The world has used Chinas golden film

In the future, high-speed train permanent magnet traction motors may adopt a new generation of silicon carbide power chip control, which requires films to have higher temperature resistance and corona resistance life. Therefore, we are developing the next generation of film products. "Dr. Zhang Bufeng, General Manager and Chief Expert of Hunan Zhuzhou Times Huaxin New Material Technology Co., Ltd. (hereinafter referred to as" Times Huaxin "), revealed in a keynote speech at the" 2025 National Petroleum and Chemical Industry Science and Technology Innovation Conference "held recently.

The film referred to by Zhang Bufeng is called high-performance polyimide (PI) film. The thin film is golden in color and as thin as cicada wings. Although it looks unremarkable, it is the material at the top of the strategic new material pyramid. High end fields such as electronic information, rail transportation, aerospace, and defense and military industries all rely on it. China has been continuously researching and developing its manufacturing process, but there have been no achievements for over 50 years.

In the past, we could only produce as many trains as others sold us materials. But when we produce this film, we can make as many trains as we want! "Tang Haitao, Chairman of Times Huaxin, said in an interview with Science and Technology Daily.

Breaking through: 'Buyer' becomes' Seller '

On May 24th, a high-performance PI film intelligent production line with a width of 2100 millimeters was operating at full capacity in a Class 1000 cleanroom of Times Huaxin.

The measured raw materials are automatically "fed" into the production line machine, accompanied by the high-speed rotation of the roller shaft at a speed of nearly 30 meters per minute. Under the action of catalyst and dehydrating agent, the film is slowly peeled off from the steel strip through low-temperature polymerization reaction.

The CR450 high-speed train prototype released in December 2024 uses our high-performance PI film on its permanent magnet traction motor. This film is both resistant to high temperatures and corona discharge, ensuring the reliability of motor operation. ”Zhang Bufeng said.

The seemingly inconspicuous film once held the "throat" of China's train manufacturing and railway development.

Around 2010, China's railway construction reached its peak period. "After the opening of the railway line, a large number of trains need to be put into operation, but it is not up to China to decide how many trains can be built. Because the traction motor, the 'heart' of the train, needs to use high-performance PI film as insulation material, which can only be imported at that time. ”In other words, the quantity of trains produced in China depends on how much material foreign suppliers are willing to sell us, "explained Tang Haitao

From the 1960s to the 1980s, China organized experts to conduct scientific research on it, but no breakthrough was achieved. In 2004, the team began searching for domestic alternatives to it, but it was difficult to find any trace in the market. In 2010, as buyers, they were forced to embark on the path of independent research and development.

There are two main technical routes for manufacturing high-performance PI films - thermal imine method and chemical imine method. In 2013, we built a thermal imine membrane production line, but practice proved that this path was not feasible, "said Zhang Bufeng.

Originally, DuPont in the United States initiated comprehensive patent protection for its independently developed corona resistant PI film with a "three-layer structure". This "blockade" allowed China to only attempt to manufacture high-performance PI films with single-layer structures. Like other domestic film manufacturers, Zhang Bufeng's team used the thermal imine method to produce single-layer high-performance PI films. Although the appearance is not much different from foreign products, the application reliability is far from satisfactory.

Afterwards, the team decisively began exploring the chemical imine method. In 2015, they established a pilot platform for the chemical imine membrane method. This time, they achieved success and formed a highly reliable and corona resistant PI film preparation technology route with completely independent intellectual property rights.

In 2017, China's first chemical high-performance PI film production line with a width of 1542 millimeters was completed and officially put into operation the following year. In the crucial field of polymer material manufacturing that constrains the development of China's high-tech industry, we are no longer inferior or subject to others! "Tang Haitao felt proud.

Nowadays, the domestically produced high-performance PI film they have produced is gradually being replaced by localization in the fields of aerospace and ship power in China.

Breakthrough: Overthrow the Thick 'Ceiling'

With the breakthrough of Huaxin in the chemical imine method for manufacturing single-layer high-performance PI films, the manufacturing of heat dissipation PI films has also achieved rapid success.

At the exhibition area of Times Huaxin, the reporter saw a roll of 200 micron thick heat dissipation PI film samples quietly displayed. After high-temperature firing at 2700 ℃, it can be made into the world's thickest artificial graphite film, reaching up to 100 microns. Flexible thermal conductive artificial graphite sheets made of graphite film are the core material for heat dissipation in electronic terminals such as laptops and smartphones.

