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Cotton Fibers and its Properties

Cotton is a seed fiber, meaning the fiber grows from seeds. It is perhaps the most important of all fibers.

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Cotton is the most important natural textile fiber, as well as cellulosic textile fiber, in the world, used to produce apparel, home furnishings, and industrial products. Worldwide about 40% of the fiber consumed in 2004 was cotton.

Cotton fibers are seed hairs from plants of the order Malvales, family Malvaceae, tribe Gossypieae, and genus Gossypium. Botanically, there are four principal domesticated species of cotton of commercial importance: hirsutum, barbadense, aboreum, and herbaceum. Thirty-three species are currently recognized; however, all but these four are wild shrubs of no commercial value. Each one of the commercially important species contains many different varieties developed through breeding programs to produce cotton with continually improving properties (e.g., faster maturing, increased yields, and improved insect and disease resistance) and fibers with greater length, strength, and uniformity.

The cotton fibers used in textile commerce are the dried cell walls of formerly living cells. Botanically, cotton fibers are trichomes or seed coat hairs that differentiate from epidermal cells of the developing cottonseed. The cotton flower blooms only for one day and quickly becomes senescent thereafter. On the day of full bloom, or anthesis, the flower petals are pure white in most hirsutum varieties. By the day after anthesis, the petals turn bright pink in color and, usually by the second day after anthesis, the petals fall off the developing carpel (boll).

Composition (% Dry Weight)
Constituent Typical % Range %
Cellulose 95.0 88.0–96.0
Protein (%N 6.25)
% N – The standard method of estimating percent protein from nitrogen content
1.3 1.1–1.9
Pectic substances 0.9 0.7–1.2
Ash 1.2 0.7–1.6
Wax 0.6 0.4–1.0
Total sugars 0.3 0.1–1.0
Organic acids 0.8 0.5–1.0
Pigment trace
Others 1.4

Growth

The wild cotton plant was domesticated in Asia, Africa, and South America nearly six thousand years ago. Ancient Egyptians made fine cloth at least four thousand years ago. Their hand-spun cotton was as fine as for today’s best. Today, cotton is grown on 77 million acres in over 80 countries – anywhere the growing seasons are long and hot. Cotton grows on bushes that are three to six feet high. Its flowers last for five to seven days.

The boll is a seedpod about the size of a golf ball. It begins to grow after the flowers drop off. Inside are 7 or 8 seeds, and attached to them are the cotton fibers. Each seed may have as many as twenty-thousand fibers – that’s as many as one hundred fifty thousand individual fibers in each boll!

Cotton is threatened by the boll weevil. It’s a beetle feeds on bolls and the blossoms. Each year the weevil causes around two hundred million dollars of damage to the cotton crop in the US alone. So cotton is treated with insecticides, often by airplanes.

Harvesting

Cotton was once harvested by hand, often by slave labor or tenant farmers. As recently as 1965, over a fourth of the U.S. cotton crop was picked by hand. Today, harvesting cotton is highly mechanized.

Harvesting machines called strippers and pickers efficiently remove the cotton while leaving the plants undisturbed. Spindle harvester, also called a picker, has drums with spindles that pull the cotton from the boll in one or two rows at a time. Even a one-row mechanical picker can do the work formerly done by 40 hand pickers.

In stripper harvesting, the stripper moves along rows of plants, passing them between revolving rollers or brushes that pull off the cotton. Strippers also pull twigs and leaves with the cotton.

Cotton gins separate the fibers, called lint, from the seeds. After ginning, the cotton goes to the bale press that packs it into 480-pound bales about the size of a large refrigerator.

Classing Cotton

Cotton buyers judge cotton on the basis of samples cut from the bales. Skilled cotton classers grade or “class” the cotton according to standards established by the US Department of Agriculture such as cleanliness, the degree of whiteness, length of the fiber, and fiber strength.

The classes pull a sample. They discard most of the cotton until just a pinch of well-aligned fibers remains. They measure the length of the fibers, referred to as staple fibers. Longer staple fibers are higher-grade cotton and are sold at higher prices. Long staples range from 1.1 inches to 1.4 inches long.

Review

  • Cotton is a seed fiber and grows in warm climates.
  • Modern harvesting of the cotton crop is highly mechanized.
  • Cotton is a good choice for clothing for its comfort and easy care.

Properties & Uses

The fibers are sent to a textile mill where carding machines turn the fibers into cotton yarn. The yarns are woven into cloth that is comfortable and easy to wash but does wrinkle easily. Cotton fabric will shrink about 3% when washed unless pre-treated to resist shrinking.

Cotton is prized for its comfort, easy care, and affordability and is ideal for clothing, bedding, towels, and furnishings.

Characteristics of Cotton Fibers and Products

  • Comfortable to wear
  • Natural, cellulosic fiber
  • Made from the cotton boll
  • Absorbs water and “breathes”
  • Slow to dry
  • Resists static electricity build-up
  • Wrinkles easily
  • Can withstand heat, detergents, and bleach
  • About 20% stronger when wet than dry
  • Will shrink unless treated
  • Can be damaged by mildew
  • Can be damaged by prolonged exposure to sunlight
  • Long staple cotton (such a Supima, Pima, Egyptian, and Sea Island) can be woven into smooth, almost silky fabrics.