tex turing

Filament Yarns and Texturing

© Copyright 2008‐2011 North Carolina State University. All rights reserved.

Slide 1


The vast scope of filament yarn types, classifications, and end uses are discussed in this module. Special attention is paid to production steps and the various ways to texture filament yarns. Composite yarn types are discussed in addition to how the quality of filament yarns is evaluated. Finally, important fabric construction and design factors influencing the optimal use of certain types of filament yarns are addressed.



Slide 2

A Little History

• Rayon was the first man‐made filament fiber, developed in the 1890s.

• Nylon was first produced in the 1940s and soon followed by the polyesters and polyacrylics.

• Polyolefins and polyurethanes were produced during the 1950s.

• Today, almost all manufactured fibers can be used in filament form in filament yarns.

• Acrylic and modacrylic are exceptions – they are typically used in staple form.

• Filament yarns are composed of one or many continuous filaments.

• Filament yarns are assembled with or without twist.

Rayon was the first man‐made filament fiber, developed in the 1890s. Nylon fiber was first produced in the 1940s, which was soon followed by the polyesters and polyacrylics. During the 1950s, the polyolefins and polyurethanes were produced. Today, almost all manufactured fibers may be used as filaments in filament yarns. Acrylic and modacrylic are exceptions – they are used typically in staple form. Filament yarns are composed of one or many continuous filaments and are assembled with or without twist.



Slide 3

Filament Yarn Uses• Carpeting and Carpet Backing• Industrial Textile Products

– tire cord and tire fabric– seat belts– industrial webbing and tape– Tents– fishing line and nets– Rope– tape reinforcement

• Apparel Fabrics– women’s sheer hosiery– Underwear– Nightwear– anklets and socks– variety of apparel fabrics

• Interior and Household Products– bed ticking– furniture upholstery– Curtains– Bedspreads– Sheets– Draperies

Filament yarns are used heavily in carpeting and carpet backing. Because of high strength requirements in many industrial textile products, filament yarns are used in a wide range of products, as seen in this slide. Many apparel fabrics such as underwear, nightwear, outerwear, socks, and hosiery also contain filament yarns. Many filament yarns are also found in interior and household products such as bed ticking, furniture upholstery, curtains, bedspreads, sheets, and draperies.



Slide 4

Filament Yarn Classifications

Filament yarns can be classified as flat or textured. Flat filament yarns have all their filaments aligned parallel to the yarn axis. Textured yarns have individual filaments lying in a curled, twisted, snarled, or crimped configuration. The most common methods of texturing are false twist, air jet, and stuffer box. These methods will be discussed later in the module.



Slide 5

Yarn Definitions

Flat continuous filament yarns are formed using very smooth and straight continuous filaments. Can be multifilament or monofilament.

Textured continuous filament yarns are formed using continuous filaments that have been modified to give bulk and/or stretch properties.

Spun yarns are formed using short or non‐continuous fibers.

Short staple spun yarns utilize fibers less than 2.5 inches long.

Long staple spun yarns utilize fibers from 2.5 up to 18 inches in length in some cases.

Flat continuous filament yarns can be monofilament, which contain only one single continuous filament. Fishing line is a good example of a monofilament yarn. Flat filament yarns can also be multifilament, with the yarn composed of multiple filaments brought together to form one continuous strand of filaments. Textured continuous filament yarns have the filaments modified in some way to give bulk and/or specific stretch properties. Spun yarns are formed using short or non‐continuous fibers. The yarn is held together by twisting the fibers in order to produce necessary fiber‐to‐fiber cohesion and adequate yarn strength. Short staple spun yarns utilize fibers less than 2.5 inches in staple length. Long staple spun yarns utilize fibers from 2.5 up to 18 inches in length. However, the most common range of staple length is 2.5 to 6 inches.



Slide 6

Flat Multifilament Yarns

• Very Smooth Surface

• Round Cross‐sectional shaped fibers typically

• Produce very compact, smooth yarns

• End Uses Include:– Seat belts, tire cord, and tire cord fabrics– Apparel with closely packed yarns for reduced air and water vapor permeability

• Have little elongation dependent upon fiber type

Flat multifilament yarns create a very smooth fabric surface. Round cross‐sectional shaped fibers are typically used, producing very compact and smooth yarns. End uses for these yarns include seat belts, tire cord, and tire cord fabrics. Apparel fabrics needing closely packed yarns for reduced air and water vapor permeability also use flat multifilament yarns. This type of filament yarn has little elongation, depending upon the fiber type that is used.



Slide 7

Textured Filament Yarn

• Term given to filament yarn which has a noticeably greater volume than conventional yarn of similar filament count and linear density.

• The yarns have a relatively low elastic stretch unless specifically developed for stretch.

• Sufficiently stable to withstand wet finishing.

• Apparent volume is achieved through physical, chemical, or heat treatments, or a combination of these.

Textured filament yarns have a noticeably greater volume than conventional filament yarns of similar filament count and linear density. The yarns have a relatively low elastic stretch, but can be developed specifically to impart stretch. The yarn is sufficiently stable to withstand wet finishing. The apparent volume of the yarn is achieved through physical, chemical, or heat treatments, or a combination of these.



Slide 8

Flat Filament Yarn Fabric

The fabric shown contains flat filament yarn. The fabric luster is high and the fabric is very smooth and tightly formed giving it a good covering property. Notice that the individual yarns are multi‐filament.



Slide 9

Textured Yarn Fabric

The fabric shown was made using textured filament yarn, giving the fabric a lower luster and different texture. Notice how the individual yarns are bulkier and more open in structure. The fabric tends to be more absorbent and softer, since it contains textured yarn rather than flat filament yarn.



Slide 10

Spun Yarn Fabric

Notice the fuzzy surface created by the hairiness of the spun yarns in this spun yarn fabric. The luster is subdued and the fabric has a soft hand, good absorbency, and comfort features. Notice also how each individual yarn is twisted to provide necessary strength to the yarn and fabric.



Slide 11

Spun Yarn Fabric

The fabric in this photograph was formed by weaving filament yarns in the warp direction and spun yarns and novelty yarns in the filling direction. Notice the filament yarns are very smooth and lustrous while the spun yarns create a more dull appearance. The novelty slub‐type spun yarns produce a variable look across the fabric width. The random slubs are very visible in each individual yarn. However, the slub yarn is only randomly used, not in every filling yarn insertion.



Slide 12

Yarn Irregularities

Filament Yarns – minor irregularities will show up as defects due to changes in luster, dye pickup, irregular yarn twist or yarn spacing. Variations in the degree of drawing during manufacturing will show up as differences in dye absorption and residual rupture elongation.

Spun Yarns – are less uniform and can afford more irregularities without resultant fabrics being defective.

Filament yarns are less forgiving when it comes to yarn irregularities. Even minor irregularities can show up as defects due to changes in luster, dye pickup, irregular yarn twist or yarn spacing in the resulting fabrics. Variable draw ratios and/or variable yarn tensions during yarn and fabric processing can create fabric streaks due to differences in dye absorption and residual rupture elongation. Unlike spun yarns, the internal molecular structure of filament yarns can be altered, leading to irreversible yarn variations and off‐quality fabrics. Spun yarn irregularities are less uniform and are more forgiving, when compared to filament yarn irregularities. Being produced from staple or short fibers, spun yarns have a natural unevenness and will pull apart before any molecular damage can be done to the fibers in the yarn by variable tension levels during fabric processing.



