Transparent wood composites are novel wood materials which have up to 90% transparency and higher mechanical properties than wood itself, made for the really first time in 1992.
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When these materials are commercially available, a significant benefit is expected due to their inherent biodegradable properties since it is wood. These materials are significantly more biodegradable than glass and plastics. On the other hand, concerns may be relevant due to the use of non-biodegradable plastics for long lasting purpose, such as in building.
History
A research group led by Professor Lars Berglund from Swedish KTH University along with a University of Maryland research group led by Professor Liangbing Hu have developed a method to remove the color and some chemicals from small blocks of wood, followed by adding polymers, such as epoxy, at the cellular level, thereby rendering them transparent.
As soon as released in between 2015 and 2016, see-through wood had a large worldwide impact, with articles in ScienceDaily, Wired, the Wall Street Journal, the New York Times, by naming a few.
Actually those research groups rediscovered a work from Siegfried Fink, a German Researcher, from as early as 1992: with a process very similar to Berglund's and Hu's, the German Researcher turned wood transparent to reveal specific cavities of the wood structure for analytical purpose.
The process
This is a three step process:
The first step consists of immersing the 4 or 5 inch block of wood in a solution of water, sodium hydroxide, and sodium sulphite at boiling temperature for two hours. This enables the lignin in the cell walls to be leached out. "Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity and do not rot easily".
The second step of oxidation with hydrogen peroxide completes the leaching of the lignin.
The third step consists of immersing the material in epoxy and putting it under alternating vacuum and atmospheric pressure; this fills the wood's natural but now disused nutrient and hydrating microscopic channels. The epoxy-filled microscopic channels create a material that has transparent refractive properties.
The new material is rated stronger than plastic, but is only in the laboratory and experimental stage, and not yet ready for commercial use.