Texture Yarn

Texturing air content and therefore greater insulating capacity, gloss reduction, improved texture, avoid pilling. Chemical fibre filaments are usually used as fibre material (in addition to acetate, tri-acetate, cupro, viscose, mainly polyamide 6/6.6, polyester, polyacrylonitrile, modacryl). Special yarns made of natural fibre (e.g. → Slack mercerization of cotton) are less significant. The extensive range of textured yarns makes it necessary to divide them simply into the following textured yarn types in accordance with their main properties of appearance and manufacture: I. Stretch-yarns: highly elastic, stretchable to approx. 5-fold length, usually made of thermoplast threads with relatively low bulk (→ Helenca principle), preferable not doubled but in Z or S form. Produced mainly by means of real or false twist process, Klingen process. (→: Core spun yarns; Elastomeric fibres). II. Crimped yarns: in addition to strong mechanical or chemically-created crimp, these are characterised by moderate elasticity and moderate to strong volume. Production particularly according to stuffer-box process, gear-wheel crimping process. (Bi-component yarn; in the case of bi-component thread material bulking is also by means of subsequent hot-air treatment in tumbler or in specialised dry-cleaning machine). III. Bulked yarns: are characterised by high volume and therefore good covering power, combined with relatively low additional elasticity. Produced mainly by air jet technique. IV. Types on the borderline of basic types I.-III, for example highly-elastic volume-yarns, elasticity-regulated (so-called modified) stretch yarns, high-volume crimped yarns and the like (e.g. →: Torque; Non-torque yarns). BISFA definition of textured yarns: – Dual-component yarn: textured yarn containing filaments which consist of two components (dualcomponent fibres). – False twist bulked yarn: texture yarns treated with false twist process producing high crimp elasticity or crimp contraction. – False twist yarn (set yarn): yarn treated with false twist process where a heat fixing process is carried out in a state of intermediate tension between complete relaxation and complete uncrimping. – Yarns with variously shrinking filaments: textured yarn made of two groups of filaments with differing shrinking properties. – Knit/de-knit yarn which is de-knitted after knitting. – Torque-yarn: yarn with a strong looping tendency. Texturing This term isused to include all process stages downstream of the actual texturing process. In the filament yarn sector these include: – Intermingling: normally accomplished by air-jet techniques, 46

– Assembling: combination of multiple yarns with zero twist, – Coning (winding): transferring the yarn onto a suitable carrier. Texturizing The treatment of smooth filament yarns by permanently modifying the orientation of the molecular structure giving it more textile character. The changes to texturized yarns are: improved softness, volume and covering power, increased thermal insulation effects and an end-use required increase in elasticity. Thermoplastic filament yarns are particularly suitable for texturizing, i.e. yarns which are deformable under the influence of heat. These are mainly polyamide and polyester yarns. The most important texturizing processes are (Fig. 1): – Twist-texturizing (including false twist): A filament yarn which has been twisted under the influence of heat is straightened again. – Air jet texturizing: Yarn is crimped in a turbulent current of air (gas or steam). – Knit/de-knit texturizing: Yarn is knitted, subjected to heat treatment and then de-knitted. – Stuffer box-texturizing: Yarn is crimped by means of compression. – Asymmetrical heat-texturizing: Contraction of the filaments on one side only is induced by asymmetrical heat treatment. – Edge-texturizing: Yarn is pulled over an edge at an acute angle. – Gear wheel-texturizing: Yarn is crimped between two sprockets. Processes have been developed for the most commonly used twist-texturizing with which the texturizing procedure is combined with stretching. Thermoplastic filament yarns are usually smooth when they have been spun and less well adapted to requirements than natural fibre yarns. The textile qualities of such yarns are improved significantly by texturizing procedures. Texturizing often increases the volume of the filament yarn by modifying the geometrical form of the filaments resulting in a certain elasticity in some cases which represents an advantage for the yarn. In the lower decitex range up to 300 dtex (frequently clothing fabrics, underwear and curtains) the false twist texturizing process is the predominant texturizing technique. This is mainly due to the economical nature of the technique but also to the elastic properties of the resulting yarn. The false twist texturizing process (Fig. 2) is based on twisting the filament to a high-twist density and fixing this twist into the molecular structure of the filaments by heating and subsequent cooling in this twisted form. The yarn is then completely straightened. As the filaments and therefore their molecules have had a migrated spiral-form configuration, back-winding the filaments does not re-align the molecules. The filaments

Texturizing False twist

Edge crimping process

Knit/Deknit process

Stuffer box process

Wavy crimp, elongation, yarn produces a loftiness crepe effect

Zig-zag to wavy crimp, low elasticity, increased

Air jet process

Working plan

Properties

Highly elastic (HE) yarn, good extensibility and large bulk volume, as stabilised (set) yarn, lofty with less elongation

Helical crimp, elastic yarn low with increased bulk volume

Inelastic yarn, increased loftiness due to capillary thread loop formation, fancy yarns

Crimp structure

Fig. 1: Comparison of the most current texturizing processes.

GEOMETRIC CONFIGURATION

MOLECULAR STRUCTURE

FIRST HEATER

SPINDLE (S)

corkscrewed HE yarn

SECOND HEATER

Fig. 2: Schematic illustration of the false twist texturizing process with the geometric and molecular structure of an individually texturized filament in different processing stages (according to Akzo).

SET corkscrewed yarn

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