000001
`
`BEDGEAR 1017
`IPR of U.S. Pat. No. 8,402,580
`
`

`
`Published in the Westem Hemisphere by
`Technomic Publishing Company, Inc.
`851 New Holland Avenue, Box 3535
`Lancaster, Pennsylvania 17604 U.S.A.
`
`Distributed in the Rest of the Wbrld by
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`
`
`
`
`
`
`Copyright ©1995 by Wellington Sears Company
`All rights reserved
`
`
`
`No part of this publimtion may be reproduced, stored in a
`retrieval system, or tlansmitted, in any form or by any means,
`electronic, mechanical, photocopying, recording, or otherwise,
`without the prior written permission of Wellington Sears Company.
`
`Printed in the United States of America
`10 9 8 7 6 5 4 3 21
`
`Main entry under title:
`Wellington Sears Handbook of Industrial Textiles
`
`Library of Congress Catalog Card No. 95-61229
`ISBN No.
`l—56676-340-1
`
`HOW TO ORDER THIS BOOK
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`

`
`
`
`named.
`liamine
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`thylene
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`' of the
`neriza-
`me and
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`zly(eth-
`1 list of
`lecular
`and an
`
`xsually
`name
`
`2.2
`
`
`Natural and Man-Made Fibers
`
`D. M. HALL
`S. ADANUR
`
`R. M. BROUGHTON, JR.
`P. H. BRADY
`
`1.
`
`INTRODUCTION
`
`1.1 Generic Names of Fibers
`
`Mankind has been fortunate that over the eons,
`natural materials could be found with suitable
`fiber properties to fabricate clothing for warmth,
`comfort and style depending upon the needs at
`the time. The most important fibers in the world
`until about 1910 were the protein fibers wool and
`silk, and the cellulosic fibers cotton and linen.
`All of these products are produced from agricul-
`ture. The production of wool, silk and linen has
`remained static for the last decade owing to the
`fact that land and facilities for cultivating these
`fibers are fixed (and for some they are declining).
`With the world population growing rapidly and
`the supply of these fibers either diminishing or
`fixed, the cost of using these fibers for ordinary
`textiles is prohibitive. Only cotton is grown in
`quantities that enable it to continue to be an
`economical source for textile manufacturing.
`About 1910, discoveries were made which
`
`allowed fibers to be spun from special solutions
`of cellulose as continuous filaments. Unlike the
`natural products, these fibers could be spun into
`varying diameters that were essentially the same
`for every fiber in the bale. Further, the filaments
`could be cut into any length uniformly unlike that
`of cotton and linen. Later it was found that they
`could be made to have cotton-like properties of
`softness and hand, have ignition, sunlight and rot
`resistance among other properties that could be
`built into the fibers as they were being spun.
`Thus, it was found that the fibers could be en-
`gineered to have specific properties depending
`upon the desired end uses of the product. Today,
`the number of different genera of fibers that have
`been produced for textile purposes is quite high.
`
`In addition to the chemical nomenclature (Sec-
`tion 2.1), the Federal Trade Commission (FTC)
`has defined generic categories of fibers based on
`chemistry and properties. Each category has
`been assigned a generic name. Basically, any
`consumer textile item sold in retail commerce
`
`must carry a label declaring the generic name and
`the percent by weight of all the component fibers
`in the composition (which exceed 5% of the
`total). Certain items like luggage, carpet back-
`ing, hats, wiping rags, furniture stuffing, and
`tarps are exempted, as are items intended for
`industrial applications. A manufacturer may
`label the fibers with trade names and other infor-
`
`mation specific to the manufacturer, but the
`generic names offibers and the percent composi-
`tion must always be present. The purpose of a
`generic name is to provide the consumer with a
`recognized name with which to associate a set of
`expected fiber properties. Some fibers find little
`or no use in consumer textiles, and may not have
`an established generic name.
`Generic names
`for manmade fibers are
`defined by the chemistry of the fiber and its
`physical properties. New names may be added
`and older ones modified in definition as
`demanded by technology and developments.
