Coconut or Coir Fiber: Properties, Manufacturing Process and Applications

Last Updated on 18/02/2021

Coconut or Coir Fiber: Properties, Manufacturing Process and Applications

Md. Ferdus Alam
Department of Textile Engineering
Southeast University
Email: ferdus.j@gmail.com

 

What is coconut fiber?
Coconut fiber is extracted from the outer shell of a coconut. It is also called coir fiber or coco fiber. It is the natural fiber of the coconut husk where it is a thick and coarse but durable fiber. The common name, scientific name and plant family of coconut fiber is Coir, Cocos nucifera and Arecaceae (Palm), respectively.

There are two types of coconut fibers, brown fiber extracted from matured coconuts and white fibers extracted from immature coconuts. Brown fibers are thick, strong and have high abrasion resistance. White fibers are smoother and finer, but also weaker. Both brown and white coir consist of fibers ranging in length from 4-12 in (10-30 cm). Those that are at least 8 in (20 cm) long are called bristle fiber. Shorter fibers, which are also finer in texture, are called mattress fiber. A 10-oz (300-g) coconut husk yields about 3 oz (80 g) of fiber, one-third of which is bristle fiber. Industries based on coir have developed in many coconut producing countries especially India, Tanzania, Kenya, Bangladesh, Burma, Thailand, Sri Lanka, Nigeria, Ghana etc.

Coconut Tree, Coconut and Coconut fibers
Fig: Coconut Tree, Coconut and Coconut fibers

Chemical Composition of Coconut Fiber:

  1. Lignin………………………..…45.84%
  2. Cellulose…………………….…43.44%
  3. Hemi-Cellulose………………………….00.25%
  4. Pectin’s and related Compound…………03.00%
  5. Water soluble…………………….05.25%
  6. Ash……………………………….02.22%

Physical Properties of Coconut / Coir Fiber:

  1. Length in inches…………6-8
  2. Density (g/cc)………………….1.40
  3. Tenacity (g/Tex)………………10.0
  4. Breaking elongation%…………..30%
  5. Diameter in mm………….0.1 to 1.5
  6. Rigidity of Modulus……….1.8924 dyne/cm2
  7. Swelling in water (diameter)…………5%
  8. Moisture at 65% RH…………10.50%

Manufacturing Process of Coconut Fiber:

Harvesting and husking of coconut:
The fruits are harvested when still green to obtain the best quality coir. Husk usually forms 35.45 percent of the weight of the whole nut, when ripe. Husks from ten to eleven month old nuts have been found to give superior quality fiber possessing a golden yellow color. The fiber from the husk is extracted on a commercial scale, either by natural retting process or by mechanical decortications.

Husking of coconut by Machine
Fig: Husking of coconut by Machine

Retting of coconut fiber:
Retting is a curing process during which the husks are kept in an environment that encourages the action of naturally occurring microbes. This action partially decomposes the husk’s pulp, allowing it to be separated into coir fibers and a residue called coir pith. Freshwater retting is used for fully ripe coconut husks, and saltwater retting is used for green husks.

Retting of coconut or coir fiber
Fig: Retting of coconut or coir fiber

For freshwater retting, ripe husks are buried in pits dug along riverbanks, immersed in water-filled concrete tanks, or suspended by nets in a river and weighted to keep them submerged. The husks typically soak at least six months.

For saltwater retting, green husks are soaked in seawater or artificially salinated fresh water. Often this is accomplished by placing them in pits along riverbanks near the ocean, where tidal action alternately covers them with sea water and rinses them with river water. Saltwater retting usually takes eight to 10 months, although adding the proper bacteria to the water can shorten the retting period to a few days.

Mechanical techniques have recently been developed to hasten or eliminate retting. Ripe husks can be processed in crushing machines after being retted for only seven to 10 days. Immature husks can be dry milled without any retting. After passing through the crushing machine, these green husks need only be dampened with water or soaked one to two days.

Extraction of Coconut Fiber:
After retting, the husks are taken out of water and washed. Outer skin peeled of, placed on wooden blocks and beaten with a wooden mallet for separating the fibers from the pith. After fibers are separated from the pith, these are cleaned and then spread on shade for drying. The fibers spread for drying are occasionally beaten and tossed up with poles to remove the remnants of pith and impurities still adhering to the fiber.

Extraction of coconut fiber
Fig: Extraction of coconut fiber

Spinning:
Spinning of coir yarn is mainly a cottage industry in India and abroad. It is produced either by wheel spinning or hand spinning or mechanized spinning. Handspun yarn is soft and the twist and thickness are even. Wheel spun yarn has a hard twist; it is stronger and more uniform in size and twist than handspun yarn. The classification of coir yarn is based on variations of color, twist, pitch, scorage etc. and also area of production like; Anjengo, Aratony, Alapat, Beach, Rope yarn, Parur, Muppiri etc.

Weaving:
Coir yarn is treated with dilute solution of sulphuric acid, which improves its color and gives a certain amount of brightness for the production of mats, Coir mats, fiber mats, especially mats, Mattings, rugs, mourzouks, carpets etc.

Dyeing and Printing:
Color and design play an important part in the marketing of coir products. Dyed yarn is exported to Australia for the manufacture of matting. The following dye stuffs are employed in coir dyeing. Chrysodin YS, Bismarck Brown, Methyl Violet, Malachite Green, Magenta, Naphthalene orange, Naphthalene Red, Naphthalene Green etc.

Applications of Coconut Fiber:

White coir spun into yarn is used in the manufacture of rope and, thanks to its strong resistance to salt water, in fishing nets.

coir rope
Fig: Coir rope

Brown coir is used in sacking, brushes, doormats, rugs, mattresses, carpet, insulation panels and packaging. In Europe, the automobile industry upholsters cars with pads of brown coir bonded with rubber latex.

coir mat and carpet
Fig: Coir mat and carpet

Geotextiles made from coir mesh (at left) are durable, absorb water, resist sunlight, facilitate seed germination, and are 100% biodegradable.

coir geotextiles
Fig: Coir geotextiles

Coir peat, a residue of milling, is gaining economic importance as mulch, soil treatment and a hydroponic growth medium.

Coco peat
Fig: Coco peat

Coir fiber Liners that are environment friendly products and are used for indoor gardening. These products offer an outstanding drainage and aeration to roots and prevent the plant from root rot.

decorative coir products
Fig: Decorative coir products

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