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Control of Fiber Form and Yarnand Fabric StructureO. Wada aa Teijin Ltd , Osaka, JapanPublished online: 01 Dec 2008.

To cite this article: O. Wada (1992) Control of Fiber Form and Yarn and Fabric Structure,The Journal of The Textile Institute, 83:3, 322-347, DOI: 10.1080/00405009208631207

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Control of Fiber Form and Yarn andFabric Structure0. Wada

Teijin Ltd, Osaka, JapanReceived 3.3.1992 Accepted for publication 15.4.1992

The perrormance of high-value-added synthetic-fiber products is greatly afTected, not only by theproperties of the polymer itself, but also by the Hber form and the structure of yarns and fabricsmade from the fiber, which can be controlled for particular uses. This paper deals primarily withpolyester-fiber fabrics in general, from the viewpoint of the classification of the shape of fibers,which is characterized by the cross-section and surface configuration, and secondly with productscharacterized by the mutual interactions between the fiber form and the structure of fiber assembl-ies, such as silk-like fabric, spunize fabric, sweat-absorption polyester-fiber fabric, brilliant-color-dcvcloping polyester-fiber fabric, pile fabric, wiping cloth, tickproof quitt covers, and so forth.

Finally, some products developed in imitation of tbe structure and functions of natural fibersare described to indicate a number of directions yet to be taken by synthetic-Hber fabrics.

For tbe development of new bigb-value-added products, it is necessary to determine the targetthrough a scientific approach, to design fiber forms and the fiber-assembly structure dependingon their intended use, and to realize them in a practical way.

1. INTRODUCTION

The properties of many high-value-added synthetic-fiber fabrics are affected by theproperties of the constituent polymer, the structure and properties of the fiber, thestructure of fiber assemblies, and their interactions as shown in Table I.

Structure plays a very important role in textile goods such as garments. Manytextile goods are produced by using standard methods of textile technology andimproved only by changing the properties of the fibers, but, in order to makesophisticated improvements in the fibers much more effective, it is usual to modifythe structure of fiber assemblies to a significant extent.

The recent development of various fiber forms is dependent on the progress ofpolymer blends and conjugate technology, and, as a result, it has become possibleto produce minute fiber forms intentionally. But the structure of natural fibers isextremely precise, and the mechanism of developing their properties is also veryskilful, for example, a suitable form is adapted according to the changing environment.

Table IPerformance of Fiber Assembly Realized by Comhination of Fiher Form, Fiber-assemhly Structure, and

Their Physical Properties

Polymer Fiber Fiber Assembly(Yarn. Fabric.

elc.)

Textile FinishedProducts

(garments, etc)

Forms andStructure

Properties

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This paper mainly concerns the functions of polyester fibers for apparel usebut excludes high-performance functions, such as super-high-tenacity and super-heatproof fibers, and other special functions, such as optical properties and dialysis.Firstly, the fiber form and the practical functions resulting from it and its assemblystructure are reviewed, and then the precise functions of natural fibers are examined.In this paper, recent patents and publications are mostly referred to, and, whennecessary, the physical data of Teijin's products are used as examples.

2. CROSS-SECTIONS OF FIBERS

2.1 Modified External Cross-sections

2.1.1 Cross-sections Obtained hy Modijication of the Shape of the Spinneret

The cross-section of a synthetic fiber made by the melt-spinning method can beeasily varied by changing the spinneret-holc shape, and accordingly various effectscan be obtained by intentionally changing it. The shape of spinneret may not conformto that of the cross-section of the spun fiber, as is shown in Fig. I. The cross-sectionis determined not only by spinneret shape, but also by the soluble adhesiveness, thesurface tension of the polymer, and the cooling conditions, after extrusion. Variouscross-sections have long been studied in the expectation that a new non-round cross-section could create new fiber charateristics'-^.

The first target of high-value-added synthetic fiber was silk. A trilobal cross-sectionwas adopted to make the feel and luster of synthetic fiber similar to those of silk.Usually, a fiber of a trilobal section shows a highly lustrous and sparkling appearance.As the number of lobes increases (for example, quintalobal. octalobal, etc.), the lusterbecomes milder because of the scattering reflection of light. Examples of variouscross-sections are shown in Fig. 2.

Differentiation of the cross-section greatly influences the feel of fibers, and it iswell known that the trilobal form is useful for creating a dry feel. Research on silk-like fabric is now continuing, and studies to improve the cross-section of the fiberare also still in progress. A sharper and more complex cross-section, which is madeby modification of the trilobal form as illustrated in Fig. 3A, can give fabrics a verycharacteristic effect such as a steady luster and a scroopy handle^.

In addition to silk-like polyester-fiber fabric, whose luster and lively hand areimproved by modification of the trilobal cross-section* as shown in Fig. 3B, fabricswith a dry feel brought about by the hexalobal cross-section of polyester staple fiber**and boa-like high-quality fur or blanket made of acrylic fiber with an exceptionallyflat cross-section are seen** in the market. Capillaries on a fiber surface composed ofa modified section, including a multilobal section, have a water-absorbing effect''"'^.

Various forms of cross-section arc shown in Fig. 4, all of which are used for

Fig. 1 (A) Shape of the spinneret ( x 3000); (B) shape of fiber cross-section ( x 3000)

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Fig. 2 (A) Round cross-section of polyester fiber ( x 1200); (B) trilobal cross-section of polyesterfiber ( X 1600); (C) pentalobai cross-section of polyester fiber ( x 1600); (D) hexalobal cross-section of nylon fiber ( x 1000); (E) oetalobal cross-section of polyester fiber ( x 1600)

Fig. 3 Modification of trilobal cross-section; (A) as used for improvement of scroopy touch of silkyfabric: (B) as used for improvement of dry feel

Fig. 4 Various forms of cross-section used for water-absorbabte cloth

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Control of Fiber Form and Yarn and Fabric Structure

polyester or polyamide fibers with concave cross-sections. The surface of the fibercan be made hydrophilic by polymer modification or the application of a finishingagent.