`When believed required, a manufacturer can
`petition the FTC for the establishment of a new
`
`the FTC will ex-
`generic name. In response,
`amine the chemistry of the new fiber as well as
`its properties, and then decide whether a new
`name is warranted. Natural fibers are labeled
`
`according to their origin. Thus cotton, linen,
`silk, wool, etc. , are legitimate generic names.
`
`37
`
`000003
`
`000003
`
`

`
`40
`
`POLYMERSANDFBERS
`
`
`
`of chemicals, and does not have extensive ap-
`plications in industrial fabrics. Other hair fibers
`will differ in size, pigmentation, scale frequency,
`and harvesting methods. Hair fibers are most
`often used for apparel and carpeting. A general-
`ized structure of a protein is shown below.
`
`nature. Synthetic fibers have no natural polymeric
`precursors. Thermoplastic polymers such as
`nylon or polyester are examples of this category.
`Table 2.2 lists common man-made fibers. FTC
`
`definition, chemical structure and important
`properties of the fibers are given below.
`
`3.1 Acetate
`
`“A manufactured fiber in which the fiber-
`
`forming substance is cellulose acetate. Where
`not less than 92% of the hydroxyl groups are
`acetylated, the term triacetate may be used as a
`generic description of the fiber.” Two varieties
`of acetate are produced which are secondary
`cellulose acetate and cellulose triacetate. As the
`
`they describe the approximate
`name implies,
`number of hydroxyls of the cellulose which are
`replaced by acetyl groups. These acetyl groups
`confer new properties to the cellulosic polymeric
`chains, chief of which is high loss of water ab-
`sorbency, i.e. , the fibers are hydrophobic (water
`hating) in nature. They are dry spun by spinning
`solutions of the cellulose derivatives dissolved in
`
`low boiling volatile solvents into hot air where-
`upon the solvent is evaporated resulting in a solid
`continuous
`thread of the cellulose
`acetate
`
`polymer.
`
`
`
`OAC
`
`During the fiber extrusion process, either pig-
`ments can be added to the spinning dope to color
`the threads or delustering agents in order to
`modify (dull) the luster characteristics of the
`fibers. In addition, other agents can be added to
`the spin solutions to impart sunlight and ignition
`resistance to the fibers. The fibers of the yarns
`can be spun into any denier, cut into any staple
`lengtl1. Further, they are resistant to mildew and
`insects that damage cellulosic fibers. The fibers
`are lighter in weight (less dense) than cellulosic
`fibers (density is 1.32 compared to 1.52 for
`cotton and rayon).
`
`Glycine
`R= Alanlne
`Hlstldlne
`Arglnine
`Aspartlc Acld Leucine
`CVSWW
`LVs"_“’
`Glutamlc Acld Methlonlne
`
`Phenylalanlne Tryptophan
`Prollne
`Tyrosine
`se.-in.
`Vanna
`Threonine
`lsoleuclne
`
`Silk
`
`Silk is a protein fiber like wool but with a much
`simpler structure. It is an extruded fiber which is
`chemically and structurally uniform across its
`diameter. The amino acids have smaller pendant
`groups than those found in wool, allowing a
`pleated-sheet structure rather than helical
`to
`occur.
`
`‘u’
`l?
`ll
`—N——cf—c—N—cf—c—N—cl:—c—
`R1
`R2
`Rm»1
`R = Alanine, Glyclne, Serine, or Tyroslne
`
`Because no cystine is present, no crosslinking
`occurs. Silk has no cellular structure, no scales,
`and no pigment. The silkworm uses the silk to
`construct a home in which to undergo metamor-
`phosis. A silkworm’ s cocoon is unwound to
`produce a natural, continuous filament fiber. Ob-
`servation of the silkworm at work gave man the
`idea for extrusion of fibers. Although wool and
`silk are generally weak, other insects, such as
`spiders, can produce a very strong protein fiber.
`Indeed it seems that with a greater understanding
`of protein structures, a fiber having an optimal
`choice of physical properties may be designed.
