Cotton Fiber

 

What is the botanical classification of cotton?

 Botanical classification of Cotton:

 

•         Cossypium harbaceum: Plant length: 3¢-6¢

                                            Flower colour:  yellow.

 

•         Gossypium hirsutum: Plant length: 6¢

                                         Flower colour:  Red

•         Both are mainly cultivated in America and India.

 

•         Gossypium peruvianum:

        They are mainly produced in Peru and other South American countries.

 

•         Gossypum barbedense: Plant length: 6¢-15¢

                                            Flower colour:  Yellow.

•         They produce fine silky Sea Island cotton.

 Mention some important/major cotton cultivating country?

Major cotton cultivating countries:

•         The main cotton producing countries are USA, India, Russia, Egypt, Brazil, USSR, China, Mexico, Pakistan, Turkey, Argentina Peru etc. The USA produces almost one-fifth the total crop

Environment of cotton cultivation:

•         Cotton cultivation mainly takes place in tropical and sub tropical climates sunshine heavy rainfall; higher humidity is required for cotton cultivation.

•         Sufficient sunshine is necessary for cultivation while frost will kill the plants

•         Cotton plants can survive in dry but best cultivation can be done in place where rain fall is 20” to 60” per year.

•         Irrigation is necessary when rainfall is less.

 

Cultivation of cotton:

•         Seed planted.

•         Two weeks later two leaves appear on the plant.

•         At five or six weeks later, the first flower appears.

•         At eight to nine weeks the first flower blooms.

•         Seed hairs start to grow inside the bolls.

•         For 16-18 days, fiber length and perimeter achieved.

•         For the next 22-50 days, cellulose is deposited inside the fibers.

•         When cellulose deposition stops, the bolls dry and cracks to open.

•         These bolls are picked up manually or by machine. This picking period is continue for 1-3 months.

•         Then ginning is done to collect the cotton fibers.

Consequence process of cotton fiber production:

•         The cotton seeds are usually shown by machine is continuous stream in raw three to four apart.

•         When the plants are a few inches high, the rows must be thinned by cutting out the undesired plants (chopping).

•         Upland cotton goods to a height of about four feet and blooms two to the three months after planting.

•         The blossoms last but a days and when they fall of the boll begins to develop.

•         These seeds pods or bolls contain the seeds to which the fibers are attached.

•         When the cotton is ripe, the bolls burst exposing a soft, fluffy mass of fibers.

•         The cotton must be picked soon after the bolls open to prevent the fibers from    

      beaming discolored and dirty from exposure to the sun and weather.

What is ginning?

Ginning:

      The freshly picked cotton has seeds in it, this cotton is called seed cotton. The treading is done in this condition also, but normally the treading is done after separation of the fibers from their seed. So, the process, involves to separate the cotton fibers from seeds is called ginning.

What is the objective of ginning?

Objects of ginning:

•         To separate fibers fully from its seeds.

•         To collect seeds and waste together.

•         To collect fiber without any faults.

•         To separate whole fiber.

Write down the types of ginning?

Types of ginning:

•         Saw ginning

•         Roller ginning

•         Macarthy ginning

Saw ginning: →

  What is procedure of saw ginning?

 Procedure of saw ginning:

      ●    The cotton with seed is stored in hopper feeder by feed table or air flow.

•         Spiked roller throws the cotton with seed on grid bar.

•         The discs of saw gin permits to entry of seed free fiber through the hole of bar.

•         The empty path of bars (both sides of saw teeth) permits to entry the fibers but not seeds.

•         The separated seeds fall on conveyors.

•         The cotton lints are separated from saw teeth by proper air flow.

•         The separated cotton lints is transported by conveyor pipe.

 What is roller ginning?

Roller ginning: →                                                     1. Feed hooper.

                                                                                                        2. Feed roller.

                                                                                                        3. Spiker drum.

                                                                                                        4. Net.

                                                                                                        5. In clined net.

                                                                                                              6. Drum.

                                                                                                        7. Ejecting drum.

                    .                                                                                         8. Accelerating drum.

                                                                                                        9. Functional roller
             

                                                                                                      10. Backing of roller.

                                                                                                      11. Doffing roller.

                                                                                                      12. Perforated sheet.

What is procedure of roller ginning?

