Fibre Classification, Cotton fibre 1

What is Fibre

Fibre is a unit matter, which possesses the properties of fineness, flexibility and a high ratio of length to thickness to be used in textile. It is a smallest unit used in a textile structure. It may be combined with others to make yarn or fabric.

Classification of Textile Fibres Based on Origin
Classification of Textile Fibres based on its chemical constitution



Cotton Fibre

- It is Natural, Vegetable, Cellulosic fibre

- It is the Oldest fibre reportedly found in found in Indus valley

- Account for more than 50% of total world fibre production

- Botanically belongs to Gossypium Family

- Productive regions accdg. to importance

1. US 2. India 3. Russia 4. Brasil 5. Egypt 6. China

Cotton - basic information

The cotton is a cellulose fibre. The molecules of cellulose is the main substance (97%), and pectin, protein, fats are the other substances present with very less proportion in the cotton fibre. Cotton is chemically resistance. It also withstands the action of water and light for a longer time. Cotton may easily ignite so fire safety rules must be strictly observed.

The properties and structure of cotton fibres are greatly dependent on the degree of maturity of separated fibres. Cotton fibre has the shape of a tube cross-section. The unripe fibre has the shape of thin walled pipe. Unripe fibres are weak and exhibits poor dyeability. The presence of such fibres impairs cotton quality. When the degree of maturity is higher, the pipe has thicker walls, and so fibres become stronger and more flexible. They also become crimpier.

General Concept of pH and Buffer

pH

Pure water contains, in addition to H₂O molecules, a very small proportion of electrically charged ions formed by electrolytic dissociation, according to the equation

Where H ⁺ is a hydrogen ion, hydrion or proton, produced from a hydrogen atom by the loss of an electron and hence carrying positive charge; and OH ^- is a hydroxyl ion, which is negatively charged.

In pure water the two ions are present in equal numbers, since the water is electrically neutral, and at 25⁰C. their concentration is 10^-7 gm-ions per litre. It can be shown (from the law of mass action) that, in any dilute aqueous solution, the product of concentrations of the hydrogen ions and hydroxyl ions is constant and is equal to 10^-14 gm-ions per litre. i.e.,

[H ⁺] X [OH ^-] = 1.0 X 10^-14

When an acid is added to water it introduces hydrogen ions. Hydrochloric acid, for example, introduces hydrogen ions and chloride ions through electrolytic dissociation

Consequently, hydroxyl ions in the water are reduced so that the product of the hydrogen ion concentration and hydroxyl ion concentration remains equal to 10^-14. For example, if the concentrations of hydrogen ions is increased to 10^-3, the concentration of hydroxyl ions must fall to 10^-11. Similarly, alkalies such as caustic soda introduce hydroxyl ions.

and so cause a reduction in the number of hydrogen ions present in the water. Solutions are acid when the number of hydrogen ions exceeds the number of hydroxyl ions, and alkaline when the hydroxyl ions are in excess of the hydrogen ions. The degree of acidity or alkalinity depends entirely on the relative proportions of the two ions.

In pure water at 25⁰C, the hydrogen ion concentration (H ⁺) = 10^-7gm-ions per litre, or –log₁₀ (H⁺) = 7. The pH value of water is therefore 7, the relation between pH and hydrogen ion concentration being expressed by the equation –

i.e., the pH value is equal to the logarithm of the hydrogen ion concentration with negative sign.