Hardcore Debut of Olefins: Supporting Extreme Aerospace Environments

When it comes to "olefins," many people may find the term unfamiliar. Olefins are a class of small-molecule organic compounds containing carbon-carbon double bonds. They are often used as raw materials and can undergo polymerization reactions to produce long-chain polymers such as polyethylene and polypropylene, which are then processed into synthetic fibers. These have wide applications in both daily life and industrial fields.

From the strict definition in organic chemistry, "hydrocarbons" specifically refer to organic compounds composed only of carbon and hydrogen elements, and alkenes are an important branch of hydrocarbons. Their core structural feature is the presence of a carbon-carbon double bond (C=C) in the molecule. The existence of this unsaturated bond makes their chemical properties more reactive, and thus they are classified as unsaturated hydrocarbons.

It is worth noting that olefins can form a vast "polyolefin family" through polymerization reactions.

These types of olefin derivatives are currently crucial in the aerospace field. By specifically modifying different kinds of polyolefins, they can be precisely tailored to meet the functional requirements of various basic components of spacecraft, such as withstanding extreme temperature variations and resisting cosmic radiation. In this way, they provide a vital first line of defense for the safe and stable operation of aerospace equipment in the complex and harsh environment of outer space.

Next, we will explore the specific application scenarios of the five core members of the polyolefin family in the aerospace field.

Aerospace fuels not only need to meet the core requirements of high energy density and stable combustion but also must adapt to special environments such as low temperatures at high altitudes and low atmospheric pressure in space. Derivatives formed through the catalytic conversion of olefins provide a key pathway to address fuel resource dependency and adaptation to extreme environments.

In the field of aviation kerosene, olefins are key intermediates for replacing fossil fuels. Traditional aviation kerosenes (such as JET-A and RP-3) rely heavily on petroleum refining, whereas through the "Fischer-Tropsch synthesis" technology, olefins can be converted from non-petroleum resources such as coal and natural gas: first, coal or natural gas is converted into synthesis gas, then into olefins, and finally into highly branched alkanes through hydroisomerization.

These highly branched alkanes can lower the freezing point of aviation kerosene to very low levels, adapting to the low-temperature environment at high altitudes, while also burning more completely, reducing engine carbon deposits, and improving fuel efficiency.

Nowadays, the technological route from coal-to-olefins to aviation kerosene has become increasingly mature, effectively easing the dependence of aviation fuel on petroleum resources and providing a new direction for the sustainable development of the aviation industry.

In the field of rocket fuels, olefin derivatives are enhancers that improve fuel performance.

The combination of olefins with hydrazine-based fuels can significantly increase the energy density of the fuel, resulting in higher rocket specific impulse and greater payload capacity. Polymer fuels formed by the polymerization of olefins, such as polyethylene-based fuels, feature high density and low volatility. In the low-pressure environment of space, they can effectively reduce fuel evaporation loss, making them especially suitable for use in small solid rocket engines. This provides stable power support for missions such as microsatellite launches and deep space exploration.

Weight reduction is a perpetual pursuit in the aerospace industry. For commercial aircraft, reducing weight by 1 kilogram can save $60,000 in fuel costs annually. For spacecraft, the economic benefit of reducing weight by 1 kilogram is nearly $100,000. For rockets, reducing weight by 1 kilogram can save approximately $20,000 in launch costs.

Polyolefin-based composites, formed by compounding olefins with fibers, have become a driving force in replacing traditional metal materials due to their "lighter and stronger" characteristics, ushering in a revolution in lightweight technology.

Carbon fiber reinforced polypropylene (CF/PP) composites are regarded as a perfect combination of lightweight and high strength. Their density typically ranges between 1.1 and 1.4 g/cm³, which is more than 50% lighter than metal materials. The tensile strength can reach 50-100 MPa, which is 2-3 times higher than that of pure PP.

In aircraft manufacturing, CF/PP composites are widely used in secondary load-bearing structures such as wing leading edges and tail skins, which not only reduce the weight of the wings but also enhance their resistance to aerodynamic impact. In the field of aerospace, satellite brackets made from CF/PP composites can significantly reduce the overall weight of satellites while ensuring structural stability, enabling satellites to carry more scientific instruments.

Glass fiber reinforced polyethylene (GF/PE) composites, with their high cost performance and excellent impact resistance, have filled the gap in mid- to low-end application scenarios.

The GF/PE protective panels of the aircraft landing gear compartment can withstand the impact of stones and dust during takeoff and landing, protecting the key components of the landing gear. The landing cushioning structure of spacecraft uses GF/PE composite material, which can absorb the enormous kinetic energy during landing through material deformation, reducing the impact damage on the main body of the spacecraft. This is particularly suitable for planetary landing missions such as Mars probes and lunar rovers.

Aerospace equipment faces a wide variety of extreme and complex environments—such as intense radiation in space, ozone corrosion at high altitudes, and high-temperature erosion from engines—all of which place special functional demands on materials.

Functional materials formed by specially modifying olefins have become specialized weapons to resist these extreme challenges.

Radiation-resistant olefin materials are enhanced by adding rare earth oxides and other anti-radiation agents, or by crosslinking modification to improve molecular chain stability, thus creating a "radiation protection suit" for spacecraft.

The radiation-resistant olefin insulation layer of spacecraft cables can effectively withstand erosion from space gamma rays and proton radiation, preventing insulation aging and damage that could lead to short-circuit failures. In nuclear-powered spacecraft, protective shells made of radiation-resistant olefin can block radiation leakage from nuclear reactors, ensuring the safety of onboard equipment and astronauts.

Antistatic polyolefin materials solve the electrostatic safety hazards in the aerospace field by incorporating conductive fillers such as carbon black and graphene.

After the inner walls of the aircraft fuel tank are made of antistatic olefin material, the static electricity generated by the flow of fuel can be promptly discharged, preventing the risk of explosion caused by static accumulation. The antistatic olefin material used in the frames of spacecraft solar panels can quickly release static electricity generated on the panel surface due to cosmic ray exposure, avoiding static interference with the power generation efficiency of the solar panels.

High-temperature wear-resistant olefin materials achieve dual resistance to high temperature and abrasion through the incorporation of ceramic particles such as alumina and silicon carbide.

The high-temperature wear-resistant olefin coating for aircraft engine blades can withstand the scouring of high-temperature airflow above 1000°C inside the engine, reducing blade wear and extending engine service life. When spacecraft re-enter the atmosphere, high-temperature surface areas rely on ceramic and other ablation materials for protection, while high-temperature wear-resistant olefin materials can be used as the non-directly heated lining of the thermal protection layer to help dissipate heat, ensuring the safe return of the spacecraft to the ground.

Olefins are fundamental raw materials in the materials industry. The level of a country's olefin industry—including production capacity, technological strength, and self-sufficiency in high-end products—largely represents the overall competitiveness of its petrochemical sector.

Taking the most widely used polyethylene as an example, it was first synthesized by the British company ICI in 1933 and achieved industrial production in the United States in 1939. However, it was not until 1976 that China built and commissioned its first polyethylene plant in Shanghai Petrochemical.

After decades of development, by 2024, China's polyethylene production capacity has exceeded 34 million tons, accounting for 21% of the global total capacity.

In terms of annual new capacity, the global polyethylene in 2024 will be 5.16 million tons, of which China will add 3.4 million tons, accounting for as much as 66%. China has become the main driving force behind the growth of global polyethylene capacity.