Chemical Composition of Natural Fibers (Cotton, Jute, Flax, Hemp, Ramie, Sisal, Coir, Wool and Silk)

Last Updated on 18/08/2022

Chemical Composition of Natural Fibers:
Every fiber consists of some chemical elements. Such as cotton contains cellulose, protein, pectin etc. Wool contains keratin, dirt, suint etc. The chemical composition and reactivity of natural fibers differ from each other leading them to have particular affinity for specific stain or dye types. Chemical composition of natural fibers are given below:

Chemical Composition of Natural Fibers

Chemical composition of cotton:
The main component of cotton is cellulose, though the precise proportion varies with the source of the cotton and the growing conditions. Also, for a given cotton fiber, the composition differs between the fiber surface and the interior of the fiber. An average composition by percentage of (dry) cotton fiber is shown in below Table.

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Chemical Composition of Cotton Fiber:

Cellulose95%
Protein1.3%
Ash1.2%
Pectin substance0.9 %
Oil, Fat and Wax0.6%
Sugar0.3%
Organic acids0.8%
Pigmenttrace
Others1.4%

Chemical composition of jute:
Jute, chemically being lignocellulosic in nature, comprises mainly polysaccharides and lignin. Although a number of minor components, such as pectin inorganic salts, nitrogenous substance, colouring mater, wax, etc. are found in it. The detail of chemical composition of the jute fiber is given in below Table.

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Chemical Composition of Jute Fiber:

Cellulose65.2%
Hemicellulose22.2%
Lignin10.8%
Water soluble1.5%
Fats and wax0.3%

Chemical composition of flax:
The main component of the flax fiber is cellulose, while secondary components are waxes, fats, hemicellulose, lignin and pectin. The chemical composition of the fibers is presented in below Table.

The average chemical compositions of flax stem and fiber are as follows:

Stem:

Cellulose49–60%
Hemicellulose10–25%
Lignin17–23%,
Pectin3–4%
Fats and waxes1.5–3%

Fiber:

Cellulose85–87%
Hemicellulose7– 9%
Lignin2.5–4%,
Pectin1.5–2.5%

Chemical composition of hemp fiber:
The distribution of chemical constituents of hemp stems varies significantly between the outer bast and the woody core.

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The average chemical compositions of hemp fiber are as follows:

Cellulose77.77%
Hemicellulose10%
Lignin6.8%
Pectin2.9%
Fat & wax0.90%
Water soluble1.73%

Chemical composition of sisal fiber:

Cellulose71.5%
Hemicellulose18%
Lignin6%
Pectin2.3%
Fat & wax0.5%
Water soluble1.7%

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Chemical composition of ramie:
Ramie is a multicellular bast fibre, by and large cellulosic in nature, having very little lignin and hemicellulose. The inter-cellular binding constituents present in significant amounts are natural gums and pectinous matters. The cells of ramie fiber may be as long as 40–45 cm, cylindrical in nature and characterized by thick walls and narrow, curved lumens. The surface of the cell is marked by distinct ridges.

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Chemical Composition of Ramie Fiber:

Cellulose68.6–76.2
Hemicellulose13.1–16.7
Lignin0.6–0.7
Pectin1.9
Fats and wax0.3
Other extractives6.1

Chemical composition of coir fiber:

Husk14%
Fiber22%
Pith16%
Kernel30%
Water18%

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Chemical composition of wool fiber:

Keratin33%
Dirt26%
Suint28%
Fat12%
Mineral matter1%

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Chemical Composition of Keratin:

Carbon50%
Hydrogen12%
Oxygen10%
Nitrogen25%
Sulfur3%

Chemical composition of silk fibers:
Silk cocoons are composed of proteins, which account for more than 95% of its content; other impurities, such as waxes, mineral salts, and ash, constitute about 4–5%. The general composition of silk fiber is detailed in below Table. The wild silk cocoon shell has a lower sericin content and higher levels of wax, minerals, ash, and other impurities. The raw silk fiber extracted from a silk cocoon is subjected to a degumming process to remove sericin from it.

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Chemical Composition of Silk Fiber:

Fibroin76%
Sericin22%
Fat & wax1.5%
Mineral salt0.5

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