Frequently Asked Question

Chemical reactions of cotton fibers are very important, both in the textile industry and in the laboratory. Cotton is composed mostly of cellulose, a polysaccharide made up of glucose units linked together by β-1,4-glycosidic bonds. The chemical reactions that cotton undergoes can be classified into four main categories:

1) Reactions with acids

Cotton can be treated with acids to improve its properties, such as its strength, lustre, and dye uptake. The most common type of acid treatment is mercerization, which involves treating cotton with a concentrated solution of sodium hydroxide. This causes the cotton fibers to swell and become more crystalline, resulting in an increase in strength and lustre. Mercerized cotton also dyes more evenly than untreated cotton.

2) Reactions with bases

Cotton can also be treated with bases to improve its properties. The most common type of base treatment is scouring, which involves treating cotton with a solution of sodium carbonate or sodium hydroxide. This removes impurities from the cotton fibers, such as waxes, oils, and pectins. Scouring also makes the cotton fibers more receptive to dyes.

3) Reactions with oxidizing agents

Cotton can be treated with oxidizing agents to improve its resistance to fire and mildew. The most common type of oxidizing agent used for this purpose is hydrogen peroxide. Hydrogen peroxide reacts with the cellulose in cotton to form peroxycellulose, which is a more stable compound than cellulose. Peroxycellulose is less likely to catch fire or to be attacked by mildew.

4) Reactions with reducing agents

Cotton can be treated with reducing agents to improve its softness and drape. The most common type of reducing agent used for this purpose is sodium borohydride. Sodium borohydride reacts with the cellulose in cotton to form hydrocellulose, which is a softer and more pliable compound than cellulose. Hydrocellulose is also less likely to wrinkle or crease.