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Identification of Identification of Textile FibersTextile Fibers

By:By:

Javad MadanipourJavad Madanipour

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Identification of textile fibers is Identification of textile fibers is comparatively simple, when the comparatively simple, when the natural fibers were in existence. natural fibers were in existence. With the advent of man-made With the advent of man-made fibers the subject has become of fibers the subject has become of considerable challenge and considerable challenge and complexity with the difficulties of complexity with the difficulties of identification in the various fibers, identification in the various fibers, which not only encountered on which not only encountered on their own, but also in their own, but also in BI, BI, and and Tri – Tri – component component blends with other blends with other fibers.fibers.

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In additions, the materials In additions, the materials may contain a variety of may contain a variety of finishing agents, themselves finishing agents, themselves synthetic in origin, which may synthetic in origin, which may cause misleading reactions.cause misleading reactions.

A series of physical & A series of physical & chemical tests are carried out chemical tests are carried out to ascertain the type of fiber to ascertain the type of fiber or fibers are being used in the or fibers are being used in the fabric.fabric.

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There are There are four major four major stages in this scheme of stages in this scheme of identification, as outlined identification, as outlined below:below:

Visual examination Visual examination Burning testBurning test Chemical testChemical test Microscopic testMicroscopic test

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Visual examinationVisual examinationThe material to be identified isThe material to be identified isexamined, by:examined, by: Luster (metallic or soft)Luster (metallic or soft) Smoothness or hairinessSmoothness or hairiness Harsh or soft handleHarsh or soft handle Color and textureColor and texture Relative strengthRelative strength

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Burning testBurning test The burning test involves The burning test involves

taking a small quantity of the taking a small quantity of the material slowly into a flame, material slowly into a flame, noting how the material noting how the material burns or if non-inflammable, burns or if non-inflammable, whether it melts or maintains whether it melts or maintains the same shape, but glows. the same shape, but glows. Six distinct types of reaction Six distinct types of reaction may be observed:may be observed:

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The material burns freely, The material burns freely, leaving a fine powdery ash, leaving a fine powdery ash, the smoke smelling of the smoke smelling of burnt paper. Any natural or burnt paper. Any natural or regenerated man-made regenerated man-made cellulose material (except cellulose material (except cellulose acetatecellulose acetate) will give ) will give this reaction, such as, this reaction, such as, CottonCotton, , LinenLinen,,FlaxFlax,,JuteJute, , KenafKenaf…etc.…etc.

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The material burn rapidly, The material burn rapidly, leaving a hard tarry bead leaving a hard tarry bead residue and a faint vinegar like residue and a faint vinegar like smell. smell. Cellulose acetateCellulose acetate is the is the only material with this kind of only material with this kind of reaction.reaction.

The material recedes before the The material recedes before the flame, but upon ignition burns flame, but upon ignition burns freely with a smoky flame, freely with a smoky flame, leaving a charred, tarry residue. leaving a charred, tarry residue. This would be an indication of This would be an indication of Polyacrylic Polyacrylic fiber.fiber.

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Similar reaction is produced by Similar reaction is produced by PolyurethanePolyurethane fibers, which fibers, which however, burn with a clear, however, burn with a clear, smokeless flame.smokeless flame.

The material burns with The material burns with difficulty, there is a tendency difficulty, there is a tendency towards spluttering a crushable towards spluttering a crushable cidercider residue remains and there residue remains and there is a distinct odor of burning is a distinct odor of burning hair hair oror feathers feathers..

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This type of burning This type of burning indicates either natural indicates either natural protein fiber (protein fiber (Wool, Wool, Silk, Hair,Silk, Hair,…..…..etc.) or etc.) or any of the man made any of the man made fibers, based on protein.fibers, based on protein.

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The material does not burn, The material does not burn, but as it is brought near to but as it is brought near to the flame it melts and the flame it melts and recedes forming a bead. If recedes forming a bead. If brought into flame too brought into flame too quickly, it may ignite. Such a quickly, it may ignite. Such a reaction is typical of a reaction is typical of a number of synthetic number of synthetic polymers, e.g. polymers, e.g. Polyamides Polyamides (Nylon), Polyesters, (Nylon), Polyesters, PolyolefinesPolyolefines..

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The material does not The material does not ignite, but if kept in the ignite, but if kept in the flame, it will glow and flame, it will glow and retain its shape. The retain its shape. The mineral fiber would be mineral fiber would be indicated by this reaction, indicated by this reaction, such as such as Fiberglass, Fiberglass, AsbestosAsbestos or or Metallic Metallic fibers.fibers.

