In 2018, the results of a surprising research were published in the scientific journal Nature: a group of researchers from Maryland, in the United States, discovered a procedure capable of transforming wood into an extremely resistant material, more than steel and even some titanium alloys.
For some time now, scientific research has been looking for a material that is easily available in nature, economical and resistant, capable of facing the challenges of the future, also and above all with a view to greater performance and lower energy consumption. From this point of view, the transformation of wood into “super wood” has something revolutionary.
The techniques used by the research team in the first phase of the experiment are usually used to increase the density of the wood, and do not in themselves have a novel character. To these, however, the team led by Jianwei Song has added two innovative treatments that have allowed the wood to obtain greater resistance, in particular maintaining its shape and increasing its resistance to humidity.
The first step of processing is of a chemical type: here the wood is immersed in a solution of sodium hydroxide (NaOH) and sodium sulphite (Na2SO3). On the one hand, this process removes part of the lignin and hemicellulose from the timber, and on the other leaves the cellulose, the most important component of wood, practically intact. It is a process very similar to that used in paper mills to obtain the pulp of the wood with which to make paper.
The second step is instead of a physical nature: the wood is pressed until the maximum degree of compaction of the material is obtained. It is then heated slightly: a fundamental process because it is thanks to the combination of pressure and this controlled increase in temperature that the chemical bonds necessary to reinforce the wood are created.
The “super wood” obtained from this experiment is 3 times denser than the original wood, and even 10 times more resistant. Depending on the treatments it is subjected to, it can become up to 50 times more resistant to compression and 20 times harder and more rigid. Despite this extraordinary strength, moreover, the “super wood” can continue to be easily processed according to the needs required by the processing.
Another relevant feature of thickened wood is its great resistance to humidity. The team of researchers tested a sample in extremely humid environments, finding that the swelling rate in a five-day window was less than 10% – a very low threshold compared to the values reached by compressed wood with other techniques. Furthermore, the test was repeated with the same variables but with the compressed wood coated with a special anti-humidity paint: a simple treatment that solved the swelling problem.
The “super wood” has only been tested in the laboratory: currently the procedure is quite long, and it takes several hours to get a thickened wooden plate of the size of a book. However, the research team is confident that advances could speed up the manufacturing process.
Once its extraordinary characteristics have been recognized, “super wood” could therefore be the subject of huge investments and produced in industrial contexts, on a large scale. The scenario that lies ahead is very interesting. The “super wood”, for example, could become an excellent alternative to synthetic materials such as carbon fiber: economically more advantageous, it requires less complex processing, as well as being obviously completely recyclable, unlike carbon fiber which has with pollutants that are difficult to dispose.
Thanks to its properties, “super wood” could replace steel or other alloys in the automotive sector or even in the aerospace industry, which has always been interested in the development of increasingly resistant alloys.