Tree for buildings: scientists have invented fireproof paper houses

Russian scientists have proposed an economically viable technology for the production of nanocellulose. Until recently, its creation required the same amount of energy as aluminum smelting. According to experts, solving this problem could lead to a revolution in the construction industry, as lightweight cellulose panels are comparable in strength to steel and are non-flammable. However, the mass use of the new material will begin only if it turns out to be more profitable than the usual concrete and other classical analogues, experts warn.

What is nanocellulose?

Specialists from the Institute of Chemistry of the Far Eastern Branch of the Russian Academy of Sciences have developed an economically advantageous technology for the production of nanocellulose material. This composite is stronger than steel in its strength and is absolutely fireproof. Until recently, its production required high energy costs, which are comparable to aluminum smelting. However, its high cost prevented its mass use — it reached hundreds of dollars per gram.

The approach of Russian scientists makes it possible to reduce costs at least tenfold, which opens up the possibility of creating environmentally friendly materials based on wood fibers for construction in the form of insulating panels, as well as sorption, medical, hydrophobic, electrical and fluorescent products.

The development of scientists will allow for the first time in the world to start industrial production of a material that, in addition to construction, can be used as sorbents, as well as for medical, hydrophobic, electrical and fluorescent devices.

— The production of nanoscale cellulose cannot be cheap, because it is a labor-intensive process with high energy costs. But we managed to reduce the cost and simplify it due to the fact that we do not bring cellulose to the final nanoscale state, but get a material with the necessary properties, including only small amounts of nanocellulose. Thanks to this, the cost has decreased by an order of magnitude," said Yuri Shchipunov, Head of the Laboratory of Colloidal Systems and Interphase Processes at the Institute of Chemistry of the Far Eastern Branch of the Russian Academy of Sciences.

Nanoscale nanocrystalline cellulose is obtained by processing conventional cellulose produced, for example, from sawdust or paper recycling. It is passed through a homogenizer, a device for creating aqueous dispersions that breaks large particles into smaller ones, down to nanocrystals. During the transition to the nanoscale state, it fundamentally changes the properties of well-known substances, including cellulose.

In the course of research, scientists have found that nanocrystals are poorly suited for practical use. During long-term studies, it was found that it is better to use an intermediate mixture of nano— and microfibrils, the filamentous structures that make up cellulose fibers. From these components, they obtained a durable and at the same time elastic aerogel, a highly porous material with 90-99% of its volume filled with air. Additives of various fillers make it possible to obtain materials with the desired characteristics and functions. For example, strong and lightweight building blocks that are not affected by bacteria, are non-flammable and do not emit harmful substances.

They have a lower thermal conductivity than wood, which is important for keeping the house warm. So far, the proposed technology is being implemented only within the walls of the laboratory, however, with industrial production and widespread distribution, it will become much cheaper, and heat-insulating panels will be able to replace blocks of synthetic polymers that easily ignite and at the same time emit toxic gases. They also do not decompose, polluting the environment.

— As a raw material for the production of aerogels, it is possible to use the capacities of enterprises that produce paper. Currently, they are partially idle due to a sharp reduction in its consumption. They prepare a dispersion of fibers in water (pulp) from wood, which is an intermediate product. In fact, these are the raw materials we need: fibers purified from other components contained in wood. They need to be mechanically processed. We are currently doing this in the laboratory, and we have enough competencies to develop an effective industrial technology. But this is only possible if the right equipment is used," said Yuri Shchipunov.

The use of nanocellulose in construction

The number of studies in the field of synthesis and application of nanocellulose is increasing every year. However, the gap between laboratory research and industrial implementation in this area has not yet been overcome, explained Victoria Shvetsova, laboratory assistant at the Department of Technology of Binders and Concretes at the National Research University MGSU. The construction industry is one of the most material—intensive sectors of the economy, so the ability to produce a finished product in the right volume and on time remains an essential condition for the widespread use of new materials.

— Cellulose nanocrystals have high rigidity, with an elastic modulus equivalent to or even higher than that of some steel grades, while maintaining low weight, biodegradability and a large surface area. This makes them ideal candidates for reinforcing various polymer matrices. Additionally, the properties of composites can be improved and the cost reduced by using multi-level dispersed reinforcement, for example, in conjunction with mineral or polymer fibers. When nanocrystalline cellulose achieves high thermal stability, it can be used as fire—resistant coatings for building structures," she told Izvestia.

The use of nanocellulose in construction could be a breakthrough in the field. The advantages of such materials are obvious: high strength, wear resistance, fire safety and environmental friendliness. With such characteristics, the material would be in high demand for creating lightweight and durable structures, says Serdar Yaziev, head of the Department of Construction Technologies and Structural Materials at the Peoples' Friendship University of Russia.

— However, the key issue here is economic feasibility. Reducing energy costs for production is certainly good news. But will the material be able to compete with concrete, steel or composite elements? The optimization of the production of these materials has reached the highest levels over the years, and it is very difficult for any newcomers to this market to gain their niche," he said.

There is another important aspect — the possibility of scaling the resulting technology. Getting excellent results in the laboratory is just the first step towards mass production. A huge number of promising developments have not been able to move on to the next stage. However, with the successful implementation of the project, Russia can become a world leader in this field. This will require serious investments, as well as support from the government and business, the expert added.