Oct 26, 2017 | By Benedict

Researchers at Switzerland’s Bern University of Applied Sciences in Biel have developed a new way to extract tannins from native tree bark in order to produce adhesives, composites, and 3D printing materials. Tannin foams are highly fire-resistant, making them suitable for light construction.

Trees are incredibly valuable sources of material. You can turn them into houses, boats, or even books, and use their wood to make fires.

But not every part of a tree is as useful as another. The bark of conifers, for example, is generally considered waste—burnt or used as mulch.

Researchers at the Bern University of Applied Sciences in Biel think this might be a waste. Why? Native tree barks, they say, could have numerous uses, even in the field of 3D printing.

“If we take cascaded use seriously, we need to find ways of using tree bark because the wood industry produces plenty of it,” explains researchers Frédéric Pichelin. “This offers new sources of income, based on a renewable resource, to saw mills and the manufacturing industry.”

The valuable part of conifer tree barks—the part that might be wasted on mulch—is tannin, a bitter-tasting substance containing gallic acid. Although generally extracted from tropical wood, there is plenty of tannin to be found in conifers native to the researchers’ Swiss home.

The particular tree being focused on is the Picea abies, or Norway spruce, which grows in several places in Northern, Central, and Eastern Europe, despite its name. Many countries around the world use the Norway spruce as a Christmas tree.

Using a two-stage water-based process, the Bern University researchers have been able to extract tannins from the Norway spruce, keeping the level of purity very high. These tannins can be used to make adhesives for board production and other things, but perhaps their most exciting potential application is 3D printing.

Tannins from tree bark can be used to bind wood products, but also other materials containing fibers. Like 3D printable composites, for example, which could be used to make any number of 3D printed products.

There are big advantages to using the natural substance too. Tannins are highly fire-resistant, which could make them ideal for making 3D printed furniture or even parts of buildings. They even have antioxidant and antibacterial properties, making them appealing to the food industry.

For the Bern University researchers, part of the inspiration behind this tree bark research is ensuring that Switzerland makes the most of the natural resources at its disposal. And with 3D printing representing a huge financial opportunity for European nations, this tannin extraction could prove highly valuable.

"The application potential of wood bark tannins is great,” Pichelin says. “Presently it is difficult to say in which direction the development will go; what is important is that Switzerland is not left behind.”

The research paper, “Hot water extraction of Norway spruce (Picea abies [Karst.]) bark: analyses of the influence of bark aging and process parameters on the extract composition,” has been published in Holzforschung: International Journal of the Biology, Chemistry, Physics, and Technology of Wood.

The other researchers were Gerald Koch, Ron Janzon, Ingo Mayer, and Bodo Saake.

 

 

Posted in 3D Printing Materials

 

 

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