The natural fibres are vegetable, animal, or mineral in origin. Vegetable fibres, as the name implies, are derived from plants. The principal chemical component in plants is cellulose, and therefore they are also referred to as cellulosic fibres.
The fibres are usually bound by a natural phenolic polymer, lignin, which also is frequently present in the cell wall of the fibre; thus vegetable fibres are also often referred to as lignocellulosic fibres, except for cotton, which does not contain lignin.
Cellulose is a fibrous material of plant Origin and the basis of all natural and man-made cellulosic fibres. The natural cellulosic fibres include cotton, flax, hemp, jute, and ramie. The major man-made cellulosic fibre is rayon, a fibre produced by regeneration of dissolved forms of cellulose.
Cellulose is a polymeric sugar (polysaccharide) made up of repeating 1,4-8-an hydro glucose units connected to each other by 8-ether linkages.
The long 1inear chains of cellulose permit the hydroxyl functional groups on each anhydrous glucose unit to interact with hydroxyl groups on adjacent chains through hydrogen bonding and van der Waal s forces. These strong intermolecular forces between chains, coupled with the high linearity of the cellulose molecule, account for the crystalline nature of cellulosic fibres.
Cotton is the most commonly used natural cellulosic fibre. Cotton fibres grow from the seeds in the boll (seedpod). Each boll contains seven or eight seeds, and each seed may have up to 20,000 fibres growing from it.
Coir is from the fibrous mass between the outer shell and husk of coconuts. It is a stiff fibre. It is usually used to make highly durable indoor and outdoor mats, rugs, and tiles.
Kapok fibre is from the seed of the Java or Indian kapok tree. The fibre is soft, lightweight, and hollow. It breaks down easily and it is difficult to spin into yarns. It is used as fiberfill and as the stuffing for pillows. It used to be used as a stuffing for lifejackets and the mattresses on cruise ships because it is very buoyant.
Milkweed has properties similar to those of kapok.
Flax is one of the oldest textile fibres, but its use has declined since the invention of power spinning for cotton. Flax fabric is linen, although the word linen is now often used to refer to table, bed, and bath fabrics made from other materials.
Ramie fibres are 4 to 6 inches long. The fibres are whiter and softer than flax. Ramie does not retain dyes well unless it is dry-cleaned. Ramie is strong for a natural fibre, but it lacks resiliency, elasticity, and elongation potential. It is resistant to mildew, insects, and shrinkage. It is used for apparel, window treatments, ropes, paper, and table and bed linens.
Hemp is similar to flax. The fibres range in length from 3 to 15 feet. Hemp production is illegal in the U.S. Hemp has a low environmental impact; it does not require pesticides. It produces 250% more fibre than cotton and 600% more fibre than flax on the same amount of land. Hemp plants can be used to extract zinc and mercury pollutants from soil. Hemp is used for ropes, apparel, and paper. Potheads are willing to pay inflated prices for hemp apparel because it is related to the marijuana plant.
Jute is one of the cheapest textile fibres, and one of the weakest cellulosic fibres. Jute has poor elasticity, elongation, sunlight resistance, mildew resistance, and colourfastness. It is used to produce sugar and coffee bagging, carpet backing, rope, and wall coverings. Burlap is made from jute.
Piña fibres are from the leaves of the pineapple plant. It is used to make lightweight, sheer, stiff fabrics for apparel, bags, and table linens. It is also used to make mats.
Abaca is from a member of the banana tree family. The fibres are coarse and very long (up to 15 feet). It is a strong, durable, and flexible fibre used for ropes, floor mats, table linens, apparel, and wicker furniture.
Classification of Vegetable Fibers
Vegetable fibres are classified according to their source in plants as follows:
- The bast or stem fibres, which form the fibrous bundles in the inner bark (phloem or bast) of the plant stems, are often referred to as soft fibres for textile use
- The leaf fibres, which run lengthwise through the leaves of monocotyledonous plants, are also referred to as hard fibres.
- The seed-hair fibres, the source of cotton, which is the most important vegetable fibre. There are >250,000 species of higher plants; however, only a very limited number of species have been exploited for commercial uses (<0.1%).
The fibres in bast and leaf fibre plants are integral to the plant structure, providing strength and support. In bast fibre plants, the fibres are next to the outer bark in the bast or phloem and serve to strengthen the stems of these reed-like plants.
The fibres are in strands running the length of the stem or between joints. To separate the strands, the natural gum binding them must be removed. This operation is called retting (controlled rotting).
For most uses, particularly for textiles, this long composite-type strand fibre is used directly; however, when such fibre strands are pulped by chemical means the strand is broken down into much shorter and finer fibres, the ultimate fibres.
The long leaf-fibres contribute strength to the leaves of certain nonwoody, monocotyledonous plants. They extend longitudinally the full length of the leaf and are buried in tissues of a parenchymatous nature. The fibres found nearest the leaf surface are the strongest.
The fibres are separated from the pulp tissue by scraping because there is little bonding between fibre and pulp; this operation is called decortication. Leaf fibre strands are also multicelled in structure.
Ancient humans used cordage in fishing, trapping, and transport, and in fabrics for clothing. Rope and cord making started in Paleolithic times, as seen in cave drawings. Rope, cords, and fabrics were made from reeds and grasses in ancient Egypt (400 BC). Ropes, boats, sails, and mats were made from palm leaf fibres and papyrus stalks and writing surfaces, known as papyrus, from the pith section.
Jute, flax, ramie, sedges, rushes, and reeds have long been used for fabrics and baskets. Jute was cultivated in India in ancient times and used for spinning and weaving. The first true paper is believed to have been made in southeastern China in the second century AD from old rags (bast fibres) of hemp and ramie and later from the bast fibre of the mulberry tree.
World markets for vegetable fibres have been steadily declining in recent years, mainly as a result of substitution with synthetic materials.
Jute has traditionally been one of the principal bast fibres (tonnage basis) sold on the world market; however, the precipitous decline in jute exports by India indicate the decreasing market demand for this fibre that has been vitally important to the economies of India (West Bengal), Bangladesh, and Pakistan.
Natural Cellulosic Fiber Characteristics