Advantages of jute as natural bast fibre for different technical textiles

Textiles and products manufactured for technical performance and functional properties are known as technical textiles. Ashis Kumar Samanta looks closely at the use of jute in these textiles.

Clothing is not the only use to which fabric is put. So-called technical textile materials and products are used in a large variety of applications other than normal clothing. They come in twelve major categories. 

For instance, fabric used to package products and crops or cereals including wheat, rice, potato, tobacco, tea leaf and coffee beans is called packaging textile (Pack-Tech). Those used in household furnishing, home crafts and floor coverings are called home textiles (Home-Tech). Fabric used as soil saver for hill slopes, protection materials or as geosynthetics for underlay or overlay in road construction, are geo textiles (Geo-Tech). Cloth used as mulch or as sapling pots or as fruit nets are agricultural textiles (Agro-Tech). Fabric used in automotive furnishings in cars, railways and aviation as components like door panels, tyre cords and fuel filters are automobile textiles (Mobil-Tech).

Those used as rigid fibre reinforced composites for wood and structural substitutes are build textiles (Build-Tech). Fabric used as rope, twine or as conveyor belting and cordage are industrial textiles (Indu-Tech); for use as filter fabric for chimney hot air/gases or effluent are eco-textiles (Eco-Tech/Oeko-Tech); for use as fire retardant, heat and cold insulated or sound insulated or pesticide barrier or rain protection are protective textiles (Pro-Tech); for use as any sports goods from textiles like swim wear, athletic wear, badminton racket etc are sports textiles (Sports-Tech); for use as bandage, suture and leucoplast, sanitary pad are medical textiles (Medi-Tech); and specialised clothing for astronauts, defence services, intelligent textile wear or smart textile wear (chemolinic or chromotropic, thermotropic etc) are clothing textiles (Cloth-Tech). 

To engineer such technical textiles, the selection of high performance fibres and design of right textile products for specific end use are essential. In some major application areas, fabric or fibrous components or their combinations are selected primarily, but not exclusively, for specific performance. These include moisture or water or air transportation, filtration, insulation from heat and thermal degradation. The engineering design and production of such end-use specific technical textiles requires intensive research and development. So, there is need to maintain extensive evaluation standards for suitability in the intended end-use.

Use of commodity fibres for manufacture of technical textile, however, centres around polypropylene, polyester and nylon chiefly, for tensile, flexural and torsional property, fatigue and abrasion resistance, compressional resilience, surface tension, thermal, hydrolic, hygral, sonic behaviour, thermal conductivity/resistance or insulation, electrical conductivity/resistance, microbial resistance, UV resistance, absorbency and breathability. For example, the designer of swimwear as competitive and high performance sports textiles has to design for water repellence and frictionless swimming.

Suitably woven jutefabric can be conveniently coated with different elastomers for products suchas rubberised hospital sheeting, double texture rubberised fabric for luggage,flexible hoods for automobiles and chemical resistant sheets for industrialhouses. High strength and low extensibility, good thermal stability, irregularsurface morphology of jute fibre appears to be advantageous for producing suchitems.

Jute fabric can also belined with aluminium foil. Tea bags produced out of such aluminium foillaminated just fabric have the potential to replace conventionally used,relatively expensive tea bag made from Kraft paper aluminium foil laminate.

Suitably woven unmodified/modified jute and/or jute-cottonand jute-polyester union fabrics may be coated with any one or a suitable blendof any two or more of chlorinated polyethylene, chlorosulphonated polyethylene,polyacrylates, natural rubber, ethylene-octene copolymer, aluminium foillaminate, metallised polyester etc. to develop products such as coatedtarpaulin, conveyer belts carrying food, awnings and canopies, compact

coated textiles, architectural textiles and cost- effective breathable protective aprons for bulk packaging material for tea and other food products.

