In recent years, fires in high-rise buildings at home and abroad have continued. From the fire in the north wing of the new CCTV site a few years ago, to the catastrophic fire in the teachers' apartment in Jing'an District, Shanghai, and on June 14 this year, the fire in the high-rise residential buildings in London, England... 1 The fires spread at a terrifying speed, and the scene was like a "purgatory on earth".

"Several high-rise building fires are shocking, and they have also sounded the alarm for China's building safety." As Zuo Yan, director of the Institute of Glass Science, China Academy of Building Materials Science, said, the frequent fires have caused the whole society to be concerned about high-rise buildings. Torture of building fire protection facilities. In 2015, the state promulgated the "Code for Fire Protection in Architectural Design", which made mandatory provisions for fire protection equipment such as fire-resistant windows.

In the event of a disaster, if there is better fireproof glass, will people have a little more hope of being rescued? This question has been beating on the research team of the Glass Institute of China National Building Materials Institute. After three years of dormancy, they finally gnawed on this "hard bone", broke the monopoly of foreign manufacturers in the high-end market in this field, and made composite fireproof glass with international competitiveness.

small bubbles big puzzle

According to the structure, fireproof glass is divided into two categories: monolithic and composite fireproof glass. Monolithic glass not only has high cost, good and bad quality, but also has the risk of self-explosion, which may bring unexpected personal injury. In contrast, composite fire-resistant glass has a higher safety factor, is more widely used, and is more popular in the market.

However, excellent performance is bound to require higher technological content. At present, the main technical problems of domestic composite fireproof glass are that it is difficult to eliminate micro-bubbles, and the appearance is not as good as that of foreign brands; the resistance to ultraviolet radiation is poor, and most products are used outdoors for a long time.

The core of the composite fireproof glass technology is the inorganic fireproof liquid between the two layers of glass. The current conventional production technology is to directly use the low modulus potassium water glass as the fireproof liquid, but the chemical stability of this material is poor, and it will appear during use. Defects such as decrease in transmittance, bubbles, and glue flow affect the appearance quality of the glass and the judgment of the fire situation.

So, can these problems be solved by increasing the modulus of potassium water glass? Mu Yuanchun, a senior engineer at the Glass Institute of China National Building Materials Institute, told the "China Science News" reporter: "The high modulus potassium water glass solution has low solid content and high viscosity, and it is extremely difficult to defoaming and spreading. A large number of micro-bubbles reduce the appearance quality and cannot be used directly as a fireproof layer substrate.”

Therefore, the development of high-performance composite fire-resistant glass without micro-bubble and excellent weather resistance, to achieve a leap in product performance and quality, and to expand the application scope of products are not only the inevitable trend of the development of fire-resistant glass technology in my country, but also the development of building energy-saving and safety glass industrialization. an important direction.

After fully understanding the pain points of the industry, Mu Yuanchun's team embarked on the road of research and development of composite inorganic fireproof glass since 2012.

The glass "core" is not fragile

However, things have not been smooth sailing. The mainstream production technology of composite fireproof glass is the flat drying method, that is, a piece of glass is placed horizontally, coated with fireproof liquid, then dried, and finally covered with a layer of glass.

"Foreign countries use specialized large-scale precision equipment for production, but importing such a complete set of equipment costs tens of millions of euros." Mu Yuanchun admitted that in order to save money, their experiments were initially done "by hand".

The middle layer of the fireproof liquid is only 1 mm thick, which requires the glass to be placed very flat. If there is a little error, the fireproof liquid cannot be evenly spread. The entire team squatted in the lab for a week and finally got the error down to less than 0.1mm.

However, this still cannot completely solve the problems of microbubbles and imprints. Due to the blockade of core technologies by foreign manufacturers, the team could not find a breakthrough point for a long time and took many detours.

It wasn't until the summer of 2015 that things took a turn for the better. In the communication with the customer, the other party proposed the idea of applying a silica dispersion with low solid content to polishing the outer surface of glass.

This made Mu Yuanchun come up with a whim: if this silica dispersion can be used to directly react with potassium hydroxide solution between the glass layers to generate potassium water glass with high modulus, it will not be possible to kill two birds with one stone and avoid the flat drying method. Are the disadvantages and disadvantages of low modulus fireproofing fluids?

