Tree bark extract produces materials for 3D printing

Powdered tannin extract of spruce bark. Image courtesy of Swiss National Science Foundation

In conversation tannins are often referred to by wine experts to discuss the bitterness and astringency of this alcoholic beverage. However, studies conducted by National Research Programme “Resource Wood” suggest that tannins are not just found in wine, but can be used to produce adhesives and composite materials.

The tannins extracted from the bark of native conifers can be used to create these materials — offering a great potential in the world of 3D printing. Advantageously, the bark is considered a waste product in the timber industry, making it widely available for extract.

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

Extracting tannins is not a new process. However, most extraction is done using tropical wood and is produced overseas, making it a costly option.

The researchers in Biel applied a similar process to their native conifer tree bark, which had never been used in commercial tannin extraction.

The team was able to extract the tannins by applying a two-stage water-based process, ensuring a high level of purity. They then tackled the challenge of developing a recipe to turn these extracts into adhesives for fibreboards and chipboards.

Tannin foam for lightweight construction and furniture-making. Image courtesy of Swiss National Science Foundation

By adding water to the spruce bark extracts, they produced adhesives that can be used in the production of boards. These test boards were produced without formaldehyde, an agent with harmful effects that is normally used in glued wood products.

The team wants to develop better extraction methods and ensure a high level of purity.  They need to reduce the variability of tannin yields and improve the reproducibility.

Researchers believe that these tannin extracts will play a key role in developing composite materials for 3D printing, where printable construction and design materials are entirely or primarily made from wood and bark.

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