2.1.2 Cross-section Modified by Conjugate Fiber

A conjugate fiber is sometimes used to obtain a sharper and more complex form ofcross-section. Various irregular forms of cross-section can be obtained by the use ofbicomponent fiber, composed of two polymers that have different solubilities. Aftermaking a textile yarn or fabric, a readily soluble polymer is removed from them.

Fig. 5 shows the cross-section that was the result of a study to achieve a silkytouch, a silk-like scroopy sound, and an elegant luster'-^'*.

2.2 Hollow Fibers

The characteristics of hollow fibers are lightness, a novel appearance, and superiorwarmth because of the inclusion of air. Compared with ordinary fibers of the samelinear density, they are stiffer and more resistant to bending and torsion and have amore opaque appearance, caused by diffused reflection of light. These fibers aregenerally used for enhancing the lively hand of fabric, wadding, carpet, and so on.The typical form of cross-section is shown in Fig. 6'^.

Recently produced hoUow fibers with a polygonal cross-section are shown inFig. 7. It is expected that woven and knitted fabrics made from these materials willhave a glistening luster, opaqueness, and a dry and rough feel'^.

Kig. 5 Conjugaie fibers to make sharp and complex cross-section; (I) regular polymer; (2) easilysoluble polymer

Fig. 6 Hollow fibers: (A) trilobal hollow polyester liber for clothing ( x 1900); (B) square hollowpolyester fiber for clothing ( x 1900); (C) hexalobal hollow polyester fiber for clothing( X 1900); (D) round hollow staple polyester fiber for padding ( x 2000); (E) cross-shapedhollow nylon fiber for carpets ( x 1000)

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Fig. 7 Polygonal hollow-fiber cross-sections

2.3. Cross-sections Composed of Sheath and Core

Fibers with many remarkable characteristics are developed by forming them frompolymers with different properties in the separate core and sheath parts. For example,fibers can be formed with a sheath polymer that lacks the independent ability toform a fiber itself, the core being formed from a conventional fiber-forming polymer.

We explain below the methods of utilization of these fibers produced by recentlydeveloped technology for the purpose of apparel uses.

A conjugate fiber with normal polyester in the sheath part and an antistaticpolymer in the core part has sufficient increase in heat-resistance to allow a false-twisting process and an alkah-reduetion treatment to be applied'^.

In a similar way, improvements in dyeability, brightness, weather-resistance, andCO lor-fastness to laundering and sublimation and tear strength suitable for sportswear are also important applications of this technology'^"^'. For improving thewhiteness of the fiber, a conjugate fiber with independent bubbles in the core partand a white pigment or fluorescent bleaching agent in the sheath part is proposed".A conjugate fiber with delustering material in the core part and without any dullmaterial in the sheath can also be expected to realize fibers with both opacity andluster after processing it by false twisting^^. The absorption of moisture is achievedby using a saponified copolymer of ethylene vinyl acetate in the core part^'* orpo]y(ethylene glycol) in the sheath part **. By making use of these methods, anincrease in wear comfort is claimed in patents. Compound fibers have zirconiumcarbide (ZrC) in the core part, which is able to absorb infra-red rays to providewarmth^^'^^. A compound fiber with a hollow between the core part and the sheathpart imparts lightness and warmth, as shown in Fig. 8^ . Furthermore, an attempthas been made to give a durable soft hand to fibers by blending polyester withhigher-aliphatic esters in the sheath part^^.

There is an interesting application of a conjugated fiber. The bicomponent polyesterfibre which contains a natural refined oil extracted from Japanese cypress in its coreparts volatilizes the perfume gradually over a long period. The volatile perfume(terpen) makes indoor air refreshing and gives an effect like forest bathing to livingspaces. Fibers of the sheath/core form containing electro-conductive material havea good static-dissipation effect^^ They are utilized in various ways by mixing themwith other fibers in woven and knitted fabrics in order to prevent the occurrence of

Fig. 8 Sheath/core hollow conjugate fibers: (1) sheath part (polyamide layer); (2) core part (polyesterlayer); (3) hollow part

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static electricity. These fabrics are commonly used as work wear in petrol stationsand petrochemical complexes, where there is danger of fire caused by electricalsparks, and in factories making electric components, processing food stuffs, etc.. andin clean rooms and other places where dust or static electricity should be completelyeliminated. There are electro-conductive fibers coated with resin-based electro-conductive material, but conjugate types containing polyester or polyamide are verycommon. Fig. 9 shows some examples of this kind of electro-conductive fiber^'"^"*.

The surface resistance of fibers can be reduced more efficiently if an electro-coductive substance exists on the surface of the fiber. A normal eleetro-conductivefiber has an electric resistance of between 10 and lO^ficm. which is sufficient forelectrostatic-charge dissipation. As the conductive fiber containing carbon is black,many studies to produce a white electro-conductive fiber have been undertaken^*'^'.

3. MICROFIBERS

Fibers of linear density around 1 den can be made by general spinning techniques,but a microfiber of around 0.5 den is quite difficult to manufacture by conventionalmethods^*". In order to obtain a super microfiber, conjugate-fiber techniques areusually used. One example of this method is that two different and incompatiblepolymers such as polyester and polyamide are separately fed and spun to conjugatefiber through a spinneret divided radially. Two elements of fiber are then divided bymaking use of swelling, differential shrinkage, or mechanical distortion, as shown inFig. 10. Fig. 11 shows some examples of the cross-section of fibers of this type. Asuperfine fiber can also be obtained by applying an alkali treatment to dissolve onecomponent of the fiber"'^. These kinds of superfine fibers are used for extremely softwoven or knitted fabrics^^.