Jute products coated with natural rubber latex or other materials may also be used as flexible composite materials to produce test fabrics, automobile hoods and covers, canopies and tarpaulin for multipurpose uses. 

Jute home textiles and jute diversified products need to focus on colour, surface texture, look, softness/drape and aesthetics with appealing designs of the products rather than functional performance. This may require specific chemical treatment to improve certain property parameters. Some properties of jute-based products may be improved or incorporated by proper chemical finishing and chemical modification or even by coating or laminating for making it suitable for better performing technical textiles.

The future seems bright for the golden fibre.

The question of bio mimicry points to the shark which swims faster because of its frictionless skin. So, swimwear needs to be given such a finish.

Fabric for speciality clothing needs to be engineered to provide efficient moisture management in varying external conditions. Usually, multilayered fabrics are designed, with a hydrophobic/wicking layer next to the skin and wicking/quick evaporating outer layer with a middle layer for quicker transporting moisture.

If jute-cotton union is to be used as fire protective furnishing fabric, the fire retardant/fire proof finish should give around 35-36 LOI (Limiting Oxygen Index) value and less than 1 or 2 cm char length after burning in standard vertical flammability tester. Smoke generated while burning has to be within specific limits. The product should be toxicity free and eco-friendly for the safety of humans, and it should withstand at least 30 to 50 washes. If, for any reason, the existing standard for other textile fabrics being used in this field cannot be achieved for any particular textile, it should be categorised as a separate class with separate functional performance standards for other fire protective uses like fire retardant brattice cloth in mines, where wash stability may not be that important.

Another example of designing technical textiles for specific end-use will be to designathletic wear for a 200 or 800 metre sprinter/runner. The technical designer has to engineer high performing materials with an inner layer that absorbs perspiration so that the sprinter feels dry and the clothes are not wet. Absorbed perspiration or salty moisture must immediately be transported to the outer layer made of a separate type of fabric, so it can spread and evaporate immediately and the athlete does not feel that the garment is heavy. So, the designer has to come up with a three-layered fabric, like Dupont's Coolmax which uses four or more channels of ultra microporous polyester conjugate fibres in the inner layer, which vertically transport moisture away from the body.

Conventional absorptive technical textile uses ordinary absorbing layers, which are not effective in cold climates or in higher activity levels like athletic wear for sprinters.

Common natural bast and leaf fibres used in technical textile manufacture are jute, flax, ramie, sisal, hemp. Specially manufactured high performing synthetic fibres used are HT/HM polyesters and nylons, ultra high modulus polyethylene (spectra/dyneema), polyaramids (nomex and kevlar), carbon and activated carbon fibres, polybenzoimidazole (PBI), polyimides (PI), polyphenyl sulphides (PPS), polyurethanes (PU) and poly lactic acid (PLA).

Bast and leaf fibres possess higher strength and stiffness and lower extensibility, compared to synthetic fibres. This indicates that these eco-friendly fibres are stronger and dimensionally more stable. Such fibres deserve attention while developing technical textiles. Jute and some other bast and leaf fibres have higher relative strength and modulus per unit cost for producing cost-effective technical textiles compared to competitive synthetic fibre. 

In the light of growing global concern for environmental preservation, there has been renewed interest in agro-based natural fibres like jute, kenaf, flax, sisal, coir and ramie. Jute and allied fibres can be considered for many eco-friendly technical textile products. They can replace products that pose a severe threat to our environment. The growing market for natural fibre-based industrial applications of textile materials offers new possibilities for jute. To meet this challenge, jute products and allied fibres should conform to stringent quality specifications.

However, preliminary life cycle analysis of jute indicates inherent eco-problems. These need to be addressed for the increased use of jute as technical textile. 

The jute plant is retted to get raw jute strands. During retting, dissolved oxygen is reduced in the water tank/pond, endangering aquatic life. However, it has been proven that the same is recovered in three to four months. Methane gas released during retting creates environmental hazards. This can be reduced by adopting newer and quicker enzyme-based retting. Common area-wise facilities or community retting tanks adopting IJIRA/NIRKJAFT's enzyme retting process is mandatory and can be implemented with the help of the state agriculture department or Krishi Vikas Kendra of ICAR.

