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Jute Composite: Technology & Business Opportunities
Jute is an attractive natural fibre for use as reinforcement in composite because of its low cost, renewable nature and much lower energy requirement for processing. The scope for using jute fibres in place of the traditional glass fibres in different forms partly or fully as reinforcing agents in composites stems from the higher specific modulus and lower specific gravity of jute (~ 40 Pa and 1.29 respectively) compared with those of glass (~ 30 GPa and 2.5 respectively). The major drawback of natural fibre reinforced composites is due to its affinity for moisture. Many experimental studies have shown that compatible coupling agents are capable of either slowing down or preventing the de-bonding process and hence moisture absorption even under severe environmental conditions, such as exposure to boiling water. Jute fibres/fabrics can be modified chemically through graft co-polymerisation and through incorporation of different resin systems by different approaches. Natural fibre composites enjoy excellent potential as wood substitutes in building industry in view of their low cost, easy availability, saving in energy and pollution free production. In order to improve upon the laboratory-industry linkages towards application development & commercialisation, the Advanced Composites Mission launched the projects on jute composites such as 'Jute-Coir Composites Boards’, 'Jute-glass composite components for railway coaches’, ' Thermoplastic composites based synthetic wood’ and others.
The composite technology of a polymeric matrix reinforced with man-made fibres such as glass, Kevlar, carbon etc. has come of age especially with the advances in aerospace applications since 1950s. The developments in composite material after meeting the challenges of aerospace sector have cascaded down for catering to domestic and industrial applications. Composites, the wonder material with light-weight, high strength-to-weight ratio and stiffness properties have come a long way in replacing the conventional materials like metals, woods etc. The material scientists all over the world focused their attention on natural composites reinforced with jute, sisal, coir, pineapple etc. primarily to cut down the cost of raw materials.
Jute, sisal, banana and coir, the major source of natural fibres, are grown in many parts of the world. Some of them have aspect ratios (ratio of length to diameter) > 1000 and can be woven easily. These fibres are extensively used for cordage, sacks, fishnets, matting and rope, and as filling for mattresses and cushions (e.g. rubberised coir). Cellulosic fibres are obtained from different parts of plants, e.g. jute and ramie are obtained from the stem; sisal, banana and pineapple from the leaf; cotton from the seed; coir from the fruit, and so on. Recent reports indicate that plant-based natural fibres can very well be used as reinforcement in polymer composites, replacing to some extent more expensive and non-renewable synthetic fibres such as glass. The maximum tensile, impact and flexural strengths for natural fibre reinforced plastic (NFRP) composites reported so far are 104.0 MN/m2 (jute-epoxy), 22.0 kJ/m2 (jute-polyester) and 64.0 MN/m2 (banana-polyester), respectively. The properties of some of the natural fibres are compared in Table 1.0. Table 1.0: Properties of Select Natural & Glass Fibres
There are many examples of the use of cellulosic fibres in their native condition like sisal, coir jute, banana, palm, flax, cotton, and paper for reinforcement of different thermoplastic and thermosetting materials like phenol-formaldehyde, unsaturated polyester, epoxy, polyethylene, cement, natural rubber, etc. Different geometries of these fibres, both singly and in combination with glass, have been employed for fabrication of uni-axial, bi-axial and randomly oriented composites. Amongst these various ligno-cellulosic fibres, jute contains a fairly high proportion of stiff natural cellulose [1,2]. Rated fibres of jute have three principal chemical constituents, namely, a -cellulose, hemicellulose and lignin. In addition, they contain minor constituents such as fats and waxes, inorganic (mineral) matter, nitrogenous matter and traces of pigments like b - carotene and xanthophyll. As in synthetic fibre composites, the mechanical properties of the final product depend on the individual properties of the matrix, fibre and the nature of the interface between the two. Where the fibre is an agricultural one, it is possible to tailor the end properties of the composite by selection of fibers with a given chemical or morphological composition. Several studies of fiber composition and morphology have found that cellulose content and microfibril angle tend to control the mechanical properties of cellulosic fibers. Pavithran et al [3] found that higher cellulose content and lower microfibril angle resulted in higher work of fracture in impact testing.