The finest fibers are mostly produced by spinning 'islands-in-a-sea' conjugate fibres,which are shown in Fig. 12^ . When the 'sea' is dissolved with a certain solvent, the

Fig. 9 Some cross-sectional forms of electro-conductive fiber: (A) concentric form; (B) wedge-shapedform; (C) sandwich form

Fig. 10 Cross-section of fiber spun radially, showing division: (A) fiber just spun out; (B) stale offiber at the start of division

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Fig. II Cross-section of fiber to be divided by dissolving: (I) polyester difficult to dissolve; (2) easilysoluble polyester

C

Fig. 12 Conjugate fiber of islands-in-the-sea form: (A) plan view of fiber cross-section; (B) perspectiveview; (C) microfiber obtained; (I) microfibcr; (2,3) elements to be eliminated

'island' polymer remains and forms the finest fibers. By using this method, fibers ofless than 0.01 den can be obtained and are chiefly used to make artificial leather.Even in the category of microfiber, an appropriate linear density must be selected inaccordance with the purposes of use.

Microfibers are used in various applications. Examples are high-grade woven andknitted fabrics with a soft hand and water- and oil-absorbent fabrics, such as towelsand typewriter ribbon. Wiping cloths, filter cloths, and clean-room garments utilizethe large fiber surface. Moisture-permeable, waterproof, and water-repellent high-density woven fabric is another use. In these end-uses, a suitable combination ofthe fiber-assembly structure and fiber material is important in realizing excellentperformance,

4. SURFACE FORMS

4.1 Voids

A common method of making a void on the surface of a polyester fiber is to removemicro-particles blended in the polyester polymer by alkali treatment. By applyingthis method to various polyester fibers, containing different types of particles, fiberswith various patterns of voids are obtained on the surface** . The micro-voids play

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a role in increasing the depth of color by the mechanism of decreasing the surfacereffection of light.

Fig. I3A, which is a photomicrograph of the surface of Silfil, produced by Teijin,shows an example of a fiber with its surface covered by micro-voids to provide adeeper color. For comparison, a photomicrograph of a normal fiber surface is shownin Fig. I3B. There are many modifications made to this type of fiber to improve itsbrilliance and depth of color by using this unique characteristic*'"*^.

Wellkey, which is a water-absorbent polyester fibre produced by Teijin. is anexample of using micro-voids'*^-*''. It has holes ranging from 0.01 to 0,03 i m indiameter, distributed uniformly on the surface and inside hollow fibers as shown inFig. 14, where some of the voids penetrate into the hollow. Water on the surface ofthe fiber passes through the penetrated voids into the hollow, runs to both ends ofthe fibers by capillary action in the hollow part, and then leaves by evaporation.

A superior drapable fabric, an example of which is Emour*' of Teijin, known asone of the Shin-Gosen fabrics, is obtained by making many micro-voids on thesurface of the fiber, as shown in Fig. 15.

Another method of forming a controlled micro-crater on the fiber surface isproposed. The fiber, pretreated by a specific resist, is exposed to a laser beam andthen treated again with chemicals. This process can control the dimensions of voids,such as their depth, length, and height, and their density. The products are used forfabrics of innovative feel, artificial hair, etc.

Fig. 13 Micro-void surface aimed at depth of color (A) surface of Silfil, color-deepened polyesterfiber; (B) surface of regular polyester fiber

Fig. 14 Wellkey porous polyester fiber with absorbability for water (A) perspective view of cross-section: (B) diagram showiitg how fiber works

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Fig. 15 Fiber surface of superior-draping material of polyester liber, Emull

4.2 Grooves

Silk fibers have extremely fine longitudinal grooves ranging from 0.1 to 1.0 |im, whichgive the characteristic hand and luster of silk. It is asumed that it is necessary toform these fine longitudinal grooves on the fiber surface in order to obtain the silkyhand and luster. A photomicrograph of the fiber surface of Sildome, which is a silkyfabric produced by Teijin, is shown in Fig. 16. One way of generating regular groovesby a conjugate method is described in a patent*^.

5. VARIATION IN THE LONGITUDINAL DIRECTION

5.1 Thick and Thin Structure

An alternating thick and thin structure is thought to be one useful element in formingspunized yarn. Conventional thick and thin fibers, which are obtained only bydiametric modification, differ remarkably in dyeability between the thick and thinparts, but this kind of monotonic variation lacks elegance. There have been manysuggestions on the utilization of thick and thin technology in order to make a higher-grade spunized yarn, for example, a color-mix effect, creation of natural bulkinessby adding partial shrinkage differences., a finer spunized effect, a modified cross-section of the thick part^", partial melting^^ and the raggedness-of-scale effect, asshown in Fig. 17^ .

The methods of making thick and thin yarn in a one-step process at the spinningstage, for creating a strong spunize effect, are suggested in patents''^-^*. The patentsclaim that high shrinkage and an extremely abnormal cross-section are useful in

Fig. 16

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Surface of fiber with thin grooves: (A) fiber surface of silky polyester fiber, Sildorm;(B) surface of wild-sitk liber

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Fig. 17 Surface of Tepla fiber with ragged scales

order to make the yarn bulkier and to create the hand and opacity that are similarto those of natural-fiber spun yarns.

5.2 Crimp

Primitive textured yarns were invented soon after the start of the production ofsynthetic fibers^^. One of the methods used was developed to make a spun-like yarnby combining yarns with various properties and configurations. The fiber configur-ations made by fundamental texturing methods are explained and shown in Fig. I8^^and spunized yarn made by fiber compounds is mentioned later. It is well knownthat false-twist and air-jet texturing are popularly utilized in the industry.

5.3 Thinned Tip

Animal hair, such as mink and fox, has a tapered tip, which contributes to its fineappearance, and the pleasing hand of fur. Many experiments to obtain a structurelike that of animal hair were carried out by tapering the tip of the fiber. For example,the tip part of polyester fiber is dipped in solvent or the fiber is cut in a heatedatmosphere^^. One example is shown in Fig. 19. Fibers with a tapered tip are usedfor brushes, painting brushes, and so forth in addition to fake fur.