Slide 13

Filament Yarn Identification

There are various factors used in describing and identifying filament yarns, which are listed in this slide. Some will be elaborated on in more detail in subsequent slides because of their importance as far as influencing fabric properties. Many of the factors include numerical descriptions. The yarn number is written as a number followed by a slash and then the number of filaments in the yarn. A 100/1 yarn using the denier numbering system describes the yarn as being 100 denier, as its yarn number, and the yarn contains only one filament, making it a monofilament yarn. A 150/34 yarn describes the yarn as being 150 denier and containing 34 filaments, making it a multifilament yarn. A 400/68 description denotes a 400 denier yarn containing 68 filaments. Various fiber cross‐sections are available in filament yarns that influence the luster and fiber stiffness. To determine the denier of the individual filaments (dpf), divide the yarn denier by the number of filaments in the yarn. For example, the dpf of a 1460/188 yarn is 7.77. The surface of a filament yarn has a spin finish that is a very low percentage of the weight of the yarn. It is usually some type of lubricant oil with anti‐stat additives. Luster of filament yarns can be controlled, which typically is accomplished by adding titanium dioxide to the polymer before extrusion. A small amount of twist is added to filament yarns to keep the filaments intact and from separating which would lead to filament breakage. Air‐entanglement or “twist substitute” can accomplish this at less cost. The first digit in describing a yarn relates to the number of plies. A 1/70/48 denotes a singles yarn while 2/220/110 denotes a two‐ply yarn. The 2/220/110 yarn will have an overall denier of 440 and overall filament count of 220. Some applications of filament yarns require tighter and smoother fabrics using flat filament yarns while other fabrics require textured yarns with more bulk and volume.



Slide 14

Filament Yarn Numbering Systems

• Denier – a number indicating the weight in grams of 9,000 meters of a specific yarn

• Tex – a number indicating the weight in grams of 1,000 meters of a specific yarn

• Decitex – a number indicating the weight in grams of 10,000 meters of a specific yarn

Note: These numbers represent the yarn linear density. The numbers are sometimes called the yarn count. These are direct numbering systems, meaning that the representative yarn numbers will become larger as the yarn cross‐sectional size increases.

In the denier system of yarn numbering the denier value equates to the weight in grams of 9,000 meters of the given yarn. Tex is a yarn number indicating the weight in grams of 1,000 meters of a specific yarn. Decitex is a yarn number indicating the weight in grams of 10,000 meters of a specific yarn. Note that these numbers represent the yarn linear density. The numbers are sometimes called the yarn count. These are direct numbering systems, meaning that heavier yarns will have higher yarn numbers and finer yarns will have lower yarn numbers.



Slide 15

Glass Fiber Yarn Numbering Systems

Two Systems Generally Used:

1. Tex System as previously defined

example: a 68 yarn designation number would represent a yarn weight of 68 grams per 1,000 meters of yarn

2. 100 yard cuts per pound

example: a 75 yarn designation number would represent 7500 yards per pound

Note: Both systems are industry‐recognized identifications

Tex is the numbering system generally used when working with glass yarns. However, on some occasions “100 yard cuts per pound” is used to designate the yarn number. For example, a 75 yarn number designation means that it takes 7500 yards of a glass yarn to weigh one pound. As noted, both systems are industry‐recognized.



Slide 16

Multiple Numbering Systems

• Worsted Count Yarn Number (Nw) – 40

• English Cotton Count Yarn Number (Ne) – 26.6

• Denier Yarn Number – 200

• Tex Yarn Number – 22.2

• Decitex Yarn Number ‐ 222

Because there are numerous numbering systems around the world, there can be a good chance of recommending the wrong yarn product when trying to replace an existing yarn or trying to develop a fabric similar to an existing fabric. The following example is an illustration of this problem: Observe the different yarn counts listed, each one using a different numbering system, while representing an equivalent yarn size or yarn thickness. Worsted Count Yarn Number (Nw) – 40 English Cotton Count Yarn Number (Ne) – 26.6 Denier Yarn Number – 200 Tex Yarn Number – 22.2 Decitex Yarn Number ‐ 222 Imagine meeting with a customer and discussing the use of a textured polyester yarn as a substitute for a 20/1 (Ne) yarn that is currently being used. If one assumes the customer is using English cotton count, which is very common, a recommendation of a 266 denier textured yarn would be made. However, if the customer is a worsted wool fabric producer, the yarn you need to recommend is actually 398 denier. Such a large difference, based on these different yarn sizes, would affect fabric weight, drape, and similar properties.



Slide 17

Yarn Count Conversions

Common Numbering Conversions to Denier:

• Denier = 5315 ÷ Ne

• Denier = 9 x Tex

• Denier = .9 x Decitex

• Denier = 7972 ÷ Nw

Shown in this slide are common conversion factors that allow one to convert from one yarn numbering system to another, in order to avoid a problem like the one just illustrated. If it is desired to determine the denier equivalent of a 20/1 cotton count yarn, divide the constant 5315 by 20, which equates to 266 denier. However, to get an equivalent denier assuming the yarn is a 1/20 worsted count, divide the constant 7972 by 20, which equates to 398 denier.



Slide 18

Yarn Denier Examples

The yarn denier value represents the relative thickness of the yarn or yarn size. In the United States, denier is used for all filament yarns except glass. It is also used for manufactured staple fiber used in staple spun yarns. Almost all other countries use the Tex numbering system. The size of the yarn determines specific fabric properties such as weight, cover or the ability to see through the fabric, strength, and appearance to name a few. One must remember that a larger denier value represents a thicker or heavier yarn and a smaller denier value represents a thinner or finer yarn. It is important that yarn denier remains uniform. Otherwise fabric defects such as wavy filling in woven fabrics and barre in knit fabrics can occur.



Slide 19

Filament Properties

There is no narration for this slide.



Slide 20

DPF and It’s Influence

• Higher DPF leads to stiffer and coarser fabric.

• Lower DPF leads to softer and more flexible fabric.

• For a silk‐like fabric, low DPF would be the choice.

• For a tent fabric, a high DPF would be preferred.

• Low DPF yarns are more expensive and should be used in “open” fabric constructions to get the full benefit.

• With the use of low DPF yarns, less yarn can be used which can be a savings factor.

Denier per filament or DPF, is the denier of each individual filament in the total yarn bundle. Assuming all the filaments are the same denier, a 160 denier yarn containing 80 filaments would have a DPF of 2. The higher the DPF, the stiffer and coarser the resultant fabric and the lower the DPF the softer and more flexible the fabric. If a silk like fabric is preferred, a low DPF yarn would be used. If a tent‐like fabric is required , a high DPF yarn would be used. For the greatest advantage, low dpf yarns, being more expensive, should be used in “open” fabric constructions where the filaments can “blossom” or expand to their full bulk. With the use of low dpf yarns, less yarn can be used which can be a savings factor.



Slide 21

Cross Section and Luster

• Some yarns contain filament with different cross‐sections.

• Cross‐section affects the luster of the yarn as it either diffuses or increases the light reflection.

• Cross‐section can affect certain fiber functions such as moisture transport.

• Cross‐section can affect fabric hand and appearance of the pile in plush fabrics.

Filament fiber cross section and luster have a close relationship relative to their effect on the fabric. Some yarns consist of a certain number of filaments with one cross section and other filaments with another. This condition is normally noted in the name attached to the particular yarn. Cross section has had a primary function of effecting the luster of the yarn as it appears in the fabric and the cross section is intended to diffuse or increase the light reflection as seen in a mirror effect. There are a number of special cross sections, such as channeled, which are designed to give the yarn and resulting fabric certain capabilities such as moisture transport. Other cross sections such as ribbon‐shaped, can affect the fabric hand and appearance of the pile in a plush fabric.



Slide 22

Cross Sections and Effect on Fabric

The most common cross section used is round which diffuses little if any light reflective effect. Octolobal, with eight “sides” to the filament cross section has the greatest diffusing effect. The cross section also has an effect on the flexibility of the fabric with a fabric using trilobal fiber having less flexibility than a fabric using round or octolobal fiber. Fiber cross section also affects fabric cover or the ability of light to show through the fabric. Round fibers will bunch closer together in a fabric and produce poorer cover compared to trilobal and octolobal fibers which do not pack as close together in the fabric, spreading out more and covering more area in the fabric. Shown in this slide are several types of cross sections and their uses.



Slide 23

Cross Sections and Functions

Shown in this slide are several types of cross sections and their uses.

•Hollow – for insulation and wicking •Clover‐shaped – for bulk •Octolobal – for glitter reduction •Multi‐channel – for bulky micro‐denier yarns

•Trilobal – for luster •Modification Ratio, also known as aspect ratio – changing or varying the inner and outer diameters of a trilobal fiber



Slide 24

Yarn Luster

• Referred to in terms such as bright, semi‐dull, dull, or full dull.