Although the tensile strength and Young’s modulus of jute are lower than those of glass fibres, the specific modulus of jute fibre is superior to that of glass and when compared on modulus per cost basis, jute is far superior. The specific strength per unit cost of jute, too, approaches that of glass. Therefore, where high strength is not a priority, jute may be used to fully or partially replace glass fibre. The need for using jute fibres in place of the traditional glass fibre partly or fully as reinforcing agents in composites stems from its lower specific gravity (1.29) and higher specific modulus (40 Gpa) of jute compared with those of glass (2.5 & 30 Gpa respectively) [4]. Apart from much lower cost and renewable nature of jute, much lower energy requirement for the production of jute (only 2% of that for glass) makes it attractive as a reinforcing fibre in composites. The comparison of mechanical properties for jute & glass fibres is given in Table 2.0. Table 2.0 : Mechanical Properties of Glass and Jute Fibres
The jute composites may be used in everyday applications such as lampshades, suitcases, paperweights, helmets, shower and bath units. They are also used for covers of electrical appliances, pipes, post-boxes, roof tiles, grain storage silos, panels for partition & false ceilings, bio-gas containers, and in the construction of low cost, mobile or pre-fabricated buildings which can be used in times of natural calamities.
There is, however, a major drawback associated with the application of jute fibres for reinforcement of resin matrices. Due to presence of hydroxy and other polar groups in various constituents of jute fibre, the moisture uptake is high (approx. 12.5% at 65% relative humidity & 20o C) by dry fibre[5]. All this leads to (i) poor wettability with resin and (ii) weak interfacial bonding between jute fibre and the relatively more hydrophobic matrices. Environmental performance of such composites is generally poor due to delamination under humid conditions. With increase in relative humidity upto 70%, the tenacity and Young’s modulus of jute increases but beyond 70%, a decrease is observed. Thus, it is essential to pre-treat the jute fibre so that its moisture absorption is reduced and the wettability by the resin is improved.
In order to develop composites with better mechanical properties and environmental performance, it is necessary to impart hydrophobicity to the fibres by chemical reaction with suitable coupling agents or by coating with appropriate resins. Such surface modification of jute fibre would not only decrease moisture adsorption, but would also concomitantly increase wettability of fibres with resin and improve the interfacial bond strength, which are critical factors for obtaining better mechanical properties of composites. Modification of jute and other natural cellulosic fibres can
be done by following means :
Jute is chemically treated with isopropyl triisostearoyl titanate (abbreviated as titanate), g - aminopropyl trimethoxy silane (abbreviated as silane), sebacoyl chloride (SC), and toluene diisocynate (TDI). All these reagents are expected to block the hydroxy groups of jute thus making the fibres more hydrophobic. These surface modifiers penetrate and deposit into lumens of cell wall of fibre, minimising the possible extent of moisture ingress. Polymeric coating of jute fibre with phenol-formaldehyde or resorcinol formaldehyde resins by different approaches are highly effective in enhancing the reinforcing character of jute fibre, giving as high as 20-40% improvements in flexural strength and 40-60% improvements in flexural modulus. These modifications improve the fibre-matrix resin wettability and lead to improved bonding [6,7]. Jute can be graft copolymerised with vinyl monomers such as methyl methacrylate, ethyl acrylate, styrene, vinyl acetate, acrylonitrile and acrylamide in the presence of different redox initiator systems such as vanadium - cyclohexanol, vanadium - cyclohexanone, etc. Grafting of polyacrylonitrile (10-25%) imparts 10-30% improvements in flexural strength and flexural modulus of the composites. Grafting of polymethylmethacrylate is also effective in this respect, though to a lower degree.
Polyester resin forms an intimate bond with jute fibres upto a maximum fibre:resin ratio (volume/volume) of 60:40. At this volume fraction, the Young’s modulus of the composite is approximately 35 GN/m2. For higher volume fraction of fibre, the quantity of resin is insufficient to wet fibres completely [8]. In order to overcome the poor adhesion between resin matrix and jute fibres, a multifunctional resin like polyesteramide polyol has reportedly been used as an interfacial agent. Significant improvement in mechanical properties of jute fibre composites was observed by incoporation of polyesteramide polyol. Also, hybrid composites of glass at surface and treated jute fibre at inner core can be a good alternative [9,10]. There are several types of unsaturated polyester resin - general purpose, flexible, resilient, low-shrinkage (low profile), weather resistant, chemical resistant and fire resistant varieties. These polyester resins are prepared from a blend of phthalic anhydride and maleic anhydride esterified with propylene glycol to form linear polyester chains having molecular weights in the range 1000-3000. For Curing of such unsaturated polyester resin with fibre, azo type initiators (R-N=N-R) and organic peroxides (R-O-O-R) are generally used.
