A year for fibres
2009 is the year of natural fibres. Brett Suddell, Senior Materials Scientist from environmental consultancy ADAS, based in Hereford, UK, reflects
The interest in natural fibres has grown significantly in the past decade with a multitude of products being developed for industries such as automotive, construction, leisure and packaging. While the use of natural fibres, especially in composites, may be viewed by some as a step backwards, a new generation of natural composite materials is proving this is not the case. These materials demonstrate high strength and toughness, and have been developed for challenging environments.
Fibres can be classified into two main groups – man-made and natural. In general, natural fibres can also be subdivided according to their origin – plants, animals or minerals. Plant fibres can be further subdivided into seven subgroups, including bast, leaf, seed, fruit and wood.
Commercially important sources of natural fibres and the main producing countries can be seen in the table. The fibres of interest in Europe are predominantly flax and hemp.
The automotive industry has been using natural fibres for a number of decades. The construction industry constitutes the second largest sector, after automotive, that employs natural materials in products, including:
• Light structural walls.
• Insulation materials.
• Floor and wall coverings.
• Thatch roofing.
In Brazil, researchers, with the support of the United Nations’ common fund for commodities, are looking at how to replace asbestos fibres, which are still used in construction products across the country, with sisal. Coir-based products from India are strong, naturally termite- and insect-resistant, waterproof, flame resistant and carpenter friendly, and have nail and screw holding properties, making them ideal materials for construction. There are also products within the UK that use straw, hemp and lime for construction.
There are a number of reasons for the increase in natural fibre products. In parallel to the increased awareness of natural materials as potential feedstocks for industrial products, there has been a major political drive towards sustainable technologies.
Western governments have been seeking polymer materials that are not reliant on crude oil, lightweight materials that can reduce carbon emissions by lowering vehicle weight, natural insulation materials to improve energy efficiency of buildings, carbon sinks such as forests (and forest products such as timber) to lock up CO2, and recyclable or compostable materials that can reduce the landfill crisis. Waste dumping is becoming increasingly costly because of landfill taxes.
These political pressures have given a considerable push to the research community. There is also a greater need for companies to be seen to use greener products and processes, although this can lead to a ‘green wash’ by some. Consumers are showing an increasing level of environmental awareness and concern over purchasing ‘environmentally friendly’ products, which is also influencing organisations.
The methods used to extract natural fibres have been inherited from the textile industry, irrespective of the intended application, which results in fibres with additional defects due to the mechanically intensive methods employed. Additional research is required to better understand the factors that affect plant properties. However, natural fibres can be used in applications without needing to replace existing synthetic materials.
One of the main impediments to the wider use of renewable feedstocks is a lack of general consumer awareness of their benefits, which results in a limited or non-existent demand. Other barriers include the cost of changing to a new feedstock compared to an established source, limited technical knowledge of the performance and application of the materials, and the perception (often incorrect) of bio-based materials as inferior in quality.
In 2006, the United Nations’ General Assembly passed a special resolution that decreed 2009 would be the ‘International Year of Natural Fibres’. As a result, the Food and Agriculture Organisation of the UN has co-ordinated a calendar of events organised across the globe to achieve the following goals:
• Raising awareness and stimulating demand for natural fibres.
• Promoting the efficiency and sustainability of the natural fibre industries.
• Encouraging appropriate policy responses from governments to the problems faced by natural fibre industries.
• Fostering an effective and enduring international partnership among the various natural fibres industries.
Further information: Dr Brett Suddell