• Most common dulling agent used is titanium dioxide with more being added to reduce the yarn luster.

• More dulling agent yields a harsher fabric with more friction or abrasion ability on the surface of the fabric.

• Combining a yarn with a low amount of dulling agent with a round cross section you get a metallic‐like appearance.

• Combining a yarn with a low amount of dulling agent with a trilobal cross section you get a fabric with a lustrous effect similar to silk.

The luster of the yarn bundle is different from the reflective nature of the yarn as previously mentioned. The luster refers to the actual physical state of the filaments and/or yarn bundle. The luster is commonly referred to in terms such as bright, semi dull, dull, or full dull. In Europe, the term matte is used instead of dull. The most common dulling agent used is titanium dioxide. The more added to the polymer, the duller the luster. The more dulling agent used the harsher the surface of the fabric. This effect also leads to a higher friction on the surface of the fabric. When a yarn with a low amount of dulling agent is combined with a round cross section the result is a metallic like appearance of the yarn in the fabric. Combining a yarn with a low amount of dulling agent with a trilobal cross section, results in a fabric with a lustrous effect similar to silk.



Slide 25

Fabric with High and Low Luster Yarns

Occasionally high and low luster filament yarns can be used in combination with each other to produce a desired appearance in a fabric. For example, the fabric shown has a diamond‐shaped dobby design. The warp yarns are of higher luster, and by permitting some of these yarns to “float” in the middle of the diamond design, a special effect is produced. All the filling yarns are of duller luster which makes the warp yarns stand out.



Slide 26

Filament Yarn Manufacturing Steps

• Filament Extrusion (Mono or Multifilament)

• Filament Drawing (FOY – POY – UOY)

• Producer Yarn Packaging

• Throwing and Twisting

• Re‐packaging

• Multiple Plying of Yarns

• Texturing

• Combining Filament and Spun Yarns

• Heat Setting Yarns

To produce filament yarns, the filaments are extruded in mono or multi‐filament form. Being very unstable at this point, the filaments must be drawn (elongated or stretched) to a certain degree, depending upon their end use. At this point the yarn is wound onto suitable packages for subsequent processing. Yarn may then go to a throwster for twisting, re‐packaging and/or plying. Yarns can remain in flat filament form or be textured. The filament yarns, flat or textured, may go on to further steps where they are formed into some type of composite yarn. Common composite yarns are single and double covered yarns and corespun yarns. Filament yarns containing thermoplastic fibers can be heatset to different degrees to produce yarns with high stretch, high bulk or both.



Slide 27

Filament Extrusion

At extrusion, a polymer solution is forced through the holes of a shower‐head‐like device called a spinnerette. The extrusion process is called “spinning.” The three typical methods of spinning are melt, dry, and wet. Melt spinning involves melting polymer chips prior to extrusion. Dry spinning involves using a solvent to dissolve the solid polymer material and then re‐solidifying the polymer by means of evaporation of the solvent once the yarn is formed. Wet spinning involves solidifying the extruded polymer in a wet bath. Spinning methods are fiber specific. Nylon, polyester, and olefin fibers are typically melt spun. Some rayon‐type fibers are dry spun and some are wet spun.



Slide 28

Engineered Yarns

• A very consistent yarn is formed through extrusion.

• The spinnerette hole size determines the filament denier.

• The number of spinnerette holes determines the filament count.

• The spinnerette hole shape determines the fiber cross‐sectional shape.

A very consistent and uniform yarn is formed through the process of extrusion. The spinnerrette hole size determines the filament denier or DPF. The number of spinnerette holes determines the filament count and the hole shape determines the fiber cross‐sectional shape. All of these parameters can be altered to produce a different type of yarn with different properties. Therefore, filament yarns can be engineered to suit desired properties needed in the final use of the yarn.



Slide 29

Slit Film Yarn Extrusion

• Yarn of a flat, tape‐like character produced by slitting an extruded film.

• The extruded film is usually a polyolefin.• The extruded film is drawn by draw rollers.• The film then goes through a slitter/embosser. • Sometimes the yarns are drawn after slitting to form the desired width and thickness.

• The slit yarns are then placed on a spool.• Spools of yarn then go to weaving to provide filling input or to warping to form a loom beam for weaving.

In addition to extruding filaments for yarn formation, a polymer film can be extruded and then cut into narrow strips to form what is known as slit film yarn. A slit film yarn is a type of tape yarn. The extruded film is usually a polyolefin. The extruded film is first drawn by draw rollers and then passes through a slitter/embosser. At times the yarns are drawn after slitting to form the desired width and thickness. The ribbon‐like structure produces a yarn that may be .003 inch (0.008 cm.) thick and about 0.25 inch (0.6 cm.) wide. Usually they do not have a cylindrical shape unless twisted. The slit yarns are then placed on a spool. Spools of yarn then go to weaving to provide filling input or to warping to form a loom beam for weaving.



Slide 30

Slit Film Yarn Fabric

Notice the flat structure of the yarn in the photograph and the width they occupy in the fabric. Many of these type fabrics are used in dust covers for furniture and in geotextile applications. They may be seen in fabrics surrounding construction areas for the purpose of controlling run‐off and erosion. Other end‐uses such as interior‐furnishing include upholstery fabrics, wall covering, and primary backing for tufted carpets. They are also used in packaging, bags, sacks, and bale wrappers, as well as in artificial turf.



Slide 31

Conversion of Tow to Staple Fibbers

• Filaments from Multiple Spinnerettes Form a Tow

• Tow Is Cut into Short or “Staple” Fibers

• Staple Fibers Produce Spun Yarns

• Man‐made Staple Fibers Can Be Blended with Natural Staple Fibers

It is worth mentioning again that man‐made staple fibers found in many spun yarns originally were in the form of continuous filaments before going through a cutting process. A large number of extruded filaments form a bundle of fibers called tow. The tow is cut into staple fibers and then the staple fiber is formed into a spun yarn as a 100% yarn or blended with other staple man‐made fibers or staple natural fibers. As previously mentioned, the man‐made fiber weight is denoted by the fiber denier.



Slide 32

Drawing Animation

The yarn shown in this animation has filaments which have not been drawn or “stretched.” In this state, the molecular structure of the filaments is very amorphous, meaning the long polymer chains are very randomly arranged within each filament strand. Notice as the yarn is stretched or drawn, the yarn size or thickness decreases. At the same time, the yarn becomes more stable. As the filaments are furthered stretched the filament yarn reaches a point where additional stretching or drawing becomes more difficult. At this point the polymer chains are in a crystalline state, with the chains being in a more parallel arrangement. Different degrees of drawing can be provided for different end uses of the yarn.



Slide 33

Yarn Orientation for Texturing

Arranging the polymer chains in filament yarns to a more organized and parallel arrangement is referred to as yarn orientation. This yarn orientation is made possible by movement of the yarn strand through two godet rollers running at increasing velocities. A draw ratio can be calculated from the velocity ratio of the two rollers. Full orientation of the polymer chains produces a FOY or fully oriented yarn. Partial orientation produces a POY or partially‐oriented yarn. No drawing at all of the yarn will produce a UOY or un‐oriented yarn. Many texturing companies today use POY yarn as the feed yarn. POY yarns can be purchased at a lower cost compared to FOY or fully drawn yarn.



Slide 34

Common Yarn Orientation Types

The take‐up speeds and different elongation values for the production of different yarn orientation types are shown in this slide. When changing from low oriented yarns to higher oriented yarns, the package take‐up speeds increase and the yarn elongation values decrease. The letters FDY represent fully‐drawn yarn.



Slide 35

Yarn Orientation and Application

• LOY/POY yarns insufficient for end‐uses

• HOY yarns has sufficient physical properties for a wide‐range of applications.

• FOY/FDY yarns are good for flat yarns of high strength

LOY and POY yarns are not recommended for some end‐uses due to their high elongation and low strength, but can be draw‐twisted/draw‐wound to produce flat yarns with acceptable physical properties or can be false twisted or air jet textured to draw and crimp the filaments. HOY is flat yarn with sufficient physical properties for a wide‐range of applications. FOY/FDY yarns are good for flat yarns when sufficient physical properties are desired for high strength applications.



