The Chemistry Of The Cotton Fiber

By Dr. BOWMAN.

Every chemist knows that cotton is chiefly composed of cellulose, CHO, with some other substances in

smaller quantities. This, although the usual opinion, is only true in a partial sense, as the author found on

investigating samples of cotton from various sources. Thus, while mere cellulose contains carbon 44.44

per cent. and hydrogen 6.173, he found in Surat cotton 7.6 per cent. of hydrogen, in American cotton 6.3

per cent., and in Egyptian cotton 7.2 per cent. The fact is that along with cellulose in ordinary cotton there

are a number of celluloid bodies derived from the inspissated juices of the cotton plant.

In order to gain information on this subject, the author has grown cotton under glass, and analyzed it at

various stages of its life history. In the early stage of unripeness he has found an astringent substance in

the fiber. This substance disappears as the plant ripens, and seems to closely resemble some forms of

tannin. Doubtless the presence of this body in cotton put upon the market in an unripe condition may

account for certain dark stains sometimes appearing in the finished calicoes. The tannin matter forms

dark stains with any compound or salt of iron, and is a great bugbear to the manufacturer. Some years

ago there was quite a panic because of the prevalence of these stains, and people in Yorkshire began to

think the spinners were using some new or inferior kind of oil. Dr. Bowman made inquiries, and found that

in Egypt during that year the season had been very foggy and unfavorable to the ripening of the cotton,

and it seemed probable that these tannin-like matters were present in the fiber, and led to the disastrous

results.

Although the hydrogen and oxygen present in pure cellulose are in the same relative proportions as in

water, they do not exist as water in the compound. There is, however, in cotton a certain amount of water

present in a state of loose combination with the cellulose, and the celluloid bodies previously referred to

appear to contain water similarly combined, but in greater proportion. Oxycellulose is another body

present in the cotton fiber. It is a triple cellulose, in which four atoms of hydrogen are replaced by one

atom of oxygen, and like cellulose forms nitro compounds analogous to nitro glycerine. It is probable that

the presence of this oxycellulose has a marked influence upon the behavior of cotton, especially with dye

matters. The earthy substances in cotton are also of importance. These are potassium carbonate,

chloride, and sulphate, with similar sodium salts, and these vary in different samples of cotton, and

possibly influence its properties to some extent. Then there are oily matters in the young fiber which, upon

its ripening, become the waxy matter which Dr. Schunk has investigated. Resin also is present, and

having a high melting point is not removed by the manipulative processes that cotton is subjected to.

When this is in excessive amount, it comes to the surface of the goods after dyeing.

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Chemical Composition of Cotton Fiber

The chemical composition of cotton fiber consists of ninety-five percent cellulose, one point three percent protein, one

point two percent ash, point six percent wax, point three percent sugar, and .8 percent organic acids, and other

chemical compounds that make up three point one percent (Wakelyn pg. 15). The non-cellulose chemicals of cotton

are usually located in the cuticle of the fiber.

The non-cellulose chemicals of cotton consist of protein, ash, wax, sugar and organic acids. Cotton wax is found on

the outer surface of the fiber. The more wax found on cotton the greater the surface area of cotton there is; finer

cotton generally has more cotton wax (Wakelyn pg. 16). Cotton wax is primarily long chains of fatty acids and

alcohols. The cotton wax serves as a protective barrier for the cotton fiber. Sugar makes up point three percent of the

cotton fiber, the sugar comes from two sources plant sugar and sugar from insects. The plant sugars occur from the

growth process of the cotton plant (Wakelyn pg. 17). The plant sugars consist of monosaccharide, glucose and

fructose. The insect sugars are mainly for whiteflies, the insect sugars can cause stickiness, which can lead to

problems in the textile mills. Organic acids are found in the cotton fiber as metabolic residues. They are made up of

malic acid and citric acid.

The non-cellulose chemicals of cotton are removed by using selective solvents. Some of these solvents include:

hexane, chloroform, sodium hydroxide solutions, non-polar solvents, hot ethanol, and plain water (Wakelyn pg. 15).

After removing all the non cellulose chemicals, the cotton fiber is approximately ninety-nine percent cellulose.

Works Cited

Wakelyn, Phillip. CRC Press (2006) 15-18. 18 Sep 2008 <http://books.google.com/books?

id=3FUVqE3zczwC&pg=PP8&dq=cotton+fiber+information&sig=

ACfU3U2V4FgM-QMQCxP6eHNZkiX4knzNJQ#PPA17, M1>.

By Chelsey Collop

Cotton Fiber and its Chemical Structure

The chemical composition of cotton, when picked, is about 94 percent cellulose; in finished fabrics is it 99 percent

cellulose. Cotton contains carbon, hydrogen, and oxygen with reactive hydroxyl groups. Glucose is the basic unit of

the cellulose molecule. Cotton may have as many as 10,000 glucose monomers per molecule. The molecular chains

are arranged in long spiral linear chains within the fiber. The strength of a fiber is directly related to chain length.

Hydrogen bonding occurs between cellulose chains in a cotton fiber. There are three hydroxyl groups that protrude

from the ring formed by one oxygen and five carbon atoms. These groups are polar meaning the electrons

surrounding the atoms are not evenly distributed. The hydrogen atoms of the hydroxyl group are attracted to many of

the oxygen atoms of the cellulose. This attraction is called hydrogen bonding. The bonding of hydrogen's within the

ordered regions of the fibrils causes the molecules to draw closer to each other which increases the strength of the

fiber. Hydrogen bonding also aids in moisture absorption. Cotton ranks among the most absorbent fibers because of

Hydrogen bonding which contributes to cotton's comfort.

The chemical reactivity of cellulose is related to the hydroxyl groups of the glucose unit. Moisture, dyes, and many

finishes cause these groups to readily react. Chemicals like chlorine bleaches attack the oxygen atom between or

within the two ring units breaking the molecular chain of the cellulose.

Works Cited

Kadolph, Sara J., and Anna L. Langford. Textiles. 8th ed. Upper Saddle River, N.J.: Prentice-Hall, Inc., 1998.

Smith, Betty F., and Ira Block. Textiles in Perspective. Englewood Cliffs N.J.: Prentice-Hall, Inc., 1982.

By Melissa Deffenbaugh

Copyright © 2008 Department of Textile and Apparel Management

University of Missouri

137 Stanley Hall, Columbia, MO 65211

Telephone: 573.882.7317 Fax: 573.882.3289

Chemical Structure of Cotton