The sisal plant.

An Indian researcher duo claims to have separated cellulosic nanofibres from sisal ( Agave sisalana ), the stiff fibre-yielding plant traditionally used to make twine ropes and dartboards. The nanofibres, claimed to be the first ever made from the plant, may find use in making stronger plastics, biodegradable composites and high strength packaging films.

The nanofibres could eventually replace nano-crystalline cellulose — nanomolecules of cellulose used to impart strength to products such as paper and film.

Navin Chand, a senior scientist at the Advanced Materials and Processes Research Institute in Bhopal, Madhya Pradesh and Suresh Chandra Prajapati an M. Tech. student at Central Institute of Plastics Engineering and Technology, Bihar are yet to publish a paper on their findings. They reported separating cellulosic nanofibres of diameter 483.32 nm at a conference of the Materials Research Society of India held in early 2011.

"We have prepared the nanofibres from the isolated cellulosic content present in sisal fibre," Chand told Nature India . The nanofibres appear to be conical in shape when observed through high resolution scanning electron microscope. Chand says the conical shape of the nanofibres is the key to their strength, which can now be put to good use to develop nano composites as well as nano fabrics. The team claims that these applications could revolutionise the use of these biodegradable fibres.

The naonfibres appear conical under the scanning electron microscope.
In separating the nanofibres from isolated cellulosic content of the sisal fibre, the researchers removed its other components such as lignin, pectin and wax in a sequential process.

Chand, who has been researching on sisal fibre for the last 27 years says no such work been done on these fibres. His interest was triggered when by a 1990 report suggested that polymers reinforced with cellulose nano crystalline fibrils or microfibrils had the potential to become nano composites. Later reports suggested that microfibrils were stronger than steel.

Sisal leaves have very strong fibres with a tensile strength of 530 MPa and tensile modulus of 9.4 GPa. This property makes it useful for making twines, fishing nets, door mats, carpets and coarse fabrics. Fresh sisal leaves have been traditionally used as a raw material to produce rope, hecogenin, wax and handmade paper.

However, by virtue of its excellent mechanical properties (as compared to other vegetable fibres like jute, cotton, flax or sunhemp) sisal fibre has been successfully used as a reinforcement in developing polymer-based composites.

Sisal being an abundantly available renewable resource and green material was an easy choice to work on for the researchers. These will be the very properties propelling the nanofibres into a variety of industrial applications, the researchers, who are yet to think of marketing their find, said.