`
`3. MAN-MADE FIBERS
`
`Man-made fibers are those produced by
`human
`endeavor. They may
`be
`further
`categorized into regenerated and synthetic clas-
`ses. Regenerated fibers (such as rayon) are those
`created from polymeric materials produced in
`
`000004
`
`000004
`
`

`
`
`
`POLYMERS AND FIBERS
`
`50
`
`acrylonitrile units —The term “lastrile”
`may be used as a generic description for
`this form of rubber.
`
`+cH,—<I:H+co+CH2—CH=CH—CH2+
`Tl
`n
`GEN
`
`0 a manufactured fiber in which the fiber
`
`forming substance is a polychloroprene
`or a copolymer of chloroprene in which
`at least 35% by weight of the fiber form-
`ing substance is composed of
`chloroprene units (— CH2 — (Cl)C = CH -
`CH2 — ).
`
`—ECH2—?=CH—CHz+ll
`Cl
`
`3.17 Saran
`
`“A manufactured fiber in which the fiber
`
`forming substance is any long chain synthetic
`polymer composed of at least 80 %’ by weight of
`vinylidene chloride units.” Saran is usually
`produced in a specialized monofilament form for
`flame retardant and chemical resistance applica-
`tions. The most familiar consumer usage is in
`film or coating form.
`
`3.19 Sulfar
`
`“A manufactured fiber in which the fiber-
`
`forming material is a long synthetic polysulfide
`in which at least 85% of the sulfide linkages are
`attached directly to two aromatic rings.” As with
`other aromatic based fibers, sulfar finds utility
`from its special stability to environmental chal-
`lenges. Sulfar is particularly chemically resis-
`tant, and finds most of its applications in
`industrial fabrics.
`
`3.20 Vinal
`
`“A manufactured fiber in which the fiber form-
`
`ing substance is any long chain synthetic polymer
`composed of at least 50% by weight of vinyl
`alcohol units (—CH2—CHOH—), and in which
`the total of the vinyl alcohol units and any one or
`more of the various acetal units is at least 85 % by
`weight of the fiber.” Although_the polymer is
`manufactured in large qualities for a variety of
`glue and coating applications, there is no vinal
`fiber currently manufactured in the United States.
`The water solubility of the vinal fiber must be
`overcome (usually by formaldehyde crosslink-
`ing) in order to produce a durable product.
`
`'.*
`'.*
`-E<,=—c.&.-
`H
`OH
`
`3.21 Vinyon
`
`“A manufactured fiber in which the fiber
`
`forming substance is any long chain synthetic
`polymer composed of at least 85% by weight of
`vinyl chloride units.” Vinyl (PVC) is almost the
`universal plastic film, finding application in al-
`most everything, e.g., notebooks, electrical
`cords, outdoor furniture, and automobile trim.
`
`—E¢—r'3-a.-
`
`
`
`H
`-E‘I=—H.-
`H
`
`3.18 Spandex
`
`“A manufactured fiber in which the fiber-
`
`forming substance is a segmented polyure-
`thane.’ ’ Spandex is an elastomeric fiber used for
`clothing materials, and finds application in in-
`dustrial textiles in such places as elastic bands in
`protective apparel. It is a block copolymer com-
`posed of stiff rigid blocks interspersed with soft
`flexible blocks. In general, the soft blocks have
`been either aliphatic polyesters or polyethers. A
`single chemical structure cannot be drawn for
`Spandex, but a generalized structure is shown
`below.
`
`i‘
`—Et;T'-N-R1-N-C-O-R2-O
`o
`
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`
`
`
`000005
`
`

`
`3.1
`
`
`Manufacture of Man-Made Fibers
`
`R. M. BROUGHTON, JR.
`P. H. BRADY
`
`1.
`
`INTRODUCTION
`
`Textile fibers are solids with distinct shapes.
`The primary task in fiber manufacture is to trans-
`form solid materials into a fiber configuration.
`The liquid state is the only condensed state that
`can easily deform or have its shape changed. In
`its simplest form, fiber manufacturing processes
`consist of liquefying a solid polymer, transform-
`ing it into the shape of a fiber, and then resolidify-
`ing the liquid.
