Properties of Cotton Fibers – An In Depth Look
Last Updated: Oct 10, 2020
If you’re someone who frequently finds himself/herself busy with textile materials-whether it’s making clothes or doing other art projects- you must have encountered cellulosic materials, especially cotton. It’s the only fiber that gets used the most among other ones.
So, ample knowledge about the properties of cotton will help you to make your tasks that much easier.
Without further chit-chat let’s get it started then.
Fiber is a pliable substance like hair, and its length is one thousand times higher than its diameter.
Now, to be textile fiber, it should fulfill some specific requirements. They should have,
Fibers are of two types: Natural fiber and Man-made fibers. In this article, we will discuss some most common natural fibers.
Natural fibers have different origins. They are found from animals (Wool and silk), vegetables (Cotton, flax), and mineral (Asbestos).
Let’s start with Cotton fiber.
One of the most major fiber in the textile industry is cotton. It can be called the backbone of the world’s textile trade produced in more than 80 countries. Cotton holds more than 50% market share in the apparel and home furnishing.
The word ‘Cotton’ is derived from the Arabic word ‘katan.’ Cotton fiber is collected in the form of unicellular hair from the seed of the cotton plant. Malvales is the order of cotton plant, Malvaceae is the family, Gossypieae is the tribe, and Gossypium is the genus.
More than 5000 years BC, cotton was first used in the middle east and India. During the invasion of Alexander the Great in India, its use spread over Europe. During the eighteenth century, England began to manufacture cotton, and it quickly spread to America. Until the invention of man-made fibers, it was the most important textile fiber. Annually around 25 million tons of cotton are produced annually, and it is increasing at a rate of 2% per annum.
The cotton plant is the purest form of cellulose available in nature. The cotton fiber grows inside an elongated capsule, which is generated in the cotton plant after flowering. The capsule bursts after the growth cycle are completed, and cotton fibers emerge.
The cotton fiber is mainly composed of Cellulose. The chemical composition is,
The fibril structure of cotton fiber consists,
The molecular weight distribution is more uniform. The fibrils in the secondary wall are 10nm thick. They are packed densely and aligned parallelly throughout the fiber lengthwise with 25-35° spiral winding to the fiber axis. That’s why they can provide immense longitudinal strength.
The lumen consists of cell, nucleus, and protoplasm before the ball opening. They are removed in the dried fiber and cause twists and convolution.
Lumen varies in dimension depending on the maturity of the fiber. Matured fiber has more secondary wall and less lumen while in immatured fiber; the lumen is broad and distinct.
There is no effect of cold, weak acid on cotton. Degradation of cellulose occurs when cotton comes into contact with cold concentrated acid, and cotton loses its strength.
Cotton is fully dissolved in highly concentrated mineral acid.
If cotton is boiled in the presence of 1-2% solution of caustic soda, it reduces the weight due to the removal of non-cellulosic matters. It is called scouring.
Treatment of cotton with 11-16% Caustic soda or 15-25% Sodium Hydroxide with or without tension increases the affinity and luster of cotton.
Cellulase produced by many of the micro-organisms causes biodegradation to cotton. Copper naphthenate and polychlorophenols can prevent the attack of micro-organisms on cotton.
Effect of water: Polar -OH groups present in cotton easily attract water, and water easily penetrates into the cellulose network. The ready penetration of water between the fibrils and amorphous region causes swelling of cotton.
Cotton fiber show higher strength in wet condition than dry due to swelling. The screw shapes arrangements of fibrils in cotton are pressed more firmly against each other due to swelling.
Cotton is highly hygroscopic due to the presence of a large number of -OH groups and so contains moisture in normal dry conditions.
Cotton fiber is highly resistant to thermal decomposition, but it is dependent on the heat and time of the heating.
Prolonged heating at 100°C – No visible change.
Heating several hours at 120°C – Litlle or no change in strength. Begins to turn yellow.
Heating below 250°C – no effect in the crystalline region. Only the amorphous region is affected.
Heating at 250-270°C – The crystalline region starts to be affected.
Instant decomposition occurs if further heating is carried out over 300°c.
Cotton fibers turn yellow and gradually losses their strength due to long time exposure in sunlight. In the presence of atmospheric oxygen, particularly high temperature and moisture cause oxycellulose formation, and so degradation of cellulose occurs.
Shorter waves of visible light and UV light causes the main damage. Exposure to sunlight for 940 hours will cause a 50% loss of the strength of cotton.
This effect is dependent on the structure of the goods. The presence of metal content also increases the sensitivity of cotton to daylight.
|1||Short staple||3/8 inch – 1 inch||Low(Low-grade fiber)||Little or no luter||13-22 micron||Coarser below 20s Ne||Inidan and asiaric cotton|
|2||Medium staple||0.5 inch – 1.25 inch||Medium||Medium||12-17 micron||Medium count 20s-34s Ne||American upland cotton|
|3||Long-staple||1 inch – 2.5 inch||High(Top quality)||Lustrous||10-12 micron||Fine count, 34s Ne and above||Sea island cotton, Egyptian cotton, American Pima.|
Fibrils are composed of microfibrils, which are the smallest morphological unit of the cellulose molecule. They constitute the cell wall of the cellulose. Generally, microfibrils are of 3.5nm diameter while finer microfibrils can be of 2nm.
During the opening time of cotton balls, the fibers dry. The removal of intermolecular water and fluids from the lumen causes cylindrical fibers to form twists or convolutions. Cotton matured fibers dry into flat twisted ribbon form. Generally, 200-300 per inch convolutions are available in a fully matured cotton fiber.
When the growth of cotton fiber comes to an end before maturity, it is known as dead fiber. Simply, they are immature fibers. Thinner cell walls can recognize them. Also, immature fiber does not become kidney or oval-shaped. Often, they show ‘U’ shaped cross-section. In commercial cotton, 10-30% of immature fibers are present.
Neps are detectable entanglements having hard central knots. The mechanical processes such as harvesting, ginning, cleaning, carding, and combing affect the amount of neps in cotton. The immature fiber is more flexible and tends to bend and tangle to form neps.
The fiber properties, mainly its fineness and maturity along with the level of biological contamination(seed coat fragments, barks, stickness), are responsible for the tendency of cotton fiber to nep. They will appear as defects in yarns and fabrics, so neps are undesirable. Removal of neps is generally very costly and sometimes impossible.
Second layers of short fuzzy hairs in some cultivated cotton are known as linters. The length of the linters is less than ¼ inch. They should be removed by combing to produce high-quality yarn.
They are used for making special photographic papers, and also as the raw material for acetate fibers.
We hope we were able to provide you with enough knowledge about the properties of cotton and other important factors.
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