Wood is a great material for … everything. From it do everything that you can imagine. The only thing that is lacking is strength. Many varieties of wood are very strong, but, unfortunately, they are not strong enough to be used more widely. Specialists from the United States have increased the strength characteristics of wood by special processing.
After the tree is treated by a new method, its strength increases tens of times, it becomes more durable than steel or titanium. At the same time, wood is still an environment friendly material, an alternative to plastics or metals.
“In fact, this is a new class of materials with great potential,” said Lee Teng, a specialist from the University of Maryland. The work of Teng and his colleagues was published on February 7 in the authoritative scientific publication Nature.
Attempts to strengthen the tree, change in some way its characteristics do not stop for decades . Some methods are successful, others are not. The selection of cellulose microfibers can be considered as successful, which makes it possible to create materials that are sufficiently resistant to external influences.
But Teng and his colleagues decided to approach the problem from the other side. Researchers focused on modifying the porous structure of natural wood. Initially, they began to try boiling different types of wood, including oak, in a solution of sodium hydroxide and sodium sulfite for seven hours. This process left the cellulose structure almost intact, but the components surrounding the cellulose were partially gone. One of these components is lignin, a polymer that binds cellulose.
Then the team placed a wooden block for a day under the press, simultaneously heating it to 100 degrees Celsius. As a result, wooden slats formed a fifth of the previous parameters. In addition, this material was three times denser than natural wood and 11.5 times stronger. Previous attempts to strengthen the strength characteristics led to an increase in this parameter by a factor of 3-4.
Scanning the fibers of a new material with an electron microscope has shown that squeezing destroys cellulose tubes that are compressed and intertwined together. “You get nanofibres placed along the tree growth axis, linked together,” one of the study participants said.
In order to test how stable the “new type of wood” is to external factors, the team began to shoot on pallets from a ballistic cannon, which is usually used to test the strength of military vehicles. As it turned out, the modified wood withstands the impact of a 46-gram steel projectile, flying at a speed of about 30 meters per second.
This, of course, is much slower than the speed of the bullet that flew from the barrel of a firearm, but still this is a solid achievement. This speed roughly corresponds to the speed of the car moving before the collision with the obstacle. Yes, Americans believe that their method allows you to create material suitable for the automotive industry.
Experts believe that the team of “tree improvers” overly complicates the process, which can be much simpler. For example, simply the effects of high temperature, steam and pressure can significantly improve the strength characteristics of the material. And you can just boil the tree for 7 hours in a solution of caustic soda. The result is a fairly strong material. 24-layer protection from such a tree delays a 9-mm bullet, which is fired from a pistol.
Mikaela Eeder, a researcher at the Max Planck Institute, believes that the impact of pressure also strengthens the tree – although in this case it is unclear how much weave the nanofibers. Nevertheless, the authors of the original work are sure that only their methods allow many times to improve the strength of the tree. Colleagues agree with them, saying that the work has great potential, and in the future it would be possible to create a commercial technology for the production of solid building materials from wood.