Natural Fibres
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Transcript of Natural Fibres
Natural Fibres• Cotton• Silk• Wool• Linen
COTTON
• Cultivation• Morphological structure• Chemical structure
Commercial classification of Cotton based on the length of the fibre
• Sea Island cotton – 5 cm or more• Egyptian cotton – 3.7 - 4.5 cm• Brazilian cotton – 3 - 4 cm• American cotton – 2.5 - 3.5 cm• Indian cotton – 2 - 3 cm• Chinese cotton – 1.5 - 2 cm
Diameter of cotton fibre = 15-20 microns
Morphological structure of Cotton
Convolutions
Lumen
The morphological structure of the fibre consists of 4 parts:a. Cuticleb. Primary wallc. Secondary walld. Lumen
a. Cuticle• Encloses the cotton fibre -> protects the fibre• Composed of cotton wax-mixture of fats and oils.• oily film -> hard like varnish.
b. Primary wall• Built from cellulose• Cellulose molecular chain randomly arranged• 0.1-0.2 microns thick
c. Secondary wall• Also composed of cellulose
d. Lumen• Cylindrical void (i.e. space) along the length of the fibre • Occupies 30-35 % of total area of cross-section
Chemical composition of cottonChemicals Composition (%)
Cellulose(glucose molecules)
88 - 97
Protein(polypeptides & amino acids)
1 - 2
Oil and Wax(glycerides & fatty acids)
0.4 - 1.5
Pectins(Ca/Mg/Fe + pectic acid)
0.4 - 1.5
Minerals(chlorides/carbonates/sulphates of
K, Ca and Mg)
0.7 - 1.6
Others 0.5 - 8.0
Cellulose• Basic unit of cellulose is anhydro D-glucose • Glucose is a monosaccharide containing 6
carbon atoms – 5 in the ring and 1 in side chain
LIFE CYCLE OF SILK WORMEgg (hatches in 8-10
days)
Caterpillar (5 mg / 2-3 mm )
After 20-30 days2-5 gm / 5-9 cm
Seeks for secretion of filament / transferred to special trays
Turns into a pupa
PRODUCTION OF SILK
Drying •To kill the pupa inside the cocoon – sunlight/heating.•Process also called stifling.• Cocoons are then stored.
Sorting •Good cocoons are sorted from bad ones like stained, irregular, flossy and thin end cocoons. • colour, shape, weight, filament length, filament diameter.
Cooking • cooked or softened in hot water• to swell and soften the sericin
Reeling • continuous silk filament is extracted from the cocoons without any break and reeled using a reeling machine.
MORPHOLOGICAL STRUCTURE OF SILK
Brin
CHEMICAL COMPOSITION
• Composed of,– FIBROIN (the silk filament), and – SERICIN (the gummy substance that holds the
filaments together)
Component Mulberry Silk
Tassar silk Muga silk Eri Silk
Fibroin 70-80 % 80-90 % 80-90 % 80-90 %
Sericin 20-30 % 8-10 % 8-10 % 4-5 %
Other 2-3 % 3-5 % 3-5 % 3-5 %
• FIBROIN and SERICIN contain amino acids
Primary structure of FIBROIN (Gly-Ser-Gly-Ala-Gly-Ala)n
• The chemical composition of SERICIN is C30H40N10O16.
Gly – GlycineAla – AlanineSer - Serine
WOOL
• Wool is the oldest and the important animal fibre.
• Major production: UK, Russia, Argentina, USA• The main physical features of the wool fibre
are its length and diameter.
GRADING OF WOOLType of Wool Fibre Length Fibre diameter
Fine 3.2 – 10 cm 10 - 30 micron
Medium 5 – 20 cm 20 - 40 micron
Long 12.5 – 35.5 cm 35 - 50 micron
Cross Bred 7.5 – 15.5 cm 20 - 40 micron
Mixed Mixed length 20 - 100 micron
Wool sorting is the process of separating the wool fibres based on its quality such as length (short or long), fineness (fine or coarse), handle (stiff or soft), etc.
MORPHOLOGICAL STRUCTURE OF WOOL
• 3 structural parts:a. Epidermis or cuticleb. Cortexc. Medulla
Chemical composition of WoolComposition Percentage (%)
KeratinGrease
MoistureSuint
Sand and dirtVegetable matter
45-75 5-15
10-122-124-300-5
• Keratin:– Composed of C (~53%), H (7 %), N (18%), O (25%) and S– S content varies largely among different types of wool.– Polypeptide composed of 15-20 amino acids
• Grease:– Insoluble in water– Ester of (high molecular weight) fatty acids and
monohydric alcohol (eg. Cholesterol)• Suint:– Water soluble– K salts of fatty acids and organic amino acids
• Sand and Dirt
Protein molecule:
Dipeptide
Polypeptide
Helps to differentiate the amino acid
Polypeptide chain can be:– Straight chain but in a zig-zag form– Folded chain (arranged forward and backward on
one plane)– Coiled chain (spiral form)
FLAX
- Bast fibre- The plant grows 170 cm in height and 1.5 cm
in diameter.- On maturity, changes from green to yellow.- Better to harvest when the seed pods have
ripened.- Dried for a week – stem is collected.
PROCESSING OF FLAX Hackling •The stems are beaten against iron spikes to remove the impurities like leaves and small branches.
Retting* •Dew retting – 10-20 days•Stagnant water retting – 30-40 days•Running water retting – 20-30 days•Chemical retting – oxalic acid for 4-8 hrs
Drying and Storing •Drying makes the fibre stronger•Woody material of the stem can be removed by hackling.
*Retting is the process of separating the fibre bundles from gummy substance surrounding it.
FLAX FIBRE - LINEN
• Strongest natural fibre – 80-90% crystalline region.• High crystallinity -> dry strength and wet strength are
the same.• Length – 90-125cm• Diameter – 14-25 microns• Cross-section - Round to polygonal with a small lumen.• Moisture regain – 12%• Used for home textiles, sheeting, canvas, threads,
twines, paper making, etc.