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Natural fibre composites and its potential as building materials

Amit Rai & C N Jha

Increasing concern about global warming, primarily due to deforestation has led to the ban on use of wood in government buildings. Subsequently, a large action plan for the development of wood substitute has resulted in creation of more awareness about the use of natural fibre-based building materials. In the past one decade or so, the joint efforts by R&D organisations, private industries and funding agencies provided the much-needed thrust for the actual transfer of technical knowhow and product to the end-users.

Most of the developing countries are very rich in agricultural and natural fibre. Except a few exceptions, a large part of agricultural waste is being used as fuel. India alone produces more than 400 million tonnes of agricultural waste annually. It has got a very large percentage of the total world production of rice husk, jute, stalk, baggase and coconut fibre. All these natural fibres have excellent physical and mechanical properties and can be utilised more effectively in the development of composite materials for various building applications.

This paper gives an overall view of natural fibre in building industry, its technical comparison with the other traditional building materials. Advantages of using natural fibre materials over traditional building materials and its possible growth in future are also discussed. A large part of the paper deals in the systematic development of the natural fibre composites in India and diversified efforts by various organisations for upgrading the technologies. The technological gap for the overall development of various natural fibre composites and its world scenario has also been covered.

From centuries, mankind has used natural fibre for various types of application including building materials. In most of the countries, users have explored the possibilities of using natural fibre from different plants, which includes bagasse, cereal straw, corn stalk, cotton stalk, kenaf, rice husk/rice straw etc. Most of the fibre were used mainly for the production of hard board and particle board. Emergence of polymers in the beginning of the 19th century has provided the researcher new dimensions to use natural fibre in more diversified fields. At the same time, necessity has also increased the interest in synthetic fibre like glass fibre which, due to its superior dimensional and other properties seems to be gaining popularity and slowly replacing natural fibre in different applications. As a result of this change in the raw material and production process of synthetic fibre based composites, energy consumption has increased.

The environmental loss suffered by society due to pollution generation during the production and recycling of these synthetic based materials has once again drawn attention to the use of natural fibre. The renewed interest resulted in new ways of natural fibre modifications/use and brought it to be at par/superior to synthetic fibres. Now it is in use from making rope to spacecraft applications and the building industry has also come up as one of its main beneficiaries.

Natural fibre composites in India

Due to the light weight, high strength to weight ratio, corrosion resistance and other advantages, natural fibre-based composites are becoming important composite materials in building and civil engineering fields. In case of synthetic fibre based composites, despite the usefulness in service, these are difficult to be recycled after designed service life. However, natural fibre based composites are environment friendly to a large extent. These natural fibre based composites came into existence after a lot of R&D efforts.

National scenario of natural fibre composites

Natural fibres as reinforcing agent in composite matrices (such as cement and polymer) are attracting more attention for various low-cost building products. The natural fibres are abundantly available locally and extracted from renewable resources. Presently, the production of natural fibres in India is more than 400 million tonnes.

The present requirement of wood in India is about 29 million cubic metres, whereas the estimated production is about 16 million cubic metres only. Apart from wood, natural fibre composites are emerging with an increasing role in building industry to replace timber, steel, aluminium, concrete, etc. Composites are being used for prefabricated, portable and modular buildings as well as for exterior cladding panels. So far, the utilisation of sisal, jute, coir and baggase fibres has found many successful applications.

Coir composites

Since coconut is available in India in abundance, the second highest in the world after the Philippines, the coir fibre has been investigated most extensively. Most importantly, coir fibre has been recognised as highly durable fibre in all types of matrices, viz, polymer, bitumen, cement, gypsum, flyash-lime, mud, etc.

Jute-coir composites

Jute-coir composite provides an economic alternative to wood for the construction industry. It involves the production of coir-ply boards with oriented jute as face veneer and coir plus waste rubber wood inside. The coir fibre contains about 46 per cent lignin as against 39 per cent in teak wood. Therefore, it is more resistant than teak wood against rotting under wet and dry conditions and has better tensile strength. The composite board namely, coir-ply boards (jute+rubber wood+coir) as plywood substitute and natural fibre reinforced boards (jute+coir) as MDF substitute can be used in place of wood or MDF boards for partitioning, false ceiling, surface paneling, roofing, furniture, cupboards, wardrobes, etc. This composite is mainly produced commercially in India by ‘Natural Fibretech’, Bangalore. National Institute of Research on Jute and Applied Fibre Technology (NIRJAFT), Kolkata has also come out with a number of technologies which help to a great extent for the commercialisation of jute/coir based composites.

