Sweden’s KTH scientists have made their see-through transparent wood composite 100% renewable and more translucent by infusing wood with a clear bio-plastic made from citrus fruit.
First developed by the KTH team in 2016, this transparent wood material has been touted as one of the most innovative new structural materials for building construction. It lets natural light through and can even store thermal energy.
The key to making wood into a transparent composite material lies in stripping out its lignin, the major light-absorbing component in wood.
This however has an adverse effect as the empty pores left behind by the absence of lignin need to be filled with something that restores the wood’s strength and allows light to permeate.
While fossil-based polymers were earlier used to fill up these pores, the KTH team has now successfully tested a more eco-friendly alternative called limonene acrylate – a monomer made from limonene – to do the job.
“The new limonene acrylate it is made from renewable citrus, such as peel waste that can be recycled from the orange juice industry,” says lead author and PhD student Céline Montanari.
According to Montanari, the new composite offers optical transmittance of 90% at 1.2 mm thickness and remarkably low haze of 30%.
Moreover, unlike other transparent wood composites developed during the past five years, this new citrus-infused material is mainly intended for structural use.
It has also proven to have heavy-duty mechanical performance with a strength of 174 MPa (25.2 ksi) and elasticity of 17 GPa (or about 2.5 Mpsi).
Possibilities for this new material include smart windows, wood for heat-storage, and wood that has built-in lighting function, says KTH’s Department Head for Fiber and Polymer Technology, professor Lars Berglund.
“We have looked at where the light goes, and what happens when it hits the cellulose.”
“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.”
Image and content: Céline Montanari/KTH Sweden
