CTD 215 Lecture 9: Textiles Chapter 9 Yarns

6 Pages
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Department
Clothing, Textiles and Interior Design
Course Code
CTD 215
Professor
Dr.Thompson

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Description
Yarn 1 From Fibers to Yarns Definition of Yarn • A yarn is a continuous strand of textile fibers, staple or filament, in a form suitable for weaving, knitting, or otherwise intertwining to form a textile fabric. • A yarn is a constructed assemblage of textile fibers, which acts as a unit in fabric formation. Classification • Yarns may be: ➢ Staple or filament ➢ Single or plied ➢ Simple or complex • In addition, filament yarns may be: ➢ Flat or texturized Types of Yarn 1. Staple (short fibers) or 2. Single (one strand) or 3. Simple (same appearance along length) or • Filament (continuous filaments) • Plied (two or more strands, twisted) ➢ *Cord (Cabled) • Complex (variable appearance along length) Filament Yarns May Be • Flat or texturized • A t-shirt would probably be knit from a SIMPLE, SINGLE, STAPLE YARN. • Fabric for a slip would probably be knit from a FLAT, SIMPLE, SINGLE FILAMENT YARN. • Cord (TOP), Single (CENTER), and Ply (BOTTOM) yarns Examples • 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 = tpc x 2.54 • Yarn properties are affected by the degree of twist, but not by the direction (S or Z) of twist. Spun Yarns • Continuous strand of fabrics held together by some binding mechanism, made from short fibers. Characteristics • Fuzzy: fiber ends protrude along length of yarn • Yarn strength related to cohesiveness of fibers and number of contract points along fiber. • Low twist yarns separate easily with force; yarn strength not related to fiber strength. • Likely to pill as fiber ends break off. • More comfortable when in contact with skin (less area of yarn in contact with skin, the more comfortable and less clammy and confining it is). • More likely to create problems with soiling. 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, which causes them to buckle and decrease in length. Woven fabrics containing these yarns have a pebbled surface texture. Yarn Twist Staple Yarns • Yarns with lower twist ➢ Harrier ➢ Pills more ➢ More comfortable skin contact ➢ Less cost Types of Yarn Twist • Crepe yarns, have a high tpi (turns per inch) • Low Twist Yarns ➢ Smooth and texturized bulk filament yarns; very low twist. • Spun Yarns ➢ Napping Twist: low twist, usually filling direction to facilitate brushing fibers to surface (napping); for flannelette, flannel, blankets, etc. ➢ Average Twist: most common type of twist, neither low nor high, used for most end uses. ➢ Voile Twist: high twist, used for voile ➢ Crepe Twist: very high twist, produces lively yarn Yarn Size • Yarn number: cotton, woolen, worsted systems are indirect systems; length per unit weight (finer yarns, higher numbers). • Denier: Direct system; weight per unit length (g/9000 m) – finer yarns, lower numbers; denier is used for yarns and fibers. • Tex System: weight per unit length (g/1,000 m); finer yarns, lower numbers (decitext or dtex) 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) continuous filament yarns, only a small amount of twist (.05 to 2.0 tpi) is inserted, to maintain the coherence of the yarn. Filament Yarns • Smooth-filament yarns: regular or conventional filament yarns. • Production: used as produced, no further processing required. • Uses: in smooth, lustrous fabrics or where high strength, compact yarns are needed. Characteristics • More expensive than staple to produce; low production rate number of holes in spinneret equal to number of fibers in yarn. • Smooth with low or no twist, except crepe twist yarns • No protruding ends (no lint, no pills) • Sheds soil • Compact with little bulk, cover, or loft Characteristics (Cont’d) • Strength related to fiber strength and multi-filaments • Fiber strength fully used • Size based on denier system; related to number and size of filaments • Characteristics related to number and size of filaments ➢ Fine fibers – soft and supple yarn ➢ Coarse fibers – stiff and abrasion resistant yarn • Fibers as long as the yarn and the fabric from which they are removed Types • Smooth-filament (mono or multi-filament) • Tape yarns (fibrillated fibers or slit films) • Network yarns – similar to tape yarns, but with greater bulk and comfort Texturizing • Fabrics made from flat continuous filament yarns exhibit specular reflectance (shone) and are smooth with minimal surface friction. • Continuous filament yarns are often texturized, in order to produce fabrics with spun-yarn aesthetics: diffuse reflectance, matte surface, and increased surface friction. • 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). • T
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