Slide 36

Texturing

Definition: The process of crimping, imparting random loops, or otherwise modifying continuous filament yarn to increase cover, resilience, abrasion resistance, warmth, insulation, and moisture absorption or to provide different surface texture that can reduce yarn luster.

Two General Types Prominently Used Today:• False Twist• Air Jet

Texturing is the process of crimping, curling, kinking, imparting random loops or otherwise modifying continuous filament yarn in order to increase cover, resilience, abrasion resistance, warmth, insulation, or moisture absorption. This yarn modification provides a different surface texture to the yarn which reduces the yarn luster. After reviewing older methods of texturing, this section concentrates in more detail in two most popular methods of texturing yarns today – false twist texturing and air jet texturing.



Slide 37

Textured Filament Yarn Sample Video

The flat continuous filament yarn seen at the top in this slide – when textured will have a completely different structure as exemplified in the bottom yarn sample. In the bottom yarn, individual filaments are no longer straight and parallel but crimped to add more bulk and volume.



Slide 38

Textured Yarn Types

A yarn composed of long, parallel filaments, which is lightly twisted or interlaced to give coherence, will form dense, smooth fabrics with a minimum of textural features. This type of fabric structure is excellent for parachute fabrics, which was used for the first woven nylon fabrics. However, the fabric proved unsatisfactory for shirts, though for a short time it was sold for this use. The market for filament yarns was very limited. The question was asked: “Could continuous filament yarns be modified to compete with spun yarns? Could they be modified to provide surface texture and appearance, softness, bulk, warmth, and absorbency as seen in spun yarn fabrics? It was the permanent set of nylon that led to the commercial success of yarn texturing. Seen in this slide are various types of textured yarns and their general structure. Some types produce stretch yarns while other types produce bulk yarns. Today, the predominant methods are false twist texturing and air jet texturing. The stuffer box method is used extensively in crimping filaments in tow form prior to cutting the filaments into staple fibers. Some older methods are discussed with great detail on the false twist and air jet methods. The older methods came into being in the 1950s.



Slide 39

Edge Crimp Texturing

Edge crimp texturing is used by many when preparing fancy ribbons and bows for gift packages. A flat and straight ribbon is pulled over a knife edge, like a scissors blade, and the result is a textured ribbon with curling. This textural structure was produced in a yarn known as Agilon.



Slide 40

Knit‐de‐knit Texturing

Knit‐de‐knit texturing is a process whereby a yarn is knitted into a fabric and the fabric is heatset. The yarn is then unraveled from the fabric and continues to have the knit loop structure.



Slide 41

Stuffer Box Texturing

In stuffer‐box texturing, the yarn is overfed into a stuffer chamber which plaits it into a folded or crimped state. The yarn is heatset in this state and then removed from the chamber as a highly crimped yarn. This texturing method produced yarn known as Ban‐Lon.



Slide 42

False Twist Principle

The basis of false twist texturing is to twist a yarn as highly as possible, set it by heating, followed by cooling, and then untwisting it. This gives a twist‐free bundle of twist‐lively filaments. In order to relieve the torque, the filaments snarl into “pigtails”, which results in a large yarn contraction. The yarn can be stretched to over five times its fully contracted length before the filaments are straightened out. The recovery power is strong. Fabrics can be highly stretched, but come back when the stretch is released. The fiber twist is important. However, the filaments want to return to their crimped form. This dictates the initial form of fiber buckling. When a fully extended stretch yarn is allowed to contract by 10 to 20%, the filaments follow helical paths, which alternate from right‐handed to left‐handed. When a yarn is set in this form, it has high bulk and low stretch.



Slide 43

False Twist Animation

To create false twist in a filament yarn bundle, the yarn must be held at two points. Between these two held points, the yarn is twisted by some mechanism. Notice in the animation that the twist direction in the upper part of the simulated yarn is S and the twist direction in the lower part of the simulated yarn is Z. Therefore, the twist put into the yarn above the twisting element will be cancelled out as the yarn flows below the twisting element. This is “false twist” – meaning that the inserted twist is only present for a short time and then “untwisting” takes place.



Slide 44

False Twist Yarn Flow

As shown in this diagram a false twist mechanism inserts twist into the yarn. The twist flows back towards the heater where it will be set into the yarn. However, as the yarn continues to move through the machine, it flows beyond the false twist mechanism where it will be untwisted in the opposite direction and thus create texture in the yarn as the filaments snarl.



Slide 45

Pin Twisting

By the 1960s and 70s, it was realized that yarn could be dragged forward over a rotating pin. Some typical pins are shown in this slide. The normal force exerted on the yarn by the pin generates the twisting torque, and the axial friction increases yarn tension. The spindles could be reduced tenfold in size to about 2 mm by 1 cm and were held by magnetic action against rotating rolls. Spindle speeds increased by an order of magnitude of 300,000 rpm. Linear speed reached 100 m/min with a production of approximately 8.0 kilograms per spindle per week. These figures are based on running a 70 denier nylon.



Slide 46

Disc Friction Texturing

The current design of friction twisting, was developed in the 1980s and 90s. Twisting the yarn involves the yarn being driven against the outer edge of discs and constrained in a three‐dimensional, zig‐zag path within three sets of overlapping discs as seen in this photograph. Friction twisting allows the spindle speeds to increase to 3,000,000 rpm with a production of approximately 80 kilograms per spindle per week using 70 denier nylon. The amount of twist inserted into the yarn is governed by two main factors: 1. The amount of contact between the yarn and the friction discs, referred to as angle of wrap. 2. The speed of the friction discs relative to the speed of the yarn which is called the D/Y ratio. The disc today are typically made from ceramic and polyurethane materials.



Slide 47

Disc Friction Texturing Animation

There is no narration for this animation.



Slide 48

Cross‐belt Twisting Animation

Crossed belt twisting is another method of friction twisting. The yarn is held at the nip point of two belts mounted at an angle and moving in opposite directions as seen in this animation. These are referred to as nip twisters. Nip twisters were introduced in 1979. Rotation of the belts imparts both twist and a forwarding action to the yarn. The twist insertion rate is controlled by three factors: the angle of the belts to each other, the contact pressure applied to the belts and the velocity ratio (V/R) , which is the equivalent of the D/Y ratio for stacked discs. It is possible to run two yarns with opposite twist through a single unit, and combine them at wind‐up.



Slide 49

Friction Twisting Machine

Most machines today use friction discs to insert the necessary twist in the yarn for texturing. A schematic of such a machine is seen in this diagram. Many of these machines feed POY yarns which will be drawn at the same time as it is being twisted and textured. The creel or framework for holding the POY yarn packages is located behind the machine on the right. The POY feeder yarns move forward into the first drawing roll, and then flow into the heater zone, followed by the cooling zone. Heating of the thermoplastic filaments brings them to a molten state while they are in a twisted configuration. This allows the helical angle of twist to be set into the yarn. The heaters may be contact or non‐contact in operation. The cooling zone, made up of cooling plates has two major functions: 1. It allows the yarn bundle to cool, while still in a highly twisted state. 2. It gives stability to the highly twisted yarn bundle between the exit from the primary heater and the entry into the friction unit. This is very important since, if the cooling plate were not present, the yarn would be very unstable in this highly twisted state and have a tendency to balloon resulting in a high break rate. At this point the yarns go through the friction disc units where twist is inserted into the yarn. The diameter and thickness of the discs, the spacing between the discs, the type of disc material and the speed of rotation all have an effect on the amount of twist that is inserted to the yarn. Below the twisting unit, a second set of rollers deliver the yarn from the discs. A take‐up system then winds the textured yarns onto tubes to eventually form a large package of yarn. The speed of the second drawing roller system exceeds the speed of the first drawing roller system. This elongates the yarn and finishes the drawing or aligning of the long chain molecules within the yarn.