Fig. 18 Side views of various textured yarns: (A| false-twist-textured yarn; (B) stuffer-box texturedyarn; (C) gear-crimped textured yarn; (D) air-jet-textured yarn

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Fig. 19 Tapered polyester fiber

6. THE ACHIEVEMENT OF PRACTICAL FUNCTIONS

6.1 The Contribution of Fiber Form and Assembly Structure

The functions and uses contributed by different fiber forms are shown in Table II.The fiber form has a strong influence on the physical properties, aesthetics, andcomfort of fabrics but less influence on their chemical and biological properties.

The practical functions of fabrics are much influenced not only by the fiber form,but also by the fiber-assembly structure of yarns and woven or knitted fabrics. Inthis section, practical functions brought about by combining different fiber formsand assembly, structures are explained in terms of the nature of fabrics.

6.2 Silky Fabrics

In order to simulate silk fabric by using synthetic fibers, physical properties whichhave a strong influence on the hand must be similar to those of silk. Polyester fiberhas similar properties to those of silk, so the effort to make the geometrical form ofthe fiber and fabric like that of silk was made at the beginning of the developmentof silky fabric^". Silky fabric in the first instance was obtained by the way in whichthe fabric composed of the optimum yarn (with regard to linear density, cross-section,etc.) and of the optimum woven structure was heat-set and reduced by alkalinetreatment to form spaces between fibers, as shown in Fig. 20

However, when silk fabric is processed in the swollen state and sericin is removed,the fabric shows the specific soft hand of silk and bulkiness owing to the spacesbetween fibers. Second-stage silky fabric was obtained by increasing the buikiness ofthe fabric. As may be seen in the cross-sectional view of the fabric in Fig. 21, thebulkiness of silk fabric is very considerable. To impart bulkiness, there are severalmethods that may be used, such as interlacing fibers with different shrinkages,interlacing two kinds of fiber of different lengths by air-texturing, and so on.

In the development of the third-stage silky fabric, there was a strong need to getrid ofthe artificial feel caused by the uniformity of synthetic fiber.

To simulate the irregularity of natural fibers, fine grooves on the fiber surface, asmentioned above and shown in the unusual cross-section in Fig. 16. were introducedto impart the scroopy hand and elegant luster. Moreover, there was a furtherimprovement to make a silky fabric having more of a natural feel by using differentthicknesses and cross-sections of the fibers^**. The technology of these silky fabricswas applied not only to the basic fabric, but also to variations of it, such as shantungand crepe^°.

A super-bulky fabric, exceeding the bulkiness of current silky fabrics, is made asAjenty by Teijin, which is recognized as typical of the so-called Shin-Gosen fabrics.Ajenty is shown in Fig. 22.

6.3 Spunized Fabric

Polyester-fiber continuous-filament yarns came to be commonly used after the devel-opment of false-twist processes in the field of medium-weight fabric, in which spun

332 •>• '"'•'- ' " " • ''^^-- *•* '*'"• -' '" Te\lile tnnilute

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Control of Fiber Form and Yarn and Fabric Structure

iz•a'

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J. Te.xi. Inst.. 1992, H3 Na. 3 '~ Te.xttle Instituu 333

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P o l y e s t e r

Hea t i ng-se t

AlkaliDe treat»ent to for»spec:es betteen fibers(10~3W •eijdit reduction)

Swe11i n 8 ~ s e tby hot w a t e r

D i s s o l v i n g e l i m i n a t i o nif s e r i c i n (about 2 0 % )

Soft 4 d r a p e - f u l f a b r i c isc r e a t e d

Fig. 20 Origins of fabric structure

Fig. 21 Cross-section of fabrics: (A) fabric of regular polyester fiber, (B) silky polyester-fiber fabric(with mixed textured yarn of different shrinkages); (C) silk fabric

Fig. 22 Superior bulky polyester-fiber fabric, Ajenty: (A) fabric surface; (B) cross-section of fabric;(C) cross-section of silky fabric, for comparison

yarn had previously been dominant because of its bulkiness. The first woven orknitted fabrics made of false-lwist yarn were inferior in hand to those of spun natural-fiber yarns because of their very monotonous hand and appearance, although theyhad bulkiness and elasticity. Even though polyester fiber imitated wool at the levelof the fiber, fiber assemblies such as yarns and woven or knitted fabrics had ratherdifferent structures from those of the natural fiber. The structure of natural spunyarn is extremely complex. In the first stage, the spunizing process for texturedcontinuous-filament yarn was developed to approach the natural spun yarn by amix of linear densities and a mix of colors. After that, combined texturing and raisingmethods were developed. These processes realize the effect of spun yarn such as large

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spaces between the fibers owing to the disorder in the fiber arrangement and alsothe effects of twist and fuzz. Elements involved in the construction of spunized yarnare shown in Table III. Diagrams of the way to combitie these elements and obtainthe processed yarn are shown in Figures 23-25. Combining bulkiness and fiberdisorder is shown in Fig. 23, adding fuzz to the filament in Fig. 24, and making thetwist-like structure in Fig. 25'^'. The compound false-twisting method was very suc-cessfully used for developing spunized fabric''^ When two fibers with different elong-ation are false-twisted together, the fibers with the smaller elongation are generallylocated in the core and the others in Ihe sheath. As a result, an alternate-twist effectis obtained. Furthermore, in the real-twisting stage of the false-twisting process, afuzzy appearance on the surface of yarn can be introduced to simulate spun yarn.As an example, the construction of a typical spunized yarn, Teijin Milpa, is illustratedin Fig. 26 in comparison with that of a conventional false-twisted yarn.

