatures, the effect of tension in hindering chain folding is greatly reduced.
Tension has a significant effect on fiber structure, and there is a close relationship between fiber structures. Therefore, it is very important to pay attention to the control of tension in any shaping process.
4. Swelling agent
Moisture has a "loose" fibrous structure that enhances the fluid-like motion of macromolecular segments. The plasticizing effect of moisture during heat-setting, thereby affecting the supramolecular structure and physical properties of fibers.