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CHAPTER 7Yarn Formation

OBJECTIVES

What is a yarn?What are the different types of yarns available?How are yarns made?How

YARNA continuous strand of textile fibers, filaments, or material in a form suitable for knitting, weaving, or otherwise intertwining to form a textile material.

BASED ON FIBER LENGTH

Spun yarns: Made from short-staple fibers.Regular or smooth filament yarns: Made yfrom long, smooth filament fibers.Textured-bulk-filament yarns: Made from crimped filament fibers.

FILAMENT YARNS

Monofilament yarns – single filament by itself used as the yarnMultifilament yarns – several filaments that make up the yarn extruded at once (30 to make up the yarn – extruded at once (30 to several thousand) and twisted together

FILAMENT YARNS Smooth-filament yarns: Regular or conventional filament yarns.

Production: Used as produced or further treatments added (dye, finishes, texture, etc.)

Uses: I th l tr f bri r h r high Uses: In smooth, lustrous fabrics or where high strength, compact yarns are needed.

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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 p gSheds soilCompact with little bulk, cover, or loft

CHARACTERISTICS (CONT’D)

Strength related to fiber strength and multi-filamentsFiber strength fully usedSize based on denier system; related to number & size of filamentsCharacteristics related to number and size of Characteristics related to number and size of filaments

Fine fibers—soft & supple yarnCoarse fibers—stiff & abrasion resistant yarn

Fibers as long as the yarn and the fabric from which they are removed

TYPESSmooth-filament (mono or multi filament) Tape yarns (fibrillated fibers/split films or slit films) Network yarns—similar to tape yarns, but with greater bulk and comfort (foamed polymer)g ( p y )

YARNS

MonofilamentMonofilament MultifilamentMultifilament

TEXTURING

False twist: Continuous process where yarns are twisted, heat set, uncoiled; widely used method.y

Knife Edge: Heated filaments drawn over an edge.

Stuffer box: Filaments stuffed into heated box; increases volume 200-300%; widely used method.

Air jet: Air tangles fiber; increases volume 50-150%; little or no increase in stretch.

Knit-deknit: Knit, heat set, unknit.

TYPES

Bulky – sweaters, carpetsCrimped - thermoplastic fibers – may be used for some stretchsome stretchTextured – mechanical, chemical and/or heat treatments used; spun or filament yarns

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TEXTURED TYPES

Bulky: From inherently bulky fibers; less stretch than stretch or textured yarns.Stretch: High degree of potential stretch & rapid recovery; moderate bulk.Loopy/Textured: Bulky yarns with comfort stretch.

BULK YARNS Greater covering power or apparent volume compared to smooth filament yarn; also called bulk continuous filament (BCF) yarns.Characteristics

Less smoothMore permeable to air & liquidsLess slipperyMore comfortable (may be more absorbent)Less static proneMore bulk, cover, and elasticity

HIGH BULK YARNS Part of tow is heat stretched.Two parts combined, cut, and spun by con entional methodsconventional methods.Immersed in hot water; heat stretched fibers shrink; non-heat set fibers create bulk in yarn.

SPUN YARNS

Continuous strand of fibers 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 contact 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 & confining it is).More likely to create problems with soiling.

SPINNING PROCESS – COTTON SYSTEM Opening: Loosens, cleans, blends fibers; removes dirt; helps determine yarn quality.Carding: Partially straightens fibers & forms into thin web; produces carded sliver.Drawing: Increases Drawing: Increases parallelism of fibers; combines carded slivers into a drawn sliver; continues blending for self-blended yarn, decreases sliver size (to a roving.)Combing: Select yarns of high quality fibers; removes short fibers & increases parallelism of fibers.

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COMPARE CARDED AND COMBED YARNS

OTHER SYSTEMS

Woolen system: Wool fibers; soft, bulky, fuzzy yarns.Worsted system: Wool fibers; more even fiber distribution & more parallel; compact, smooth, strong yarns.Flax system: Tow yarns—shorter & less parallel fibers; Flax system: Tow yarns shorter & less parallel fibers; line yarns: longer and more parallel fiber.

