report on fibers
TRANSCRIPT
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