Natural Fibre Composites And Its Potential As Building Materials

Abstract:

Increasing concern about the 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 organizations, private industries and funding agencies provided the much needed thrust for the actual transfer of technical know-how 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 a 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 utilized 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 organizations for upgrading the technologies. The technological gap for the overall development of various natural fibre composites and its world scenario has also been covered.

Introduction:

From centuries, mankind has used the natural fibre for various types of application including building materials. In most of the countries, users have explored the possibilities of using the 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 19^thcentury has provided the researcher the new dimensions to use the natural fibre in more diversified fields. At the same time the 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 the 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 the society due to the pollution generation during the production & recycling of these synthetic based materials has once again drawn the attention for the use of natural fibre. The renewed interest resulted in the 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 out 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, a few of these important composites are summerised in the following text.

Background:  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 approximate production of various type of natural fibres is given in Table 1.

Table 1 Availability of natural fibre in India and its applications in building materials 

Item	Source	Qty. in Mt/Yr.	Application in building material
Rice Husk	Rice mills	20	As fuel, for manufacturing building materials and products for production of rice husk binder, fibrous building panels, bricks, acid proof cement
Banana leaves/stalk	Banana plants	0.20	In the manufacture of building boards, fire resistance fibre board
Coconut husk	Coir fibre industry	1.60	In the manufacture of building boards, roofing sheets, insulation boards, building panels, as a lightweight aggregate, coir fibre reinforced composite, cement board, geo-textile, rubberized coir
Groundnut shell	Groundnut oil mills	11.00	In the manufacture of buildings panels, building blocks, for making chip boards, roofing sheets, particle boards
Jute fibre	Jute Industry	1.44	For making chip boards, roofing sheets, door shutters
Rice/wheat straw	Agricultural farm	12.00	Manufacture of roofing units and walls panels/boards
Saw mill waste	Saw mills/wood	2.00	Manufacture of cement bonded wood chips, blocks, boards, particle boards, insulation boards, briquettes
Sisal fibres	Sisal plantation	.023 (Asia)	For plastering of walls and for making roofing sheets, composite board with rice husk, cement roofing sheet, roofing tiles, manufacturing of paper and pulp
Cotton stalk	Cotton plantation	1.10	Fibre boards, panel, door shutters, roofing sheets, autoclaved cement composite, paper, plastering of walls

The present requirement of wood in India is about 29 million cubic metres, where as, 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.

Table 2 shows the cellulose and lignin contents and some other properties of a few fibres available in India. So far, the utilisation of sisal, jute, coir and baggase fibres has found many successful applications. 

Table 2 Properties of some vegetable fibres used in India for composites

Fibre	Cellulose content (%)	Lignin content (%)	Dia (um)	UTS (MN/m2)	Elongation Max. (%)	Elastic Modulus
Banana	64	5	50-250	700-780	3.7	27-32
Sisal	70	12	50-200	530-630	5.1	17-22
Pineapple	85	12	20-80	360-749	2.8	24-35
Coir	37	42	100-450	106-175	47	3-6
Talipot	68	28	80-800	143-263	5.1	10-13
Polymer	40-50	42	70-1300	180-250	2.8	4-6

Coir composites:

Since coconut is available in India in abundance, the second highest in the world after 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% lignin as against 39% 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 Pvt. Ltd., 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 commercialization of jute/coir based composites.

Bamboo and its composites in housing:

Bamboo is a very well known and popular construction material through out 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. Table 3 gives a technical comparison of natural fibre composites over the other conventional materials.

