Starch is often used in fabric weaving to avoid breaking of the thread. It increases the strength of thread and also decreases the friction during weaving. This starch is must to remove before any kind of dyeing or chemical washing of garment. A number of desizing process (removal of starch /size) Â are in practice in industry.
Starch forms a very dark blue-black compound with iodine. The indicator is not disturbed by the presence of iodide (I-). Starch forms an un-stable complex (blue colored) in low concentrations of Iodine. However, this complex is highly stable in high concentrations of Iodine solution (It can’t be decolorized and it spoils the reaction medium). Starch indicator solutions may be synthesized in the laboratory. Alternatively, commercially available preparations are also available.
When a garment is desized, then to check the extent to which starch is removed, a few drops of starch indicator are dropped on the garment. If it changes its color to blue-black, that indicates that desizing process is incomplete and starch is still present there.
Starch or Amylum (C6H10O5)n) is a polysaccharide carbohydrate consisting of a huge number of glucose units joined with one another by glycosidic bonds. Starch is formed by all green plants as an energy store and is a main food source for humans.
Pure starch is a white, tasteless and odorless residue that is insoluble in cold water or alcohol. It is made up by two types of molecules: the linear and helical amylose and the branched amylopectin. Depending on the source plant, starch generally contains 20 to 25 percent amylose and 75 to 80 percent amylopectin.Glycogen, the glucose stockpile of animals, is a more branched form of amylopectin.
The word “starch” is derivative from Middle English sterchen, meaning to harden, which is appropriate since starch can be used as a thickening or glueing negotiator when dissolved in water and heated, giving wheatpaste.
In Textile it is used to decrease breaking of yarns during weaving, the warp yarns are sized. Starch is one of the main agents utilize for cotton sizing. Starch also is used as printing thickener.
Iodine solution is used to test for starch; a blue color points to the existence of starch. The details of this reaction are not yet completely known, but it is thought that the iodine (I3âˆ’ and I5âˆ’ ions) fits inside the twirl of amylose, the charge transfers between the iodine and the starch, and the energy plane spacingâ€™s in the resulting complex match to the absorption spectrum in the visible light region. The strength of the resultant blue color depends on the amount of amylose present.
Starch indicator solution containing of water, starch and iodine is regularly used in redox titrations: in the existence of an oxidizing agent the solution turns blue, in the presence of reducing agent the blue color vanish because triiodide (I3âˆ’) ions break up into three iodide ions, dis-assembling the starch-iodine complex. A 0.3% w/w solution is the typical concentration for a starch indicator. It is made by accumulation 4 grams of soluble starch to 1 litre of heated water; the solution is cooled prior to use keep in mind that starch-iodine compound becomes unstable at temperatures above 35 Â°C).
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.