IMPORTANT PROPERTIES AND USES OF NATURAL FIBERS :-
1. COTTON
Cotton is a fiber that grown from the surface of seeds in the pods or balls of a bushy mallow plant. It is composed basically of a substance called “cellulose”. Cotton fibers were comes in three steps,
Cultivation
Harvesting
Ginning & baling
In India, cotton is cultivated mainly in Maharashtra, Gujarat, Haryana, Punjab, Rajasthan, Tamil Nadu and Madhya Pradesh.
A) Cultivation of cotton:
Cotton is cultivated in black clay soil. It needs warm climate.
The sowing of cotton crop is done in early spring.
Cotton plants are bushy and about 1-2 meters tall.
- The plants start flowering in about 60 days and give whitish – yellow flowers.
The flowers turn reddish in a few days. Flowers slowly grow into spherical walnut-like structures. These are called cotton ball.
Fibers of cotton grow on these seeds. After some time green cotton balls turn brown.
At maturity, the cotton balls burst open and the white cotton fiber can be seen.
B)
Harvesting:
After the cotton balls are burst, it is ready for harvesting.
That time the balls have all opened and some leaves fallen.
To remove all the leaves, by spraying them with a chemical, is causes the remaining leaves also falls.
The process of removing cotton seeds, leafs, dirt and other material from pods is called ginning.
Ginning was traditionally done by hand. Now-a-days, machines are used in ginning
The process of making yarn from fibre is called spinning. The raw cotton is supplied to industry in the form of bales.
PHYSICAL PROPERTIES OF COTTON:-
Tensile strength (or) tenacity:
The tenacity of the fibre is 3-5 gms/denier.
Elasticity:
At 2% extension, elastic recovery is 74%
Moisture contents:
Cotton takes upto 5% -8% moisture absorption of water result in increases the fibres strength.
Specific gravity:
The specific gravity of cotton is 1.54%
Effect of sunlight:
Cotton lose its strength gradually and turns yellow, when it exposed to sunlight.
Effect of heat:
It has excellent resistance to de-gradation by heat. It turns yellow after several hours at 120 degree Celsius.
Burning characteristics:
Burns quickly with large yellow flames gives smell of burning paper.
Effect of ageing:
When stored cotton loses only less strength.
Microscopical appearance:
Cross-section – flat to circular
Longitudinal – twisted ribbon with the thickened edges.
CHEMICAL PROPERTIES OF COTTON:-
Action of organic acid:
Organic acid like acetic acid which is used in printing and dyeing
Action of insect:
Cotton is not attacked by moth and insects.
Action of H2So4 (Sulphuric Acid)
When cotton is treated with h2so4 it produces the effect called “organdie effect”
Organdie effect increases affinity of cotton for direct colors. (direct dyes, reactive dyes)
Action of HCl (Hydro Chloric Acid)
Action is similar to h2so4 but tendering is greater.
4% HCl destroys the cotton structure and cotton fibre will dissolve.
Action of HNO3 (Hydrogen Nitrate)
The action with cotton for short time gives mercerization effects.
Uses of cotton:-
Cotton is commonly used for men's, women's and summer wear.
It is also used for household fabrics like bed sheet, towels, rugs and carpets.
Cotton can also be used in industrial application as tyre cords bags shoes medical supplies and equipment's.
It is also used to manufacture of sewing threads, different types of ropes, furnishing fabrics, cycle tyre, shoe lace, filter cloths, canvas, bandage cloths etc.
2. SILK
CULTIVATED SILK (MULBERRY)
The cultivated silkworm is known as “bombyx mori” which lives on only “mulberry trees”. It is a domestic animal. It cultivated two types of silks,
Uni-voltine
Multi-voltine
SEQUENCE OF PROCESS:-
PHYSICAL AND CHEMICAL PROPERTIES OF SILK:-
Elongation:
Silk will be elongate upto 10%-25%
Specific gravity:
The specific gravity is 1.35
Effect of heat:
Silk can with stand the temperature between 120 degree Celsius – 140 degree Celsius and rapid integration set at 170 degree Celsius
Effect on sunlight:
When silk filament is long exposure on sunlight, it will damage.
Moisture regain:
The moisture regain of silk filament is 11%
Burning characteristics:
When silk filament is exposed to flame, it produces the hair burning smell.
Tenacity:
Tenacity 4.3-5.2gms/ denier
CHEMICAL PROPERTIES:-
Acid of mineral acid:
Mineral acid in moderate concentration is used to produce crepe effect in fabric.
Cold concentration sulphuric acid and hydrochloric acid dissolve the silk.
Action of organicacids:
Dilute organicacids are observed by silk increasing its lusture.
Effect of bleaching agent:
Hydrogen peroxide(h2o2) is used for bleaching. It is commonly used for silk fabric.
Affinity for dye-stuff:
The silk has direct affinity towards acid dyes and basic dyes
USES OF SILK:-
Silk is used for producing apparels, draperies (carpets), upholstery (curtain)
Silk fabrics are lustrous in nature.
It is more durable and easy clean.
Both woven and knitted fabrics are produced.
3. WOOL
The different types and grades of wool
The sheep is a valuable animal and it is found in every corner of the world.
It provides skin, mutton and wool.
There are several varieties of sheep's in the world, they are
1.
fine wool (merino)
2. medium wool
3. long wool
4. cross breed wool
5. carpet wool
The manufacturing process sequence:-
PHYSICAL AND CHEMICAL PROPERTIES OF WOOL:-
Hydroscopic property:
It can up take 30% of moisture without feeling wet.
For scoured wool is 13.5%.
For raw wool is 16%.
Increase in moisture decrease the strength of the wool.
Specific gravity:
Its elasticity is 1.304.
Elasticity:
Its elasticity is upto 30%.
Crimp:
Crimp is defined as the curliness or waviness of the wool fibre.
Color:
Yellowish but may be brown or black.
Microscopic appearance:
The longitudinal view is rod scale on surface and cross sectional view is noted.
Burning property:
The flame of the wool produces hair burning smell.
CHEMICAL PROPERTIES:-
Action on heat:
Wool withstands the temperature upto 140 degree celsius.
Action of acid:
4% of sulphuric acid is commonly used for wool dyeing.
Action of bacteria:
Wool fibre is attacked by bacteria easily.
Action of insects and moths:
Wool fabrics are easily eaten by moth and insects
Affinity for dye stuff
Good affinity.
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