Heatsetting

When using heat setting for carpet yarns, desirable results include not only the diminishing of torquing but also the stabilization or fixing of the fiber thread.

All processes using temperature and/or moisture to give textiles one of the above-mentioned attributes are known as heat setting.

The crinkle tendency is due to the technological conditions of the spun yarn production and the physical fiber properties.

Above all, the "technological conditions of the spun yarn production" means the turning moment of the thread.

During the spinning process this spot took up more twists and is therefore subjected to higher inner tensions, which ultimately break the thread core.

Further positive aspects of steaming are the reduction of curling and, at the same time, the setting of the physical properties of closeness and extension imparted to the yarn by twisting.

Due to the increase of temperature in the fibers during steaming an oscillation of the molecules is produced which leads to the bursting of the hydrogen bridges; now residual valencies are set free which are able to saturate with the dipole water.

Now the individual polypeptide chains can no longer be shifted against each other and the fibers regained their former closeness, however without having remarkable tensions inside.

In crystalline domains physical forces of attraction are acting between the closely parallel lines of polymers.

The increase of oscillation that can be influenced by the degree and the period of heating dissolves the electric bond forces in the fiber; at first in the amorphous domains, later in the crystalline ones and at last in the polymers.

The problem of synthetic fibers is that the reduction of the binding forces only takes place between the so-called deformation point (start of changing the firm solidified – amorphous fiber domains into a visco-elastic – easily deformable state) and the distortion point (the crystalline fiber domains change into a visco-elastic state, too) which is in a relatively high temperature range.

The quality of cut pile carpets is improved significantly by a reduction of inner tensions in the yarn.

Especially for cut-pile and its variations (Saxony, shag, frieze) the heat setting process is of highest importance.

A cut pile carpet with frayed yarn ends would have a poor appearance, a shorter life cycle and ergonomic disadvantages for the "walker" as scientific research has proven.

A carpet manufactured from heat set yarn is more attractive, durable and comfortable for the user.

Normally a heat set carpet can be identified by its grainy structure, which is called "pinpoint tip definition" in the industry.

After steaming and drying, the bobbins are transported on to the winding machine where they are re-wound onto a cross-wound package.

In the Power-Heat-Set process, the yarns and filaments oxidize slightly on the surface due to the existing oxygen in the surrounding atmosphere and the higher temperatures.

In the TVP3 process yarn is placed on a conveyor belt and inserted through a lock into a pressure tunnel that could be up to 15 m long.

The yarn which is still hot and moist is dried and cooled after heat setting and fed to the winding process.

In the Power-Heat-Set process yarn is heat set with superheated steam in an open system at atmospheric pressure.

One way is to place the yarn in coils or a "figure 8 pattern on a belt or to wrap it onto ropes arranged as a polygon in order to convey it through the process.