qualitative analysis of textile fibers

QUALITATIVE ANALYSIS OF TEXTILE FIBERS1. SCOPE: The qualitative analysis of textile fibers (fiber identification) test

methods apply to fibers which are shown below grouped by generic classification:

a. NATURAL FIBER: i) Vegetable (Cellulosic) Fibers:

(a) Seeds: Cotton, Kapok. (i) Bast :

1. Low Lignin Content: Flax, Ramie. 2. High Lignin Content: Jute, Hemp.

(b) Leaf: Sisal. ii) Animal (Protein) Fibers:

(a) Epithelial growth: 1. Animal Hair: Cashmere, Mohair, Alpaca, Camel. 2. Wool: Sheep.

(b) Animal Secretion: Silk iii) Mineral Fibers: Asbestos

b. MAN-MADE FIBERS: i) Regenerated (Modified) Fibers:

(a) Rayon(Regenerated Cellulosic fiber): Viscose, Modal, Lyocell(Tencel), Polynosic.

(b) Regenerated Cellulose Ester: Acetate, Triacetate. ii) Synthetic Fibers:

(a) Polyester: PET( Dacron-USA/Terylen-UK), PBT (b) Polyamide: Nylon (c) Polyvinyl Derivatives: (d) PolyAcrylonitrile : Acrylic, ModAcrylic (e) Polyurethane: Spandex (f) PVC, PVA, PS

QUALITATIVE ANALYSIS OF TEXTILE FIBERS

2. APPARATUS: a. Microscopeb. Glass Slides and Cover glassesc. Flame Source-Bunsen Burner/Lighterd. Scissors, etc.

3. REAGENTS: a. Bleaching Agent-Sodium Hydrosulfiteb. Kayastain(Q)c. Potassium Iodide + Iodine Solutiond. 100% Acetonee. 80% Acetonef. 5% NaOClg. 5% NaOHh. 60% H2SO4i. 70% H2SO4j. 80% H2SO4k. 20% HCll. 35% HClm. 65% KSCNn. Di Methyl Formamide(DMF)o. m-Cresol, etc.

4. TEST METHODS: a. Visual Appearance and Feeling Test b. Twist on Drying Test c. Floatation Testd. Flame Test

a. Chlorine Detection Testb. Burning Tests

e. Stain Testsa. Kayastain(Q) Testb. Coloration Test With Iodine and Potassium Iodide

f. Microscopic Analysisa. For Longitudinal Examinationb. For Cross Section Examination

g. Solubility Tests h. Refractive Index Methodi. IR Spectroscopy Testj. Thermal Analysis –DSC, TGAk. Density Measurement Testl. Melting Point Measurement Testm. X-ray Diffraction Test

of 9MD.ROKIBUL ISLAM, QTEC DHAKA LAB


5. PROCEDURE: The identification of fibers is usually carried out by subjecting specimen to a variety of selected tests until enough information is obtained to make a satisfactory judgment as to the generic class or specific type.The selection of tests and order in which they are performed can be changed depending on the knowledge already available and results of the preliminary tests.

Most widely used methods are-5.a Visual Appearance and Feeling Test: 5.b Twist On Drying Test: 5.c Burning Test: 5.d KayaStain(Q) Test(JIS method)5.e Coloration Test With Iodine + Potassium Iodide Solution:5.f Microscopic Analysis for Longitudinal Examination: 5.g Solubility Test

5.a Visual Appearance and Feeling Test: Only skilled personnel can percept the fibers by visualizing and touching textile goods. But, possibility of misperception is very high.

5.b Twist On Drying Test: i. Separate out a few parallel fibers.ii. Dip in water and squeeze off excess.

iii. Tap the end of the bundle to make separate fibers flare out.iv. Hold over a hot plate in warm air to dry the fibers.v. Hold the fibers so that the free ends point toward the observer.

vi. Note the direction of twist as the fibers dry.Flax and Ramie twist in a clockwise direction; hemp and jute twist in a counter clockwise direction.

5.c Burning Test:

i. Take a small tuft of fibers forceps and place close to the side of a small flame.ii. Note if the fibers melt or shrink from the flame.

iii. Move the fibers into the flame. iv. Note whether the fibers will burn when held in the flame.v. Remove from the flame very slowly and carefully.

vi. Note whether the fibers continue to burn outside of the flame.vii. Blow out the flame, if still burning, and smell the smoke.

viii. Note the odor and examine the color of the smoke.ix. Note the color, and nature of any ash, or bead residue.



BURNING CHART

FIBERSMELTS NEAR

FLAME

SHRINKS FROM FLAME

BURNS IN

FLAME

CONTINUES TO BURN SMELL CHARACTERISTICS

OF ASH/BEAD

CELLULOSIC(Cotton,Jute,Flax)

No No Yes Yes Paper burning

Little, Soft, Greyish.

WOOL Yes Yes Yes Slowly Hair burning

Irregular black, can be

crumbled.

SILK Yes Yes Yes Slowly Hair burning Soft black bead

RAYONS No No Yes Yes Paper/Leaf burning

Almost nothing, very

soft.

ACETATE Yes Yes Yes Yes Vinegar smell

Hard, black, irregular bead.

