UNIT 2 TF

Textile Fibres

Unit 2: Natural Fibres

  • Course Context: Focused on agriculture and processing of natural fibres in textiles.

Vegetable Fibres: Cotton Fibre

Overview

  • Cotton is known as the "King of all Fibres."

  • Provides 50% of the world’s textile fibre.

  • India is the second-largest producer of cotton, following China.

  • Cotton fibres are sourced from the outer covering of seeds.

  • The seeds are also a source of valuable oil for cooking.

  • Cotton can be used as a single component for yarn or blended with man-made yarns.

Cultivation

  • Cotton plants thrive in moderately hot climates.

  • Planting: Occurs in April/May, seeds are planted 1-10 cm deep in rows 1 meter apart.

  • Germination: Takes 8-12 days under warm and moist conditions.

  • Flowers appear in June, lasting just one day.

  • Post flowering, seeds are surrounded by soft fibrous substance.

  • Cotton fibres develop inside pods, bursting when seeds mature, releasing whitish fibres.

  • Each seed can produce up to 20,000 fibres, while a single boll may contain over 150,000 fibres.

  • Harvesting is done 6-7 months post seeding.

Factors Affecting Yield

  • Timely planting and regular addition of soil and fertilizers.

  • Use of quality seeds and weed control measures.

  • Essential to control insects and ensure proper irrigation.

  • Defoliation and timely harvesting are crucial for maintaining yield.

  • Average yield: ~370 kg globally, ~170 kg in India per acre.

Development of Cotton Fibre

  • First Phase: Sprouting of epidermal cells and growth continues for 25 days.

  • Second Phase: Thickening of the fibre occurs through layered deposition over 35-40 days.

  • Total Development Duration: Approximately 200 days (150 days for growth and 50 for boll and bursting).

Botanical Classification

  • Genus: Gossypium

  • Different species based on cultivation regions:

    • Gossypium Arboreum (India)

    • Gossypium Herbaceum (Middle East, Egypt, India)

    • Gossypium Barbadense (Peru, Egypt, Sea Islands)

    • Gossypium Hirsutum (America, West Indies)

Classification by Length

  1. Long Staple (>24 mm) – Superior quality, 50% of Indian production, found in Punjab, Haryana, and Maharashtra.

  2. Medium Staple (20-24 mm) – 44% production, found in Rajasthan, Punjab.

  3. Short Staple (<20 mm) – 6% production, found in UP, AP.

Commercial Classification

  1. Sea Island Cotton - Long, fine and soft; staple length 5 cm or more.

  2. Egyptian Cotton - Long and soft, staple length between 3.7-4.5 cm.

  3. Brazilian Cotton - Dull white, staple length 3-4 cm.

  4. American Cotton - Staple length 2.5-3.5 cm.

  5. Indian Cotton - Poor quality, staple length 2-3 cm.

  6. China Cotton - Poorest quality, staple length 1.5-2 cm.

Structure of Cotton Fibre

  • Cellulose Composition:

    • Cellulose forms primary component of the fibre's cell walls.

  • Morphological Structure:

    • Comprised of four main parts: Cuticle, Primary Wall, Secondary Wall, and Lumen.

Detailed Description

  1. Cuticle: Protects the fibre from damage; composed of fats, waxes, and oils.

  2. Primary Wall: Composed of cellulose and provides peripheral strength; thickness varies.

  3. Secondary Wall: Main weight contributor, making up ~90% weight, arranged in concentric spirals.

  4. Lumen: Center void in fibre, shrinks after drying, containing coloring matters.

Properties of Cotton Fibre

  1. Tensile Strength: 26.5 to 44.1 gm/tex

  2. Elongation: 5-10%

  3. Density: 1.54 gm/cm3

  4. Moisture Regain: 6-8% at 65% RH

  5. Chemical Resilience: Dissolves in sulfuric acid, resistant to alkalies.

  6. Biological Resistance: Generally robust against insects; affected by fungi.

  7. Longevity: Can last over 10 years with minimal strength loss.

Bast Fibre: Jute

Overview

  • Jute ranks second after cotton in global natural fibre production.

  • Major production in India and Bangladesh (~85%).

  • Sourced from the stems of plants like Corchorus Capsularis and Corchorus Olitorius.

Cultivation Requirements

  • Prefers low-lying, acidic, alluvial soils with high humidity (65-90%) and warm temperatures (25-40 °C).

  • Top cultivation areas include West Bengal, Orissa, Assam, and Bihar.

  • Sown from February to March, reaching full height by 90 days (2-5 meters in height).

Retting Process

  • Extraction of fibres through retting, soaking stalks in various methods:

    1. Dew Retting - Exposed in humid conditions for 7-15 days.

    2. Stagnant Water Retting - Immersed in still water for 10-20 days.

    3. Running Water Retting - Flowing water immersion for 20-30 days.

    4. Chemical Retting - Uses chemicals like NaOH for 6-8 hours.

Chemical Composition

  • Jute primarily comprises cellulose (65%), hemicellulose (12%), lignin (11%), and 10% water.

Structure and Properties of Jute Fibre

  • Multi-cellular fibre, characterized by bundle structure supported by a gummy material.

  • Individual fibres noted for being polygonal with thick walls and a broad irregular lumen.

  • Properties:

    • Density: 1.48 gm/cc

    • Length: 5-12 feet

    • Color: Yellow to brown

    • Natural silky lustre, coarse to touch.

  • Jute exhibits low extension under stress and minimal recovery.

Applications of Jute

  • Utilized in hessian cloth, sacks, carpets, wall coverings, canvas, geotextiles, and backing for rugs.