The working procedures:

•         The seeded fiber comes in contact with feed roller by the help of feed hooper.

     

●    The seeded fibers are embedded on the two feed roller and are feed to spiked   

       roller.

•         The trash are removed by the action of spike and are stored on trash chamber by perforated sheet.

•         Then seeded fiber pass through inclined net by air flow and attached to the spiked drum. Here accelerating drum separates the cotton fiber and pass it.

•         The accelerating drum transports the cotton fibers.

•         Rough surface of functional roller takes only fibers and the seeds are retained on backing roller.

•         The doffing roller separates the fibers from functional roller and transports through delivery pipe and the seeds fall on conveyor.

 

 

Classification of cotton fiber according to maturity:

1)                  Mature fiber: Well-developed secondary sell wall and very small humen.

2)                  Immature fiber: Fibbers with thinner secondary sell wall, larger lumen.They can not exhaust the dye molecules properlyin dyeung or printingthats why  they produce paler shade in dyeing.

3)                  Dead fiber: So called dead fibers have essentially only the primary cell wall .The lumen occupied the bulk of fiber .They remain undyed in dying.

 

Bangladeshi cotton:

Mainly American cotton are produced in Bangladesh, Commercially hybrid cotton are producing at Meherpur, Jessore,Kustia and Gazipur.The quality or Bangladeshi cotton is improving now. Length, colour, maturity are also very good. It is possible to produce minimum 60^s yarn from Bangladeshi cotton fibers.

 

Chemical composition of raw cotton:

Component	Main location	Relative amount (%)
Cellulose	Secondary wall	86.8
Oil and waxes	Cuticle	0.7
Pectins	Primary was	1.0
Carbohydrate	Primary was	0.5
Proteins	Lumen	1.2
Salts	Lumen	1.0
Water		6.8
Others		2.0

 

The oils and waxes of cotton consists of:

1)                  Glycerides, which are readily saponifiable oils and fats.

2)                  Waxes which are difficult to saponify.

3)                  Unsaponifiable oils

4)                  Free fatty acids.

5)                  Traces of soaps.

 

 

Grading of cotton:

In order to grade the quality of raw cotton, the rating is done according to the level of the length, fineness, strength, colour, lusture, natural strands and impurities in the fiber. These are divided in different ways according to the production land.

 

Quality of cotton:  Quality of cotton depends on-

·         Colour.

·         Staple length.

·         Fineness.

·         Strength.

·         Maturity.

·         Trash content.

·         Uniformity ratio.

 

Considerable points of grading of cotton:

The assessment of cotton is carried out traditionally by the cotton ‘classer’ who depends upon personal skill and long experience in judging cotton quality by inspection and feel.

 In arriving at his assessment, the classer takes note of (1)The staple length,(2)The colour and (3)The amount of impurity in the cotton and the quality of its preparation.

 

Grading of cotton of different countries:

         (From high grade to low grade)

American cotton	Egyptian cotton	Indian cotton
Middling fair	Extra fine	Super choice
Strict good middling	Fine	Choice
Good middling	Good	Super fine
Strict middling	Fully good fair	Fine
Middling	Good fair	Fully good
Strict low middling	Fair	Good
Low middling		Fully good fair
Strict good middling
Ordinary
Good ordinary

 

Polymer system of cotton fiber:

Cotton is a crystalline fiber, cellulosic  polymer. The repeating unit in the cotton polymer is cellubiose which consists of two glucose units. Its polymer system is about 65-70%crystalline and corresponding about 35-30%amorphous.              

Degree of polymerization:   2000+

Functional group:   OH,    Cell-CH₂OH        

 

Cross sectional structure of cotton fiber:  

1.                  Cuticle: the outermost layer of cotton is known as the cuticle and is a thin film of fats, pectines and waxes.

2.                  Primary cell wall: Inside the cuticle the primary wall is composed mainly of cellulose in which the fibers are arranged in a criss-cross pattern.

3.                  Secondary cell wall:

• Under primary wall, secondary wall is composed of cellulose which constitutes the balk of the fiber.

unknown.

 

Convolution:

The mature fiber can be recognized by the  Under the microscope, the cotton fiber looks a twisted ribbon or a collapsed and twisted tube. These twists are called convolution. Convolution of Egyptian cotton: 230 /cm and of Indian cotton: 60/cm.