`In the 16005, Robert Hooke and other scien-
`
`tists noted that spiders and silkwonns had
`developed the process of converting solids to
`liquids, and back to solids, but reshaped as fila-
`ments. These early scientists speculated that man
`would one day be capable of duplicating this
`natural extrusion process. Early researchers
`were able to extrude fibers by drawing or pulling
`liquid threads from solutions of natural gums and
`resins. An industrialist in Manchester, England,
`is credited with the design and construction ofthe
`first fiber producing machine. However,
`the
`materials used in this instrument were not
`suitable fiber forming polymers. Audemars was
`awarded a patent for the production of cellulose
`nitrate fibers in 1855, but the first commercially
`successful concept of production was not
`developed until the 1880s. In 1891, Chardon-
`net’s facility began production of regenerated
`cellulose fibers. This success was followed by
`the development of the cuprammonium process
`by Despeisses, which was commercialized in
`1897. Cross and Bevan invented the viscose
`
`process about 1892, which was further refined to
`a more practical process by Steam and Topham
`between 1895 and 1900. These early pioneers
`not only had to develop the chemistry necessary
`to dissolve and resolidify cellulose without
`
`severe degradation, they also had to invent the
`machinery necessary for fiber production. Table
`3.1 shows the important events in the history of
`man-made fibers.
`
`Energy is required to convert a solid polymer
`to its liquid state. That energy can be developed
`either from heat, chemical solvents, or a com-
`bination of the two. If heat supplies the energy,
`the polymer is solidified in fiber shape simply by
`cooling. If chemical solvents are used, there are
`two ways ofresolidifying the polymerinto a fiber
`shape. The solvent can be evaporated, or the
`polymer solution can be precipitated by immer-
`sion in a non-solvent. The three ways of re-
`solidification are used as a basis to classify fiber
`extrusion processes (Table 3.2). This rather
`simple classification scheme does not reveal the
`true complexity of the processes. Some of the
`more recently developed polymers require very
`sophisticated processes. For example, high
`strength aramid fibers are produced through a
`wet spinning process, but the polymer solution
`exists in a liquid crystalline state. High strength
`polyethylene fibers are created through the ex-
`trusion of an ultra high molecular weight melt or
`gel state. This meltlgel is highly viscous, having
`some of the characteristics of a solid. Even the
`
`viscose process has chemical reactions proceed-
`ing during the solidification, so it is not entirely
`a precipitation.
`
`2. MELT SPINNING (EXTRUSION)
`
`A diagram of the basic melt spinning (ex-
`trusion) process is shown in Figure 3.1. Some
`operations which proceed directly from polymer
`manufacture to extrusion may use a pump instead
`of a screw type extruder. All fiber spinning sys-
`
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`57
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`

`
`
`
`3.2
`
`Manufacture of Continuous Filament Yarns
`
`
`
`S. ADANUR
`
`
`
`The manufacture of continuous filament yarn
`is a relatively simple matter of collecting the
`number of individual filaments necessary to
`produce the desired yarn size. As manufactured
`by the fiber producing companies, they are called
`“producer’s yarns.’ ’ They contain minimum
`twist, ranging from about zero to 2.5 turns per
`inch, which is just sufficient to maintain the
`yarn’ s integrity.
`Most producer’s yarn is delivered with a thin
`resinous finish or size which protects the fila-
`ments from damage due to abrasion and snag-
`ging. The finish, amounting usually to less than
`one percent by weight, may or may not be water
`soluble. Such finishes should not be confused
`with water soluble sizes such as starch, gelatin,
`or synthetic resins, which are applied to warp
`yarns at the mill to give additional protection
`during weaving. Sometimes a light lubricant is
`also applied to the yarn by the producer or the
`mill. This improves running quality by reducing
`static and friction, and reduces abrasion of the
`yarn and wear on the textile machinery guides,
`rollers, etc.