WOOLEN (TOP) AND WORSTED (BOTTOM) YARNS

SPINNING PROCESS (CONT’D)

Roving: Reduces size of drawn sliver, increases fiber parallelism; adds small amount of twist. Repeated several times (blending often occurs here).Inserting yarn twist: Several options to reduce size g y p& add full amount of twist; winds finished yarn on bobbins.

INSERTING YARN TWIST

Ring or conventional: Series of operations. Open end rotor: Eliminates roving & ring twisting (faster roving & ring twisting (faster process, but weaker yarn).Friction spinning: Combines rotor & air techniques; more even yarns; freer of lint, & loftier, but weaker.

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ALTERNATE SPUN YARN PROCESSES

Air jet: Similar to rotor, but twist formed by moving air; rougher & less elastic yarns than rotor spun yarns.Direct: Similar to conventional; roving eliminatedeliminated.Compact: Variation of ring spinning that condenses the roving before final twist insertion; smoother & stronger yarn.

ALTERNATE SPUN YARN PROCESSES

Vortex: Twist develops as fibers swirl around spindle; eliminates shorter fibers.Twistless: Eliminates twist; holds fibers together with starch or sizing; soft, lustrous, g gopaque fabric with good dyeability & durability.Self-twist: Inexpensive way to ply 2 yarns of different twist (1S & 1Z) direction.

SPINNING FILAMENT TOW INTO SPUN YARNSTow-to-top (sliver system): Tow converted into staple by diagonal cutting (cut to desired length) or break stretch (stretched until fiber breaks at weakest point, uneven length) and formed into sliver; spun by conventional system.

Tow-to-yarn: Direct spinning system where fibers are broken at weakest point and spun into yarns in continuous process.

ENVIRONMENTAL IMPACT

Hearing protection required.Opening steps create air-borne dust (controlled by vacuum heads or humidity levels)levels).Waste recycled whenever possible.Ring spinning often in low cost labor countries with related issues of social responsibility.

TWIST

Spiral arrangement of fibers within a yarn.Direction: S or Z (Z is most common)Amount of twist: Varies with length of fiber, yarn i & d l i g g l size, & end use; low, napping, regular,

high/voile, or crepe twist.

TYPES OF YARN TWIST

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LOW TWIST YARNS

Smooth and textured 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.

SPUN YARNS

Average Twist: Most common type of twist, neither low nor high, used for most end uses.

SPUN YARNS

Voile Twist: high twist, used for voile

SPUN YARNS

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 Denier: Direct system; weight per unit length (g/9,000 m)—finer yarns, lower numbers; denier used for yarns and fibers.Tex system: Weight per unit length (g/1,000 m); finer yarns, lower numbers (decitex or dtex).

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YARN TYPES

Simple: All parts are alike.

Single: Spun or filament.

Ply: Two or more singles; increases diameter, tr gth d rf r ( ll r ) strength, and performance (usually spun yarns).

Cord: Ply yarns are twisted together.

Uses: Industrial products.

SINGLE, PLY, AND CORD YARNS

CORD (RIGHT), SINGLE (LEFT), AND PLY (BOTTOM) YARNS

SEWING THREAD

Yarn intended for stitching materials together by machine or hand process.Available in several sizes and structures: ply, corded, cable, braided, textured filament, smooth filament, monofilament, and core spun.L b i fi i h f ili iLubricant or wax finish to facilitate sewing.Many fibers used.Sized as denier, tex, count, yarn number, or ticket number.

FANCY, NOVELTY, OR SPECIALTY YARNS

Single: 1 partComplex: 2 or more parts

Ground or foundation or core componentFancy or effect componentFancy or effect componentBinder

Uses: Usually in filling only; adds interest; may add crease resistance to fabric; decreases durability; increases cost; fashion component.

