A new transparent and sustainable wood, which allows natural light through its surface and that can store thermal energy, is the result of research conducted at Stockholm’s KTH Royal Institute of Technology. The new transparent wood is unique and unlike other transparent woods, is intended for structural use.

A tested sustainable alternative
In previous iterations of their composite, the KTH researchers had used conventional petroleum-based polymers. Now they have successfully developed and tested a sustainable alternative which uses limonene acrylate – a monomer made from limonene.

“The new limonene acrylate is made from renewable citrus, such as peel waste that can be recycled from the orange juice industry,” said Céline Montanari, a PhD candidate and lead author of the study.

Montanari and her colleagues used an extract from orange juice production to create the polymer, which was suitable for restoring the strength of the delignified wood while allowing light to pass through. At a thickness of 1,2mm, the composite material offers 90% optical transmittance and surprisingly low haze. Notably, the material is intended for structural use; it demonstrated heavy-duty mechanical performance with strength and elasticity suitable for structural applications.

Nanotechnology applications
According to Professor Lars Berglund, head of the university’s Department of Fibre and Polymer Technology, the group wanted to create a sustainable version of the wood composite for years.

“Replacing the fossil-based polymers has been one of the challenges we have had in making sustainable transparent wood,” he said. He said that the material is made with no solvents and all chemicals are derived from bio-based raw materials.

According to the researchers, the advances could enable an exciting and unexplored range of applications such as in wood nanotechnology, with the possibilities including smart windows, wood for heat storage, a wooden laser and wood with a built-in lighting function. The researchers are working with the KTH photonics group to explore these possibilities further.

“We have looked at where the light goes and what happens when it hits the cellulose,” Berglund added. “Some of the light goes straight through the wood and makes the material transparent. Some of the light is refracted and scattered at different angles and gives pleasant effects in lighting applications.”

Thanks and acknowledgement are given to the KTH Royal Institute of Technology’s Department of Engineering and Technology for the information contained in this article.

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