`Because of filament uniformity and the com-
`plete absence of protruding fiber ends, con-
`tinuous filament yarns are particularly smooth ‘
`and lustrous. Such properties are advantageous
`in the manufacture of many fabrics, but a high
`degree of filament and yarn uniformity is neces-
`sary. Even minor irregularities will be observed
`as fabric defects due to changes in luster, dye
`pickup,
`irregular yarn twist or yarn spacing.
`Producers must always be on the alert to insure
`yarn uniformity, both within a package and
`among packages. Any differences in the amount
`that the yarn is drawn during manufacture will be
`manifested as differences in optical and physical
`properties, for example, dye absorption and
`66
`000007
`
`residual rupture elongation. Excessive elonga-
`tion at the beginning or end of the yarn package
`can result
`in fabrics with visually obvious
`defects. Staple yarns, being less uniform, can
`afford more irregularities, without the danger of
`the resulting fabrics being considered “defec-
`tive.”
`
`1. THROWING AND TWISTING
`
`There are so many different filament yarn
`constructions required by textile mills that it is
`quite impossible for the man—made fiber manu-
`facturer to have all of them available, or make
`them on order. Instead the fiber producer sells
`several popular sizes, packaged usually on a
`standard spool. The textile mill must then ar-
`range to have the producer’ s yarn converted into
`the desired yarn of proper weight, twist and ply,
`properly sized, lubricated, and packaged for sub-
`sequent mill operations. These procedures are
`collectively called “throwing.” Throwing may
`be carried out by the mill which will ultimately
`weave or otherwise use the yarn, or by a com-
`mission ‘ ‘ throwster.’ ’ The term usually applies to
`the preparation of relatively lightweight yarns,
`in contrast to “twisting” which pertains to the
`preparation of heavier yarn constructions. More
`recently, the term also applies to a company that
`specializes in texturing yarns.
`It is usually impractical to make a heavy yarn
`by twisting many units or ends ofproducer’ s yarn
`together in the same direction. Such a yarn would
`be soft, bulky, unstable, and might have low
`strength. Instead, plied yarns are constructed.
`Several turns oftwist are inserted in one direction
`into the singles producer’ s yarn, and then several
`of these are twisted together, usually in the op-
`posite direction, to make the plied yarn. Several
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
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`
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`
`
`
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`
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`000007
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`

`
`
`
`4.1
`
`
`Classification of Fabrics
`
`R. P. WALKER
`S. ADANUR
`
`A fabric may be defined as a planar assembly
`of fibers, yarns or combinations of these. There
`are many different methods of fabric manufactur-
`ing, each capable of producing a great variety of
`structures dependent upon the raw materials used
`and the setup of control elements within the
`processes involved. The particular fabric selected
`for a given application depends on the perfor-
`mance requirements imposed by the end use
`and/or the desired aesthetic characteristics of the
`
`end user with consideration for cost and price.
`Fabrics are used for many applications such as
`apparel, home furnishings and industrial. The
`most commonly used fabric forming methods are
`interlacing, interlooping, bonding and tufting.
`
`INTERLACING (WEAVING
`1.
`AND BRAIDING)
`
`Weaving—interlacing of a lengthwise yarn
`system (warp) and a widthwise yarn system (fill-
`ing) at 90 degrees to one another with fabric
`flowing from the machine in the warp direction
`[Figure 4. 1(a)].
`Braiding—interlacing of two yarn systems
`such that the paths of the yarns are diagonal to
`the fabric delivery direction forming either a flat
`or tubular structure [Figure 4. l(b)].
`
`INTERLOOPING (WEFT AND
`2.
`WARP KNITTING)
`
`Knitting—interlooping of one yarn system
`into vertical columns and horizontal rows of
`
`loops called wales and courses respectively with
`fabric coming out of the machine in the wales
`direction [Figure 4.1(c) and Figure 4.1(d)].
`
`3. TUFTING
`
`“Sewing” a surface yarn system of loops
`through a primary backing fabric into vertical
`columns (rows) and horizontal lines (stitches)
`forming cut and/or uncut loops (piles) with the
`fabric coming out of the machine in the rows
`direction as shown in Figure 4.1(e). Fabric must
`be back-coated in a later process to secure tufted
`loops.
