IDENTIFICATION OF TEXTILE FIBERS

Assignment on

A number of methods are available for characterization of the structural, physical, and chemical properties of fibers. Various methods are used for fiber identification like microscopic methods, solubility, heating and burning method, density and staining etc. End-use property characterization methods often involve use of laboratory techniques which are adapted to simulate actual conditions of average wear on the textile or that can predict performance in end-use.

TYPES OF TEST

The Non technical Test○ FEELING TEST○ BURNING TEST

The Technical Test○ MICROSCOPIC TEST○ CHEMICAL TEST

Tests for identification

Handle/Feel Test Visual Examination Burning test Twist on Drying Floatation Test Microscopic analysis Chemical Analysis

Requirements for tests

Preparation of test specimen Apparatus for microscopic examination Reagents used for chemical tests Other tools and equipment

THE NON-TECHNICAL TESTS

Feeling test Burning test

FEELING TEST

The feeling test requires perception if it is to be of any value.

Skilled perception is acquired only after handling many different fabrics over a period of time.

Limitations of this test become apparent when examining and comparing fabrics of different fiber content.

BURNING TEST

To recognize the composition of fabrics by the burning test ,the sample of fiber, yarn of fabric should be moved slowly towards a small flame and the reaction to heat carefully observed .One end of the sample should be put directly into flame to determine its burning rate and characteristics. The burning odour should be noted and the characteristics of the ash such as amount ,form, hardness and color should be examined

IDENTIFICATION OF FIBRES THROUGH BURNING TEST

Cotton :○ When ignited it burns with a steady flame and

smells like burning leaves. The ash lefties easily crumbled. Small samples of burning cotton can be blown out as you would a candle.

Linen:○ Linen takes longer to ignite. The fabric closest to

the ash is very brittle. Linen is easily extinguished by blowing on it as you would a candle.

Cotton Fiber Linen Fiber

Silk: It is a protein fiber and usually burns readily, not

necessarily with a steady flame, and smells like burning hair. The ash is easily crumbled. Silk samples are not as easily extinguished as cotton or linen.

Wool It is also a protein fiber but is harder to ignite than

silk as the individual "hair" fibers are shorter than silk and the weave of the fabrics is generally looser than with silk. The flame is steady but more difficult to keep burning. The smell of burning wool is like burning hair.

Silk Fiber Wool Fiber

Man Made Fibers

Acetate: Acetate burns readily with a flickering flame that

cannot be easily extinguished. The burning cellulose drips and leaves a hard ash. The smell is similar to burning wood chips.

Acrylic: Acrylics burn readily due to the fiber content and the

lofty, air filled pockets. A match dropped on an acrylic blanket can ignite the fabric which will burn rapidly unless extinguished. The ash is hard. The smell is acrid or harsh

Acrylic FiberAcetate Fiber

Nylon: Nylon melts and then burns rapidly if the flame

remains on the melted fiber. If i can keep the flame on the melting nylon, it smells like burning plastic.

Polyester: Polyester melts and burns at the same time, the

melting, burning ash can bond quickly to any surface it drips on including skin. The smoke from polyester is black with a sweetish smell. The extinguished ash is hard.

Polyester Fiber Nylon Fiber

Rayon:It is a regenerated cellulose fiber

which is almost pure cellulose. Rayon burns rapidly and leaves only a slight ash. The burning smell is close to burning leaves

Rayon Fiber

Fiber burn chart

LIMITATION OF BURNING TEST

It is apparent that many fibers have similar burning reactions that might cause doubt and occasional confusion.

TECHNICAL TESTS

There are certain technical tests performed for identifying various fibers. These tests require high technology laboratory equipment and are much more reliable than the non technical fiber tests.

Technical tests require high skilled personnel and technical know how of handling chemicals and their accurate analysis. These tests are very valuable for those fabrics that are a blend of different yarns and also have certain special properties including flame retardance etc.

TYPES OF TECHNICAL TEST

Microscopic test Chemical test

MICROSCOPIC TEST

Microscopic test is a technical test that involves identifying the fabric with the help of a microscope with a magnification of minimum 100 power.

The test can easily distinguish between fibers. The test identifies the natural fibers more

easily as compared to man made ones. Synthetic fibers are very similar in appearance

and the increase in the number of varieties, makes it a little tough to distinguish the fibers even under a microscope

MICROSCOPIC TEST FOR NATURALFIBERS

COTTON: ○ It is a single elongated cell. Under the microscope,

it resembles a collapsed, spirally twisted tube with a rough surface.

○ The thin cell wall of the fiber has from 200 to 400convolutions per inch.

LINEN:○ Under the microscope, the hair like flax fiber

shows several sided cylindrical filaments with fine pointed ends.

○ The fiber somewhat resembles a straight, smooth.

Cotton Fiber Linen fiber

WOOL:○ Under the microscope , wool’s cross section shows three

layers- epidermis, cortex and the medulla.

