Vegetable fibers

In this chapter production ,phsical and chemical properties ,physical and chemical structures as well as end use applications of cotton and other bast fibers will be studied.

1. CHAPTER TWO LECTURE 2 ON NATURAL FIBERS OF VEGETABLE ORIGIN BAHIR DAR UNIVERSITY (EiTEX) By : Bademaw Abate(Lecturer)

2. NATURAL FIBERS OF VEGETABLE ORIGIN   Cotton Flax Jute Hemp Sisal  

3. Cotton Almost pure cellulose, cotton is the world's most widely used natural fibre and still the undisputed "king" of the global textiles industry. The  cotton  fibre grows on the seed of a variety of plants of the genus  Gossypium . Of the four cotton  species cultivated for fibre, the most important are  G. hirsutum , which originated in Mexico and produces 90% of the world's  cotton , G. barbadense , of Peruvian origin, which accounts for 5%. World average  cotton  yields are around 800 kg per hectare.

4. Cont… Cotton Fibres - the king of fibres Cotton is a soft staple fibre that grown in a form known as a boll around the seeds of the cotton plant, a shrub native to tropical and subtropical regions . Cotton-cultivation Cotton is grown in more than sixty countries of the world, but United States, India, Russia, Brazil, Egypt and China are some of the largest producers of cotton. The planting season varies depending on the geographical location. When the cotton bolls are ripe, they burst, exposing a soft mass of cotton fibres.

5. Cont… In former times cotton harvesting was a hand operation, requiring considerable amount of hard labour . Now machine harvesting is also practised . In the picking method the cotton sections of the opened balls are removed from the burs leaving the burs on the stalk. In the pulling method, the open balls and burs are removed together. Sometimes leaves and other foreign matters also find their way in the cotton collected. Hence, pulled cotton is not as clean as picked cotton.

6. Ginning-Cotton   The picked cotton contains about 66% seeds, 33% cotton fibers and small amounts of leaf and dirt. The separation of seeds and fibers is carried out by a process called ginning. The complete ginning process consists of :- preliminary cleaning and drying of cotton separation of seeds from fibers, which are sometimes called cotton lint or linters, pressing and wrapping into a bale.

7. Cotton Fiber Structure and Components

8. Cont…. Each cotton fiber is composed of concentric layers. The cuticle layer on the fiber itself is separable from the fiber and consists of wax and pectin materials. The primary wall, the most peripheral layer of the fiber, is composed of cellulosic crystalline fibrils. The secondary wall of the fiber consists of three distinct layers. All three layers of the secondary wall include closely packed parallel fibrils with spiral winding of 25-35 o  and represent the majority of cellulose within the fiber .

9. Cont…. The innermost part of cotton fiber- the lumen- is composed of the remains of the cell contents. Before boll opening, the lumen is filled with liquid containing the cell nucleus and protoplasm. The twists and convolutions of the dried fiber are due to the removal of this liquid. The cross section of the fiber is bean-shaped, swelling almost round when moisture absorption takes place.

10. Raw Cotton Components: 80-90% Cellulose 6-8% Water 0.5 - 1% Waxes and fats 0 - 1.5% Proteins 4 - 6% Hemicelluloses and pectin’s 1 - 1.8% Ash

11. Chemical structure of cotton Cellulose is a polymer consisting of an hydroglucose units connected with 1,4 oxygen bridges in the beta position. The hydroxyl groups on the cellulose units enable hydrogen bonding between two adjacent polymer chains. The degree of polymerization of cotton is 9,000-15,000. Cellulose shows approximately 66% crystallinity.

12. PHYSICAL PROPERTIES OF COTTON   Fiber Length: Length of cotton fibre varies from 16mm to 52 mm depending upon the type of cotton. Length Uniformity: Low uniformity index shows that there might be a high content of short fibers, which lowers the quality of the future textile product. length uniformity uniformity index [%] Very High >85 High 83-85 Intermediate 80-82 Low 77-79 Very Low <77

13. Cont… Fineness of cotton fiber: Longer the fibre, finer the fibre in case of cotton fibre. It is expressed in term of decitex and it varies from 1.1 to2.3 decitex. Strength and extension of cotton fiber: Cotton fibre is fairly among natural fibres in relation to tenacity which is 3-3.5g/ dtex . Its tensile strength is between wool and silk fibre but disadvantage is low extension at break which is 5-7%. Elastic properties of cotton : Recovery from deformation of cotton fibre, yarn or fabric from applied load is very low. By applying heat it can’t be achieved. This property can be achieved by :- 1.Chemical treatment to improve crease recovery, but the problem is the materials become harsher due to chemical treatment . 2. blending or mixing of cotton with elastic fibre, e.g. polyester, blend ratio depends on the end use of the fabric. The initial modulus is fairly high=0 5 g/ dtex (wool=0.25 g/ dtex )

14. Cont...    Color: There is five recognized groups of color: white, gray, spotted, tinged, and yellow stained. As the color of cotton deteriorates, the process ability of the fibers decreases . Trash: A trash measurement describes the amount of non-lint materials (such as parts of cotton plant) in the fiber. The values of trash content should be within the range from 0 to 4%.

15. CHEMICAL PROPERTIES OF COTTON Cotton swells in a high humidity environment, in water and in concentrated solutions of certain acids, salts and bases. The swelling effect is usually attributed to the sorption of highly hydrated ions. The moisture regain for cotton is about 7.1~8.5% and the moisture absorption is 7~8%. Cotton is attacked by hot dilute or cold concentrated acid solutions. Acid hydrolysis of cellulose produces hydro-celluloses. Cold weak acids do not affect it.

