ReportIdentification of FibersSubmitted By: Zobia Hamid TS1

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 etc.

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.

Cotton

Longitudinal Mature flat and ribbon like with

convolutions, thick wall and small lumen

Immature very thin wall and large lumen with few convolutions

Dead very thin and almost transparent

• Cross Sectional• Kidney Shaped • Elliptical • Very thin like a strip• Nearly round or circular

Linen

Longitudinal Smooth and Bamboo like

with cross marking nodes, no lengthwise striations, narrow lumen

• Cross Sectional• Sharp polygonal shape

with straight sides. Immature oval shape with large lumen

Wool Longitudinal Cylindrical , irregular, rough

surface, scale like structure, dark medulla may appear on coarse wool fibres.

• Cross sectional• Nearly round or circular• It shows three layers-

epidermis, cortex and the medulla.

Silk Longitudinal Smooth surface, Structure

less, triangular shaped transparent rod(Wild silk/Tussah silk - broader fibre with fine, longitudinal lines passing across filament)

• Cross sectional• Triangular shape with rounded

corners(Tussah silk flat wedge or spindle shaped

Rayon

Longitudinal Normal type fairly dense

longitudinal striations or fine lines

Special type-may be smooth and Structure less

• Cross sectional•Irregular with serrated outline•Oval or round

Polyester• Longitudinal• Structure less, uniform

diameter, rod like appearance

• Cross sectional• Generally,  polyester

fibers are smooth and straight and the cross-section is round

Polyester

Acrylic Longitudinal Smooth surface, uniform

diameter, rod like appearance , some types with irregularly spaced striations

• Cross sectional• Rounded or Dumbbell

shaped

• Longitudinal• Uniform in width with a

few distinct longitudinal striations

• Cross sectional• Irregular with serrated

outline

Acetate

Burn Test

Burn test is the most accepted method for identifying the true nature of any fabric. This test is carried out to know whether a fabric is made up of a natural fiber, man made fiber, or a blend of natural and man made fibers. 

Cotton : It is a cellulose fiber. It burns and

may flare up when lit. When ignited it burns with a steady flame and smells like burning leaves.

Small samples of burning cotton can be blown out as you would a candle. No melted bead is left by it. After burning, it continues to glow.

It gives out smell like that of a burning paper. The smoke is gray or white. The ash is fine, soft that can be easily crumbled.

Linen: A cellulose fiber, it 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.

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. It sizzles and curls away from flame and may curl back onto fingernail.

It leaves beads that are brittle, dark, and easily crushed. It is self-extinguishing and leaves harsh ash from crushed bead.

Silk: It is a protein fiber and usually burns

readily, not necessarily with a steady flame

The ash is easily crumbled. Silk samples are not as easily

extinguished as cotton or linen. It leaves dark bead which can be easily

crushed. It leaves ash that is dark, gritty, fine

powder. It smells like burned hair or charred

meat. It gives out a little or no smoke and the fume has no hazard.

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

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.

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.

Nylon: Nylon melts and then burns rapidly if the flame remains on the melted fiber.

If we keep the flame on the melting nylon, it smells like burning plastic

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.

Solubility 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.

Distinguishing vegetable from animal fibers with an acid : As dilute acid destroy vegetable fibers, a 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 animal from vegetable fibers with an acid : As strong alkali destroy animal substances, a 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 Nylon from other fibers: 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 Silk from Wool : The use of concentrated cold hydrochloric acid will dissolve the silk and the wool fiber swells.

DISTINGUISHING POLYESTERS FROMOTHER FIBRES: Polyester is soluble in hot meta cresol

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 SILK FROM WOOL: The use of concentrated cold hydrochloric acid will dissolve the silk and the wool fiber swells.

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 POLYESTERS FROMOTHER FIBRES: Polyester is soluble in hot meta cresol