Many other examples of the use of compound false-twisting methods are shownin Fig. 27 and the details of them are explained below. A soft and highly resilientworsted-like medium-weight fabric called Delite has a double structure of thick andthin yarns, with which the feeling of warmth and comfort can be created in accordance

Mainclement

Sub-clement

CoRSlruction

Bulkiness

Random orientationof fiberarrangement

Fuzzy effect

Effect of yarntwisting

Color-mix

Table IIIElements of Spunized yarn

XKVK

Compound texturing process

Air-jet texturing process

Mix of different linear densities

/ /

/

Compound of staple fiber

Fuzzing process (yarn, fabric)

Alternate twisting

Mix of different-color fibers

Thickness Thick and thin drawing

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Technology

False twisting

Heat set

F a l s e t w i s t i n g

CoBpound false tiisting

Elongation difference

Fal se t w i s t i n g

Air turbulance

Air- jet nozzle

Yarn s t ruc ture

Twist ing Untwisting

T w i s t i n g U n t w i s t i n g

Fig. 23 Yarn-processing technique to give fiber disorder and bulkiness to a continuous-filament yarn

with the degree of twisting. Pamio is a cotton-like fabric and Cifola a woolen-likefabric with a rough appearance. Easel is a compound yarn made with a coarser fiber(2 den) inter-spreading uniformly in a superfine fiber (0.4 den). It has a spun-yarntouch and soft feeling, and its characteristic bulkiness and resilience make a beautifulsilhouette for ladies" and men's clothes. A wild-silk-like spun-yarn fabric, Fiveyfeatures the luster of slab yarn, which is a super-bright yarn processed by a texturingmethod.

Topel is a double-phase compound-textured yarn made of nylon, which has thesoft and good draping effect peculiar to nylon. There is also Topel II, in which asuper-multi nylon yarn is utilized to emphasize this softness.

6.4 Polyester Fiber with Sweat Absorption

Cotton has commonly been used for sportswear, but, when cotton absorbs waterduring physical exercise, its modulus decreases to nearly half its original value andit swells by about 20Vo owing to the absorbed moisture. Hence the touch of wovenor knitted cotton fabric changes very considerably and it becomes sticky to the skin.Moreover, since its drying rate is very slow, a chill feeling remains after exercise andlasts for a long time. Cotton is not always comfortable. It is quite important tocontrol the sweat produced by physical exercise. From this point of view, the porouspolyester fiber Wellkey shown in Fig. 14 was developed. Wellkey can make sweat onthe surface of the fiber flow through porosities into the hollow while some of the

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Technology Yam stnicturc

Yarn raising

\ S

OOGrinder

Air turbulence

Air jet nozzleoOriginalstrength

Lowstrength

Coapound false tvisting

Ordinarystrength

O"—' *Low Falsestrength twist ing

\ J

Twisting Untwisting

Fig, 24 Yarn-processing lechnique to give fuzz to a coniinuous-fiiamenl yarn

Technology

Part ia1 Iy fuse and

fa l se twist ing

Heat fus ion

CoBpound fa l se twist ing

Elongat ion Fa l se

d i f f e r e n c e t w i s t ing

X>8 O

Yam structure

Twisting Untwisting

Twisting Untwisting

Fig. 25 Yarn-processing technique lo give a twist-like structure to a continuous-filament yarn

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B

Fig. 26 Illustration of textured-yam siructure: (A) compound double-layer textured yarn, Milpa;(B) ordinary false-twist yarn

' D e l i t 'Ease

W o r s t e d l i k e U l t r a s o f t t o u c h

•PamI Five

C o t t o n l i k e / ^ C O M P L E X E D X S p u n s i l kT E X T U R E D J — l i k e -

.YARN

Tope

W o o l e n like

S u p e r soft touch(Nylon)

-Clfoli

Fig. 27 Variations of compound textured yams

sweat is evaporated through the fiber end and the surface. This mechanism plays animportant role in hiding sweat inside and preventing the sticky feeling. Its criticalwater content to perceived wetness is nearly the same as that of cotton, whichamounts to four or five times that of regular polyester fiber"~*^ In order to confirmthis performance, the following test was carried out. A person wearing a T-shirt ranon a treadmill in a climate-room. The difference in wear comfort between materialswas remarkable after the running stopped. Cotton, because the drying rate afterperspiration was slow, kept a chill feeling for a long time, but, because polyester fiberdried more quickly, the duration of a chill feehng was very short. In the case ofregular polyester fiber, a chill feeling was strong. In Wellkey, on the contrary, coolnesswas sensed only briefly, and the initial state is regained very quickly. These differencescorrespond not to the absolute value of skin temperature but to the differential valueof change of skin temperature. As represented in Fig. 28, a less sticky and chill feelingwas experienced for Wellkey than for cotton.

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1.0

0.8c E

-r^ 5

o

0.4

0.2

0

-0.2

-0.4o.>, E*-• V TD

C - O-0.6^'^ -0.8i> in

- 1 . 0

Water absorbentpolyester

—-' Ordinary polyesterCotton

50

Fig. 28

30 40

tm. i — RunningConditioning

Differential values of change of skin temperature

60 70Rest Time(min)

In some woven or knitted fabrics the textile structure plays an important role inabsorbing sweat and removing it from the inside of the fabric, next to the skin, tothe out.side. For example, if the driving force to absorb sweat by the outer layer isgreater than that needed to absorb it by the inner layer next to skin, a double-layerfabric can retain comfort in wear. By this mechanism, this type of fabric can remaincomfortable. A fabric made of 100% polyester fiber and consisting of a coarser fiberin the inner layer and a finer fiber in the outer layer is shown in Fig. 29^^. A wovenor knitted fabric with a cellurosic fiber^'' or the above-mentioned Wellkey as theouter-layer fiber*"** has also been developed for the same purpose. As another example,a fabric for keeping warm during perspiration is suggested, in which an inner layeris made uneven and can quickly transport sweat to the outer layer **.

6.5 Fiberflll

Fiberfill is very commonly used for such applications as bedding, pillows, garmentpads, and cushions for furniture or car seats.