Slide 50

Single Heater Friction Twisting Machine

This animation is a view of a single heater friction type false twist texturing machine. Notice that it has only one heater. The feed yarn packages are shown on the right and the four yarns are fed into a nip roller and then pass through the single heater. After this, the yarn filaments are cooled before entering the friction discs. After exiting the discs, the yarn passes through another nip roller and is then collected onto a yarn package. This is a close‐up of the four feed yarns joining together at the first nip roll system and then passing through the heater. Three stacks of discs provide the twisting of the yarn bundle at a very high rate. The twist inserted flows backwards from the discs through the heater and stops at the nip roll system. Below the friction discs, the yarn twist is removed, and the yarn takes on the textured appearance. It is then delivered from the machine and formed into a large package.



Slide 51

Two Heater Machine

In a two heater machine, after the yarn passes through the twisting device, it can pass through a secondary heater tube usually between 1.0 and 1.3 meters in length. At this point the yarn is heated under controlled relaxation. The purpose of the secondary heater is to reduce the amount of skein shrinkage or crimp and stretch left in the yarn after exiting the twist‐insertion device. If this is not done, and a secondary heater is not used, it is known as either a single‐heater or high‐extension yarn. Though suitable for certain end uses in this condition, particularly where a fabric of dense construction or stretch is required, it is not suitable for many other applications. The higher the temperature in the secondary heater the lower the amount of crimp left in the yarn. These are called double‐heater or set yarns. They find use in all types of fabrics and because of their low shrink character, give a crisper feel to the fabric and drape better than single‐heater fabrics.



Slide 52

Application of Coning Oil

Upon leaving the main frame of the texturing machine, the yarn will be lubricated with coning oil. This allows the yarn to be processed more efficiently during knitting or weaving. This lubrication reduces yarn to metal friction and yarn to yarn friction which helps to maintain proper yarn strength and abrasion resistance during fabric processing. Oil on the yarn also helps provide bundle cohesion, static dissipation, and other processing aids. Proper level of lubricant is extremely important for the processing performance of a yarn. The amount of oil applied to the yarn typically varies from 1 to 3%. No coning oil is applied to the yarn if it is going to be dyed in the yarn state.



Slide 53

Take‐up and Package Build

The textured yarn in this photograph is now on a package suitable for the next process. All take‐up systems consist of a package support, a drive for the package and a traversing system to prevent the formation of pattern bands in the wound package. Package build must allow for smooth unwinding in subsequent processing. Package density must be controlled, whether the yarn is dyed requiring lower density or whether the yarn is put directly onto a high speed weaving or knitting machine, in which case it would require a higher density. The winding angle chosen for a given package of yarn will affect the way the yarn packs on the package and thus affect dyeing and unwinding efficiency of the yarn.



Slide 54

False Twist Process Variables

The key parameters employed during false twist texturing and their influence on the properties of the yarn as shown in this diagram. 1. Draw Ratio – The draw ratio is the amount of yarn stretched between the input roller and the output roller which follows the twisting mechanism. The meters of yarn traveling per minute through the output roller divided by the meters of yarn traveling per minute through the input roller is how the draw ratio is calculated. The draw ratio will determine the final textured yarn elongation, the yarn denier, and the yarn tenacity which is a value calculated from the yarn breaking strength and the resultant denier. Higher draw ratios will create excessive broken filaments, low dye uptake, and reduction in residual shrinkage. Low draw ratios create the opposite of these. 2. Primary Heater Temperature – Increasing primary heater temperature will increase yarn bulk and filament breaks while decreasing dye uptake. Decreasing the temperature will create the opposite of these factors. 3. D/Y Ratio – The D/Y ratio is the ratio of speeds between the friction discs and the linear speed of the yarn. The most common method of changing the amount of twist inserted in the yarn is by changing the speed of the discs, keeping the number of discs and the spacing between them constant. 4. Second Heater Temperature and Overfeed – The higher the temperature in the second heater the lower will be the final yarn shrinkage. If a high second heater overfeed is employed, the tension on the yarn in the heater tube is low allowing the heat available to have its maximum effect. 5. Package Build – Off‐winding performance of the yarn is crucial to meeting customer needs. Factors affecting this performance and the form of a package include yarn skein shrinkage, yarn denier, intermingling level, take‐up overfeed, wind angle, taper angle, traverse stroke length, and winding tension.



Slide 55

Air Jet Texturing Overview

Air jet texturing works by mechanical interlocking, not by heat setting. It can, therefore, be applied to any continuous filament yarn, including rayon, glass and the new high‐performance fibers, as well as nylon, polyester and polypropylene. The method was invented by DuPont in the 1950s and an early jet design is shown in this slide. The basis of the method is that yarn is overfed into a compressed air jet‐stream, so that loops are forced out of the yarn. Since the loops need to be locked into the yarn, this can be achieved by twisting the yarn at the take‐up. The alternative, which is the current practice, is to design the jets and the yarn path so that there is sufficient entanglement in the core of the yarn to stabilize the loops. Air jets are also added to false twist texturing machines which enables yarns of a different character to be produced.



Slide 56

Air Jet Animation

In the animation shown, the yarn entering the texturing zone where air (represented in blue) entangles the filaments can be seen. The air turbulence creates twisted loops of yarn on the yarn surface. This causes the yarn to be fuzzy, similar to a spun yarn. It will, therefore, exhibit a spun yarn like appearance and have a spun yarn like hand or feel.



Slide 57

Air Jet Processing Variables

An image illustrating air jet processing variables can be seen in this diagram. 1. Draw Ratio: The draw ratio is the amount the yarn is stretched before entering the texturing zone. When feeding two yarns, the draw ratio has to be set for each yarn. In addition to overfeed and subsequent stretching and relaxing, the draw ratio determines the final yarn denier. Over drawing causes broken filaments while under‐drawing causes the yarn to be plastic or non‐elastic when stretched under load. This may be desirable when a fabric is to be stretched into the shape of a seat or some other object. 2. Hot‐pin or Draw‐pin: Polyester is widely available in the form of POY and, therefore, any texturing process suitable for this market has to include the means for drawing POY. Common practice is to use a heated draw‐pin located between the first two draw rolls which provides a fixed draw point and a means of heating the POY. Typical temperature for polyester ranges from 135 to 160 degrees celcius. This higher temperature reduces residual shrinkage. 3. Yarn Overfeed: Yarn Overfeed has a direct influence upon the bulk or specific volume of the yarn. Different yarns can have different overfeed rates and create core‐effect type of yarns. Surface loops can be formed to make spun‐like yarns. Changing the core yarn overfeed has a direct influence on the strength of the textured yarn as well as its stability or resistance to removal of the surface loop structure under load. Since the core overfeed affects the length of the textured yarn, it has a major influence on the denier of the yarn. The yarn overfeed determines the size of the loops. It also has an indirect influence upon the number of loops per unit length and also on the denier. 4. Yarn Wetting: Heavier yarn requires more water to be applied. Water helps to reduce the yarn to yarn friction with the feeding of multiple yarns under different tensions and feeding rates. Water and spray are collected in the jet box and removed by means of a gravity drainage system. 5. Air‐texturing Jet: From 500 to 5000 denier yarns can be used with either an axial or radial type of jet. Radial jets are used with lower overfeeds and higher processing speeds. Axial jets operate with considerably higher net overfeeds in the range of 4 to 20% to impart stability to the textured yarn. A final textured denier of 1215 prepared for weaving could be made from feeder yarn of only 750 denier at the point of entry into the jet. This means that the total increase in denier is 60%. 6. Mechanical Stabilization: Similar to tightening a knot in shoelaces by pulling, the stability of an air‐jet textured yarn is improved considerably by stretching after the texturing zone. This stretching is done by using at least two yarn feed units after the jet box. The higher the (core) overfeed the greater will be the effect of stretching on the yarn stability. From 2 to 10% is normal. Heat may be applied within the mechanical stabilization zone as a means of inducing tension in the yarn. 7. Heat‐setting: Air‐jet textured yarns are much more dense than false twist textured yarns of the same denier and, therefore, the effect of heat‐setting is not as noticeable in the end product. Nevertheless the effect of applying heat means that overfeeds of up to 10% are used, depending upon the residual shrinkage of the textured yarn. The applied overfeed must be absorbed by the shrinkage of the yarn or else the process would break down.



