The purpose and function of stretching

Drawing is an essential and important process in the manufacturing process of polyester fiber, which is often called the second stage of polyester fiber forming, or the second forming. It is not only a necessary means to improve the physical and mechanical properties of the fiber, but also a gateway to test the quality of its previous processes. During the stretching process, the macromolecular or agglomerative structural elements unfold and align along the fiber axis. At the same time of orientation, it is usually accompanied by the change of phase state and other mechanism characteristics.

Due to the tension in the process of the macromolecular along the fiber axis orientation inside the fiber, and increase the hydrogen bond and dipole button, and other types of intermolecular forces, fiber plus a number of molecular chain tension increased, so that the breaking strength of the fiber increased significantly, extending degree of decline, the frictional resistance and fatigue strength of different kinds of deformation are also improved obviously.

Principle of drafting unit

The main purpose of tow drafting is to improve the orientation of the molecular chain so that it has a certain strength and elongation. The draft is produced between two draft mechanisms. The wire bundles between the front and rear drawing mechanisms are stretched due to the difference in surface velocity of the drawing roller. The ratio of the surface velocity of the drawing roller of two drawing mechanisms is called the stretching multiple. In fact, there is slippage on the surface of the draft roller, the actual draft multiple will be lower than its theoretical value. Because the total denier number of the tow is very large, up to 1 ~ 2 million denier or even higher, and the drafting force required is also very large, the help drafting mechanism must be made very strong.

The main function of the draft machine is to apply external force in the axial direction of the wire bundle under certain conditions, to pull down the single fiber in the wire bundle, improve the orientation degree, and change the single fiber from the plastic state of low strength and high elongation to the elastic state of high strength and low elongation.