2. Texturing of Filament Yarns Flashcards
Processing filament yarns
By making use of their thermoplastic properties, manufactured yarns can be textured into softer, bulkier yarns with increased warmth, comfort and absorbency.
Texturing yarns that contain fibres that are not thermoplastic, such as rayon or glass
Are sometimes textured mechanically, without heat, by using air-jet or fluid texturing.
Texturing Methods
False-twist method Knife-edge method Stuffer-box method Air-jet method Gear-crimping method Knit-de-knit method Bicomponent texturing Spinnerette texturing
False-twist method
A twist is inserted into simple filament yarns. By applying heat, this twist is heat-set into the yarn. After cooling, the yarn is untwisted. A permanent kink remains in the yarn.
Knife-edge method
The yarn is passed over a heated knife edge. The yarn then curls, similar to paper gift ribbon when drawn quickly over a sharp knife or scissor blade.
Stuffer-box method
Filament fibres are forced into a container and then heat-set in this cramped condition, causing a zig-zag crimp.
Air-jet method
This method is also called fluidtexturing because a fluid stream of air is used. A stream of air or steam hits the filaments when they are in a relaxed state. Loops or curls are formed in the individual filaments making up the multifilament yarn. They become entangled and form a yarn with high bulk. No heat-setting is required.
Gear-crimping method
The filaments are passed between the teeth of two heated gears. The form of the gears is set into the fibre.
Knit-de-knit method
The filament yarns are knitted into fabric, heat is applied, and after cooling, the knitting is unravelled. The unravelled yarn now has the characteristic curl of unravelled knitting permanently.
Bicomponent texturing
In the section on bicomponent yarns in the CLO2601 module, it was mentioned that this can also be used as a method of texturing. Two types of the same generic fibre, for example, two types of nylon, are extruded simultaneously. One type will shrink more on cooling than the other, and since they now cling together to form one filament, the filament will curl or kink.
Spinnerette texturing
Filament yarns can be textured by modifying the shape of the spinnerette, by changing the air flow at the spinnerette or by vibrating the spinnerette. These methods are not frequently used.
1 Why are yarns sometimes textured?
Multi Filament yarns are smooth and slippery to touch so they need to be modified to make them softer and bulkier. This improves their properties and they behave more like natural fibres.
2 Describe the texturing process that can be applied to rayon filaments.
Texturing can be applied to thermoplastic and non thermo plastic fibres, but the technique differs, for non thermo plastic fibres, such as rayon, an air jet is used.
3 List the texturing processes that make use of the thermoplastic properties of filaments.
Thermo plastic fibres becomes soft when heated and again when cooled down. There are various texturing methods available which makes use of this property, for example: false twist, stuffer box, knife edge, knit de knit, air jet and gear crimp.
4 Explain the principle on which bicomponent texturing is based.
Bi component texturing also makes use of the softening and hardening of thermoplastic fibres but in this case the filament is made of two types of the same fibres which shrinks at different rates upon cooling.
