It is 9 times more resistant than the conventional thanks to this innovative method

The prehistoric man had two options to take refuge in bad weather and the threat of fauna: take refuge in caves, caves and other natural accidents or build a refuge with what he had the most by hand. He quickly discovered The advantages offered by Wood as a structural solutionSomething that, according to the latest archaeological investigations, started 500,000 years ago. In the past 200 years, materials such as steel or concrete have moved the use of wood in construction, but new technological developments even raise all kinds of skyscrapers and housing buildings, also in Europe.

These latest advances are based on the opposite or CLT wood, capable of competing with the properties of the best materials used in the sector and much more durable. However, there are other approaches that seek to increase the resistance and hardness of natural wood through chemical processes. The most recent comes from a team from the University of Nanjing (China), which obtained a “super resistant but light” wood, with “great application potential as a sustainable engineering material Replacement of traditional structural materials such as metals and alloys“.

The study, presented in the scientific journal Bioresources and bioproduct logDescribe how researchers have designed and applied an innovative self-control strategy, a microstructural change that improved its properties to make it if or more resistant than steel. And they reached it without resorting to a hot pressing, a technique previously used with the same objective and this implies high energy consumption.

Auto-controlled wood

Wood which is extracted every day from forests for all types of uses, from the manufacture of paper to furniture or components for construction, is a natural material designed by nature to be strong, flexible and resistant. Its main component is Cellulose, which gives a grouping of structural resistance in long fibers. The other key element is lignin, which gives rigidity and makes it resistant to compression, in addition to protecting it from external agents such as water or different microorganisms.

The mixture of the three elements forms the walls of Long hollow tubes that operate longitudinally inside the wood. This inner void of the fibers is known as the light, and this is what limits the resistance of wood. To improve their properties, researchers used an innovative method that allowed them to obtain what they call as “Supermadera”.

This technique for release and reorganize wood fibers Start boiling the block of porous natural wood in a mixture of sodium sulfite and sodium hydroxide (which we know under the name of bleach), a process that eliminates part of the lignin. Then, the wood undergoes “a LICL / DMAC inflated process”, plunging into a heated mixture of lithium chloride and dimethylacetamide salts, an organic solvent often used by the pharmaceutical industry.

The result is that cellulose and what remains of lignin in the swelling block moving inwards, filling these voids with light. To obtain optimal results, the wood was washed with distilled water and allowed to dry at room temperature for 10 hours. In this phase, call for self-testimony, the material has contracted uniformly reduce its volume to 79% and increase their density up to three times. The curious thing is how the block has maintained its original length, due to the orientation of the fibers.

Strong, resistant and flexible

To check in the laboratory how these changes in the structure of the wood had affected their composition, the engineers used an electronic scanning microscope (SEM), which allowed them to observe the swelling and compacting processes. After, The resulting blocks have undergone a series of tests to demonstrate its mechanical properties.

According to tests, self-controlled wood has obtained extraordinary results. For example, Its tensile resistance is approximately nine times higher than that of the original woodreaching 496.1 MPa. He also showed an excellent combination of resistance and tenacity, resolving a common limitation in conventional materials and even compressed wood.

As for compression resistance, it is double that of natural wood, while Its resistance to flexion in the direction of growth is five times higherNow uniform behavior under load, unlike other densified woods. This makes it suitable for complex mechanical environments, either in infrastructure such as bridges, or in support beams.

These improvements are due to its aligned and extremely dense microstructure. During the self-control process, nanocellulose fibers were reorganized by forming a large number of hydrogen bonds longitudinally, which Increase in internal cohesion. In addition, the cellular structure has changed tubular to a compact configuration, reducing defects and improving its resistance.

It has also been found that this method works in different types of wood, reaching Up to 14 times more resistance in raft woodEverything without warm in a hurry. To demonstrate the versatility of the equipment, the researchers even made a wooden nail, which has exceeded steel in different loading tests.

Although there are still challenges to overcome in the next stages of the investigation, such as climbing processes until they make them compatible with series production, The potential applications of this new method are enormousIn particular in the construction sector and in complex mechanical environments.