Accordingly, several properties corresponding to each use, such as warmth reten-tion and shock-absorbability, are required. For warmth retention, it is very commonto consider how to hold air inside the structure. The fibers commonly used for thesepurposes are hollow fibers with voids inside and increased irregularity of the cross-section to enlarge the surface area. It is important to make fiber assemblies as bulky

Hg. 29 Illustration of 100% polyester-fiber woven fabric of double-layer structure with sweat-absorption effect

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as possible provided that the range is limited so as not to cause air convection.Quilts require bulkiness and lightness comfortable to the skin and for good warmthretention. For this purpose, hollow fibers and high-crimped fibers are generally used.

Fiberfills for quilts that provide absorption of sweat, deodorization, anti-bacterialproperties, and so on have been developed. Cushion materials require resilience,controlled by the fineness, void content, and crimp and utilize the basic resilience ofpolyester fiber. For cushions requiring elasticity, component materials in which thefibers adhere mutually to elastic materials are used. The development history ofvarious fiberfills in the Teijin company is shown in Table IV and some especiallycharacteristic cross-sections of these fibers are shown in Fig. 30.

6.6 Development of Deep-dyed Polyester-fiber Fabric

A deep-black color was very difficult to obtain by dyeing conventional polyester,and extensive work has been done to achieve this over a long period. To obtain thiseffect, it is necessary to decrease light reflection and to increase light absorption andlight transmission.

To overeome this difficulty, several methods were tried as follows, such as coatingthe fiber with a low-refraetive-index resin and forming a micro-void on the fibersurface by using the method described previously*". In addition to modification of

Table IVImprovement or Various Paddings

Improvement Discrimination Researchof quality of quality for function

Research forcomfort

Quilt Highbulkiness

Down-like Sweal Warmth Wool-mixabsorbability type

Tickproof Aroma, anti-bacteria

Hibal Supeviol Polity Issac Meleed Mighly top Liberty

Mat Cotton-mixtype

Hibal M

Mattress use

T-117

Cushionmaterial

Use for pillows. Blowing Furniturecushions use use

Cushionsfor car

TLllI Cryster Sefarlon TUK

1975 1980 1990 Year

Fig. 30 Some types of padding: A: Hibai used for quilt with high bulkiness: B: Issac used for sheetfor keeping warm; C: Meleed wool-mix type; D: Sefarlon, for furniture-cushion use

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the fiber surface, it is also important to modify the fabric structure to achieve lesslight reflection and more light absorption in the open spaces between fibers as shownin Fig. 31.

Milpa is one example of a fabric made of multi-layered bulky yarn, whose structurehas many microscopic openings so as to absorb light easily. The visual dye density(the KIS value) of this fabric is 30% higher than the conventional depth of black.Polyester-fiber fabric utilizing this advantage is widely used for formal wear, dresses,suits, and so on.

6.7 Research on Pile Fabric

There are many types of pile fabrics, such as velvet, carpet, sealskin fabric, fake fur,and so on. Car-seat fabrics, which are widely used, are described below.

Polyester fiber is very popular for this purpose because of its excellent light-stability and abrasion-resistance. T-31 fibers, with a unique flat cross-section asshown in Fig. 32. are arranged along a certain direction. This can get rid of the glarepeculiar to flat-cross-section fiber and achieves a feeling of softness owing to theunevenness of the contour of the fiber surface.

Pile effects obtained by using tlat fiber are apt to cause speckles in the reflectionof light and to become whitish owing to permanent bending of the pile in use. Thecross-section shown in Fig. 33 is not as apt to cause these problems as a conventionalflat cross-section. A fiber with a hexalobal cross-section as shown in Fig. 33A is

Fig. 31 Bulky fabric with multilayer structure: (A) illuNtralion of lighl-absorplion work of bulky.multilaycrcd-structure fabric: (B) surface of Milpa bulky fabric

. 32 Cross-section of easily straightened pile fiber: (A) illustration showing piltng properly of thisHber (T-31); (B) diagonal cross-section

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Fig, 33 Cross-section of pile fiber that is hard to cotnpress: (A) fiber having moderate rigidity andresilience; (B) fiber not falling in parallel direction

thought to have moderate stiffness and resilience^^ Moreover, fibers with the cross-section shown in Fig. 33B do not lie parallel to a certain direction, which preventsa glaring luster^^.

In order to decrease the glaring luster, light reflection from the fiber surface isreduced by forming irregular micro-voids on the cross-section and the surface offiber^^-^*. The other way to decrease the difference between the surface reflectionand that of the cross-section of the pile yarn is to use a conjugate fiber of the sheath/core type that consists of two different polyesters''^ and does not show the differencein total color-tone, or to use a conjugate fiber composed of cationic-dyeable andregular polyesters''^, by which means the color differences between the cross-sectionand the surface are eliminated.

6.8 Wiping Cloth

Wiping cloth can be made of a knitted fabric of split microfibers from a multi-layerconjugate fiber, which is spun so that polyester fiber and nylon are alternatelyarranged as shown in Fig. 10 and Fig. 34. When a microfiber is used together witha flat-cross-section fiber in a wiping cloth, the fiber is tender and sticks to the objectand then removes the pollutant effectively owing to its knife-edge effect on the surfaceof the object. The finer the fiber used for a wiping cloth, the larger the total surfacearea of fiber becomes. This contributes to an increase in the quantity of pollutantabsorbed and included in the fibers.

6.9 Tickproof Bed Cover

One interesting use of a super-microfiber is in a tickproof bed cover, known asMicro-guard. As shown in Fig. 35. it is a high-density fabric made of a super-microfiber, with micro-openings in the fabric to prevent the ticks from penetratingit but allow the air to permeate through it. This material can reduce the very seriousproblems of bronchial asthma in childhood caused by ticks.

