Nano-pulp, a new frontier for the forest industry

Nanotechnology offers many great opportunities for different industries, and people.

In the nano world, the proportions are a millionth of a millimeter to a thousandth of a millimeter. The aim of nanotechnology is to study and manipulate matter on a molecular scale.

There are many practical applications of nanotechnology, such as electronics, coatings and cosmetics.

The forest industry is increasingly becoming interested in nanotechnology.

With nanotechnology, cellulose material can be durable, lightweight, environmentally friendly and cheap. Such high-performance materials can be used in advanced electronics like cars, aircrafts and medical products.

The technique is based on wood fibers broken down into their smallest components and then reassembled into new materials.

At the Royal Institute of Technology (KTH) in Stockholm, Professor Lars Berglund is leading research into nano-cellulose technology. Berglund is also director of the Wallenberg Wood Science Centre (WWSC) at KTH and Chalmers, Gothenburg, a new research center aimed to develop alternative uses of forest resources.

Disassembling cellulose fibers

“Nano-cellulose consists of fibrils that are about 10 nanometers thick. If fibrils are 100 times longer than they are thick, they have many interesting properties that may be utilized in various applications,” says Berglund.

“Bio-composites, reinforcing materials, and viscosity agents in the food industry are examples of this. Nano-cellulose is also biodegradable and more moisture resistant than the normal cell walls of wood.”

“Pressed together, the cellulose can form transparent films for use as barrier materials in packaging. Fibrils can also be mixed into the pulp for paper production and make the paper stronger by tying paper fibers together.”

How do you get the fibrils?

The cellulose fibers, one of the major components of wood, are made up of individual micro-fibrils. By opening the fiber cell wall the fibrils become available.

This is done through mechanical homogenization in combination with mechanical and chemical pre-treatment. Overall, it is a very energy intensive process.

The non-profit foundation Innventia has long worked on developing methods for exploiting nano-cellulose. It recently presented the world’s first pilot plant for production of nano-cellulose in higher volumes.

“The focus of our work was to develop an energy efficient process. We have obtained an energy savings of up to 98 percent,” says Mikael Ankerfors, who leads Innventia’s research into nano-cellulose materials.

“Reducing energy consumption is made possible through various pre-processing steps, which weakens the fibers so that they can more easily be ground down to the fibrils. On a laboratory scale, we could previously produce one kilogram of nano-cellulose a day, but in the new pilot plant we can do a ton per day.”

Magnetic nano-paper

In 2011, scientists at the WWSC presented their findings about magnetic nano-particles in super strong nano paper. The new nano paper is extremely lightweight, strong and flexible and can be used to prevent counterfeiting and to filter out metal particles.

“Magnetic nano-paper is easy to produce and has unique characteristics, but also shows the product’s potential in R&D for the forest industry,” says Professor Berglund at KTH. “Besides using magnetic nano-paper to prevent document fraud, other applications include implants for the human body, and in small motors and sensors. Compared with metallic magnetic materials, strong magnetic nano-paper is much more malleable. The new preparation method can also be used for other forest products.”

Nano-paper consists of very strong and flexible nano-fibrils from cellulose. The first thing that is produced is an extremely porous “airgel,” which contains only two percent cellulose fibrils. The remainder of the gel is made up of pores. Dipping the porous gel in a salt solution creates the magnetic particles. These are about 40 nanometers high and consist of a mixture of cobalt and iron oxide and bind very strongly to the cellulose.

The properties of the finished product can be controlled in several ways, for example by affecting the amount of magnetic particles formed. Further, the porous paper can be compressed so as to provide the required strength and flexibility.

This article was published in March 2012

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Facts about WWSC and Innventia

  • The Wallenberg Wood Science Center (WWSC) is a research center at the Royal Institute of Technology (KTH) that works in collaboration with the Chalmers University of Technology. The aim is to develop a materials research program in which material from the Swedish forests can be used in new ways. The Knut and Alice Wallenberg Foundation funds the center.
  • INNVENTIA is a Swedish research institute engaged in R&D in the pulp and paper, packaging and the publishing industries. The activities range from basic research to direct consulting and development projects in three industrial areas with the final products being bio-based energy, chemicals and materials, graphic media products and packaging and logistics. The Swedish state is a partner in Innventia with a 29 percent share, while the paper industry owns the other 71 percent.