The textile industry uses many different kinds of fibres as its raw materials .Some of these fibres were known and used in the earlier years of civilization , as well as in modern times . Other fibres have acquired varied degrees of importance in recent years The factors influencing the development and utilization of all these fibres include are
- The ability to be spun .
- The availability in sufficient quantity .
- The cost or economy of production.
- The desirability of their properties to consumers.
Among the list of Natural fibres various vegetable fibres gained importance in textile industries like Cotton boll , Flax stalk, Jute stalk , Hemp or abaca stalk., Agave leaf, Kapok tree, Rhea or China grass , Coconut husk and pineapple leaf .
Besides the above the textile industry uses other natural fibres in addition to those already studied .Each has its field of usefulness .Some have qualities that make them suitable for purposes that none of the above fibres could fulfill satisfactorily .Others can be used as acceptable substitutes or even adulterants , as long as the finished goods fulfill the purpose for which they are intended and the selling price is in line with the value of the product.
In Africa , there is a plant Hibiscus cannabinus in the Malvaceae family . which has long been used as a source of fibre for making cordage and coarse fabrics . The fibre is known as Kenaf, Guinea Hemp , Mesta , Bimli, Ambary , Ambary Hemp , Deccan Hemp , Dah and Bimlipatum Jute . As ,however, in recent years the name Kenaf seems to be adopted for it almost universally. Grown for over 4,000 years in Africa where its leaves are consumed in human and animal diets , the bast fibre is used for cordage, and the woody core of the stalks burned for fuel. Kenaf is a soft bast fibre from the kenaf plant . The fibre is long , light yellow to gray , and harder and more lustrous than jute . Like jute , it is used for twine , cordage , and other industrial purposes . Kenaf has been grown in India for thousand of years , but the fibre was unknown in Western Europe until about two hundred years ago .It has been used since then as a sacking fibre , but did not really arouse any great interest until World War II The shortage of jute during and after the war stimulated production of Kenaf in U.S Cuba ,Mexico and other countries . Kenaf is one of the allied fibres of jute and shows similar characteristics .
Most of the world’s Kenaf is grown in India , Bangladesh , Central Asia ,Africa and some Central American countries and to a small extent in southeast Europe . This crop was not introduced into southern Europe until the early 1900 s . Kenaf is being investigated by researchers as a source of paper fibre and in blends with cotton.
PRODUCTION AND PROCESSING –
It is an annual or biennial herbaceous plant ( rarely a short –lived perennial ) growing to 1.5 -3.5 m tall with a woody base . It grows well in the hot damp climate of tropical countries . The stems are 1-2 cm diameter , often but not always branched . The leaves are 10-15 cm long long , variable in shape , with leaves near the base of the stems being deeply lobed with 3-7 lobes , while leaves near the top of the stem are shallowly lobed or unlobed lanceolate . The flowers are 8-15 cm diameter , white ,yellow or purple ; when white or yellow ,the centre is still dark purple . The fruit is a capsule 2 cm diameter , containing several seeds.
It matures in 100 to 1000 days . About 9,000 cultivars are produced.
The stem contains two types of fibres
- primary .
- secondary
- In other words they are also called as fibrous and non-fibrous materials.
The methods used for harvesting and processing kenaf are similar to those used for jute The stalks are retted and then beaten to free the fibre from unwanted material.
The time at which Kenaf is harvested is important from the point of view of both fibre yield and fibre quality . If the plants are harvested when they are too young , the yield of fibre will be low , and many of the fibres will be immature and soft , and may be lost when the fibre is extracted .
The best time to harvest the plants for fibre , therefore , is when about ten of the flowers are in bloom –at which time the fibre is at its best quality and can be separated from the other parts of the plant without too much difficulty . When the plants are ready for harvesting , they are cut by following two ways
- By hand with a matchet in the same way as jute is harvested . It is carried out in areas where labour is available and cheap .
- By a cutter- bar mounted on a tractor . The cutter cuts a swath of about 3 ft in one operation. It is quicker than the hand method.
The fibre is extracted from the stems of the plants by retting in water in the same way as jute is retted.The leafy tops of the stems are cut off before retting . The retting takes place in ditches, ponds ,etc . The retting time takes about 5-15 days time. When retting is completed , the fibre is stripped from the stems as with jute , and is then washed in clean water and dried in sun. The principles involved in retting Kenaf are much the same as those involved in retting flax or jute , although it is possible that different micr-organisms may be responsible for the retting process .