Table 3 Comparative technical features of RFPC and other materials

Test conducted	Unit	RFPC	MDF	PVC	Teak	Particle board
Density (tested as per IS:2380 part III: 1977)	G/cc	1.72-1.76 (1.65-1.7)	0.5-0.9	1.3-1.58	0.62-0.64	0.5-0.9
Moisture content	%	0.2-0.38	5-8	NA	10-12	5-15
Modulus of rupture (tested as per IS:2380 part IV:1977)	N/mm2	85-95 (min 28)	12.5-15	68-110	11.6-14	12.5-15
Tensile strength (tested as per IS:2380 part V & VI:1977)	N/mm2	22-24 (min 17)	0.6-0.7	NA	NA	0.4-0.45
Compression perpendicular to surface	N/mm2	78.48-101	NA	NA	2.5-4	NA
Compression parallel to surface	N/mm2	44-51	NA	NA	6.4-8.8	NA
Water absorption (tested as per IS:2380 part XVI: 1977)
2 hours	%	0.15-0.4 (max 10%)	6-10	NA	NA	6-10
24 hours	%	1.1-1.5 (max 10%)	6-10	NA	NA	17-20
Swelling in water (tested as per IS:2380 part XVII:1977)
Length	%	0-0.36 (Max .5%)	0.3-0.35	NA	NA	0.45-0.5
Width	%	0-0.47 (Max.5%)	0.3-0.35	NA	NA	0.45-0.5
Thickness	%	0-1.38 (Max.5%)	3.5-4	NA	NA	6.5-8
Fire retardency (tested as per BS:476 part V:1979;BS:476 part VII:1987)	-	Self extinguishing in 15 seconds	NA	NA	NA	NA
Note: Figures in brackets show codal values

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, the 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 the 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 (Table 4).

Table 4 Composite board facilities in North American countries

Material	Country	Capacity (thousand cubic meters)
Particle Board	US Canada Mexico Total	9350 2845 834 13024
Extruded particle board	US	41
Medium Density Fibre board	US Canada Mexico Total	3363 1236 60 4659
Planned expansions MDF	US and Canada	2434
Currently using agriculture fibres	US and Canada	298
Plan to use agriculture fibres	US and Canada	707

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 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 products, 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 into production of a number of products based on plant fibres. These products may be divided into two main groups i.e.

Mats:Filters, Growth media, Insulation, Geotextiles and

Composites: Fibre/composites, Fibre/cement composites, composite product design etc.

Work done by the Building Materials & Technology Promotion Council

The BMTPC have provided extensive encouragement, technical and financial assistance for the R & D projects, appropriate machine development and commercialization of the technologies related to development of fibre based composites. The chief among them are:

·        Jute fibre-red mud polymer door composite (FRPC)

·        Sisal fibre-red mud-polymer composites (SRPC)

·        Cotton fibre-phinolic resin medium density fibre board (MDF)

·        Poplar/rubber wood laminated split lumber (P/RLSL)

·        Banana leaf medium density board

·        Bamboo based corrugated roofing sheet and flooring mat

Conclusion:                                                                                                                                   The research and development work carried out by the different agencies has established that natural fibres due its technical superiority over the synthetic fibres has proved that it is a versatile material for application in rural areas to high tech applications. 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 man made synthetic composites. But, still more research and development is required for the extraction and characterization of the basic materials i.e. fibres so to avoid any set back during the finalization of the complete process for upscaling of technology from lab scale to commercial level.

Acknowledgement:

Authors are grateful to the ED, BMTPC for providing  chance to contribute the paper in the seminar.

Bibliography:

1.       Building Materials in India: 50 years, A Commemorative Volume, Edited by T. N. Gupta, 1998.

2.       Proceedings of International Training Course on, Materials design and production processes for Low Cost Housing, Trivandrum, India, 27-31 March, 2001.

3.       International Conference, Waste and Byproducts as Secondary Resources for Building Materials, 13-16 April, 1999, New Delhi, India.

4.       Cities for all, Building Materials News, World Materials News, World Habitat Day, 4 October, 1999.

5.        Proceedings of Advances in Polymeric Building Materials, 6-7 March, 2003, Roorkee, India.

6.        TIFAC, News and Views, Articles, Development of Natural Fibre Composite in India.

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