`
`4. BONDING (NONWOVENS)
`
`textile,
`Nonwovens—using either
`extrusion or
`some
`combination of
`
`paper,
`these
`
`technologies to form and bond polymers, fibers,
`filaments‘, yarns or combination sheet into a
`flexible, porous structure [Figure 4.1(f)].
`
`000008
`
`87
`
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`
`

`
`
`
`(f)nonwovcn ‘ 4 4 4
`(0)weftknit
`FIGURE4.1Typesoffabrics.
`knit
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`Yarn
`
`R. P. WALE
`S. ADANU
`
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`yarns, the
`preparation;
`Of packages
`and in many
`not suitable‘
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`quired beft
`specific pref
`on the typ:
`preparation
`are as folloi
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`0 weavi
`drawil
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`(e)tufted
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`

`
`126
`
`FABRIC MANUFACTURING
`
`the traditional weaving machine. These devel-
`opments include the circular loom and several
`different multi-phase weaving systems such as
`warp direction shed waves and weft direction
`shed waves. These multi-phase concepts offer an
`advantage in production rate, gained by pro-
`viding segmented sheds along either the warp or
`
`the filling direction of the structure coupled with
`progressive, simultaneous filling insertions. Al-
`though some of these new multi-phase systems
`and circular looms are being used in limited
`fabric markets, none of them has challenged
`traditional weaving machines in major fabric
`markets so far [5].
`
`
`
`
`
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`
`C/-‘DU
`
`000010
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`- 4.5
`:_____
`Knitting
`
`R. P. WALKER
`S. ADANUR
`
`1.
`
`INTRODUCTION
`
`As defined earlier, knitting involves the inter-
`looping of one yarn system into continuously
`connecting vertical columns (wales) and hori-
`zontal rows (courses) of loops to form a knitted
`fabric structure. There are two basic types ofknit
`structures as shown in Figure 4.1: weft knit and
`warp knit. Figure 4.46 shows a circular weft
`knitting machine.
`In weft knitting, the yarn loops are formed
`across the fabric width, i.e. , in the course or weft
`direction ofthe fabric. In warp knitting, the loops
`are formed along the fabric length, i.e., in the
`wale or warp direction of the cloth. In both
`knitting systems the fabric is delivered in the
`wale direction. Special needles are used to form
`the yarn loops as shown in Figure 4.47. The latch
`needle is the most common type in use for weft
`knitted fabrics and the compound needle is used
`mostly in warp knitting. Spring beard needles are
`becoming obsolete.
`The basis of knit fabric construction being the
`continuing intersecting of loops, any failure of a
`loop yarn will cause a progressive destruction of
`the loop sequence and a run occurs. Thus, knit-
`ting yarns must be of good quality in order that
`yarn failures be kept at a minimum. Other impor-
`tant geometrical definitions relating the knit
`structures are as follows:
`
`0 count: total number of wales and courses
`per unit area of the fabric
`
`0 gauge: the number of needles per unit
`width (the fineness or coarseness of the
`fabric)
`,
`0 stitch: the loop formed at each needle
`
`(the basic repeating unit of knit fabric
`structure)
`0 technical face: the side of the fabric
`where the loops are pulled toward the
`viewer
`
`0 technical back: the side of the fabric
`where the loops are pulled away from the
`viewer
`’
`
`Industrial application areas of knit structures
`include medical products
`such as artificial
`arteries, bandages, casts, and surgical gauze and
`flexible composites. Knit fabrics are used as
`reinforcing base for resins used in cars, boats,
`and motorcycle helmets.
`
`2. WEFT KNITTING
`
`Weft knit goods are made by feeding a multiple
`number of ends into the machine. Each loop is
`progressively made by the needle or needles.