Mineral jute batching oil (JBO) is used at the yarn manufacturing stage. It has low but objectionable degrees of toxic chemicals or polynecular hydro carbons such as trypsin and pyrene. So, JBO is not regarded safe for use in packaging food grain that has high fat content. Use of vegetable oil like rice bran oil or palm oil to replace mineral jute batching oil is a partial solution. However, rice bran or modified rice bran oil technology costs a packet and causes higher wastage, residue and dust and lowers productivity. Further R&D is needed to match viscosity and other properties of JBO by mixing or blending different vegetable oils or by modifying any vegetable oil for desirable results.

Objections have been raised over more than permissible limits of silica in raw jute and in some jute products, particularly jute used to make paper and composites.

Doubts have arisen over the presence of low or trace amounts of pentachlorophenol (PCP) or lauryl penta chloro phenol (LPCP) in jute hessian tobacco bags and in other jute products. This is an eco-parameter that goes against declaring jute products as eco-friendly. Earlier, it was detected that this was used as a preservative in mineral oil type jute batching oil and as a preservative in sizing paste, which has now been withdrawn. Still, occasional contamination is a matter of concern.

Life cycle analysis of jute has yet not been fully analysed with sufficient experimental data tested by internationally accredited labs. Nor has it been internationally standardised with detailed scientific data supported by authentic experimentation following standard test protocols to judge its carbon credit values. Hence, different questions and doubts still remain though there is some data available indicating and partially proving its biodegradability and eco-friendliness and showing positive carbon credit in many stages. Yet, an integrated study should be made, acceptable internationally.

Jute fibre may be considered a composite like fibrous material having aniosotropic cellulose micro-fibrils acting as the load-bearing entity in an isotropic lignin matrix with hemicellulose acting as the coupling agent between two. Cellulose is a linear condensation polymer consisting of D- anhydroglucopyranose units joined together by 1- 4- ?- glycosidic bonds. Degree of polymerisation of cellulose in jute is reported to the lowest among vegetable fibres and approximately 1100-1150.

Cellulose reacts as a trihydric alcohol with one primary and two secondary hydroxyl groups per glucose unit. The reactions of cellulose may be conversely divided into two kinds: (i) those involving hydroxyl groups leading to substitution, addition and oxidation

Hemicellulose is generally composed of a backbone of ?-D-xylopyranose units with every seventh unit carrying a terminal 4-O-methyl-?-D-glucouronic acid residue linked through position C2. Some of the xylose units in the main chain are also acetylated. The degree of polymerisation (DP) of hemicelluloses in jute, as estimated by osmotic pressure method is reported to be nearly 140-150 (DP ? 150) also possessing reducing (-CHO) end groups in it.

Lignin is believed to be formed by oxidative polymerisation of the phenyl-propane units to give large cross-linked molecules containing carbon-carbon and ether linkages. It is a short-chain, isotropic and non-crystalline material with an average DP of about 25-60.The structural units of lignin precursors are aromatic alcohols with a phenyl-propane backbone, such as, p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol. Thus, the functional groups found in lignin are mainly hydroxyl (alcoholic and phenolic), methoxy, dioxyethelene (-OCH2O-), iodoform yielding complex.

There are different opinions about the origin of acidity of jute; an early group of investigators attributed this to -COOH groups of hemicellulose while another drapes explained the free acidity of jute fibre is due to the presence of phenolic groups of the lignin component.

Jute has moderately good thermal stability up to temperature of 150-1700C; mass loss of jute after one hour at 1800C is about 5 per cent. The degradation temperature of hemicellulose is nearly 2930C, that of cellulose is nearly 3640C and the same for lignin is about 4250C. Ignition temperature of jute fibre under flame is about 1930C and ignition time is more than 10 seconds.

