Chemical modification makes wood more durable

One of our new research projects 2019 aims to replace environmentally unfriendly materials with wood.

Text: Mats Hannerz

 

Bridge in the Netherlands from acetylated pine wood. Photo: Gerhard Büttner, CC BY-SA 3.0

In some construction uses, such as when exposed to open air and moisture, wood must be durable and resistant to fungal degradation. This is sometimes a drawback for wood as an alternative to more climate-impacting materials.

Historically, wood has been treated with preservatives such as creosote or copper compounds, but the use of such substances is now very restricted.

Environmentally friendly methods

But, there are environmentally friendly methods to improve the durability of the wood. Chemical acetylation is one method that has proved successful in making wood more resistant to fungi.

However, we don’t know how acetylation improves the wood. It is known that the water in the cell walls is reduced, but water is present in many places and forms in wood. This is why the researchers are asking: “Where is the water in acetylated wood?”, and this is also the title of a new SNS-funded project.

Investigate the influence of acetylation

The project combines specific equipment and expertise from Sweden, Denmark and Norway to investigate the influence of acetylation on the amount, location and state of water in wood.

The hypothesis is that acetylation not only affects the amount of water, but also the location and state of it. Wood from Norway spruce will undergo chemical treatment and then the amount of water will be measured (at Lund university) and the location and state of water determined (at University of Copenhagen). The amount of cell wall water and capillary water in the wood will also be measured at Nibio.

 

Acetylation

Unlike pressure treatment, in which preservatives such as ammoniacal copper quaternary compounds are infused into wood, acetylation chemically modifies wood. In the process, acetic anhydride reacts with the hydroxyl groups on large molecules such as lignin and hemicellulose in the plant cell wall. The reaction replaces hydroxyl groups with acetyl groups and yields acetic acid as a by-product. (Source Chemical and Engineering News)

 

Project name: Where is the water in acetylated wood? Studies of amount, location and state of water in acetylated wood for development of more durable wood products.

Cooperation between: Lund university (Sweden), University of Copenhagen (Denmark), Nibio (Norway).

Coordinator: Maria Fredriksson, Lund university. maria.fredriksson@byggtek.lth.se

Project page

 

Read about our project SNS-126

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