16. Cont.. The fibers show excellent resistance to alkalis. There are a few other solvents that will dissolve cotton completely. One of them is a copper complex of cupramonium hydroxide and cupriethylene diamine . Cotton degradation is usually attributed to oxidation, hydrolysis or both. Oxidation of cellulose can lead to two oxy-cellulose .

17. Uses of cotton An estimated 60% of  cotton  fibre is used as yarn and threads in a wide range of clothing, most notably in shirts, T-shirts and jeans, but also in coats, jackets, underwear and foundation garments. Cotton  is also used to make home furnishings, such as draperies, bedspreads and window blinds, and is the most commonly used fibre in sheets, pillowcases, towels and washcloths. Its is made into specialty materials suitable for a great variety of applications: fire-proof apparel, cotton wool, compresses, gauze bandages, sanitary towels and cotton swabs. Industrial products containing  cotton  include bookbindings , industrial thread and tarpaulins.

18. Flax One of nature's strongest vegetable fibres, flax was also one of the first to be extracted, spun and woven into textiles The plant Flax  fibres obtained from the stems of the plant  Linum usitatissimum  are used mainly to make linen. The fibre Like cotton,  flax  fibre is a cellulose polymer, but its structure is more crystalline, making it stronger, crisper and stiffer to handle, and more easily wrinkled.  Flax  fibres range in length up to 90 cm, and average 12 to 16 microns in diameter. They absorb and release water quickly, making linen comfortable to wear in hot weather.

19. Uses of flax Fine and regular long  flax  fibres are spun into yarns for linen textiles. More than 70% of linen goes to clothing manufacture, where it is valued for its exceptional coolness in hot weather - the legendary linen suit is a symbol of breezy summer elegance. Linen fabric maintains a strong traditional niche among high quality household textiles - bed linen, furnishing fabrics, and interior decoration accessories .

20. Cont… Shorter  flax  fibres produce heavier yarns suitable for kitchen towels, sails, tents and canvas. Lower fibre grades are used as reinforcement and filler in thermoplastic composites and thermoset resins used in automotive interior substrates, furniture and other consumer products.

21. Jute The strong threads made from jute fibre are used worldwide in sackcloth - and help sustain the livelihoods of millions of small farmers. The plant Jute  is extracted from the bark of the white  jute   plant, Corchorus capsularis  and to a lesser extent from tossa   jute  ( C. olitorius ). The fibre Dubbed the "golden fibre",  jute is long, soft and shiny, with a length of 1 to 4 m and a diameter of from 17 to 20 microns. It is one of nature's strongest vegetable fibres and ranks second only to cotton in terms of production quantity. Jute  has high insulating and anti-static properties, moderate moisture regain and low thermal conductivity .

22. Uses of jute During the Industrial Revolution,  jute  yarn largely replaced flax and hemp fibres in sackcloth. Today, sacking still makes up the bulk of manufactured jute  products. Jute  yarn and twines are also woven into curtains, chair coverings, carpets, rugs and backing for linoleum. Blended with other fibres, it is used in cushion covers, toys, wall hangings, lamp shades and shoes. Very fine threads can be separated out and made into imitation silk ( below ). Jute  is being used increasingly in rigid packaging and reinforced plastic and is replacing wood in pulp and paper. Geotextiles made from  jute are biodegradable, flexible, absorb moisture and drain well. They are used to prevent soil erosion and landslides 

23. Hemp Easy to grow without agrochemicals, hemp is used increasingly in agrotextiles , car panels and fibreboard , and " cottonized " for clothing. The plant Hemp  fibre is obtained from the bast of the plant  Cannabis sativa L. It grows easily - to a height of 4 m - without agrochemicals and captures large quantities of carbon. The fibre Long, strong and durable, hemp  fibres are about 70% cellulose and contain low levels of lignin (around 8-10%). The fibre diameter ranges from 16 to 50 microns.  Hemp  fibre conducts heat, dyes well, resists mildew, blocks ultraviolet light and has natural anti-bacterial properties. Shorter, woody core fibres ("tow") contain higher levels of lignin.

24. Uses of hemp Hemp  has been used for centuries to make rope, canvas and paper. Long  hemp  fibres can be spun and woven to make crisp, linen-like fabric used in clothing, home furnishing textiles and floor coverings. In China,  hemp  is de-gummed for processing on flax or cotton machinery. Blending with cotton, linen, silk and wool gives  hemp  a softer feel, while adding resistance and durability to the product. In Europe,  hemp  fibres are used mainly in the special paper industry - thanks to lower lignin content, it can be pulped using fewer chemicals than wood.

25. Sisal Too coarse for clothing and upholstery, sisal is replacing glass fibres in composite materials used to make cars and furniture. The plant Sisal  fibre is obtained from Agave sisalana , a native of Mexico. The hardy plant grows well in a variety of hot climates, including dry areas unsuitable for other crops. After harvest, its leaves are cut and crushed in order to separate the pulp from the fibres

26. Cont.. The fibre Lustrous and creamy white, sisal fibre measures up to 1 m in length, with a diameter of 200 to 400 microns. It is a coarse, hard fibre unsuitable for textiles or fabrics. It is strong, durable and stretchable, does not absorb moisture easily, resists saltwater deterioration, and has a fine surface texture that accepts a wide range of dyes.

27. Uses of sisal Sisal  is used in twine and ropes, but competition from polypropylene has weakened demand. But other markets are emerging - today,  sisal  can be found in specialty paper, filters, Geotextiles, mattresses, carpets and wall coverings. It is used as reinforcement in plastic composite materials, particularly in automotive components, but also in furniture. Another promising use is as a substitute for asbestos in brake pads.(It is also the best material for making dart boar. By-products from  sisal extraction can be used for making bio-gas, pharmaceutical ingredients and building material .

28. Thank you!