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Chemical (Stain) testChemical (Stain) test Staining techniques, for Staining techniques, for

example, are easy to apply and example, are easy to apply and very useful in identifying un-very useful in identifying un-dyed materials. Best known in dyed materials. Best known in this field is the this field is the Shirlastains A, Shirlastains A, C C , , DD and and NeocarmineNeocarmine can be can be employed, in order to identify employed, in order to identify fibers from their origin.fibers from their origin.

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Shirlastain AShirlastain A Shirlastain A is for the identification Shirlastain A is for the identification

of Non-thermoplastic fibers (i.e. of Non-thermoplastic fibers (i.e. Cotton, WoolCotton, Wool and other natural fibers; and other natural fibers; Viscose rayon, Cellulose acetateViscose rayon, Cellulose acetate…..….. etc.etc.

It must be emphasized, that the It must be emphasized, that the results obtained from this, as from all results obtained from this, as from all such staining tests, may be invalidated such staining tests, may be invalidated by the presence on the fibers of any by the presence on the fibers of any foreign matter. Therefore, the test can foreign matter. Therefore, the test can only be applied to fibers in the only be applied to fibers in the natural, scoured or bleached state.natural, scoured or bleached state.

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Test method:Test method: The sample is first wetted thoroughly. The sample is first wetted thoroughly.

This is especially necessary with such This is especially necessary with such materials as grey or materials as grey or raw cottonraw cotton, which , which may with advantage be first of all may with advantage be first of all boiled in water. Then sample is boiled in water. Then sample is immersed in the cold stain for immersed in the cold stain for one one minuteminute with stirring, after which it is with stirring, after which it is removed, washed thoroughly in cold removed, washed thoroughly in cold water, and dried. Particular care must water, and dried. Particular care must be taken to rinse thoroughly, those be taken to rinse thoroughly, those samples that in the cloth form, as any samples that in the cloth form, as any stain retained in the interstices of the stain retained in the interstices of the fabric may make the true color fabric may make the true color developed on the fiber. A fresh developed on the fiber. A fresh portion of stain should be used for portion of stain should be used for each individual sample.each individual sample.

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The multi fiber fabric strip, which contains The multi fiber fabric strip, which contains bands of the principle fibers are sequenced, bands of the principle fibers are sequenced, as in below order:as in below order:

Cellulose acetate (Bright Celanese Staple)Cellulose acetate (Bright Celanese Staple) Mod acrylicMod acrylic Arnel (Bright filament)Arnel (Bright filament) Cotton (Bleached)Cotton (Bleached) Creslan 61Creslan 61 Polyester (Dacron 54, no optical brightener)Polyester (Dacron 54, no optical brightener) Polyester (Dacron 64)Polyester (Dacron 64) Nylon 6.6Nylon 6.6 Acrylic (Orlon 75)Acrylic (Orlon 75) SilkSilk PolypropylenePolypropylene Viscose rayonViscose rayon WoolWool

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FiberFiber ColorColor Bleached CottonBleached Cotton Pale purplePale purple WoolWool Golden yellow (cold)Golden yellow (cold) Copper Copper

brown (at boil)brown (at boil) SilkSilk Brownish orange Brownish orange Viscose rayonViscose rayon Pink (cold)Pink (cold) Purple (at Purple (at

boil)boil) Cellulose acetateCellulose acetate Bright greenish yellowBright greenish yellow

(cold & at boil)(cold & at boil) Nylon 6.6Nylon 6.6 Pale dull yellowPale dull yellow PolyesterPolyester UnstainedUnstained PolypropylenePolypropylene UnstainedUnstained Acrylic (Orlon)Acrylic (Orlon) UnstainedUnstained

Table 1.Table 1.shows the colors by textile fibers, when stained with shows the colors by textile fibers, when stained with Shirlastain A.Shirlastain A.

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Shirlastain CShirlastain CIt is important to It is important to mention, that mention, that Shirlastain Shirlastain A A does not completely does not completely differentiate between the differentiate between the various various cellulosiccellulosic fibers, fibers, but somewhat finer but somewhat finer discrimination is possible discrimination is possible by the use of by the use of Shirlastain CShirlastain C

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Test MethodTest Method The sample of fiber to be tested is The sample of fiber to be tested is

prepared as for the prepared as for the Shirlastain A Shirlastain A test test and when thoroughly wetted, is and when thoroughly wetted, is immersed in cold immersed in cold Shirlastain C Shirlastain C for 5 for 5 minutes, during which time it is minutes, during which time it is stirred occasionally. It is then stirred occasionally. It is then removed, rinsed well with cold water, removed, rinsed well with cold water, and dried. As before, a fresh portion and dried. As before, a fresh portion of stain should be used for each of stain should be used for each sample. This specific stain is used to sample. This specific stain is used to differentiate between cellulosic differentiate between cellulosic materials, such as, materials, such as, Jute, Flax, RamieJute, Flax, Ramie …etc.…etc.

