Yarn Processing 2/26/2008. Smooth filament yarns: Regular or conventional filament yarns.

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1 Yarn Processing A continuous strand of textile fibers, filaments, or material in a form suitable for knitting, weaving, or otherwise intertwining to form a textile material. 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. 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 1

2 Strength related to fiber strength and multifilaments Fiber strength fully used Size based on denier system; related to number & size of filaments Characteristics related to number and size of filaments Fine fibers soft & supple yarn Coarse fibers stiff & abrasion resistant yarn Fibers as long as the yarn and the fabric from which they are removed 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 Monofilament Multifilament Greater covering power or apparent volume compared to smooth filament yarn; also called bulk continuous filament (BCF) yarns. Characteristics Less smooth More permeable to air & liquids Less slippery More comfortable (may be more absorbent) Less static prone More bulk, cover, and elasticity 2

3 Compare spun, smooth filament, and bulk filament yarns (left to right). False twist: Continuous process where yarns are twisted, heat set, uncoiled; widely used method. Draw texturing: Drawing & texturing in one step; faster; cheaper; yarns of equal or better btt quality. Stuffer box: Filaments stuffed into heated box; increases volume %; widely used method. Air jet: Air tangles fiber; increases volume %; little or no increase in stretch. Knit deknit: Knit, heat set, unknit. Bulky: From inherently bulky fibers; less stretch than stretch or textured yarns. Stretch: High degree of potential stretch & rapid recovery; moderate bulk. Textured: Bulky yarns with comfort stretch. Continuous strand of fibers held together by some binding mechanism, made from short fibers. 3

4 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 ih 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. Opening: Loosens, cleans, blends fibers; removes dirt; helps determine yarn quality. Carding: Partially straightens fibers & forms into thin web; produces carded sliver. Drawing: Increases parallelism of fibers; combines carded slivers into a drawn sliver; continues blending for self blended yarn, decreases sliver size. Combing: Select yarns of high quality fibers; removes short fibers & increases parallelism of fibers. 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; line yarns: longer and more parallel fiber. 4

5 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 & add full amount of twist; winds finished yarn on bobbins. Ring or conventional: Series of operations. Open end rotor: Eliminates roving & ring twisting (better quality yarns, fewer knots). Friction spinning: Combines rotor & air techniques; more even yarns; freer of lint, & loftier, but weaker. Air jet: Similar to rotor, but twist formed by moving air; rougher & less elastic yarns than rotor spun yarns. Direct: Similar to conventional; roving eliminated. Compact: Variation of ring spinning that condenses the roving before final twist insertion; smoother & stronger yarn. 5

6 Vortex: Twist develops as fibers swirl around spindle; eliminates shorter fibers. Twistless: Eliminates twist; holds fibers together with starch or sizing; soft, lustrous, opaque fabric with good dyeability & durability. Self twist: Inexpensive way to ply 2 yarns of different twist (1S & 1Z) direction. Tow 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. Part of tow is heat stretched. Two parts combined, cut, and spun by conventional methods. Immersed in hot water; heat stretched fibers shrink; non heat set fibers create bulk in yarn. 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). Combination: Two unlike yarns twisted together to form a ply (simple or novelty yarn). 6

7 Combine different fibers to get better combination of characteristics in product; achieve characteristics that are combinations of the fibers in the blend Improve processing and uniformity Obtain better hand, texture, and appearance Economize Obtain cross dyeable effects 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 of yarn. Other possibilities Blended filament yarn: two unlike filaments blended together Fasciated yarns: filament & broken filament Hearing protection required. Opening steps create air borne dust (controlled by vacuum heads or humidity levels). Waste recycled whenever possible. Ring spinning often in low cost labor countries with related issues of social responsibility. 7