8. Yarn Build and Lubrication: Due to air‐jet textured yarn having a much lower stretch or elongation, the take‐up overfeeds applied are lower. Methods of applying lubricant to the yarn and varying the quantity are identical to those for false twist textured yarns.



Slide 58

Air‐entangling and co‐mingling should not be confused with air jet texturing. Air‐entangling of the filaments to keep them together is more economical than inserting twist. Air jets are used to entangle yarn filaments in programmed and repeating areas called nodes or tack points. This makes it easier to process the yarn in preparation and fabric forming steps. It also aids in co‐mingling or tying down plied yarns. Frequency of tack points is described as points per meter of yarn. The key to successfully weaving textured yarn is co‐mingling unless the yarn is twisted. Tack points should remain in the yarn through weaving but should come out in fabric preparation processes prior to dyeing and finishing of the fabric. If they are not removed, then pin holes will be noticed in the fabric which is unacceptable.



Slide 59

Hot‐fluid Jets for BCF Yarns

Bulked continuous filament or BCF yarns are another type of textured yarn using jets. BCF yarns are used as coarse carpet and upholstery yarns. Its origins lie in DuPont research on jets. The yarn is produced by using fluid texturing with steam to produce textured nylon and polypropylene carpet yarn. These yarns have a three‐dimensional crimp that is preferred for carpet appearance and performance. The steam provides heat to set the bulk in the yarns. In the production of BCF yarn, the yarn is fed through a hot‐fluid jet. The yarn is then collected in a “caterpillar” configuration and cooled to stabilize the set, before being taken to the wind‐up. The turbulent hot fluid produces an asymmetric shrinkage, which causes filaments to buckle. The buckling effect is set, and a high bulk yarn is produced.



Slide 60

Yarn Quality and Performance Properties




Slide 61

Texturing Concerns

The chart shown lists some of the quality performance parameters for textured yarns. • Yarn Breaks – The yarn break rate is the number of yarn breaks that take place per unit weight of textured yarn produced. Yarn breaks can create short yarn packages, lost production and increased labor and packaging costs. The breaks can be caused by low quality POY yarn should be segregated and machine speeds should be lowered. Process related causes can be an excessively high draw ratio, excessively high primary heater temperature, and high processing speeds, causing instability and surging in the thread path. Poor machine maintenance creating such things as worn or damaged ceramic discs, poor thread path alignment, and damaged nip rolls and aprons can also cause yarn breaks. • Intermingling Faults – Mainly involve the frequency or strength of the intermingling knot and the irregularity or unevenness of intermingling along the length of the textured yarn. The choice of jet must match with the overall denier, filament denier, and the speed of the process in order for the intermingling to be strong and uniform. Process conditions such as air pressure, yarn tension, speed, and jet location should be optimized. Age and cleanliness of the jets must also be considered. • Bulk Variation – Can be either end‐to‐end variation around the texturing machine or variability of the yarn along the yarn length. Causes can be uneven heat penetration due to the yarn core being more dense than the surface filaments. This is more likely when low filament denier yarn is being textured. Other causes of bulk variation may be low draw ratio or incorrect rate of twist insertion for the particular process. This may be remedied by changing either the D/Y ratio or the number of friction discs employed. • Dye Variation – May be an overall drift in shade towards light or dark dye or an increase in end‐to‐end variation within the machine. Change in polymer, POY variations, dirty primary heaters, wear of polyurethane discs, and yarn not fully drawn can all lead to dye variation. • Package Density Problems – Particularly important for packages designated for dyeing. Yarn shrinkage and intermingling properties must be correct. Incorrect winding tension, errors in the thread path, incorrect taper angle, and improper wind angle can all lead to wrong package density for a given product of textured yarn. These factors must meet required specifications. • Surging – Instability in the thread line. It manifests itself in a lean untextured appearance. Surging can be caused by properties of the POY feed yarn, incorrect machine parameters, draw ratio being too low, wrong throughput speed for a given product, irregular application of spin finish, and irregular yarn orientation along the length of the yarn. • Package Build Faults – One of the more common package build faults is bulging, caused by using small wind angles. Another is webbing or scrambling of the yarns on the package, many times caused by a too low wind angle for intermingled products. High density packages produced with high take‐up tensions will also result in webbing. Overthrown ends, ridges, shouldering, and no‐tail packages are other common package build faults. • Broken Filaments – Textured broken filaments may be related either to the yarn type, POY contributing factors, to mechanical damage within the thread path or to the settings of the texturing machine on which the yarn is produced. Broken filaments are a more common occurrence on low denier rather than high denier products. • Tight Spots – Take the form of a very short length of untextured yarn and are most easily detected by inspecting long lengths of yarn, examining a knitted sleeve or by on‐line monitoring. The causes of tight spots are those mentioned previously for surging and the same remedial actions can be taken.



Slide 62

Specific Performance Properties

• Tack Retention

• Twist Direction

• Twist Level

• Torque

• Skein Shrinkage

• Residual Skein Shrinkage

The properties shown in this slide are specific to textured or drawn yarns. They are generally not applicable to POY yarns. ‐ Tack Retention: The ability of tacks to withstand stretching. This is important when processing imparts different degrees of strain on the yarn. Tack retention quantifies the “strength of the tack to withstand strain and, therefore, provide bundle cohesion for processing. ‐ Twist Direction: The rotational direction by which twist is present in a yarn. It can be designated as “S” or “Z”. ‐ Twist Level: The number of turns of twist in a yarn per a given length of yarn. For twisted yarns, the level of twist is critical for the degree of bundle cohesion needed for processing and yarn strength. In the texturing process, the twist level has a significant impact on the crimp level of the yarn. ‐ Torque: The tendency of a yarn to rotate and kink upon itself in an effort to relieve twist. The impact of torque, causing kinks in the yarn, can lead to processing problems. Torque can often be observed in fabrics. Torque can be balanced by plying “S” and “Z” yarns, or minimized with jets. ‐ Skein Shrinkage: The length contraction of a skein of yarn, held at a prescribed load and after heating under prescribed conditions. Tests are designed to simulate various down‐stream processing conditions. Some tests simulate the restraining forces experienced in fabric dyeing and finishing, and is used to design textured yarns for different types of fabric applications. ‐ Residual Skein Shrinkage: The residual shrinkage test utilizes a much lower restraining load than other tests and is a better indicator of the ultimate shrinkage potential of the yarn.



Slide 63

Compound or Composite Yarns

Composed of multiple yarn strands. A core component and a wrapping component

Two General Types • covered yarn • core‐spun

1) with a filament core/staple fiber wrap 2) with a staple fiber core/filament wrap 3) with a staple fiber core/staple fiber wrap

Compound or composite yarns are yarn structures consisting of at least two strands, one forming the center axis, or core, of the yarn, and the other forming the covering or wrap of the yarn. One of the strands can be filament yarn and the other a spun yarn or both can be filament yarns in order for the classification to be a compound or composite filament yarn. These yarns are generally available in the same size ranges as filament and spun yarns. In general there are two types of compound yarns, covered and core‐spun. In covered filament yarns, the wrap is the yarn which can be either a filament yarn or a spun yarn. The core might be an elastomeric fiber, such as rubber or spandex, or a hard fiber, such as polyester or nylon. Covered yarns may have either a single covering or a double covering. The second covering is usually twisted in the opposite direction from the first covering. Core‐spun yarn has a hard or elastic yarn core along with a sheath of staple fibers on the yarn surface. A very common core‐spun yarn has spandex fiber in the core and cotton staple fiber twisted around the surface of the yarn. Core‐spun yarns can be of three types – filament core/staple fiber wrap, staple fiber core/filament wrap, and staple fiber core/staple fiber wrap.



