Unexpectedly! Paper that cannot be burned by an open flame at 500℃ is actually the insulating material in the "heart" of high-speed rail?

The traction drive system is an important part of high-speed railways and is the key to the conversion of mechanical energy and electrical energy. The traction motor that allows high-speed railways to maintain high-speed operation is called the "heart" of high-speed railways. The key to its manufacture is the insulating material aramid paper, which has high electrical strength, high temperature resistance and fire retardancy.

What does a piece of paper have to do with high-speed rail? Isn't paper a flammable material?

Aramid paper is not ordinary paper. The reason why it is so "hard" is its main raw material, aramid fiber. Under the premise of equal quality, the strength of aramid fiber is about 5 times that of steel.

Aramid insulation paper

Image source: Zhuzhou Times New Materials Technology Co., Ltd. official website

01 What exactly is the aramid fiber that is said to be able to build rockets?

The full name of aramid fiber is "aromatic polyamide fiber". In the 1960s, aramid fiber was first developed by DuPont in the United States and successfully realized the industrialization of aramid fiber.

The series of "papers" developed from para-aramid fiber can be used to prepare honeycomb sandwich composite materials, which have the characteristics of light specific gravity, high specific strength and specific stiffness, impact resistance, excellent sound insulation, heat insulation and flame retardant properties, good high temperature stability and electromagnetic wave penetration performance. It is a strategic material urgently needed for major national projects.

For a long time, high-end aramid materials have been monopolized by foreign companies. my country has been subject to foreign control for a long time and has to pay huge "expenses" for this every year. In order to truly grasp the initiative in competition and development, my country began to study aramid paper in the late 20th century and early 21st century.

Aramid Honeycomb Paper

Image source: Zhuzhou Times New Materials Technology Co., Ltd. official website

02 Intangible cultural heritage techniques give high-tech materials the “Made in China” stamp

How did the intangible cultural heritage become related to this cutting-edge technology? Little did people know that the wet copying method in the ancient papermaking technique of Cai Lun was used to turn aramid fiber into aramid paper.

In 105 AD, Cai Lun of the Eastern Han Dynasty improved the papermaking process and produced high-quality and inexpensive paper. Human civilization took a big step forward from then on, and papermaking became one of my country's four great inventions.

In the research, development and production of domestic aramid materials, scientific researchers have innovated and developed traditional technologies such as "pounding" and "copying", and carried out a series of work from single material development, insulation system design to prototype production verification. The independent aramid paper finally achieved comprehensive application performance at the same technical level as imported materials.

In 2019, the first batch of aramid paper developed and manufactured by Zhuzhou Times Huaxian Material Technology Co., Ltd. was officially put into production, breaking through the hydraulic headbox forming technology and high-temperature roller pressing technology, realizing the engineering application and domestic substitution of independent aramid paper in major fields such as high-speed rail, aerospace, etc., and promoting innovation and breakthroughs in the bottleneck field of new materials in my country. At present, CRRC aramid paper has been used in batches on EMUs, locomotives, and subway traction motors.

High-speed rail traction motor. Image source: CCTV Video

Not long ago, relevant scientific researchers also systematically introduced the application of independent aramid paper in rail transit traction power equipment in the CCTV program "China in Intangible Cultural Heritage".

Field experiments show that honeycombs made of aramid paper can not only withstand temperatures of 500°C, but also withstand the test of being run over by heavy trucks due to their high strength! A 20-ton truck ran over them without any damage.

The host lit ordinary paper and aramid paper at the same time and found that the aramid paper would go out as soon as it was away from the fire.

GIF source: CCTV Video

Today, thanks to the efforts of scientific researchers, we have achieved independent domestic research and development of high-performance aramid insulation paper and aramid honeycomb paper, allowing this thin piece of "paper" to be widely used in rail transit, aerospace, new energy and other high-tech fields. The fusion of intangible cultural heritage and modernity has allowed us to gain pride and confidence from the ancient wisdom.

Salute to the outstanding Chinese scientific researchers!

Comprehensive sources: CCTV Video, Science and Technology Daily, Hunan Daily, etc.