But the premise of all this is the need to prepare low viscosity, high solid content silica dispersion to achieve filling. If the ordinary nano-silica is directly mixed with potassium hydroxide, the viscosity is too large and cannot be formed.

The attack has once again reached a stalemate. At this time, Mu Yuanchun thought of the paint experiments he had done during his Ph.D. study. He once solved the problem of film-forming properties of paints through particle design. "In a nutshell, the method is to coat the silica particles with a layer of material, so that the silica particles do not agglomerate with each other, but are evenly dispersed."

Simultaneously requiring low viscosity and high solids content is an almost impossible task. Zuo Yan admitted that when Mu Yuanchun proposed this idea, his heart was beating: "We ordinary people know that if we add less water, the dough will be sticky, but what Mu Yuanchun has to do is to ask for less water. If you add more noodles, you have to make a uniform thin soup, and you can't have any gnocchi."

He took this plan and consulted a circle of experts in the field of glass deep processing, and everyone said it was impossible.

However, Zuo Yan still chose to believe this young man. In his view, glass processing technology is originally a multi-disciplinary integration and intersection. If you want to innovate, you should encourage researchers to try boldly.

The scientific research team optimized the particle size, specific surface area, composition of functional monomers and other factors of silica, and finally overcome the problem of preparing potassium water glass-based fireproof solution with low viscosity, high solid content and high modulus. The composite fireproof glass prepared by this new method completely solves the limitations of micro-bubble, cannot be physically tempered, cannot be used for curtain wall, and cannot have curved special-shaped structure.

In this way, Mu Yuanchun's team developed an ultra-thin composite inorganic fireproof glass. They have successfully developed products of various sizes and sizes that meet the requirements of the national Class A and Class C standards, and have successfully passed the fire resistance limit test of a third-party testing agency; they have applied for more than ten patents in intellectual property (including PCT International Patent 1 Items), authorized 3 invention patents and 2 utility model patents.

Growing "Hidden Champion"

This new type of composite fireproof glass preparation technology, which can increase production efficiency by more than 5 times, reduce production costs by nearly half, cost only 1/3 of foreign products, and can realize continuous production, has quickly been favored by the market.

In May 2017, China National Building Materials Institute participated in the 28th China International Glass Industry Technology Exhibition with the newly developed new type of composite inorganic fireproof glass of different specifications. The audience was amazed at the appearance, and received extensive attention from domestic and foreign customers.

Cooperation and orders are coming like snowflakes. Due to the mastery of core technologies and the realization of localization of key equipment, China National Building Materials Institute has signed technical service agreements with more than ten domestic glass deep-processing enterprises to provide them with fireproof solutions and guide compounding. The industrialized production of fire-resistant glass is planned to produce 1 million square meters of composite fire-resistant glass for fire-resistant windows annually, driving the output value of the related glass door and window industry to exceed 1.5 billion yuan. .

As the earliest aviation glass production base in China, with the largest number of models and advanced technology, the Institute of Glass has created one after another "China's first" in history, and is known as "the cradle of China's aviation glass". In recent years, the Institute of Glass has implemented the development strategy of combining military and civilians, and has firmly grasped the technical commanding heights in the field of glass deep processing by means of innovation.

"We are a national research institute, and what the country urgently needs is what we have to do." Zuo Yan said, "Our research team will keep up with the forefront of science and technology and forge ahead on the road of industry-university-research integration."

At present, the Glass Institute of China National Building Materials Institute has undertaken the "13th Five-Year" national key research and development plan "Intelligent glass and high-safety glass key technology development" project, and will continue to improve the production technology of fire-resistant glass, draft relevant industry standards, and prepare for establishment Industry alliance to promote the transformation and orderly sustainable development of China's fireproof glass industry.

If you don't fly for three years, you will fly into the sky. With the innovative technology of Mu Yuanchun's team, China National Building Materials Institute has successfully achieved a "counter-attack" in the field of composite fireproof glass. The key technical fields have won a place, which really made China's fireproof glass "fire".

- Transferred from "Chinese Journal of Science"