 

Chemical structure of cotton fiber:  

 

Features (structural) of cellulose:   

• Cellulose is a polymer of  ₿– D glucose.
• Branchless linear large polymer.
•   ₿-D glucose are linked by   ₿-glycocydic bond.

·         Bond is made between C₁ and C₄ atom of  ₿ -D glucose.

·         Molecular weight is above 5,00,000.

·         One cellulose polymer contains 300-1500 glucose polymer.

 

Chemical Characteristics:

• Water insoluble but soluble in NaOH and CS₂ mixture, Ammoniacal Cu (OH) ₂ etc.
• Do not react with I_2.

Properties of cotton fiber:

1.         Molecular structure: Cellulosic.

2.         Physical properties:

i)          Length: .3 cm to 5.5 cm.

ii)        Diameter: 16 to 20 microns.

iii)              Cross section: Kidney shape

iv)               Colour: White, grey, cream.

 

3. Tensile properties:

i) Tenacity(gm/den): 3.0-5.0  (In dry state)

                                    3.6-6.0   (In wet state)

ii) Elasticity: Elongation at break 3.0-7.0%

iii) Resiliency: Low.

iv) Moisture regain: 8.5%and raised to around

                                    25-30% water at 100% Relative humidity.

v) Specific gravity: 1.54          

4.. Chemical properties of cotton fiber:

i) Effects of bleaches: – Resistance to bleach, but H₂O₂, NaOCl, NaOCl₂, Ca (OCl)Cl are used as bleaching agents for cotton processing.

ii) Effects of acids and alkalis: Dissolved in high concentrated mineral acids such as HCl, H₂SO₄ but high resistant to alkalis that’s why NaOH, Na₂CO₃, and used for scouring of cotton. Concentrated NaOH is also used for cotton mercerizing.

iii) Effect of organic solvents: Have resistant ability to most organic solvents such as dry cleaning agents.

v)                 Effect of heat: Cotton has an excellent resistance to degradation by heat. It begins to turn yellow after several hours at 1200c and decomposes markedly at 1500c as a result of oxidation.

vi)               Effect of sunlight: There is a gradual loll of strength when cotton is expressed to sunlight and the fiber turns yellow.

vii)            Effect of insects: Cotton is not attacked by moth grubs or beetles.

viii)          Micro-organism: Cotton is attacked by fungi and bacteria.

ix)               Dye ability: Direct, Reactive, Sulfur and Vat dye.

 

Faults of cotton fiber:

Þ    Neps : Small groups of entangled fibers, which form at cotton processing. In spinning neps are difficult to eliminated or to comb. They impair the quality and outward appearance of yarns.

Þ    Fiber strings: Strongly roped groups of fibers of different shapes. The same as neps, fiber strings appear at cotton processing. They can be well combed in spinning but as neps may appear which are difficult to eliminate.

Þ    Coils: Slightly roped groups of fibers. Their presence is undesirable as they easily form neps and strings. Mainly short fibers and ill fibers are form this type of faults. This presence renders difficult yarn production and impairs the quality.

Þ    Trash: Trash is defined as particles above 500 micro meters trash typically accounts for 1%to 5% of baled cotton. Mainly bits of leaves, boll parts, and stems are defined as trash.

Þ    Motes: Small and immature seeds and their fragments which fall through the grates in grains.

Þ    Crushed seed: Parts of seeds crushed during primary cotton processing.

Þ    Bearded motes: Small bits of seed hull with fibers. Formed at seed crushing during primary cotton processing and at further seed cult to eliminate.

Þ    Dust: Defined as representing particles between 50 and 500 micrometer, dust maybe exhausted into a waste collector.

 

Chemical reaction of cellulose:

Cellulose is an active chemical with three hydroxyl groups attached to each glucose residue. Those in the 2 and 3 positions behave as secondary alcohols; the hydroxyl ion the 6 positron acts as a primary alcohol.

These hydroxyl groups take part in normal chemical reactions and a great number of cellulose esters and ethers have been made.

Oxidation of cellulose gives rise to oxycellulose.