Hybrid composite of glass and jute fibre can be fabricated initially by the hand lay-up technique for making the sheet-moulding compound and subsequently by using a compression-moulding machine. 10-ply hybrid laminates containing 8 inner plies of untreated/silane/titanate/TDI treated jute fibre sandwiched between two outer plies of glass fibre (weight content of jute :25-27%) can be made by the aforesaid process. Curing is done at 80oC under a pressure of approx. 2X105 N/m2 for a period of 90 min. Jute composites are at present being used commercially in Phenolic resins is one of the first synthetic resin exploited commercially for fabrication of jute-composite products mainly because of its high heat resistance, low smoke emissions excellent fire retardance properties and compatibility with jute fibres. Phenol-formaldehyde based jute composites products have been used for quite sometimes as wood & ceramic substitutes. Today, where costs & performance have a high impact on economics, phenolic resins have been accepted in many high performance applications in composite materials. Compression moulding of composites based on jute-phenolic system has been commonly practised since few decades. In this process, jute is impregnated with the phenolic resin by spraying process followed by drying under hot air drier. These pre-impregnated jute layers are arranged together for desired thickness and compression moulded at high pressure of 700-800 kg/m2 and at temperature of around 120-1400 C. A report from the National Institute of Research on Jute and
Allied Fibre Technology (NIRJAFT), Pultrusion is a another unique process that converts primary raw materials directly into finished products, continuously and automatically, utilising most of thermoset/thermoplastic resins. Jute, available in continuous forms such as mat, roving, tapes, yarn etc., is impregnated with resin & passed through hot die to cure the product. The speed of pultrusion ranges from 0.4 mtr. to 1 mtr. per minute depending on the complexity of the products. The loading of jute is anywhere between 50-70%. Pultruded jute composites have good electrical insulation, corrosion & high resistance properties. They find applications in roofing sheets, cable trays, doors & window frames, panelling, sections for wardrobe, partitions, etc. The characteristics of natural fibre composite boards are as
follows:
A composite has three entities that are susceptible to failure - the reinforcement, the matrix and the interface. The failure of one can initiate failure of the others, and the actual process that takes place in any particular case is determined by the stress required to activate each individual mechanism. The mechanism activated by the lowest stress will normally govern composite failure. Thus, In order to increase the potential application area of jute fibres as reinforcement in composites, it is necessary to concentrate more on three major aspects (a) fibre modification (b) resin matrix and (c) coupling agents.
The jute composites can be very cost-effective material especially for building & construction industry (panels, false ceilings, partition boards etc.), packaging, automobile & railway coach interiors and storage devices. A survey of international patents establishes the potential applications of jute composites in various sectors. These are summarised in the following sections : In a recent US patent [12] by Plummer et al., the project innovation relates to a natural fibre composite for fabrication of structural components such as rails, sills, tracks, stops and non-structural members such as grid, cove, bead etc. for residential & commercial architecture. The composite material, extruded in the form of pellets, comprises thermoplastic matrix (polyester, polyvinyl alcohol, PBT, nylon, spandex etc.) and short/long fibre reinforcements. A variety of fibres has been tried out by the inventor. A large array of natural fibre such as jute, flax, hemp, ramie, cotton, palm leaf, coir etc. can be used. The composite material is pelletized and the pellets are further extruded or injection moulded as per the desired shapes/profiles. Medoff et al. In a The European patent [14] granted to Neuhold et al. describes the process of fabricating a low density insulating board made from natural fibres. The natural fibres are opened up into single fibres which are then wetted with a natural (starch, protein etc.) or synthetic thermoset resin and further compressed by rollers & cured in oven into desired shape with a density of 30-100 Kgs/m3. The development of a door module for motor vehicle has been described by Neuhauser et al. in the European patent [15]. The module comprises an internal lining component, which accommodates a side air bag & gas generator. The internal lining component is made of plastics or PU foam with synthetic or natural fibre reinforcing inserts. In a European patent [16]
