By Andrew Liszewski
The days of having to decide between paper, plastic or cast iron bags at the grocery store are numbered thanks to the development of a new type of extremely tough nanopaper. The paper is made from nanosized (oh I get it!) cellulose fibers making it both stronger and lighter than traditional papers.
Conventional paper is made from cellulose, a crystalline polymer of glucose that’s the primary component of plant cell walls. At the nanoscale level, cellulose can be extremely strong, with individual fibers capable of withstanding more stress than glass fibers or steel wire. But paper processing generates relatively large cellulose microfibers riddled with defects that can break apart under stress. That leaves most commercial paper with a tensile strength that tops out at about 30 megapascals (MPa), says Lars Berglund, a lightweight structures engineering expert at the Royal Institute of Technology in Stockholm, Sweden.
To toughen paper up, Berglund and his colleagues kept the cellulose fibers small. They did this by breaking down wood pulp in water with a combination of enzymes and mechanically beating it further. The result: defect-free nanofibers about 1000 times smaller than typical cellulose fibers. As a final step, the researchers treated their nanofibers with carboxymethanol, which coated the fibers in carboxyl groups. These groups readily form hydrogen bonds that helped the fibers make tight contacts with one another, further strengthening the material. The final result–published in the current issue of Biomacromolecules–was a paper with a tensile strength of 214 MPa, far above the 130 MPa of cast iron and the previous record of 103 MPa for a high-strength paper.
Besides allowing you to pack a grocery bag full of canned food without the worry of it tearing, the nanopaper also has the potential to replace other expensive but strong and lightweight materials like carbon fiber or even carbon nanotubes. Maybe these researchers should hook up with the Japanese Aerospace Exploration Agency who are trying to launch that paper airplane from space.