The paper becomes transparent – and has properties such as plastic

A wood fiber consists of small cellulose nanofibrils – and the research world has used them for decades, but few products have succeeded in taking the step from the laboratory to industry.

Yunus Can Görür is a research student at KTH, and he has developed a new method that circumvents the conventional process.

In a few minutes you have a nanopaper. The material keeps out moisture, oxygen and can contain the gases that the food industry uses to keep food fresh. According to the researcher, the transparency is as good as with plastic.

– If you put it directly on a product, there is no difference from plastic. I replaced the plastic in a typical pasta box where you can see the pasta through a small window, and it looks identical. At the same time, the material is very strong, and it has better properties than plastic as a barrier. Plastic protects well against water but not as well against oxygen – this material is effective in both areas, says Yunus Can Görür.

New method: two steps

Bleached pulp fibers are modified in two oxidation processes, in a combination that has not been used before.

– By raising the pH value, the fibers fall apart into nanofibrils. The material becomes strong, more transparent and forms a barrier. We can do this in a matter of seconds rather than hours, and this is what has been the main problem – because time is money in all industrial processes. There have been so many good materials in the laboratories but no practical ways to put them into production. In that respect, this project is an attempt to give the wood fibers a chance to compete with plastic. Not only in terms of properties, but also in the fact that the material can be manufactured at a reasonable speed, says Yunus Can Görür to ​​Ny Teknik.

Time is money in all industrial processes. There have been so many good materials in the laboratories but no practical ways to put them into production.

At a low pH value, the paper acts as one might expect, but in a weakly basic environment the cellulose fibers swell. In the first step, carboxylic acid renders all nanofibrils negatively charged, which means that they are pushed apart. And in the second stage, the structure of the swelling fibers is weakened so that they rupture and release the nanofibrils.

Recycling is an important factor in the environmental profile, and while the paper is strong when used, recycling is simple – you only need to increase the pH level slightly for the paper to degrade.

Takes several years before it reaches the end consumer

So-called odor studies remain, but Yunus expects no problems there. His nanopaper is water-based and in the process only the surface layer is modified, a total of 20 percent of the material. Cellulose is already used for this in medicine capsules and as a thickener in food and cosmetics.

The new manufacturing method is patent-pending together with Billerud Korsnäs AB, which is the project’s industrial partner, but it will be a long time before the nanopaper can reach consumers.

– For this project to get from the laboratory to the store shelf, you have to count on 5-10 years, as with all innovations, he says.

Yunus describes, however, that the project is a platform that can be used for a variety of other things. Among other things, KTH has demonstrated that their material can be used as a smart filter. At a low pH, everything can get through the paper, but if you then increase the pH level, the fibers swell, which prevents a flow-through. You can also mix the material with clay to make fireproof paper.

– Now we are working on being able to use these materials to make anodes for batteries.

The material is strong and can be manufactured quickly. You can mix them with leading materials such as graphite and create renewable bio-batteries, says Yunus Can Görür.

In his work, he has been supervised by Associate Professor Per Larsson and Professor Lars Wågberg at KTH.