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This specific stain is used to This specific stain is used to differentiate between cellulosic differentiate between cellulosic materials, such as, materials, such as, Jute, Flax, Jute, Flax, RamieRamie …etc. …etc.

FiberFiber ColorColor Bleached CottonBleached Cotton PinkPink

Table 2.Table 2.shows the color by shows the color by cottoncotton fiber, fiber,

when stainedwhen stainedwithwith Shirlastain C.Shirlastain C.

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Shirlastain DShirlastain DThis identification stain is This identification stain is in powder form and should in powder form and should only be made up in liquid only be made up in liquid stain immediately before stain immediately before use, as fresh prepared use, as fresh prepared stain gives better results. stain gives better results. 10 grams of this powder 10 grams of this powder makes 2.3 liters of stain.makes 2.3 liters of stain.

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Preparation:Preparation: Weigh 1/4 gram of the powder and Weigh 1/4 gram of the powder and

dissolve it in 50 ml of distilled water dissolve it in 50 ml of distilled water at room temperature. Stir at room temperature. Stir vigorously. Then immerse an undyed vigorously. Then immerse an undyed fiber, yarn or fabric sample in the fiber, yarn or fabric sample in the liquid stain for 5 minutes. Sample liquid stain for 5 minutes. Sample then be rinsed thoroughly in cold then be rinsed thoroughly in cold running water. running water.

Result on Result on CottonCotton will be blue and on will be blue and on Viscose rayonViscose rayon will be green. will be green.

The re-use of stain D already used The re-use of stain D already used on a test is not recommended.on a test is not recommended.

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Shirlastain EShirlastain E This identification stain is This identification stain is also in powder form and also in powder form and should only be made up in should only be made up in liquid stain immediately liquid stain immediately before use, as fresh before use, as fresh prepared stain gives better prepared stain gives better results. 10 grams of this results. 10 grams of this powder makes 4.6 liters of powder makes 4.6 liters of stainstain

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PreparationPreparation

It is first necessary to prepare a dilute It is first necessary to prepare a dilute solution of sulphuric acid as follows:solution of sulphuric acid as follows:

Add 25 ml of dilute (10% by weight) of Add 25 ml of dilute (10% by weight) of sulphuric acid to 225 ml of distilled sulphuric acid to 225 ml of distilled water. This mixture referred as a water. This mixture referred as a diluted sulphulic acid. diluted sulphulic acid.

A quantity of A quantity of Shirlastain E Shirlastain E should now should now be added to the diluted sulphuric acid be added to the diluted sulphuric acid either by weight or volume, using a either by weight or volume, using a stainless steel scoop. stainless steel scoop.

- ½ gram by weight of - ½ gram by weight of Shirlastain EShirlastain E should be dissolved in the diluted should be dissolved in the diluted sulphuric acid by mixing at room sulphuric acid by mixing at room temperature and stir vigorously.temperature and stir vigorously.

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- By Volume one scoopful of the - By Volume one scoopful of the stain should be dissolved in the stain should be dissolved in the diluted sulphuric acid by mixing diluted sulphuric acid by mixing at room temperature and stir at room temperature and stir vigorously.vigorously.

The prepared solution should be The prepared solution should be brought to the boil, stirring all brought to the boil, stirring all the time and the undyed fiber, the time and the undyed fiber, yarn or fabric should be immersed yarn or fabric should be immersed in the boiling solution for in the boiling solution for 2 2 minutesminutes The sample should then The sample should then be rinsed thoroughly in warm be rinsed thoroughly in warm running water, preferably at 50°C running water, preferably at 50°C (120°F).(120°F).

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FiberFiber ColorColor Cotton (bleached)Cotton (bleached)Grey (LilacGrey (Lilac WoolWool Bottle GreenBottle Green SilkSilkNavyNavy Viscose rayonViscose rayon Reddish Lilac Reddish Lilac Cellulose acetateCellulose acetate GoldGoldNylon 6.6Nylon 6.6 OliveOlive Polyester 54 (No optical)Polyester 54 (No optical)Lemon yellowLemon yellow Polyester 64 (Dacron)Polyester 64 (Dacron)SalmonSalmon PolypropylenePolypropylene MagnoliaMagnolia Acrylic Acrylic (Orlon 75)(Orlon 75) Dull orangeDull orangeCreslan 61Creslan 61 TangerineTangerine Arnel (Bright Arnel (Bright filament)filament) YellowYellow Modacrylic (SEF)Modacrylic (SEF)TerracottaTerracotta

Table 3.Table 3. showsshows the colors by textile fibers, when the colors by textile fibers, when

stained with stained with Shirlastain E.Shirlastain E.

