Cotton is the most common textile fiber. Almost three quarter of our textile fabrics are made from cotton. Cotton is also blended with other natural as well as man made fibers to develop a variety of Textiles. At present, almost sixty countries of the world are producing cotton. Cotton fabrics were made by the ancient Egyptians and by the earliest of Chinese civilizations using different techniques. Samples of cotton fabrics have been found in Indian tombs dating back to year 3000 B.C. There is no doubt about the fact that spinning and weaving of cotton was started by Indians. Later, this technique was adopted by European countries. It is natural cellulosic fiber. It has hairy growth on the seeds of plant named Genus Gossipium which is cultivated in tropical areas.
a) Cotton Crop:
The cotton is an annual crop. It is sown in March to April and the crop is ready to be picked in September to October.
b) Formation of Fiber:
Cotton seed is sown in spring. After two to three months, many creamy white flowers appear, which turn pink towards the end of the first day. On the third day, the flower dies to leave a small green seed pot or ball. After a few days, fibers start growing around the cotton seed. The growth of cotton fibers carries on throughout the ball ripening period.Â Each cotton seed may produce as many as twenty thousand fibers on its surface and a single ball contains about 150,000 fibers or more. The ball itself is called fruit.
c) Fiber Growth:
For the first six days, the growth of young cotton fiber is comparatively slow. For the next 15 days, it is much more rapid. Then, for the next three days, it grows more slowly until the length wise growth come to sudden stop. During the period of rapid growth, the cotton fiber is in state of a thick walled tube of cellulose with one end attached to the seed. After the stoppage of length wise growth , the cell opens and the finer is ready to be picked in a few days.
Cotton picking is carried out by hands during the autumn. As the balls on the plant do not mature all at the same time, field has to be picked, over several times. Mechanical picking has also been developed but it is not in universal use.
Many varieties of cotton plant are grown commercially in different areas of the world, under a wide range of growing conditions. As a result, there are many different grades and qualities of cotton which vary widely in their properties and characteristics.
The assessment of cotton is a difficult job, requiring great experience and skill. In general, quality is linked directly to the fiber length. Cotton is specified into following categories with respect to its fiber length.
Varieties of Cotton
|Sr. #.||Fiber Length||Quality||Country|
|1||1 to 2.5||Fine Quality||Egypt, USA|
|2||0.5 to 1.30||Medium Quality||USA, Peru|
|3||0.4 to 1||Coarse Quality||Pakistan, China, India|
It is a comfortable fiber with soft hand.
ii. Burning Properties:
It burns with papery smell without forming beads. Scorching begins above 2100C.
iii. Effect of acids and alkalis:
It is severely attacked by acids. Dilute alkalis have no effect on it. Conc. Alkalis reduce its strength.
It dissolves in 80% Sulphuric acid cold.
v. Moisture Regain:
It has good absorbency.
It can be dyed and printed with a variety of dyes and has good fastness properties.