Slide 64

Core Spinning Operation Animation

This animation illustrates the making of a covered yarn with a spandex core. The core could also be a hard filament yarn, textured or flat, or a hard spun yarn. The supply package of spandex is surface driven at a controlled rate. The yarn passes from the package drive‐roll to a driven feed roll called a star wheel. The yarn then passes through two hollow spindles on which spools of covering yarn are mounted, and to the driven take‐up wheels or to nip rolls. For double‐covered yarns, spools revolve at high speed in opposite directions, wrapping the hard‐fiber yarn around the stretched core of spandex with sufficient wraps per unit length to permit the yarn to have the desired stretch. The bottom cover yarn normally controls the stretch, while the top cover serves to balance and give a smooth appearance to the surface of the covered yarn. With a bottom and top wrapped in opposite directions, “S” and “Z”, what is produced is a torque‐free double‐covered yarn with definite stretch limits. For single covered yarns, a single spool of covering yarn is mounted on the bottom spindle to wrap the stretched core of spandex with sufficient wraps per unit length to give the desired yarn aesthetics and protection to the core. The covered yarn is allowed to relax partially above the take‐up star wheel, and is then wound onto the take‐up package. The surface speed of the take‐up package drive‐roll, relative to that of the take‐up star wheels, governs the relaxation of the covered yarn. The total draft is chosen to give the best balance between the weight and cost of the spandex, machine productivity, and the appearance of the covered yarn for the power and stretch required. In practice, lower drafts are generally used to give the best balance of yarn properties. Excessive drafting can cause broken filaments in the spandex core. A covered yarn with such a core will contain slubs and show variations in power. Covered yarns of low denier per filament (dpf) will produce smoother covered yarns and better coverage of the core. With double‐covered yarns the stretch is controlled by the number of wraps of the bottom cover per unit length. The balance of the yarn is controlled by the number of wraps of the top cover.



Slide 65

Double Covered Yarns

During the covering process, the yarn coils produced by the covering yarns are spaced apart. However, upon relaxing the yarn, the coils become closer and more compact. As previously mentioned, with double‐covered yarns the stretch is controlled by the number of wraps of the bottom cover per unit length. The balance of the yarn is controlled by the number of wraps of the top cover.



Slide 66

Core Spun Yarns

Filament core/staple fiber wrap core‐spun yarns have filaments in the center of the yarn which are completely surrounded by a wrap of staple fibers. The wrap is sometimes referred to as a sheath because it is composed of untwisted staple‐length fibers. This type of yarn has applications in apparel, household, and technical areas. When plied, polyester core/cotton wrap yarns make sewing threads marketed as ‘cotton covered polyester”. Some protective clothing and flame‐resistant curtains are composed of fiberglass‐filament core, surrounded with aramid fiber, aramid blends, or PBI fiber. Other yarns may have carbon fiber in the core for these same applications. Some protective gloves may have steel wire surrounded by aramid‐fiber blends. When cotton is the sheath fiber, it allows for good dyeing, good hand, and protection for the elastomeric fiber. Yarns of this type provide stretch in denim, knit, and hosiery products. Staple‐fiber core/filament wrap core‐spun yarns have a core of untwisted, parallel stape‐fiber strand in the core of the yarn and a filament wrapped around the core. This type of yarn can be a good source for using waste fibers, which can be placed in the yarn core. Since twist is not inserted, the most expensive aspect of producing a spun yarn is eliminated. The majority of the development and production of staple‐core/staple‐fiber wrap yarns has focused on the use of polyester staple for the core and cotton fiber for the wrap.



Slide 67

Core Spun Yarn

As this slide illustrates, a filament core/staple fiber wrap core‐spun yarn has a sheath of staple fibers which cover a filament yarn core. When the sheath fibers are cotton, the result is the softness, low luster, good dyeability, and comfort of the cotton fibers and the strength and or elasticity contributed by the core filaments. Fabrics containing core‐spun yarns with a spandex core are usually heat‐treated to adjust the elastic properties of the fabric to meet the needs of a particular application.



Slide 68

Core Spinning Spandex

Core‐spun yarns containing spandex provide the fabric designer with broad possibilities, since stretchable yarns can be constructed with a wide range of properties using virtually any type of “hard” fiber as the cover yarn. On a ring spinning machine, the spandex is fed into the back of the top front roller of the drafting system. The spandex forms the core, which is wrapped by cotton fibers which have been drafted from a package of roving as seen in the diagram shown. In air jet spinning a package of spandex can be fed into the air nozzle component, and the wrapping staple fibers come from the drafting of cotton slivers. The basic requirements to produce an elastic core‐spun yarn is to stretch an elastomeric filament yarn before it enters the spinning frame. This action provides elasticity in the final yarn by retraction of the elastomeric core when stress is removed, thus compacting and bulking the spun yarn core. The core spun yarn can be extended to the point where the nonelastic cover yarn is stretched to its limit, thus resisting further extension of the core spun yarn. Elastic core‐spun yarns are usually made on cotton, worsted, or woolen spinning systems.



Slide 69

Twist Direction

After flat filament and textured filament yarns are produced, they can remain a single yarn bundle, called a singles yarn, or they can be joined with other yarns in a twisted configuration to produce plied yarns. As illustrated, there are several combinations of twist directions when plying yarns together.



Slide 70

Yarns made from Filament Silk

Silk is the only natural continuous filament fiber that can be formed into filament yarns. Silkworm cocoons are immersed in hot water to soften the sericin holding the silk filaments to each cocoon. Brushing the outside of the cocoons allow the ends of filaments to be detected. Filaments are then picked up from several cocoons and combined. Much of the process can be automated, but picking up the end of the filament from each cocoon must still be done by hand by a highly skilled associate. Two to twelve filaments are normally combined. The reeling operator must be quick to detect diameter changes and then add or take away one or more filaments when needed in order to produce uniform yarn. The silk is formed into skeins and graded according to evenness, size, color and cleanliness. Any remaining sericin must be boiled off from the silk. Several silk yarns may be twisted together. A tremendous number of spindles are required to insert twist and ply the yarns.



Slide 71

Filament /Textured Yarns in Fabrics




Slide 72

Woven Fabric Structure

A typical structure for a woven fabric is shown in this diagram. The vertical yarns along the length of the fabric are called warp yarns or warp ends while the horizontal yarns interlacing with the warp yarns are called weft yarns, filling yarns, or simply picks. Warp yarns are fed from beams on the weaving machine. The making of these beams will be covered in the next few slides. The filling yarn is supplied by individual yarn packages located on one side of the weaving machine. This is true for all shuttleless machines in operation today.



Slide 73

Warping of Yarns for Weaving

Prior to weaving flat and textured yarns, the yarns are transferred from yarn packages onto a section beam. Direct warpers with V‐shaped creels, as shown in this photograph, are often preferred for textured yarns. Straight‐line creels are often preferred for flat filament yarns. Condition of warper yarn guides and beam flanges is critical for filament yarns, especially those containing micro‐denier filaments. Yarn package size, and especially yarn length, are very important parameters to control in yarns designated for warping. The dimensions of the yarn package must fit the warper creels and all the packages must have identical yarn lengths in order to minimize waste and maintain accurate section beam yardage.



Slide 74

Slashing or Sizing of Warp Yarns

As shown in the photograph of a slasher, section beams of yarn are then combined on a slasher creel, and sheets of yarn enter a size box where they are treated with a size solution containing some type of adhesive which helps to adhere or “tack” the individual filaments together to prevent filament separation during weaving. Sizing textured yarns can give cohesion to the yarn bundle and supplement the air entanglement of the filaments. The sheets of yarn are then put onto a loom beam, which will be the warp yarn supply during the weaving process. Size can coat the tack points in air‐entangled yarns to give the tack points more stability during weaving. With spun yarns, the objective in sizing is to encapsulate the entire yarn surface.



Slide 75

Drawing‐in of Warp Yarns

Drawing‐in is the process of threading each individual warp yarn through different elements on the weaving machine. The drop wires seen here are typically metal devices designed to act as a stop‐motion so weaving machines will not continue to run when a yarn breaks. Each yarn is then drawn through a heddle which is located in a device called a harness. The harnesses move up and down to produce the desired weave design in the fabric. Heddles and drop wires must be free of any rough spots or burrs which would abrade the yarn and break filaments. So called “flashes” or tight ends in the fabric can occur due to rough spots on the drop wires and heddles which causes the yarn to snag and increase in tension. Yarn lubrication and application of size help the yarn to get through these potential abrasive devices. It is important to remember, that when spun yarns or abrasive yarns like Nomex have been running on a weaving machine, the heddles and drop wires must be replaced before running filament and filament textured yarns. Otherwise broken filaments will result and lead to machine stops, low weaving efficiencies, and fabric pilling. Coated heddles should be used with filament yarns.