In India Kenaf is used on a large scale by the jute mills , which use as much as 40-60% of the fibre in admixture with jute , for Hessian and sacks . It is spun on any ordinary jute machinery without any modification . The fibre is graded according to colour,lustre and percentages of extraneous matter ( stalks,dirt etc) contained in it .
The fibre is not popular with jute spinners , as they consider that it is rather woolly and is not so easily spun as jute , at least on jute machinery. There is no doubt that it is quite suitable for spinning into yarns for the coarser types of bags , although it cannot be used for making the fine yarns for which jute is particularly employed.
STRUCTURE AND PROPERTIES –
Kenaf is a pale – coloured fibre which contains less non-cellulosic material than jute . It has the lustre which is characteristic of many bast fibres .
Kenaf has a breaking strength similar to that of low –grade jute , and it is weakened only slightly when wet .
The cells of kenaf are short , reaching only 6 mm ( ¼ in ) in length . They are cylindrical and the surface is striated and irregular . The lumen varies greatly in thickness at different points in the cell , sometimes disappearing altogether .
Seen in cross-section , the cell of Kenaf fibre is polygonal and has a thick wall .It is coated with a layer of lignin . The fibre ends are thick and blunt .
In comparison with jute , the Kenaf fibre is somewhat coarser and less supple , although matured Kenaf fibre has more lustre and is stated to be more resistant to rotting .It is not so fine as jute but it has a high breaking strength and breaking length.
The composition of Kenaf fibre is as follows ;
Water – 7-10%.
Cellulose – 51-52%.
Hemicellulose – Nil
Lignin – 17%
Ash – 2.9% to 4.2% .
The dyes used are Acid dyes, Basic dyes , Reactive dyes , and Vat dyes. The scouring and bleaching process is same as per Flax and Ramie fibres. Hydrogen peroxide , an environmentally –safe bleaching agent that does not create dioxin , has been used with much success in the bleaching of Kenaf .
It can be compared with Hemp fibre also.
Comparison of Properties of Kenaf fibre
| Fibre | Ultimate stress
Mpa |
Strain % | Modulus ,Gpa | Density ,Kg/m3 |
| Ramie | 800-1000 | 1.7 – 3.0 | 50-80 | 1560 |
| Pineapple | 400-1000 | 08 – 1.6 | 34-82 | 1440 |
| Banana | 500-700 | 2-3.5 | 7.7 – 20.8 | 1350 |
| Sisal | 500-600 | 3.0-7.0 | 9.4-16.0 | 1450 |
| Coir | 100-200 | 15-20 | 4.0-6.0 | 1150 |
| Jute | 400-700 | 1.5-2.0 | 2.5-15 | 1450 |
| Hemp | 400-700 | 1.6-2.5 | 35 | 1480 |
| Kenaf | 350-600 | 2.5-3.5 | 40 | 1500 |
| Cotton | 300-600 | 5.0-8.0 | 4.0-12.0 | 1520 |
| Flax | 900-1200 | 2.0-3.0 | 100 | 1540 |
USES OF KENAF FIBRE –
The main uses of Kenaf fibre have been rope, twine, coarse cloth ( similar to that made from jute ), and paper . It is mainly used for canvas and sacking . Some of the better quality fibre is made into carpet materials . It is also used for animal bedding and feed .Emerging uses of kenaf fibre include engineered wood , insulation , and clothing –grade cloth . Panasonic has set up a plant in Malaysia to manufacture Kenaf fibre boards and export them to Japan . It is used as oil absorbent , soil –less potting mixes , animal bedding , packing material ,organic filler for blending with plastics for injection molding . It is used as an additive for drilling muds , and various types of mats , such as seeded grass mats for instant lawns and moldable mats for manufactured parts and containers .
The use of Kenaf in paper production offers various environmental advantages over producing paper from trees . It has been found that Kenaf newsprint made for stronger , brighter and cleaner pages than standard pine paper with less detriment to the environment . Due partly to Kenaf fibres being naturally whiter than tree pulp , less bleaching is required to create a brighter sheet of paper .
Various reports suggest that the energy requirements for producing pulp from Kenaf are about 20 % less than those for wood pulp , mostly due to the lower lignin content of Kenaf .
In India various spinning mills development department are working on Kenaf in making yarns by blending with cotton, polyester , etc