Fig. 34 Knitted microfiber wiping cloth; (A) surface of knitted fabric; (B| tross-^cclion of knittedfabric

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Fig. 35 Surfaco of bedding cover cloth ( x 100): (A) Micro-guard tick-protect ion cover cloth;(B) ordinary 100% cotton cover cloth

7. LEARNING FROM NATURAL MATERIALS

7.1 Lotus Leaf: Superior Water-repellent and Vapor-permeable Fabric

Leaves of the lotus and taro can repel water well. The surface of a lotus leaf has aminute ragged structure, as shown in Fig. 36. The waxy material that covers thesurface helps lotus leaf to repel water well, because the surface tension of the waxymaterial is small. Air enclosed in the hollow part below the tops of the projectioncauses water drops to float above the surface of a leaf and make it easy for them toroll down it. A silvery shine below the water drops on a lotus leaf can be observedunder the rays of the sun as a result of this mechanism.

One example of a superior water-repellent and vapor-permeable fabric is SuperMicroft. which was developed by imitating the surface structure of a lotus leaf. Aspecific bulky yarn made from microtibers with a fine crimp was first developed, andthen the yarn was woven into a high-density fabric and given a water-repellenttreatment after being dyed. Thus the fabric with a similar surface structure to thelotus leaf, which had a uniform and minute raggedness on the surface, was developed.A photomicrograph of a cross-section of this fabric is shown in Fig. 37. The contactangle of this surface with water increases so much that a drop of water becomesround. Accordingly, vapor-permeability does not decrease when it is raining, andhumidity is not felt when a garment made from the fabric is worn.

7.2 Morpho-butterfly: Fabric with a Strong Color Tone

Morpho-buttertlies inhabit only Central and South America, and their wings aresaid to have the color of transparent cobalt blue and a metal-like luster. These wingshave a scale-like structure and thin sheet-like materials, which are arranged in aparallel vertical direction at a regular interval of around 0.7 [.tm. The cross-sectional

ifi. 36 Surface of lotus leaf ( x 600)

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Kig. 37 Superior water-repKllent fabric, super Microft ( x 100)

Structure of these materials is said to have fins of from seven to nine stairs at a pitchof about 0.2 jim. Accordingly, when the light getting into the structure is totallyinternally reflected, this structure causes a shiny color to be produced by lightinterference. A fabric made from a synthetic fiber with a structure in which thelongitudinal axis of a flat-cross-section fiber is aligned vertically on the fabric surfaceis presented^*^ and shows the effect of a remarkably brilliant color.

7.3 Burdock Seed: Velcro Fasteners

Velcro fasteners, which secure seat covers very neatly, for instance, in an airplane,have many small hooks made of plastics material on a tape, and those hooks areattached firmly to another soft-pile tape by a light pressure^^. The two surfaces canbe easily separated without being broken. This structure is very similar to that ofburdock seed, which becomes attached to animal fur, is transported elsewhere, andis then released by some external force.

7.4 Plumage

The characteristics of the bulkiness of a plumage quilt are that the bulkiness is veryhigh under an extremely low weight and recovery after removing the pressure isgood. There are feathers and down in plumage, but down has much better character-istics than feathers. The structure is shown in Fig. 38. In down, twigs of plume withmany tiny plumelets jut radially from the central axis, and the plumelets have hooksin places. The fineness of the plumelet entraps the air and provides warmth as wellas giving moderate compressive elasticity. Moreover, the form of the hook and theexclusive properties of down are connected with good restoration in beating.

Fig. 38 Various forms of down: (A) a pkimc; (B) n plumcLM; (t I enlarged views of the liook ot aplumelet

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7.5 Other Structures

There are many structures designed precisely and purposely and having excellentfunctions in nature. Tiny plants called 'moss of bird's nest', growing in Mexico, showan interesting reaction to the humidity in the air. In desert zones, life has to surviveeven under drought conditions lasting for four years. In low humidity, the plantsbecome ball-Iike by shrinking so as to keep the loss of water to a minimum, but.when rain starts, they begin to open within minutes, and their green colour is restored.The structure is very simple. The surface of the top of the tiny twiggy part consistsof tine scale pieces. It absorbs water and inflates quickly and easily, while the root,being influenced by moisture, winds and expands. Such a phenomenon is veryinteresting, and, if it can be applied to garments, excellent comfort and adaptabilityto a dry or wet climate will be achieved.

A gigantic lotus, which grows on banks in the Amazon basin, is a structure withamazing strength and capacity for loading in spite of the fact that its leaves are verylarge but very thin. The structure which makes tiny props diverge from a few mainmasts and ties them together with many fine ribs is the framework of it.

Many structures and their functions in nature, such as a mechanism to distributewater from the root to the tips of a huge tree, and the structure of a light seed thatis blown like a feather by the wind, show many remarkable phenomena, which areworth studying in order to control fiber form and arrangement to produce desirableeffects.

8. CONCHJSIO^

In order to realize higher levels of performance, various developments and modifi-cations of the form and structure of fibers, yarns, and fabrics are required.

From the technological point of view, the combination of a new polymer andadvances in the technology of spinning and complex texturing will introduce innov-ative and refined yarn materials. Effective textile and structural design should befollowed so that the new materials can fully perform their functional capacity.

On developing new functional fibers and textile materials, it is very important toset definite targets of performance based on scientific principles and practical con-sumer science. In garments, comfort in wear and use will usually be required andsupplied.

Even now, the fine structure and mechanical performance of natural fibers suggestto us much useful information.

REFERENCES

' H, Bieser and R, Hesse. Chemiefas.serti. 1967. 17. 262.^ G,W. Meacock. Text. Wkly, 1958, 58(2). 159.^ Kurarc. Japanese P. 1989/104811 (21 April. 1989),•• Kurare. Japanese P. 1989/104812 (21 April. 1989)."• K. Sakai and T. Kikuchi. J. Text. Mach. Soc. Japan. 1986. 39, P436." Y. Suzuki. J. Text. .Mach. Soc. Japan. 1986. 39, P387.• Mitsubishi Rayon, Japatiese P. 1985/259618 (21 Dec. 1985).*• Unilika, Japanese P, 1987/6983 (13 Jan.. 1987)," Teijin, Japanese P. 1987/299565 (26 Dec. 1987).'" Kurare. Japanese P. 1990/234915 (18 Sept.. 1990)." Du Pont. Japanese P. I99I/3I803 (8 May. 1991).'^ Du Pont. Japanese P. 1991/31804 (8 May. 1991)." Toray. Japanese P. 1991/14940 (27 Feb.. 1991).'•* Toray. Japanese P. 1991/14941 (27 Feb., 1991).'^ K. Nakagawa and K. Yoshimura iti illustration of Fiber Form' (edited by Scn-i-Gakkaishi), Asakura-

Shoin. Tokyo. Japan. 1983. p, 174.'" Toray. Japanese P. 1991/124807 (28 May, 1991).