 

Increased strength of cotton fiber for wetting:

When water molecules penetrate into the interior of fiber, it lies between the fibrils and into the amorphous regions of the fiber polymer where they can easily form hydrogen bonds with free cellulose hydroxyl groups and the water absorption causes the swelling of the secondary sell was but little fiber elongation. Although absorbed water acts as a plasticizer, it also cements the cellulose chains and fibrils together by hydrogen bonding .These are the reasons of increasing the strength of cotton fiber for wetting.

 

Chemically Modified cotton:

1. PA cotton: Treatment of cotton with acetic anhydride in acetic acid converts it to partially acetylated cotton (PA cotton). This material looks like original cotton. It has no smell and is non-toxic. But in many of its properties, PA cotton differs from the normal cotton fibers. Most important of all, it has a great resistance to heat than cotton. At 250° C, cotton looses one-third of its strength in three minutes where as PA cotton in similar yarn looses one third of its strength after twenty-five minutes at the same temperature. For these properties of PA cotton it can be used to make laundry press cover and lasts for long time.

• It also withstands the attacks of micro-organism of mildew and rotting.
• It has chemical resistance. In 20% HCl, it looses its one-third of its strength in eight hours, where as ordinary cotton looses about two-thirds.
• Better electrical insulator.

Uses:

Sand bags, fishing nets and lines, weather resistance fabric etc.

 

2. AM COTTON: When cotton is treated with 2-aminoethylsulphuric acid in sodium hydroxide, another form of chemical modification takes place. The fiber retains its essential structure, but its properties have changed. The new fiber is known as AM cotton.

3. CM cotton: Cotton treated with monochloroacetic acid and then sodium hydroxide is converted into CM cotton.

4. CN Cotton: Treatment of cotton with acrylonitrile yields a chemically modified cotton described as cyanoethylated(CN).

5. PL cotton: Treatment with propiolactone converts cotton into a modified cotton described as PL cotton.

 

Average maturity of cotton fiber:

The proportion of immature fiber to mature fiber is called average maturity, which is an important factor in determining the quality of the cotton.

In ordinary commercial cotton, about one quarter of the fibers will be immature. Sometimes, the proportion of mature cotton reaches 90 per cent, but such high ‘maturity count’s are rare. In commercial upland cotton, maturity counts of more that 84 per cent are described as ‘hard-bodied’. Average maturities like between 68 and 78 percent and cotton with maturity counts below about 67 percent are regarded as immature.

Absorbency of cotton fiber:

The molecules are called hygroscopic nature. Cotton is very absorbent fiber. Cotton consists – OH group, which is polar. Its positive portion affects the negative portion of water and negative portion affect the H⁺ of H₂O. So, cotton can absorb easily in water.

The amorphous polymer system also liable for its being absorbent. It is the crystalline regions are too small for the water molecules. The amorphous region, which has enough empty places, permits easy entry of water and this it is more absorbent.

 

Lingo cellulose & Pecto-celloulose:

             Pecto cellulose: Cellulose fiber containing cotton and pectin is called pecto – cellulose.

 

             Ligno-cellulose: Cellulose fiber containing lignin is called ligno cellulose.

 

 

Diference between pecto and lingo-cellulose:

Properties	Pecto-celloulose	Ligno-cellulose
Strength in all condition	Stronger	Weak
Stiffness	Moderate	High
Resiliency	Good	Bad
Alkali	Non resistant	Resistance to alkali
Bleach	Affected by it	No Affected by it
Cellulose	High	Medium
lusture	Low	High

Ultimate:

The unit cell beyond which subdivision is not possible without loss of fiber’s identity.

End uses of cotton:

• Cotton fabrics combine remarkable durability with attractive wearing qualities. Cotton fabrics have a pleasant feel or handle. They are cool in hot weather.
• Cotton is used in great quantity as a fabric for hot-weather wear; it is able to provide warmth as well.
• Cotton garments are therefore comfortable and cool, passing on the perspiration from the body into the surrounding air.
• The absorbency of cotton makes it an excellent material for house-hold fabrics such as sheets and towels too.
• Cotton is widely used in making rain wear fabrics.
• The versatility of cotton has made it into the most widely used of all textile fibers. Cotton is made into every type of garment and house-hold fabric. It goes into boots and shoes, carpets and curtains, clothing and hats. Heavy cotton yarns and materials are used for tyre cords and marquees, tarpaulins and industrial fabrics of all description.