by Ulrich Josef from The process for making a multi-layer composite body comprising a thermoplastic layer and layers of natural fibre bonded to thermoplastic resin was patented in US by a German Company [17]. The composite body has at least one reinforcing layer made of an open-cell fabric of melting fibres penetrated on one or both sides of the melting thermoplastic materials. The composite body has excellent mechanical properties particularly bending stress & impact resistance. A A In a The process of moulding thermoset composite reinforced with natural fibres was patented [21] by a German company in 1993. The inventors used a resin mixture comprising unsaturated polyester with styrene and acrylic acid esters. The process involves impregnating the natural fibre with the aforesaid resin formulation and hot pressing it to a desired shape. Pradom Ltd., A The Marlo Company Inc., Newton, Connecticut, USA in their patent [24] describe a packing material comprising glass in combination with organic fibre such as sintered polytetrafluroethylene (TFE) with or without impregnant. A preferred impregnant could be a lubricant with a binder. The process also talks of substitution of sintered TFE fibre by natural and other fibres. In their application dating back to 1974, M/s. Care Inc.,
Due to an occurrence of a wide variety of natural fibres in
the country, Indian researchers have directed efforts for quite some time in
developing innovative natural fibre composites for various applications.
Development of diversified composite materials as wood substitutes is being
considered an attractive solution with a view to conserve forest resources.
The existing wood substitute materials such as particle/fibre board and other
materials cannot meet the increasing demand of wood without renewed efforts.
The national institutions such as National Institute of Research on Jute
& Allied Fibre Technology (NIRJAFT), Indian Jute Industries Research
Association (IJIRA), Central Glass & Ceramic Research Institute (CGCRI),
Department of Textile Technology-IIT Delhi, Regional Research Laboratory
(RRL)- NIRJAFT has developed a whole set of novel jute & other natural fibre composite products based on hot press moulding and hand lay-up techniques. A lot of efforts has gone into the studies on resin/fibre ratio, physical & chemical characterization of jute composites, water absorption properties etc. apart from developing products such as panels, boards, packaging material etc. The grading of raw material and its implementation for the benefit of both cultivators & industry has been one of the significant contributions of NIRJAFT. A commercially viable technology has been developed by them for the manufacture of particle boards from jute stick, which is an agro-waste. IIT-Delhi has been quite active in developing jute-based geo-textiles for applications in prevention of soil erosion, leaching etc. CGCRI-Calcutta has worked on jute-glass hybrid components for cost reduction without sacrificing the mechanical properties [11]. An excellent example for commercial exploitation of jute composites has been the fabrication of automobile interiors (door panels) by Birla Jute Industries Ltd. CBRI's research activities provided new insight into the contribution of the interface to the properties of the composites. A marked improvement in the properties of composites can occur when proper coupling agent treatment is applied to the reinforcements. The use of surface modified natural fibres in polymer matrices has been studied by several researches at CBRI. The control of fibre-matrix adhesion is a critical factor to achieve optimal properties of composites. While the national research agencies in The project on 'Jute-based Composites -
An Alternative to Wood Products' has been launched in collaboration with
M/s Duroflex Limited, Two major categories of composite boards namely, coir-ply boards (jute + rubber wood + coir) as plywood substitute and natural fibre reinforced boards (jute + coir) as MDF substitute have been developed under the project. These natural materials have all the properties required for a general purpose board and can be used in place of wood or MDF boards for partitioning, false ceiling, surface panelling, roofing, furniture, cupboards, wardrobes etc. Duroflex has also explored new product possibilities focussing on panel & flush doors etc. The detailed properties of jute-coir boards tested as per IS-12406 against the specified values of MDF a board is given in table 3. Table-3: Properties of jute-coir boards tested as per IS-12406