Slide 76

The Reed

The reed is made of pieces of wire which separate the warp yarns into specific groups of yarns. It controls the separation of the yarns during weaving, the weaving fabric width, and assists in the insertion of the filling yarns. The empty space between the wires of the reed is referred to as air space. The air space in reeds is increased for high bulk and stretch yarns to protect the yarn from damage and to allow it freedom to perform as desired in the fabric. Notice the numbers on this reed. The number 7.0 represents the reed number or the number of dents (open slots) in the reed while 65‐75% represents the amount of air space in the reed. Spun yarns and flat (FOY) yarns can use lower air space reeds such as 45‐55% while machines running textured yarns require 55‐65% air space in the reed. Machines running spun yarn may have 4 ends per dent in the reed, but if running textured yarn, may have 3 yarns per dent. The key point to remember relative to the use of textured yarn and the method of fabric formation is that for effective bulking and stretching and shrinking of yarns to take place, there must be sufficient open area in the fabric for it to happen. However, too much air space normally results in an unstable fabric and is often seen as a bagging effect. It also results in seam slippage because there is not enough interlocking of warp and filling yarns to hold the fabric together when under stress and strain. The choice of reed for a given warp yarn product is very critical as it affects weaving performance and fabric quality.



Slide 77

The Reed Action Video

The reed moves back and forth on a weaving machine as seen in this video. Yarn chafing can result if there is not proper space between adjacent yarns and reed wires. Width‐in‐the‐reed or WIR is important, especially when weaving elastic yarns in the filling direction. Expanding the WIR will allow elastic filling yarns more room to elongate and recover.



Slide 78

Fabric Construction and DPF

Fabric construction or fabric count refers to the number of warp yarns per inch (or cm.) and the number of filling yarns per inch (or cm.) in the finished fabric. There are guides to follow for weaving different DPF yarn products. If one is changing from a staple spun yarn to a micro‐denier or low DPF yarn product, the fabric construction should be reduced in the warp direction by 10 – 12% and by 16 ‐18% in the filling direction. When changing from a high DPF yarn to a low DPF yarn the fabric construction should be reduced in the warp direction by 4 – 6% and by 8 – 10% in the filling direction.



Slide 79

Filling Insertion on Shuttleless Weaving

The common methods of inserting the filling yarn when weaving are by use of projectiles, rapiers, air jets, or water jets, as shown in this diagram. Some filament and textured yarn manufacturers have a specific package wind for the type of loom used, whether projectile, rapier, air jet, or water jet. Rapier and projectile machines tend to perform better when weaving stretch yarns in the filling direction than air jet machines.



Slide 80

Influence of Weave Design

Frequently, the weave design is chosen so that a given filament or textured yarn product creates the desired appearance in the woven fabric. For example, a basket weave design, as shown in this fabric schematic , might be a good design choice when using trilobal bright yarns in the warp direction and trilobal full dull yarns in the filling direction. This would yield a checkerboard pattern with alternating high and low luster squares in the design.



Slide 81

Twill Weaves

Twill weaves contain long floats where the warp yarn weaves over multiple filling yarns on the face of the fabric. This means there are fewer warp and filling yarn interlacing points. Thus there is room for stretch yarns to perform at a higher level. Due to the floating of filling yarns on the back of twill fabrics, stretch yarns can be employed in the filling fabric direction and perform well. There is also a greater opportunity to highlight special effect warp yarns because of the greater visibility of the warp yarns on the face of the fabric. A 3/1 twill is classified as a warp face twill, meaning more warp yarn is showing on the face of the fabric. A 1/3 twill is classified as a filling face twill, meaning more filling yarn is on the face of the fabric. So one has to determine what yarn product is to be placed in the warp and what yarn product is to be placed in the filling in order to get the fabric look and appearance that is desired.



Slide 82

Crepe Weaves

A crepe fabric is usually woven with high twist yarns. “S” and “Z” twist yarns are often used. The weave has a random distribution of floats designed to produce an effect in the fabric that disguises the pattern repeat. The fabric texture or crepe look is created by the higher than normal amount of twist in the yarns, producing a crinkled texture on the fabric surface and a rather harsh hand or feel to the fabric.



Slide 83

Satin Weaves

Satin weave fabrics contain the longest floats in the filling and warp directions. Therefore, visual effect yarns are readily visible in these fabrics. The representation shows the face of a five harness satin fabric and also the back where filling yarns produce long floats. If trilobal bright yarns are used in the warp direction in a warp satin weave where the warp yarns float, the fabric will appear very lustrous. Filling yarns in these fabrics can be lower priced commodity yarns, because they will not show on the fabric face but are pronounced on the back of the fabric.



Slide 84

Weft Knit Fabric Structure

Knit fabrics are formed by looping yarns together. As seen in this knit fabric structure, the horizontal rows of loops are called courses. Each vertical column of loops is called a wale. Instead of a number of ends and picks per square inch as in a woven fabric, knits have courses and wales per square inch in the fabric. Each course is formed by needles knitting yarn from the same yarn package, while each wale is formed by an individual needle knitting from different yarn packages.



Slide 85

Weft Knit Fabrics

Due to the loop structure in knitted fabrics, yarns with visual effects and high stretch, and even bright yarns are generally as effective in knit fabrics as they are in woven fabrics. High torque yarns are a problem in circular jersey knit fabrics due to the tubular fabric’s tendency to be skewed. A major use of filament and textured yarns in knit fabrics is in double knits where more elaborate designing can be done. This permits the use of visual yarns which can be placed in the fabric to be highly visible. Jersey knit fabrics, shown here, are good candidates for microdenier and other low denier textured and filament yarn products.



Slide 86

Warp Knit Fabric Structure

Filament type yarns are used frequently in warp knitting, while spun yarns are not commonly used. Shown is a schematic of a common warp knit fabric structure. Warp knit structures can contain one type of filament yarn on the fabric face and back while other types of yarns can be employed between the face and back loops. Tricot warp knit fabrics containing fine denier filament yarns are found in ladies’ underwear and lingerie. Raschel warp knit fabrics containing filament yarns are found in apparel, interior furnishings, automotive applications, and many technical fabrics. Sports‐related fabrics in mesh‐like structures predominate in raschel warp knitting. Lace and net fabrics also are produced on raschel warp knit machines.



Slide 87

Warp Knitting Animation

The animation shown depicts a typical warp knit machine with yarns being fed from beams and entering a straight line of needles. Each yarn must be threaded through a guide bar eyelet. The guide bars loop the yarn around the front of the needles to form overlaps and then form underlaps of yarn on the back of the needles in many various patterns. This is discussed in greater detail in the warp knitting module.



Slide 88

Knit and Woven Fabric Summary

In a knit structure yarns often play a secondary role, unlike in many woven fabrics. Knit fabrics, because of the nature of their loop structure, have built‐in stretch and recovery. This property can be increased by the use of covered yarns. However yarns with special stretch features are not as effective as in woven fabrics. Bright yarns such as trilobal textured do not appear as lustrous in a knit fabric as they do in a woven fabric because a smaller “platform” exists to highlight the special yarn characteristics of luster. In woven fabrics, the yarns are straight, and there is sufficient length of yarns seen which allows the visual effects of thick and thin textured yarns and other special effects to be more readily seen.



Slide 89

Fabric Preparation

• Prepares fabric for dyeing and finishing.

• Includes desizing to uniformily remove size of warp yarns.

• Includes washing or scouring of the fabric to remove oils and waxes and other impurities.

• Good preparation allows for uniform application of dyes and finishes.

After weaving and knitting of fabrics, they are prepared for dyeing and finishing processes. This mainly includes desizing (for woven fabrics) and washing. These steps are critical to the quality of the dyeing and finishing of the fabrics. For desizing, it is important to know what type of size is on the fabric for successful removal. If the size is not completely removed or removed non‐uniformily, then dyes and finishes like flame‐retardency will not be as effective. Thorough washing of the fabric will remove any chemicals or foreign materials that may interfere with the application of dyes and finishes.

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