Cotton is a natural vegetable fibre produced in the cotton plant in many countries of the world even in bangladesh also. Some important properties of cotton fibres are discussed very briefly below:
1. Length:
physically the individual cotton fibres consist of a single long tubular cell. Its length is about 1200-1500 times than its breadth. Length of cotton fibre varies from 16 mm to 52 mm depending upon the type of cotton.
Indian cotton: 16-25mm.
American cotton: 20-30mm.
Sea island cotton: 38-52mm.
Egyptian cotton: 30-38mm.
2. Finenss:
longer the fibre, fibre the fibre in case of cotton fibre. It is expressed in term of decitex and it varies from 1.1 to 2.3 decitex (discussed in yarn count)
Indian = 22-2.3 dtex
American = 2.1-2.2 dtex
Egyptian = 1.2-1.8 dtex
Sea island = 1.0-1.1 dtex.
Finess may be more in case of immature fibre. So it is necessary to express maturity with finenss.
3. Strength and extension:
cotton fibre is fairly strong among natural fibres in relation to tenacity which is 3-3.5g/dtex. Its tensile strength is between wool & silk fibre but disadvantage is low extension at break which is 5-7%.
4. Elastic properties:
Recovry from deformatiom of cotton fibre, yarn or fabric from applied load is very low. By applying heat it can't be achieved. This property can be achieved by 1. Chemical treatment to becomes harsher due to chemical treatment 2. Blending or mixing of cotton with elastic fibrc, e.g. Polyester (67% polyester +33% cotton), blend ratio depends on the end use of the fabric. The initial modulus is fairly high = 0.5 g/dtex (wool = 0.25 g/dtex).
5. Coross section:
Cross-section of cotton fibre is some what ribbon like. The cell wall is rather thin and the lumen occupies about 2-3 of the entire breadth and shows up very prominent in polarized light. Fibre cross section becomes round when mercerized.
6. Effect of chemica:
a) water- when cotton is wetted, its strength increases about 10%-20%. Under standard atmosphere its regain is 8.5%.
B) Alkali- Cotton in alkali shrinks & changes its x-sectional shape which is seen in mercerization. Slack mercerization is done for special affects. In 20% caustic solution, 2 minute treatment under tension is sufficient for mercerization. As a result cotton becomes stronger, round in x-section and lusterous. Absorption of dye or chemical capacity also increases. Mercerization is done for hing quality cotton yarn, fabric, sewing thread etc. In dilute alkali a very little change.
C) Acid- cotton is susceptible to damage by the action of acid. This action is utilized in woollen industry in carbonizing the wool to remove vegetable or cellulosic materials in 5% H2SO4 acid solution.
D) solvent- cotton is quite good in solvent washing.
7. Effect of heat:
Cotton fibre, yarn, fabric when brought near flameitburns & smellislike burningpaper.Its doesnotmelts.
8. Biological agents:
mildew, bacteria, grow in worm damp condition and attack the fibres and damage it. It can be protected by special chemical treatment.
9. End use:
Because of relatively high cost, however, relatively ease properly e.g. Easy wash it is extensively used in the following fields:
Household- towel, sheets, table cloth, certain etc.
Apparel- Shirts. Under wear's , socks, suits, saree, blouse etc.
Industrial- canvas, string, tape
Medical- Bandages, gauge, etc.
Organic Cotton - Moral Fibre Part 1