The main process conditions for heat setting are 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 existing wrinkles are eliminated, the surface flatness is improved, and the fabric's dimensional thermal stability is improved
Time is another major process condition for heat setting. Fabric entry the hot zone, the time required for heating and setting can be divided into the following parts:
(a)After the fabric enters the heating zone, heat the surface of the fabric,the time required to reach the setting temperature,this called heating time.
(b)After the surface of the fabric reaches the setting temperature, the fibers all have the same heat penetration time as the set temperature.
(c)After the fabric reaches the setting temperature, the molecules in the fiber,the time required to adjust according to the set conditions,this named molecular adjustment time.
(d)The fabric exits the drying chamer, so that the size of the fabric is fixed.The time required for cooling,it's cooling time. The setting time usually refers to the time required for the first three items.
It does not include the fourth item. The time required for heating and thermal penetration depends on the performance of the heat source, the GSM, and the fiber thermal conductivity
and moisture content of fabrics. The tension experienced by the fabric during heat setting affects the quality of the setting, including the thermal stability of the fabric size
qualitative, strength and elongation all have a certain effect. The thermal stability of the warp dimension increases with the increase of the overfeed in the warp direction, and
weft dimension thermal stability decreases as the degree of stretching increases. The average single yarn strength of the shaped fabric is slightly higher than that of the unshaped fabric.
The change in the zonal direction is more obvious than the warp direction. After shaping, the elongation of the fabric decreases with the increase of the stretch, and the warp increases following overfeeding .
In order to obtain good dimensional thermal stability of the fabric and to improve the wearability of the fabric, heat setting there should be proper overfeeding in the warp direction, and the weft extension should not be too high.
For this reason, it is required not to use a large warp tension in the pretreatment to avoid excessive elongation and forcing a greater contraction in the latitudinal direction, so that a larger stretch is required in the end.
The presence of swelling agent on the fabric during heat setting has a certain relationship with the setting effect.
When setting in damp heat, the heat setting temperature should be reduced accordingly. Commonly used swelling agents are water or steam, moisture presence or absence has a significant effect on nylon dyeing properties.