US researchers develop superdense wood with steel-like strength

09 February 2018

A team of US researchers has developed superdense wood, a highly-compacted wood that matches steel in strength, but is much more lightweight.

The highly desirable physical properties of this material can be traced back to its production. The material starts as regular blocks of wood in a water-based solution of sodium hydroxide (lye) and sodium sulphite which is brought to a boil. These chemicals strip the wood of its lignin and hemicellulose content (two organic compounds that give wood its structure and rigidity), making it more malleable.

This wood is then pressed at 5 megapascals (50 times the atmospheric pressure at sea-level) between two metal plates heated to 100 Celsius.

The process eliminates the gaps between cells in the wood, and shrinks the blocks to about 20 per cent their thickness, increasing density three-fold.

The pressure triggers a chemical bonding process between the different forms of atoms that make up the wood's cellular structure, greatly strengthening the material in the process.

According to the scientists, the robust material, which can stop bullets, could be used in cars, aeroplanes, buildings, and even body armour.

"This could be a competitor to steel or even titanium alloys, it is so strong and durable. It's also comparable to carbon fiber, but much less expensive," said lead researcher Liangbing Hu, The Sun reported.

According to the researchers, the treatment can be applied to bulk amounts of wood at once, and allows them to bend and mould the material into the desired shape at the start.

Co-author, Teng Li a mechanical engineer at the University of Maryland in College Park notes that another advantage of the process is that the chemicals used to scrub lignin and hemicellulose from the wood will not pose any significant pollution concerns.

According to Li, superdense wood could become an eco-friendly alternative to steel or other metallic alloys for construction works and also find application in the manufacture of more light-weight, more fuel-efficient vehicles.

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