Jute is one of the cheapest natural fibres. Jute fibres are composed primarily of cellulose (major component of plant fibre) and lignin (major component wood fibre). It is thus a ligno-cellulosic fibre that is partially a textile fibre and partially wood. It falls into the bast fibre category (fibre collected from bast or skin of the plant) along with kenaf, industrial hemp, flax (linen), ramie, etc. The industrial term for jute fibre is raw jute. The fibres are off-white to brown, and 1–4 meters (3–12 feet) long. Jute is the common name given to the fiber extracted from the stems of plants belonging to the genus Corchorus, family Tiliaceae.
Depending on demand, price and climate, the annual production of jute and allied fibres in the world remains around 3 million tonnes.
Sacking and Hessians (Burlap) constitute the bulk of the manufactured products. Sacking is commonly used as packaging material for various agricultural commodities viz., rice, wheat, vegetables, corn, coffee beans etc. Fine Hessian is used as carpet backing and often made into big bags for packaging other fibres viz. cotton and wool.
Formation of Jute Fibers
Jute fibre develops in the phloem or bast region of the stem of the plants; in transverse sections of the stem. They appear as wedge-shaped bundles of cells intermingled with parenchyma cells and other soft tissue.
Extraction of Jute Fibers
The plants are harvested by hand with a sickle and cut close to the ground. The cut stems are then tied into bundles, the leaves removed as much as possible, and the bundles submerged in water for retting. This is the process by which the bundles of cells in the outer layers of the stem are separated from the woody core and form non fibrous matter by the removal of pectins and other gummy substances. The action involves water, microorganisms, and enzymes, and takes between 5 and 30 days to completion, depending on the temperature of the water. Constant supervision is required, and the time of removal is critical, because if the degree of retting is insufficient, the fibre cannot easily be stripped from the woody core and may be contaminated with cortical cells; and if retting proceeds too far. The fibre cells themselves may be attacked and weakened by microorganisms. Stripping the fibre from the stem is done by hand, after which the fibres are washed and dried. A difficulty in the retting procedure is that the thicker parts of the stem take longer to ret than the thinner parts do; consequently, if the butt ends of the stem are fully retted, the top ends are overretted and damaged. This can be avoided by stacking the bundles of stems upright with the butt ends in water for a few days before immersing the whole stem
- Retting process: Retting is the bacterial decomposing of natural glues that adhere the bast fibre to the herd. Traditionally, this is accompanied in one of two ways; either dew retting or water retting. With the former, the swath of the stem material, after mechanical harvesting is left for about 4-6 weeks in the fields for dew and rainfall to affect the process; however, prolonged excessively wet conditions can turn retting to rotting.
- Scutching process: It is a process in which the retted plant is separated or ‘transformed’ into its basic parts: the hurd and the bast fibre. While transforming the plant, the fibres are kept at full length so at the end they can be cut to the length required for further processing.
Application of Jute Fibers
The large historic markets for jute in sacking, carpet backing, cordage, and textiles have decreased over the years as jute has been replaced by synthetics. Fibre from jute can be used in the handicraft industries, to make textiles, to make paper products, or to produce a wide variety of composites.
When the long fibre is separated, the byproduct is a large amount of short fibre and pith material that can be used for such products as sorbents, packing, light-weight composites, and insulation. By utilizing the byproduct of the long fibre isolation process, the overall cost of long-fibre utilization is reduced. The isolated long fibre can then be used to make mats which have value-added applications in filters, geotextiles, packaging, molded composites, and structural and nonstructural composites.
The long bast fibres, like in jute, can be formed into flexible fibre mats, which can be made by physical entanglement, nonwovens needling, or thermoplastic fibre melt matrix technologies. The two most common types are carded and needle-punched mats. In carding, the fibres are combed, mixed, and physically entangled into a felted mat.
Geotextiles derive their name from geo and textile and, therefore, mean fabrics in associated with the earth. Geotextiles have a large variety of uses. They can be used for mulch around newly planted seedlings. Jute fibre mats have good moisture retention and promote seed germination. Low- and medium-density fiber mats can be used for soil stabilization around new or existing construction sites. Steep slopes without roots to hold the soil erode and top soil is lost. Medium- and high- density fibre mats can also be used below ground in road- and other types of construction as natural separators between different materials.
Medium- and high-density fibre mats can be used for air filters. Air filters can be made to remove particulate and/or can be impregnated or reacted with various chemicals as air freshners or cleansers.
Medium and high-density mats can also be used for oil-spill clean-up pillows.
A structural composite is defined as one that is required to carry a load in use. In the housing industry, for example, structural composites are used in load-bearing walls, roof systems, subflooring, stairs, framing components, furniture, etc.
As the name implies, nonstructural composites are not intended to carry a load in use. These can be made from a variety of materials such as thermoplastics, textiles, and wood particles, and are used for such products as doors, windows, furniture gaskets, ceiling tiles, automotive interior parts, molding, etc.
Fibre mats are similar to the ones described for use as geotextiles except, during mat formation, an adhesive is added by dipping or spraying the fibre before mat formation, or it is added as a powder during mat formation . The mat is then shaped and densified by a thermoforming step. Within certain limits, any size, shape, thickness, and density is possible. These molded composites can be used for structural or non-structural applications as well as for packaging, and can be combined with other materials to form new classes of composites.
“Gunny” bags made from jute have been used as sacking for products such as coffee, cocoa, nuts, cereals, dried fruits, and vegetables for many years. While there are still many applications for long fibre for sacking.
Combinations with Other Resources
Composites of agro-based fibre and glass fiber can be made by using the glass as a surface material or combined, as a fibre, with lignocellulosic fibre. Composites of this type can have a very high stiffness-to-weight ratio. The long bast fibres can also be used in place of glass fibre in resin injection molding (RIM) or used to replace, or in combination with, glass fiber in resin-transfer-molding (RTM) technologies.
One of the biggest new areas of research in the value- added area is in combining natural fibres with thermoplastics. Prices for plastics have risen sharply over the past few years, but adding a natural powder or fibre to plastics reduces cost (and in some cases increases performance as well). To the agro-based industry, this represents an increased value for the agro-based component.
Fibre Matrix Thermoplasticization
The approach most often taken involves the chemical modification of cellulose, lignin, and the hemicelluloses to recrystallize/modify the cellulose and to thermoplasticize the lignin and hemicellulose matrix in order to mold the entire lignocellulosic resource into films or thermoplastic composites.
In this type of composite, the thermoplastic is bonded onto the lignocellulosic in such a way that there is only one continuous phase in the molecule.
Jute a versatile, eco-friendly, recyclable and economical fibre. Jute is also often blended with other fabrics like cotton (called JUCO) that are ideal for clothing, accessories and home furnishing. In order to make sophisticated products like fashion garments, jute needs to be blended with fibres like wool, nylon, rayon, acrylic or polypropylene. These blends enrich the fibre in feel, appearance, durability, resilience and washability.
Fancy Bags and Handicrafts
The versatile Jute fibre is now being used to create exciting new products, the most popular one are Hand Bags, Shopping Bags, Luggage Bags, Wallets, Casual Bags and Fashion Bags.