`Figure 4.48 shows the loop forming process with
`a latch needle. The previously formed yarn loop
`actually becomes an element of the knitting
`process with the latch needle. This is why the
`latch needle is referred to as the “self-acting”
`needle. As the needle is caused to slide through
`the previous yarn loop,
`the loop causes the
`swiveled latch to open, exposing the open hook
`(head) ofthe needle. The newly selected yarn can
`now be guided and fed to the needle. If a simple
`knitted loop is to be formed, the previous loop
`(the one which opened the latch) must slide to a
`point on the needle stem allowing it to clear the
`latch. Having the needle reach this clearing posi-
`tion allows a reversal of the sliding action which
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`128
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`FABRIC MANUFACTURING
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`FIGURE 4.46 Circular weft knitting machine.
`
`in turn pulls down on the new yarn and uses the
`previous yarn loop to close the latch trapping the
`new yarn inside the hook. The previous loop is
`now in a position to ride over the outside of the
`latch and be cast off the needle head, thus becom-
`ing a part of the fabric while the new yarn loop
`is pulled through the previous loop.
`Depending on the structure in weft knitting,
`several types of knitting stitches are used includ-
`
`ing plain [Figure 4.1(c)], tuck, purl (reverse),
`and float (miss) stitch which are shown in Figure
`4.49. The plain stitch fabric has all of its loops
`drawn through to the same side of the fabric. The
`plain fabric has a very smooth face and a rough
`back. Other stitches produce different effects
`depending on the arrangement of the loops. Spe-
`cial stitches are also available to prevent runs.
`Weft knitting machines may be either flat or
`
`
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`lfllch
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`spring beard
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`FIGURE 4.47 Needle types used in knitting.
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`4.5 Knitting
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`129
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`afl-
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`it
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`_
`latch opening
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`clearing and
`yam feeding
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`[mch dosing
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`custoff -.tntl_
`loop formation
`
`FIGURE 4.48 Loop forming on a latch needle.
`
`circular, the former knitting a flat single layer of
`fabric, the latter knitting a continuous tube. No
`matter which machine configuration is used,
`weft knit manufacturing involves the same fun-
`damental functions:
`
`0 yam selection and feeding
`0 needle knitting action
`I fabric control during knitting
`0 needle selection
`
`0 fabric take-up and collection
`
`yarn break sensors
`fabric hole detectors
`needle “ closed latch” sensors
`
`air blowing systems to keep needles clear
`of lint
`
`centralized lubrication dispensing unit
`0 computer interfaces for production
`monitoring
`0 computer interfaces for pattern entry
`0 computer aided design systems
`
`There are several devices added to weft knit-
`
`ting machinery for improving quality of the
`product and/or operation of the process. A par-
`tial list of these added features includes:
`
`Knit fabrics can be classified as single knits
`and double knits. Single weft knits have one layer
`of loops formed with one yarn system. Three
`major types of single weft knits arejersey, rib and
`purl structures. Double knits have two insepa-
`
`
`
`purl (reverse) stitch
`
`float (miss) stitch
`
`tuck stitch
`
`FIGURE 4.49 Types of stitching in weft knitting.
`
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`
`(reverse),
`n in Figure
`)f its loops
`fabric. The
`
`nd a rough
`ent effects
`
`oops. Spe-
`ent runs.
`
`her flat or
`
`
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`0 do not wrinkle easily and have good
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`130
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`FABRICMANUFACTURING
`
`rable layers of loops. Each yarn forms loops that
`appear on both faces of the fabric. Two major
`types of double knits are rib double knit and
`interlock double knit.
`The major characteristics of weft knit fabrics
`are as follows:
`
`0 can be either manufactured as net-shape
`or cut to shape and sewn
`0 form a run the wale direction if a yarn
`breaks
`
`0 have good stretch especially in the course
`direction
`0 do not ravel
`
`recovery from wrinkling and folding
`3. WARP KNITTING
`
`Warp knit fabrics are manufactured by prepar—
`ing the equivalent of a warp beam containing
`several hundred ends. Each end passes through
`its own needle and is formed into loops which
`intersect with adjacent loops. Thus, a flat looped
`fabric is knitted using only “warp” yarns
`without the necessity of “fllling” yarns being
`interwoven.
`.