PARTS OF A NOVELTY YARN

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EXAMPLES OF NOVELTY YARNS TYPES

Slub or flake: Single, spun fancy thick-thin yarn.The twist can be varied at regular intervals.The thicker part can be twisted less than the thinner part.

Spiral or corkscrew: Two parts twisted together; differ in color, size, or texture. Ratiné: Spiral effect with loops at intervals. Knot, spot, nub, or knop: Effect twisted many times in one spot.

TYPES

Spike or snarl: Open loops at intervals.

Loop, curl, or bouclé: Closed loops at intervals.

Metallic: Metal incorporated with yarn.

Chenille Sh t il fib h ld i l b t bi d Chenille: Short pile fibers held in place by two binder yarns twisted together.

FABRICS WITH NOVELTY YARNS

EFFECT PLY FOR SEVERAL KINDS OFFANCY YARNS FIBER BLENDS

Blend: Intimate mixture of different fibers (varied by type, length, size, color, etc.) in one yarn.

Mixture: One type of yarn used in one fabric place (i.e., warp) & another type used in another fabric place (i.e., filling).(i.e., filling).

Combination: Two unlike yarns twisted together to form a ply (simple or novelty yarn).

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REASONS FOR BLENDS

Combine different fibers to get better combination of characteristics in product; achieve characteristics that are combinations of the fibers in the blendImprove processing and uniformityObtain better hand, texture, and appearanceEconomizeObtain cross-dyeable effects

BLENDS

Blend levels: Related to end use and performance specifications.

Stage of blending: Earlier in processing, blend is more uniform. Light density fiber works to outer edge more uniform. Light density fiber works to outer edge of yarn.

Other possibilitiesBlended filament yarn: two unlike filaments blended togetherFasciated yarns: filament & broken filament

FIBER DISTRIBUTION IN YARNS COMPOSITE YARNS

Regular in appearance with unlike components.Types:

Covered: Yarn wraps around spandex/rubber.Core-spun: Fiber completely covers core of another fiber.Wrap spun: Staple fiber core wrapped with filament.Fasciated: Filament wrapped with staple fibers or filament yarn wrapped with filament fibers.Polymer with staple fibers; inexpensive.

YARN PERFORMANCE

Characteristics & performance measured to ensure consistent fabric and product quality and performance.

Size twist bulk evenness & appearanceSize, twist, bulk, evenness, & appearanceStrength, resistance to abrasion, & other performance aspects

YARN QUALITY Thin spots assessed to minimize problems with processing, fabrication, and finishing.Neps: Small knot of entangled fibers; assessed to minimize problems with dyeing and finishing. Hairiness: Excessive fiber ends on yarn surface make the yarn more sensitive to abrasion and ypilling; assessed to minimize problems with fabrication and performance.

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SUMMARY

A yarn is a continuous strand of staple fibers, filament(s), or some other material that can be used to make a textile.The categories that yarns can fall into are: spun yarns, smooth filament yarns, or textured filament yarns.

Filament yarns can be either monofilament or multifilament. They can also be made as tape or network yarns.Textured filament yarns can be created in a variety of ways and utilized for texture, bulk, stretch or comfort.

Filament yarns are created through the extrusion process previously coveredSpun yarns refer to staple length fibers. They go through a general process of cleaning, combing in various ways and stages, and twisting to form the yarn.

Spun yarns can go through more or less combing, which affects how strong and smooth the yarn is. If it goes through less combing it is called either combed (cotton process) or woolen (wool process); if it goes through more combing it is called carded (cotton process) or worsted (wool process).

Yarns can twist in a clockwise or counter-clockwise direction: z-twist or s-twist. The z-twist is the most common.Yarns can have a low amount of twist or a high amount. This will affect what type of fabric and ultimately, what type of end-use the yarn is for.Yarns can be twisted into a certain type of grouping: single spun, ply yarn, cord or fancy yarncord or fancy yarn.Yarns can be blended in a variety of ways and for different reasons.Quality must be monitored at every level.