Kinds of Natural Fibres and Its Special Characteristics
To stimulate interest in natural fibre and materials, the year 2009 is considered as the International Year of Natural Fibres - IYNF.1 Natural fibres represent a substantial cultivated biomass that contributes towards the economy and supports the nation’s environmental policy. The widespread use and accessibility of natural fibres can reduce pressure on forests and agriculture. The usage of diverse natural fibres as raw materials will help to retain the ecological balance of nature.2 Therefore, an increase in the usage of composites reinforced with natural fibre has been attempted due to numerous advantages such as easy availability, light weight, nonabrasive nature, low cost, low C02 emission, recyclable, renewability, and biodegradability.
Natural fibres from stalks, leaves, bast, stems, fruit, and seed plants possess individual and inherent physical, mechanical, and unique surface properties. Consequently, a vast knowledge of the special characteristics of natural fibres and their blends is required to manufacture quality composites. The properties of fibre together with a great effort in terms of their processing technologies to select a set of machineries and machine parameters and techniques for blending natural fibres will result in a compatible product at minimum cost.
The hydrophilic and hydrophobic nature of natural fibres results in distinctive and interesting sorption phenomena. Composites with natural fibres have advantages such as lower density, better thermal and sound insulation, and electrical insulation along with good mechanical properties, which favour the functional application of composites.
Composites with natural fibres are one of the smart alternative solutions to the problem of the negative environmental impact of industries. The annual yield of natural fibres in India is approximately 14.5 million tons compared to the world yield of 45.5 million tons.' Banana, coir, jute, sugar cane, turmeric, kapok, kenaf, palmyra, and pineapple are dominant. A tropical agricultural environment has huge potential for the growth and use of fibre derived from agricultural waste. Natural fibres are thus an important by-product of the extraction process and can be used as reinforcement material in composite products.4
Most natural fibres have considerable differences in mechanical properties and moisture absorption and have poor thermal characteristics, creating problems in the production of natural fibre composites. Fibre matrix adhesion has also become a topic of interest in research into producing good quality composites. For natural fibre composites to meet market requirements, it is becoming essential to consider the issues of fibre blend proportions, fibre matrix, process and method of selection, and product optimization through statistical methods.
Increasing demand for automotive materials with sound insulation qualities and low weight (for fuel efficiency) could be met by using natural fibres as alternatives. Natural fibres from renewable resources will offer a complete solution to the demands of industrial society and lead to the agricultural production of alternative materials. The use of natural plant and animal-based fibres as reinforced polymeric composites has become a key design criterion for designing and manufacturing elements for all industrial products.5 Renewable agro crops, which are going to be incorporated to prepare or make sustainable composite materials, need to be considered for its life cycle assessment from its starting stage to the end stage at various phases including its recyclability and disposal.6 Recovery of raw materials using gasification to methanol, biodegradation and C02 neutral thermal utilization is being examined.7
In automotive applications, the demand rate for natural fibre composites as alternatives to plastic composites was forecasted as 15%-20%. In building sectors, for some selected applications, it was forecasted to be 50%. Other consumer applications like flowerpots, tiles, and home and commercial furniture are emerging markets.8
Manufacturers are encouraged to produce composite materials to support environmentally friendly approaches such as (i) reducing the amount of toxic waste produced in manufacturing, (ii) reusing raw materials, (iii) repairing damaged or defected products, and (iv) recycling needs to be done up to the extent level, and finally (v) the scarabs are disposed of to the landfills.5