`The two major types of warp knits are tricot
`and Raschel. Based on the number of yarns and
`guide bars used, tricot knits are identified as
`single [Figure 4.1(d)], two (Figure 4.50), three
`and four (or more) bar tri°°tS' Raschel knitting
`is suitable for making highly patterned,
`lacy,
`crocheted or specialty knits (Figure 4.51). In
`general, Raschel machines are used for the
`production of knit structures for industrial ap-
`plications. For increased structural support in the
`filling direction, additional filling yarns can be
`inserted as shown in Figure 4.52.
`Figure 4.53 shows a schematic of a warp knit-
`ting machine. The knitting elements required for
`a warp knitting machine include:
`
`0 needles arranged in one or more solid
`bar to function as a unit (called a needle
`bar)
`, yam guides, one for each warp yam,
`arranged in solid bars one for each
`different warp, to function as a unit
`(called guide bars)
`
`°a“°”3)-
`
`_
`FIGURE 4.51 Simple Raschel crochet knit (courtesy of
`Noyes Pub|icafions)_
`
`
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`FIGURE 4.52 Weftinserted warp knitstructure (courtesy
`of Kan Mayer)"
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`5.1
`
`
`Dyeing, Printing and Finishing
`
`W. PERKINS
`
`Greige fabric as it comes from the manufac-
`turing machine may or may not be ready for its
`end-use function. If fabrics are to be dyed,
`coated,
`impregnated, preshrunk or otherwise
`finished, it is usually necessary to remove the
`warp size and other impurities which may inter-
`fere with dyeing or prevent proper adhesion of a
`coating or finish.
`
`1. PREPARING FABRICS FOR DYEING
`AND FINISHING
`
`textile materials and fabrics require
`Most
`pretreatrnents before they can be dyed and
`finished. The required preparatory treatments
`depend on the type of fiber in the material and
`particular dyeing and finishing treatments that
`are to be done. Generally, fibers containing the
`most types and the greatest amount of impurities
`require the greatest amount of preparation for
`dyeing and finishing.
`Most preparatory processes for dyeing and
`finishing involve heating the fabric or treating it
`with chemicals. Therefore,
`the potential
`is
`present for thermal and chemical damage to the
`fibrous polymer comprising the fabric. Fabrics
`can also be damaged mechanically in most
`preparatory processes. High temperature ther-
`mal treatments are often beneficial to fabrics
`containing thermoplastic fibers while these treat-
`ments are not beneficial or desirable on fabrics
`
`containing only non-thermoplastic fibers.
`The following discussion of preparation for
`dyeing and finishing is general and reference
`is made to many types of fibers and textile
`materials.
`
`Typical processes for preparation of materials
`for dyeing and finishing are as follows:
`
`heat setting
`singeing
`desizing
`scouring
`bleaching
`mercerizing
`
`The sequence shown is common but many
`variations may be used. Virtually all materials go
`through some of these processes prior to dyeing
`and some materials in fabric form are subjected
`to all of them.
`
`1.1 Heat Setting
`
`The dimensional stability, dyeability, and
`other properties of thermoplastic fibers are af-
`fected by repeated heating and cooling, or the
`heat history, of the material. The main purposes
`of heat setting are as follows:
`
`0 to stabilize the material to shrinkage,
`distortion, and creasing
`0 to crease, pleat, or emboss fabrics
`0 to improve the dyeability of fabrics
`
`Heat relieves stresses in the amorphous re-
`gions of thermoplastic fibers. When the fiber is
`heated above its glass transition temperature, the
`molecules in the amorphous regions can move,
`and the material can be formed into a new shape.
`When the temperature is decreased, the material
`stays in its new shape. Thus, creases that have
`developed in the fabric can be pulled out, and the
`width of the fabric can be changed somewhat in
`the heat setting process. Creases can be per-
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`FABRIC FINISHING AND COATING
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`manently set in the fabric by heat setting if
`desired. Heat setting is used to permanently set
`twist and crimp in yarns.
`.
`Problems or defects that may be caused by heat
`setting or improper control of the heat setting
`process include the following:
`