Identification of textile fibers.
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Transcript of Identification of textile fibers.
ASSIGNMENT ON
I D E N T I F I C AT I O N O F T E X T I L E F I B E R S
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
M I C R O S C O P I C T E S T F O R N AT U R A L F I B E R S
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
M I C R O S C O P I C T E S T F O R M A N M A D E F I B E R S
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 TESTSChemical 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.