The heat dissipation PI film manufactured by Times Huaxin has stood out in the competition with three top companies, DuPont in the United States, Zhongyuan Chemical in Japan, and SKC in South Korea, becoming the exclusive supplier of Samsung's new products and attracting more and more manufacturers such as Apple, Huawei, Xiaomi, OPPO, etc. to seek cooperation.

What exactly made Time Huaxin's heat dissipation PI film popular among well-known mobile phone manufacturers at home and abroad, and made the world use China's "golden film"?

We have continuously broken through the industry's definition of the thickness of such films and become standard setters, "said Zhang Bufeng.

Before 2018, the thickness of the heat dissipation PI film used to manufacture artificial graphite film was 75 microns. The thicker the film, the greater the heat flux and the faster the heat dissipation. However, the thicker the film, the faster the expansion after high-temperature sintering, which makes the graphite film sintered from PI films with a thickness of over 75 microns prone to pulverization and unable to form. ”Zhang Bufeng explained.

The expansion of graphite is mainly caused by the release of gases generated inside the PI film during the firing process. To avoid such severe expansion, it is necessary to find a way to quickly release these "nowhere to escape" gases.

To this end, the team invented carbon nanotube modified film technology, cleverly utilizing the hollow properties of carbon nanotubes and the bridging properties between graphite layers to effectively regulate the release rate of gas, successfully solving industry problems such as exhaust difficulties during the graphitization process of ultra thick PI films.

In 2019, the team was the first in the world to develop ultra thick products with a thickness of over 90 microns, which can be used to prepare high-power artificial graphite films with a thickness of over 50 microns.

One generation of materials, one generation of equipment. The breakthrough in materials has driven the innovation of equipment.

The breakthrough in thickness has made artificial graphite film gradually become a "substitute" for metal heat dissipation plates, starting from being used only for auxiliary heat dissipation in power devices. In 2024, Times Huaxin once again took the lead in developing a super thermal conductive artificial graphite PI film with a thermal conductivity of over 2000W/(m · K) globally, increasing the thermal conductivity of traditional materials by 70% and reaching a maximum thickness of 230 microns, continuing to lead the development of industry technology.

Solution: Comprehensive localization of production lines

At the Times Huaxin factory, China's second 2100 millimeter ultra wide chemical imine production line is urgently assembling industrial equipment. Unlike its two existing production lines, this is a production line that fully realizes "Made in China" from design to equipment manufacturing, engineering, and production technology.

During the construction of the first chemical imine membrane production line, Times Huaxin purchased core membrane equipment from foreign manufacturers. However, during the debugging process, they found that the problem was not with the domestically produced equipment they had "mentally prepared" for, but with the imported core film making equipment.

If the first production line construction surprised them to some extent, then the construction of the 2100mm ultra wide film production line in 2018 demonstrated the determination of Times Huaxin to embark on the path of breaking through single line production capacity.

At that time, the annual production capacity of foreign counterparts with the same width of production lines was only 600 tons. With a comprehensive understanding of film making processes and equipment technology, the team boldly carried out design innovation, resulting in a single line annual production capacity exceeding 800 tons for the first time in the world. This new equipment technology upgrade not only quickly narrowed the scale gap between the company and its foreign counterparts, but also gave China the highest annual production line of the same width single line in the global production of high-performance PI films.

The experience of building two production lines has made the team deeply realize that equipment localization is the only way to ensure the security of the high-end strategic raw material supply chain. We need to thoroughly address potential risks! "Said Zhang Bufeng. After achieving full localization, the overall manufacturing cost of the new production line is expected to decrease by 60% compared to before. At the same time, the new production line has significantly shortened the time from core equipment manufacturing to production, greatly improving production efficiency.

At present, the national production line of Time Huaxin's ultra large amplitude wide high-performance polyimide (PI) film has been basically assembled and is about to enter debugging. ”Zhang Bufeng stated.

"Through independent innovation, Time Huaxin has solved the technical problems that our country has failed to overcome for more than 50 years, breaking the long-term foreign technology monopoly." Jian Xigao, an academician of the CAE Member, commented, "They have not only accumulated in technical depth, but also achieved breakthroughs in the height of independent technological innovation. Amazing!"