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Toray in 'Collected Data of New Fiber Materials and Products'. Textile Machinery Society of Japan.Osaka. Japan. 1968. p. 109.Mitsubishi-Rayon. Japanese P. I99!;l 13017 (14 May. 1991).Kancbo. Japanese P. 1991/113030(14 May, 1991).Ktirare. Japanese P. 1991/113070 (14 May. 1991).Toray. Japanese P. 1991/193916 (23 Aug.. 1991).Unitika. Japanese P. 1990,169808 (5 Nov.. 1990).Toray. Japanese P. 1990/32372 (19 July, 1990).Kurare. Japanese P. 1991/113015 (14 May. 1991).Toray. Japanese P. 1991/130416 (4 June. 1991).Desanto. Unitika. Japanese P. 1989/132816 (25 May. 1989).Kanebo. Japanese P. 1991/137274(11 Jan.. 1991).Toray. Japanese P. 1991/124857 (28 May, 1991).Toray. Japanese P. 1990/210022 (21 Aug.. 1990).M. Yamamoto. J. Texl. Mach. Soc. Japan. 1985, 38, P329.Kurare. Japanese P. 1980/122018 (19 Sept.. 1980).Unitika. 1979/134117 (18 Oct.. 1979).Kanebo. Japanese P. 1981/37322(31 Aug.. 1981).Teijin. Japanese P. 1980/107504 (18 Aug., 1980).Kurare. Japanese P. 1990/289118 (29 Nov., 1990).K. Malsumoto in "Enjoyable Textiles for the 2lst Century", Hokulo Printing, Kyoto, Japan, 1991.p. 65.Kurare. Japanese P. 1990/145812 (5 June, 1990).K. Ichihasi and T. Takeda. J. Te.xt. Mach. Soc. Japan, 1986, 39, P383.Toray. Japanese P. 1991/21643 (25 March. 1991).T. Suzuki and O. Wada. Seii-i Gakkaistu. 1985, 41, P401.Teijin. Japanese P. 1982/139118 (27 Aug. 1982).Kurare. Japanese P- 1984/24233 (7 June. 1984).Toray. Japanese P. 1982/143523 (4 Sept., 1982).Mitsubishi Rayon. Japanese P. 1991/161510(11 July. 1991).Teijin. Japanese P. 1985/43858 (30 Sept.. 1985).Teijin. Japanese P. 1986/60188 (19 Dec, 1986).M. Tani. Sen-i Gakkaisbi, 1990. 46. P27!.Toray. Japanese P. 1990/251670 (9 Oct.. 1990).Kanebo. Japanese P. 1991/124840 (28 May. 1991).Toray. Japanese P. 1980/80524 (17 June. 1980).Kanebo. Japanese P. 1989/26715 (30 Jan.. 1989).T. Matubara. J. Texl. Mach. Soc. Japun. 1986. 39. P432.Monsanto. Japanese P. 1979/42415 (4 April. 1979).Teijin. Japanese P. 1985/259615 (21 Dec, 1985).K. Kawasaki in 'Outline of Processed Yam', Textile Machinery Society of Japan, Osaka, Japan. 1967.p. i i .M. Anahara and T. Minakami in 'Illustration of Fibrous Form' (edited by Sen-i-Gakkaishi), Asakura-Shoin. Tokyo, Japan, 1983, p. 203.Kurare. Japanese P. 199 M 6424 (5 March. 1991).S. Tsubaki. Sen-i Gakkaislti. 1967. 23. S148.Nihon-Esuteru. Japanese P. 1987/21827 (30 Jan., 1987).O. Wada. Sen-i Gakkaishi. 1981. 37, P429.M. Tani in Proceedings of Textile Research Conference. 'New Textile Materials', Sen-i-GakkaishiHokuriku Branch Office. 1986.K. Hashiba. J. Te.xi. Mavb. Soi: Japan. 1981. 34, P326.O. Wada and Y. Takatera. J. Text. Mach. Soc. Japan, 1983. 36, P42.O. Wada and Y. Takatera. J. Text. Mach. Soc. Japan (Eng. Edn), 1984. 30, 91.W. Koerner. Chewiefasern. 1979. 29, 452.Toray. Japanese P. i977/25l68 (24 Feb.. 1977).Unitika. Japanese P. 19/220844 (22 Dec. 1983).Teijin. Japanese P. 1988/15384 (4 April. 1988).Teijin. Japanese P. 1990/20742 (10 May. 1990).S. Yamada and M. Tani. J. Dyeing; Industrv. 1986. 34, 112.Unitika. Japanese P. 1990/17594 (9 July. 1990).Toray. Japanese P. 1991/64550 (19 March. 1991).Toray. Japanese P. 1990/160908 (20 June. 1990).

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'* Kurare. Japanese P. 1990/264068 (26 Oct.. 1990)."' Asahikasei. Japanese P. 1991/124858 (28 May. 1991).'" Asahikasei. Japanese P. 1991/51343 (5 March, 1991).'• F. Shibata and S. Kawasaki. Sen-i Gakkaishi. 1988, 44. P94.'" Y. Hirano and A. Kubolsu. Sen-i Gakkai.shi, 1988. 44, PI02."'* F.R. Paturi in "Geniale Ingenieure der Nature' (Japanese edition), Hakuyosha, Tokyo, Japan, 1980.

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