Fabrics & Processing | Market Reports | News & Insights

CLOTHING FROM KENAF FIBRES

Published: October 11, 2019
Author: TEXTILE VALUE CHAIN

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

  1. primary .
  2. secondary
  3. 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

  1. 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 .
  2. 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

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