From fibers to yarns
Definition of Yarn
• • • • A yarn is a constructed assemblage of textile fibers which acts as a unit in fabric formation.
Yarns may be:
• Staple or Filament • Single or Plied • Simple or Complex
In addition, Filament yarns may be:
* Types of Yarn
1. Staple (Short fibers) 2. Single or (One Strand)
3. Simple or (Same appearance along length) Filament (Continuous Filaments) Plied *Cord(Cabled) (Two or more strands, twisted) Complex
(Variable appearance along length)
Filament Yarns may be
• Flat or Texturized • A T-shirt would probably be knit from a SIMPLE, • • Fabric for a slip would probably be knit from a FLAT,
• Staple Fibers twisted together • Filament fibers laid side by side, with some twist applied • Single filament fiber • Strips made by lengthwise division of a sheet of material
The direction and amount of twist
• Twist in staple (spun) yarns is given in units of turns of twist per unit length, either turns per inch (U.S.) or turns per centimeter (Europe, Asia). • tpi= • • Yarn properties are affected by the degree of twist, but not by the direction (S or Z) of twist.
Effect of Twist on Staple Yarn Properties
• As twist increases, yarn strength and yarn stiffness increase up to a point, level off, then begin to fall at very high twist levels. • Yarns with extremely high levels of twist are called “crepe yarns”; these yarns possess a high degree of torque • • • Woven fabric containing these yarns have a pebbled surface texture.
Yarn Twist Staple Yarns
• Yarns with lower twist
– – – –
Harrier More comfortable skin contact Less cost
Crepe yarns, have a high tpi (turns per inch)
Continuous Filament Yarns
• Continuous filament yarns are assemblies of continuous filament fibers twisted together; each individual fiber runs through the entire length of yarn. • For flat (not texturized) • • • Texturizing • Fabrics made from flat continuous filament yarns exhibit specular reflectance (shine) and are smooth with minimal surface friction.
• Continuous filament yarns are often texturized, in
order to produce fabrics with spun-yarn aesthetics:
• Texturizing processes all increase yarn bulk, and most increase yarn stretch. Texturizing continuous filament yarns are often referred to as BCF yarns (bulked continuous filament yarns). • The rationale behind texturizing is that all manufactured yarns are made in continuous filament form. Many of these are then cut into staple lengths and put through the complete spinning process, restoring them to a continuous strand of twisted staple fibers to be woven or knit. *
Characteristics Texturized Filaments
• More absorbent • • • • Better bulk, cover, elasticity • Not pill or shed
• The most common texturizing process is the false-twist process • • Twist is inserted in a heated zone, then removed in an unheated zone. When the yarn is relaxed, it reverts to its twisted state. 50 to 60 tpi can be inserted at very high production rates.
• Stuffer box texturizing was originally used for BAN-LON™ products. Filaments in stuffer box yarns have a highly irregular 3-D crimp. Filaments jammed into heated box to create random crimp. • Knife edge texturizing (Agilon™) increases yarn stretch and bulk. Filaments have a spiral 3-D crimp; • • Filaments are run across a heated knife edge, like curling ribbon • Other processes include twist-heatset-untwist (Helanca™) and knitdeknit.
• Air-jet texturizing (Taslan™, Rotofil™) increases yarn bulk moderately but does not increase stretch. Air-jet texturizing ranks behind falsetwist texturizing in use. • FALSE-TWIST 75% • AIR-JET 20% • ALL OTHERS 5% • All texturizing processes except Air-Jet require that the filament fibers may be _______________(e.g. polyester, nylon). Any fiber type may be used...
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