London, June 7 : Swedish researchers have created a sort of 'super-paper' that they claim is stronger than cast iron.
Lars Berglund, a researchers from the Swedish Royal Institute of Technology in Stockholm, reckons that his nanopaper may be used to reinforce conventional paper, produce extra-strong sticky tape, or help create tough synthetic replacements for biological tissues.
The researcher says that he uses cellulose, a biological material found in conventional paper, to make his nanopaper.
"Cellulose nanofibres are the main reinforcement in all plant structures and are characterised by nanoscale dimensions, high strength and toughness," New Scientist magazine quoted him as saying.
Berglund says that he and his colleagues have created a gentler process that prevents the loss of strength of cellulose, which results from the mechanical processes used to extract fibres from wood, and to make paper from them.
He has revealed that the new method involves breaking down wood pulp with enzymes, and then fragmenting it using a mechanical beater.
According to him, the shear forces produced cause the cellulose to gently disintegrate into its component fibres, and the end result is undamaged cellulose fibres suspended in water.
Berglund says that as the water is drained away, the fibres join together into networks held by hydrogen bonds, and form flat sheets of "nanopaper".
Conducting mechanical tests on their nanopapers, the researcehrs have found that it has a tensile strength of 214 megapascals, which is much stronger than cast iron's tensile strength of 130 megapascals.
"A regular paper network has fibres 30 micrometres in diameter, here we are at a scale three orders of magnitude smaller. The material [has] very small defects compared with a conventional paper network," says Beglund
Stephen Eichhorn, a polymer scientist at the University of Manchester, UK, said: "This (work) shows quite clearly the potential for cellulose nanofibres to provide a basis for reinforcement."
A research article describing the new paper has been published in the journal Biomacromolecules.