There can be a good demand for jute-coir composite boards for sleeper berth backing & partitions in railway coaches, by CPWD for building interiors, doors & windows besides in the transportation sector as backings for seat & backrest in buses. Typical MDF boards do not prove well on the grounds of moisture absorption & screw holding strength. The Mission has launched another project in collaboration with M/s. Fabtech Industries, Calcutta with technology support from CGCRI-Calcutta for manufacturing cost-effective 'Jute-glass composite components’ for glass shutter assembly and louver shutter assembly for railway coaches. The products made of jute-glass composites can be used as a replacement of high-cost sheet moulding compound & low-strength dough moulding compound based glass-fibre composites. The technology for the fabrication of hybrid composites incorporating jute felt and glass fibre using polyester resin as a matrix has been developed successfully by CGCRI. A detailed evaluation of the material has also been carried out at CGCRI. Jute fibre is not as efficient as glass fibre in its resin distribution properties. It has greater flow resistance and it tends to be less buoyant in dry state and compressed more readily thereby entrapping small air bubbles in the laminates. Some of these deficiencies can be overcome be pressure moulding and by using jute-glass hybrid composites. In these composites, jute can play a role as filler fibre in the applications where strength and modulus requirements are not demanding. Moisture absorption can be reduced from 25% to 6% by weight using glass fibre layer on either side of the jute fibre layer. Replacement of glass fibre reinforcement by 80% by weight of jute and replacement of filler (calcium carbonate) by 25% by weight of jute in DMC formulation increase the mechanical properties of the composite at a greater level. Such judicious selection of jute fibre for making hybrid composite with glass fibre brings down the cost of the laminate by almost 28%. A comparative study has been done on DMC & Jute-glass hybrid composite as given in Table 4. Table-4 : Comparative properties of Dough
Moulding Compound (DMC) and
Another project being considered under the Advanced Composites Mission deals with the development of 'Thermoplastics & Natural Fibre based Composites' for wood substitute. The project would aim at developing natural fibre reinforced thermoplastic composite granules (termed as 'POLYWOOD') made of natural fibre waste compounded with thermoplastics. The project would utilize industrial (Polypropylene & Polyethylene waste) & agro-wastes (jute/saw/rice mill waste) as raw materials. The granules would be moulded/extruded by a cost-effective production process for the products viz. crates, pallets, trays, boxes, bobbin, spool, suitcase shell etc. and other applications in railways, automobile, electrical & electronics and chemical industries. The mechanical characterisation, compounding formulations and standardisation & certification of products etc. would be investigated under this project. The raw materials, intermediates & final products produced would be tested at every stage to establish their characteristics. The Mission is also considering a project on Jute Based Composite Components for Footwear. The end products to be developed under the project are toe puff, counter stiffener, insoles and cut & skived components for ready to use as per customer requirement. Toe puff is used in toe (front) portion and counter stiffener is used in backside of footwear. Both are inserted between the leather & lining material for the purpose of stiffness, shape retention etc. The main target of the project is to replace the existing materials as produced from leather board, man made synthetic non-woven, woven cotton fabrics etc. with jute fabrics or jute mixed with other fabrics. Jute Non-woven or Jute/cotton woven fabrics are impregnated in the Adhesive or Emulsion made of Polystyrene- SBR, Latex, PVA etc. for the purpose of obtaining stiffness in the materials. Since jute has good strength & compatibility with rubber, thermoplastics hot melt adhesives, this new technology could lead to better shape retention, strength, mouldability, flexibility etc. of the footwear component apart from considerable cost reduction. The properties of all the items to be developed viz-a-viz existing products would be evaluated at various stages. Further, necessary modifications would also be carried out based on the material characterisation report.
It can thus be inferred that jute fibre can be a very potential candidate in making of composites, especially for partial replacement of high-cost glass fibres for low load bearing applications. As such, commercial exploitation of jute composites for non-structural applications promises excellent potential. Jute fibre (density, 1.3 g/cc) being lighter than glass fibre (density, 2.5 g/cc) offers additional advantages. From the point of view of wood substitution, jute composites could be an ideal solution. With ever depleting forest reserves and corresponding premium on wood, a composite based on renewable resources such as jute, coir, sisal etc. is poised to penetrate the market. Indigenous wood supply for plywood industry having been stopped virtually and with increasing landed cost of imported plywood veneers, the jute composite boards provide very good value for the customers without any compromise in properties. With increasing emphasis on fuel efficiency, jute composites
would enjoy wider applications in automobiles and railway coaches. In fact,
the market segments such as railway coaches & buses for public transport
system in
For further information, please contact Mr. S. Biswas at mailto:
biswas@alpha.nic.in |
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