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Microscopic testMicroscopic test A simple Microscope is A simple Microscope is

often quite positive as many often quite positive as many fibers have characteristic fibers have characteristic cross-sectional or cross-sectional or longitudinal appearance and longitudinal appearance and comparisons with known comparisons with known samples or with illustrations samples or with illustrations help in identifying the help in identifying the distinctive features.distinctive features.

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The difficult group of synthetic The difficult group of synthetic polymers, many of which have polymers, many of which have similar microscopic similar microscopic appearance, can be further appearance, can be further separated by the use of specific separated by the use of specific organic solvents and the fact organic solvents and the fact that a given material dissolves that a given material dissolves in one and not in another in one and not in another solvent is often sufficient to solvent is often sufficient to determine exactly its origin.determine exactly its origin.

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Longitudinal view

Cross-sectional view

Wool

Camel Hair

Dog Hair

Longitudinal view

Cross-sectional view

Cashmere

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Cotton Hemp

FlaxCotton

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Soybean (Protein fiber)

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Bamboo Bamboo FiberFiber

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Solid roundSolid round:: This is the standard cross section for This is the standard cross section for

most synthetic fibers. It has a most synthetic fibers. It has a minimum surface to volume ratio, minimum surface to volume ratio, but in most cases it is used simply but in most cases it is used simply because it is usually less expensive because it is usually less expensive than modified cross sections.than modified cross sections.

Longitudinal view

Cross sectional view

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Hollow:Hollow: The hollow cross section has at The hollow cross section has at

least one hollow void enclosed least one hollow void enclosed within the fiber and running the within the fiber and running the entire length of the entire length of the fiber. Hollow fibers are usually fiber. Hollow fibers are usually round and their features are:round and their features are:

Higher specific surface areasHigher specific surface areas Thermal insulation properties Thermal insulation properties

due to trapped airdue to trapped air

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Hollow fibers are generally NOT useful for wicking of aqueous fluids.

Higher specific rigidity, so long as Higher specific rigidity, so long as the hollow void does not collapsethe hollow void does not collapseA delustered (less shiny) A delustered (less shiny) appearanceappearance

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Tri-lobal:Tri-lobal:A tri-lobal fiber gives a A tri-lobal fiber gives a fiber rigidity and fiber rigidity and resilience, and the many resilience, and the many reflecting surfaces are reflecting surfaces are efficient at scattering light efficient at scattering light to hide dirt. For these to hide dirt. For these reasons, tri-lobal fibers are reasons, tri-lobal fibers are often used in often used in carpetscarpets..

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The reflective surfaces can also give the The reflective surfaces can also give the fiber a sparkling appearance.fiber a sparkling appearance.The typical fibers, by this nature are The typical fibers, by this nature are Acrylic, NylonAcrylic, Nylon ….etc. ….etc.

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Ribbon:Ribbon:A ribbon cross section A ribbon cross section provides large flat surfaces provides large flat surfaces for specular reflection of for specular reflection of light, so its appearance is light, so its appearance is highly sparkling. It also highly sparkling. It also has a preferred bending has a preferred bending direction, which makes it direction, which makes it difficult to card. difficult to card. 

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If a segmented bi-component cross If a segmented bi-component cross section section (like a (like a pie wedge) is made with a ribbon cross section, it is exceptionally easy to split into micro-fibers.PolypropylenePolypropylene and and PolyethylenePolyethylene are are the typical fibers.the typical fibers.

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Multi-lobal:Multi-lobal:This highly modified cross This highly modified cross section was created for section was created for moisture transport, using moisture transport, using capillary wicking in its capillary wicking in its many grooves. It is the many grooves. It is the most effective moisture most effective moisture transport fiber transport fiber commercially available. commercially available. 

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Its high surface area and Its high surface area and deep grooves also make it deep grooves also make it highly effective in thermal highly effective in thermal insulation, filtration, and insulation, filtration, and in delivering materials in delivering materials from its grooves.from its grooves.

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Bowtie:Bowtie: The bowtie cross section was The bowtie cross section was

developed for a side-by-side bi-developed for a side-by-side bi-component filament yarn that component filament yarn that provides gentle stretch provides gentle stretch recovery. The cross section recovery. The cross section optimizes the separation of the optimizes the separation of the centers of mass of the two centers of mass of the two respective polymers, thus respective polymers, thus enhancing the stretch recovery of enhancing the stretch recovery of the helically-coiled fibers.the helically-coiled fibers.

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