In addition to being mildly acidic, jute is also chemically reducing in nature. Copper number of jute varies roughly between 1.5 to 2. Compared to cotton and ramie, jute is somewhat more resistant to the action of acid due to presence of lignin. Jute fibre, like other natural fibres, is hygroscopic. With water, jute filament swells 23 per cent in diameter, 40 per cent in cross section and 0.06 per cent in length. Absorption of water vapour changes the dimensions of the filament as well as its mechanical and electrical properties. Moreover, as a result of the empty lumens of the ultimate cells of jute and thus hollow nature of jute may impart required sound insulation property. May jute not be suitable for all types of technical textiles, but may be for some specific areas. Fore discussing those applications of jute as technical textiles, it is necessary to understand all important criteria and properties favourable for its use as specific applications of technical textiles as discussed below.

Jute-based technical textiles

The growing disinclination to use artificial fibres and increasing preference for natural fibres may revive the importance of jute. Jute fibre has high strength and modulus with low extensibility, low price and agro-renewability with high realisation of strength and modulus/unit price providing cost effectiveness, reasonably good durability with high level of dimensional stability, higher coefficient of friction. It also has good thermal, sound and electrical insulation properties, relatively more thermal stability, unique irregular surface morphology, high moisture regain, low specific heat and low thermal conductivity, eco-compatibility, vegetation support, easy and bulk availability, medium density, negative health hazard, soil friendliness and ability to add nutrients to the soil after degradation. 

Moreover, heaviness (weight/unit cost) and appreciable thickness, required draping quality, ability to withstand initial stresses of road construction, stiff body preventing differential settlement on soil, high permittivity and transmitivity, irregular surface morphology preventing lateral and rotational slides, high water absorption performing well in filtration and drainage and soil consolidation (caking) functions, resistance towards abrasion, fatigue and fracture for jute based properly designed fabrics indicate its suitability for technical textiles, not explored earlier.

These merits of jute, if properly utilised, may produce inexpensive technical textiles for specific end-uses. Jute fibre, abundantly available in West Bengal, Assam and Andhra Pradesh, will boost the economy of farmers if the outlook is modified.

With growing concern regarding environment, mainly because synthetic fibre is not biodegradable and is more toxic, market opportunities for different technical textiles from jute are increasing. Environmental legislation/regulation by the Central Government may open up a new market for jute and allied fibres. Jute will find favour with consumers focusing on eco-friendly materials from sustainable resources. Therefore, concerted efforts need to be made to explore design and production of marketable non-traditional jute products (for both domestic and foreign markets) as technical textiles.

The advantages of jute for these seven categories of technical textiles are major thrust areas of application of jute products. They are discussed and depicted below in Table-2.1 - 2.7, with mention of relevant property advantages and specific end-uses for jute products.

  Reference:

1. R. David, The World Technical Textiles Industry and its Markets: Prospects to 2005, Published by Messe Frankpuit/Techtextile (1997).

2. A. K. Samanta, Ph.D Thesis "Effect of Chemical Texturising, Bleaching and Resin Finishing on Jute/Polyester and Jute/Cotton Blended Textiles" Department of Plastics and Rubber Technology,Calcutta University, 1996.

3. P. Ray, A. K. Samanta & M. Datta, Virtue of Jute Fibre In The Global Technical Textile Market, Proceedings of International Symposium cum Exhibition on Jute-2004, at Technical University of Liberech, Czechoslovakia (Check-Republic), 28th & 29th May,2004, p-6.

4. D. Das, R B Chavan, M. Datta and S K Datta, Coating of Jute with Natural Rubber, J.Appl.Polym.Sc.98 (2005), pp 484-490.

5. Samanta A K, Chemical Finishing of Jute and Jute Blended Textiles: A Review, Colourage, February (1995) p37.