SILK:○ It appears somewhat elliptical and triangular in cross section

when we see under the microscope.○ It is composed of fibroin, consisting of two filaments, called

brin which is held together by sericin.

Silk fiber Wool fiber

MICROSCOPIC TEST FOR MANMADEFIBERS

RAYONS:○ Rayon fibers have a glasslike luster under the

microscope and appear to have a uniform diameter when viewed longitudinally.

ACETATE:○ The cross sectional view has a bulbous or

multi global appearance with indentations.○ These indentations appear as occasional

markings.

Acetate fiber Rayon fiber

NYLON: The basic microscopic appearance is generally

fine ,round, smooth, and translucent. It is also produced in multilobal cross-sectional

types. POLYESTERS: 

Generally, polyester fibers are smooth and straight and the cross-section is round.

 This general characteristics may be altered to achieve certain characteristics.

Polyester fiberNylon fiber

ACRYLICS: The methods of manufacturing of the acrylic fibers differ, the appearances vary accordingly.

ACRILAN ACRYLIC: It has a bean-shaped cross section, its longitudinal appearance is straight and smooth.

ORLON ACRYLIC: It has a flat, nut-shaped cross section.

CRESLAN ACRYLIC: It has an almost round cross section.

MOD ACRYLICS: it is of two types verel mod acrylic

and SEF mod acrylic.

SPANDEX: Spandex fibers are unique in appearance, they appear to be groups of fibers fused together.

GLASS: The fiber is smooth, round, translucent, highly lustrous, and quite flexible.

Asbestos fiber: This method is for the analysis of asbestos in air by Phase Contrast Microscopy. Results are reported as fibers per cubic centimeter and depend on the volume of air sampled. PCM analysis is not asbestos fiber specific and will count all fibers meeting the methods criteria for fiber determination.

CHEMICAL TESTS

Chemical tests are another technical means of identifying fibers. But chemical tests are not intended for the general consumers.

Different types of chemical tests are under taken to establish the identity of the fibers used.

These tests give accurate and precise analysis.

The tests are conducted in research laboratories.

TYPES OF CHEMICAL TEST

Stain Test:○ Also known as the Double Barrel Fiber

Identification(DBFI), the test is based on the theory that each fiber has its own distinct two- color reaction when treated with stain. A fiber will turn to a particular color in the presence of dilute acetic acid and to some other specific color when stained in the presence of a mild alkali.

Solvent Test:○ The test involves treating the fibers in

certain solvents for identifying them. The technical test is becoming difficult to conduct as most of the manufactured fibers and their blends are chemically similar. There is no individual chemical or solvent test for separating or identifying the fibers in combinations.

Distinguishing animal from vegetable fibers with an acid :As strong alkali destroy animal substances, a 5%of soda

lye solution in water can be used to eliminate wool and silk fibers from a sample that contains a mixture of fiber. The vegetable fibers will not be affected by this solution.

Distinguishing vegetable from animal fibers with an acid As dilute acid destroy vegetable fibers, a 2%sulphuric

acid solution can be used. A drop of solution is placed on the sample, which is then pressed with a hot iron. The spotted area will become charred if the sample is cotton linen or rayon.

DISTINGUISHING SILK FROM WOOL:○ The use of concentrated cold hydrochloric acid

will dissolve the silk and the wool fiber swells. DISTINGUISHING NYLON FROM OTHER FIBRES:

○ If the fabric is thought to contain nylon, the fabric may be immersed in a boiling solution of sodium hydroxide. The nylon is insoluble in such a solution

DISTINGUISHING POLYESTERS FROMOTHER FIBRES:

○ Polyester is soluble in hot meta cresol; however ,unlike acetate it is not soluble in acetone, and unlike nylon it is not soluble in concentrated formic acid.

DISTINGUISHING ACRYLICS FROMOTHER FIBRES:

○ Acrylic fibers will dissolve in 70 percent solution of ammonium thiocyanate at 130 degree Celsius but the other fibers will not.

DISTINGUISHING LINEN FROM COTTON○ Cotton and linen are immersed in a 1% solution of

fuchsine in alcohol to give red rose color. Later ,they are washed and immersed into ammonia, linen retains the red coloration but cotton does not.

DISTINGUISHING GLASS FIBERS FROM OTHERFIBRES:

○ There are two specific solvents for quick identification of glass fibers, they are hydrofluoric acid and hot phosphoric acid.

Advantages:•More reliable than the non technical tests.

•Used for both man made fibers and natural fibers.

•Easily conducted.

Limitations •Certain manufacturing and finishing processes like mercerizing, affects the appearance of the fibers under the microscope.

•Very dark colored fabrics cannot be identified under microscope.

•Dye stuffs must be removed from fabrics.

Submitted To: Sir Imran Raza

Submitted by: Huzaifa Amin (Tmm-01)