Before building its first city, its first castles, man made fabrics to cover himself. And he continued to manufacture them for thousands of years using fiber as raw
material from plants or animals.
In plants, fibers form the backbone that supports the soft and pulpy parts of leaves, roots, and stems. In animals, fibers are found in meat, skin, muscle, and fur. All these fibers are extremely thin (their length is about two thousand times their thickness) and consist of a long chain of molecules roughly parallel to each other. Plant fibers like cotton and flax are cellulose, which is a compound of carbon, hydrogen, and oxygen; animal fibers such as wool and silk are made from many kinds of proteins, compounds of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur (
in wool).
To meet the needs of current manufacturing methods and modern machinery, fibers must be strong, durable, flexible, shiny, and nearly uniform in size. They are expected to be at least 12 mm (preferably 35 mm or more) but are often just a few centimillimeters. They should be rough or wrinkled, so they intertwine tightly when twisted to form a yarn, thereby increasing resistance to slippage and preventing the fibers from pulling apart when subjected to tension.
Only some of the
natural fibers meet all or most of these requirements, among them cotton, very strong and resilient; wool, warm and uncreasable; silk, soft and shiny; and linen, crisp and bright. Cortical fibers, which include jute, hemp, sisal, and ramie, are strong and resilient, but too rough for clothing and are used especially for ropes, twine, bags, and mats.
Since the capabilities of
natural fibers are limited, the
textile industry fully exploits man-made fibers that have been produced over the last 75 years. Between 1890 and 1920, chemists discovered how to make many varieties of cotton fiber from pulp and wood. The most successful were rayon viscose rayon and cellulose acetate, which are still manufactured on a large scale. Initially, rayon fibers were called artificial silk for their silky smoothness and great luster.
Like all natural fibers, rayon absorbs water and thickens when washed, but there is a key difference: natural fibers remain strong when wet and swollen, and cotton even becomes stronger; rayon, however, when it absorbs an amount of water equal to its weight, loses about a third of its strength. This weakening is only temporary, because once dry, rayon regains all its initial properties. It is clear, however, that the quality of a fiber is better if it does not lose its strength when washed.
The discovery of nylon by Carothers was particularly important because nylon, which is the first of the so-called synthetic fibers, is at least two times stronger than cotton, absorbs a small amount of water, and keeps its shape intact even when wet. The success of nylon led to the discovery of other synthetic fibers with similar properties.
No fiber has all the advantages or disadvantages of all we have discussed. Natural fibers and rayon fibers first resist heat and those organic solvents that are sometimes used in dry cleaning. On the other hand, they are attacked by moths and bacteria. The new synthetic fibers, however, are not attacked by insects and bacteria, but they can be damaged by a hot iron.
Since rayon and
natural fibers quickly absorb water, they are particularly suitable for clothing that easily comes into contact with sweat. For the same reason, they can be dyed and finished with water-soluble substances. But fabrics made of synthetic fibers repel water and therefore require more complex and expensive dressing and dyeing processes. Also, synthetic fibers require special procedures to be spun and woven.
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