ACRYLIC Yes Yes YesYes, with

black smoke

Smell like meat

Hard, black, irregular bead.

POLYESTER Yes Yes YesYes, with

black smoke

Plastic burning

Very hard, black round

bead.

NYLON Yes Yes Yes YesNylon rope

burning, distinctive

Hard grey round bead

SPANDEX Yes No Yes Yes Chemical odor

Sticky bead, tends to drip.

RUBBER*

(Not a fiber) Yes Yes Yes NoRubber like

Tyre burning

Irregular mass



5.d Kayastain(Q) Test:

i. Bleach the textile by 1% sodium hydrosulfide(boil) solution, then squeeze and dry.ii. Heat the 1% Kayastain(Q) solution by Bunsen burner.

iii. Add the textile to the liquor before it boils.iv. Allow the boiling to continue for 5 minutes.v. Then rinse and dry the textile without delay.

vi. Compare the shade of the textile with reference table below mentioned.

Fig (5.d): JIS Multi Fiber Fabric (After Kayastain)

5.e Coloration Test With Iodine + Potassium Iodide Solution: i. Place a few fibers on a microscope slide.ii. Apply a drop of iodine solution and cover with a cover glass with taking care to avoid

bubbles.iii. Examine the fibers for staining.

Cotton, ramie, and hemp stain violet; flax stains brownish violet; Jute stains brown; silk stains yellow brown.Most of the synthetic fibers do not absorb iodine solution due to lack of the porosity in their structure, that’s why generally they do not stain.


POLYESTER COTTONNYLONACETATEWOOLRAYONACRYLICSILK


5.f Microscopic Analysis for Longitudinal Examination: i. Sample Preparation for Identification: o If the sample is a fabric, separate out the yarns by unraveling or cutting.o If the sample is woven, separate warp and filling (weft) yarns.o If yarns differ in color, luster, size, or other apparent ways, make a physical

separation of these yarns separate identification.

ii. Test Operation: o Place a small quantity of fibers on a glass slide.o Tease fibers apart, mount with a drop of iodine solution or other immersion fluid,

cover a glass cover slip.o Place the slide on the microscope stage, and examine the slide by scanning top to

bottom, left to right.

Observe the fiber characteristics and classify into five general classes:

#1, Fiber with surface scales. These are the animal hair fibers including wool, cashmere, mohair, alpaca, etc.Additional confirmation of this class may be made by Kayastain(Q) test, Burning test, and Solubility test etc.

#2, Fibers with cross markings. These are the vegetable fibers (except cotton) including Flax(Linen), Ramie, Hemp etc.To distinguish Flax and Ramie from Hemp, perform twist on drying test.Additional confirmation of this class may be made by Kayastain(Q) test, Burning test, and Solubility test etc.


FLAX

WOOL


#3, Twisted fibers. This class includes cotton and silk. These two are easily distinguished by Kayastain(Q) test, burning test, and solubility test.

#4, Fibers with stripe or steak. These class are regenerated cellulosic fibers including viscose rayon, modal, acetate etc.

#5, Other fibers. This class includes all of the man-made fibers.The man-made fibers are best identified by burning test, solubility test, or other properties which relate to chemical nature rather than shape.


COTTON SILK

RAYON ACETATE MODAL

LYOCELL


5.g Solubility Test:

TYPES OF FIBERS NAME OF FIBERS SOLUBILITY

NATURALFIBERS

COTTON, LINEN, JUTE, RAMIE,

HEMP

Soluble in 70% sulfuric acid

Not soluble in 60% H2SO4

SILKSoluble in 5%NaOCL, 5% NaOH

Soluble in 35%HCl, different from wool

WOOL, ANIMAL HAIR

Soluble in 5%NaOCl, 5%NaOH

Not soluble in 35%HCl, different from silk

REGENERATED FIBERS

RAYON,MODAL


Not soluble in 100% Acetone (different from acetate, tri-acetate)

ACETATESoluble in 80%acetone, different from rayon, and tri-acetate

Soluble in 70%H2SO4

TRIACETATE Soluble in 100% acetone, different from Rayon

Not soluble in 80%Acetone, different from Acetate

LYOCELL(TENCEL)

Get sticky in 60% sulfuric acid


CUPRA,POLYNOSIC


Soluble in 35%HCl, but not in 20%HCl

SYNTHETICFIBERS NYLON

Soluble in 20%HCl, m-Cresol(Cold), different from polyester

DMF(boil)-Nylon6 soluble, Nylon66 insoluble


NYLON POLYESTER

ACRYLIC SPANDEXDEX


VINYLON(PVA)

Soluble in 20%HCl

Soluble in 85%HCOOH, different from nylon

POLYESTERSoluble in m-Cresol(boil) and in 97-98%H2SO4

Insoluble in cold m-Cresol and 20%HCl, different from nylon

ACRYLICSoluble in 65%KSCN, different from other fibers.

Soluble in warm DMF

MOD ACRYLICSoluble in cold DMF

Insoluble in 65%KSCN, different from Acrylic

SPANDEX(POLYURETHANE

)

Soluble in 80%H2SO4 and Hot DMF, different from Rubber

It has stretch property, different from other fibers


qualitative analysis of textile fibers

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