Bamboo and its composites in housing

Bamboo is a very well known and popular construction material throughout the tropics, particularly in bamboo rich regions. Bamboo is the fastest growing plant and possesses excellent physical and mechanical properties - weight by weight it is stronger than steel. IPIRTI, Bangalore in association with BMTPC has successfully developed and transferred the technologies for manufacturing Bamboo Mat Board (BMB), Bamboo Mat Veneer Composites (BMVC) and Bamboo Mat Corrugated Sheets (BMCS). One commercial plant has been set up in Meghalaya for manufacturing BMCS, an excellent eco-friendly roofing product, having manufacturing capacity of 3000 sheets per month.

Sisal fibre and its applications

Sisal fibre obtained from the leaf of sisal plant has been proved to be very suitable reinforcement in various polymeric matrices. The Central Building Research Institute, Roorkee and Regional Research Laboratory, Bhopal have investigated several techniques for sisal fibre surface modification for its use in the production of roofing sheets. BMTPC, New Delhi & TIFAC (DST) has also sponsored a number of schemes/projects for natural fibre reinforced composite building materials. Apart form the above natural fibre composite materials, a number of reports and research papers published by RRL, Trivandrum and other research laboratories suggest use of bagasse, pine needles, banana leaves, flax cotton fibres, etc for the development of different building materials. In RRL, Trivandrum, a lot of research has been carried out on the development of different natural fibre-based composites and a number of these technologies are at commercialisation stages.

Natural fibre composites in other countries

World production of the plant fibres is estimated to be around 3100 million tonnes in which the share of cotton fibre is around 1750 million tonnes and of straws is about 1300 million tonnes. Compared to the cost of various fibres, cotton fibre is the most expensive, followed by flax, abaca, sisal, coir and jute. Straw is cheapest one if we compare the worldwide cost of all fibres. A focused research work is in progress in almost all natural fibre-rich countries, for developing appropriate technologies for fibre-reinforced composites. A survey of planned facilities in North American countries indicates use of over 700 thousand cubic metres of agricultural fibre in the manufacturing of MDF and particles board.

A literature search was conducted at the USDA (USA) forest service. Forest Products Laboratory survey showed that almost every conceivable type of natural fibrous material could be considered for some type of building material and many of them are being used worldwide today. This account provides a good encouragement and opportunity for utilisation of natural fibres in India also for production of composites for building.Technological gaps and future areas

Building components made from agricultural materials fall into the same product categories as other wood based composition products. Low-density insulation boards, medium-density fibre boards, hard boards, particle board and other building components such as walling and roofing can be manufactured using natural fibres. Binders used may be synthetic, thermosetting/thermoplastics, resins, modified naturally occurring resins like tannin or lignin, starches and other organic and inorganic binders, or binder may not be required at all. There seems to be little restriction to what has been tried and what may work. But still the large-scale availability of natural fibres in different geographic regions suggests that a lot of research and development work is required for proper utilisation of available natural fibres.

Gaps in research are mainly that which relate to knowledge of fibre extraction technology, chemical and physical characterisation, possible modification of the fibre interfaces and the processing techniques and their relation to the manufacturing technologies for final products. In case of aspect ratio of the plant fibres, a distinction is to be made between individual fibres and fibre bundle. Diameter and length of the fibres are also very important factors while designing any product, because varying length and diameter can be deciding factors for the properties of the final products. There is a wide range of variation in density because of central void or lumen. Voids are seen as initiating cracks and allowing their propagation may lead to failure of composite dimension or abnormal delimitation. The renewed interest in industrial use of plant fibres has led to worldwide research in production of a number of products based on plant fibres.

Conclusion

The research and development work carried out by different agencies has established that natural fibres, due to their technical superiority over the synthetic fibres, have immense versatility and are appropriate especially for use in high-tech applications in rural areas. The need of the hour is to use these naturally available materials in order to save the environment and energy consumption which is required in the processing of manmade synthetic composites.

The authors are with BMTPC, New Delhi