PA6, PA66, PA12 And Other Nylon Materials in The Automotive Industry Application And Prospects

PA6, PA66, PA12 And Other Nylon Materials in The Automotive Industry Application And Prospects

China's automobile industry capacity growth is rapid, automotive engineering plastics industry development space is broad. Engineering plastics are replacing metal materials and gradually expanding from decorative parts to structural and functional parts.

PA is an excellent engineering plastics, its chemical properties are very stable, and it has excellent resistance to lubricating oil and gasoline. Under the social background of energy saving and emission reduction, the penetration rate of PA materials in the automotive industry is gradually increasing due to its advantages in light weight, heat resistance, oil resistance, flame retardancy and other aspects. Currently PA materials are used in automotive engine systems, electrical systems, and chassis systems, as shown in the table below.

Table 1 PA applications In Automobiles

Among them, the amount of PA6 and PA66 accounted for more than 90% of the total amount of various types of PA materials. PA11 and PA12 have good flexibility, corrosion resistance, oil resistance and dimensional stability, in the fuel pipe, fuel cap, brake pipe and other components have also been widely used.

I. Typical Applications of PA6 Material in Automobiles

The battery box is mainly used to protect and support components such as the power battery module, battery thermal - management system, and battery management system, preventing the power battery system from being damaged under external impacts or mechanical stresses. The battery box is of great significance for ensuring the mechanical safety of the power battery system. Therefore, it has high requirements for mechanical properties such as impact strength and tensile strength.

Currently, some battery boxes are made of PA materials, with PA6 being the most commonly used. Flame - retardancy is also an important reference index for the selection of materials for new - energy vehicle battery boxes. The limiting oxygen index of unmodified PA6 materials is generally only 20% - 22%, and the flame - retardant grade can only reach UL94 V - 2, which is difficult to meet the strict flame - retardant requirements of new - energy vehicles. Flame - retardant modification is required.

Generally speaking, flame - retardants for PA6 include various types such as halogen - based, phosphorus - based, and nitrogen - based ones. Among them, halogen - based flame - retardants generate corrosive gases and carcinogenic fumes during the combustion process. After the European Union issued the "Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment" directive in early 2003, their use has been restricted.

In recent years, many researchers have carried out research on halogen - free flame - retardant PA6 materials and achieved many results.

Many engineering plastics companies are also committed to the research and development of halogen - free flame - retardant PA6 materials. For example, Lanxess Group has launched three types of Tepex materials with PA6 as the matrix. Tepex materials contain a high amount of fibers, so they not only have extremely high stiffness, strength, and energy - absorption levels, but also have a flame - retardant property of UL94 V - 0 grade.

Among them, Tepexdynalite102fr - RG600(x)/47% is reinforced with roving glass fibers, and these fibers are arranged in a multi - axial manner. It can not only achieve a good flame - retardant effect but also accurately match the load paths in components, and can be applied to high - voltage components such as the control unit housing, partition, and cover plate of new - energy vehicle battery boxes.

The application of long - glass - fiber - reinforced PA6 in automotive structural parts is also gradually becoming popular. As the reinforcing skeleton, glass fibers penetrate the PA6 matrix, which can effectively enhance the impact resistance, creep resistance, and dimensional stability of plastic products. Long - glass - fiber - reinforced PA6 has many advantages comparable to metals and is suitable for manufacturing complex automotive module products.

Take the instrument panel cross - member as an example. The instrument panel cross - member is directly connected to the vehicle body, bears and transmits the loads of human - machine interaction devices and decorative parts, and forms a cockpit safety system with other safety components, directly affecting the handling and safety of the vehicle. The instrument panel cross - member can buffer the impact force transmitted from the front cabin during a frontal collision and provide support for the inflation of the passenger airbag.

In addition, the system composed of the instrument panel cross - member, steering wheel, and steering column needs to meet certain NVH (Noise, Vibration, and Harshness) modal requirements to avoid resonance.

The long - glass - fiber - reinforced PA6 instrument panel cross - member has been successfully developed and widely used in some vehicle models. While fully meeting the rigidity and strength that the instrument panel cross - member, as a load - bearing part, must have, the long - glass - fiber - reinforced PA6 instrument panel cross - member has excellent creep resistance, fatigue resistance, and high - and low - temperature impact resistance. The design of the all - plastic instrument panel cross - member not only improves production efficiency but also helps to achieve lightweight and NVH goals.

II. Typical Applications of PA12 Material in Automobiles

In the field of traditional internal combustion engine vehicles, large - scale engineering plastics companies such as DuPont, Arkema, and Basf have developed PA12 materials with different temperature - resistance grades. These materials are widely used in oil and gas pipelines, including fuel tank filling pipes, fuel delivery pipes, crankcase ventilation pipes, engine intake pipes, and vacuum brake pipes.

However, since the high-temperature resistance of PA12 is not particularly outstanding, it cannot be used for long-term applications in piping systems with higher working temperatures. For example, the engine cooling hoses in internal combustion engine vehicles are generally still made of metal or rubber hoses, rather than PA12 hoses. Generally speaking, the working temperature of the electric motor cooling system in new energy vehicles is usually below 80°C, and the working temperature of the battery cooling system is usually below 60°C. The material PA12 can fully meet the temperature resistance requirements of the cooling systems in new energy vehicles.

Compared with rubber hoses, PA12 hoses can effectively reduce the system weight. The density of PA12 is 1.02 g/cm³, while the density of EPDM rubber, which is commonly used in traditional automotive hoses, is 1.1 to 1.2 g/cm³. Moreover, the walls of PA12 hoses are relatively thinner. For example, for hoses with an inner diameter of 15 to 18 mm, the wall thickness of PA12 hoses is only 1.25 to 1.5 mm, while the wall thickness of EPDM rubber hoses is generally 3.5 to 4 mm.

Overall, the use of PA12 material can reduce the weight of the piping by 65%. For example, a certain model of Guangzhou Automobile Group Co., Ltd. adopted a PA12 piping solution, and the actual weight reduction of the piping system compared to traditional metal and piping rubber was 56%.

Moreover, due to the relatively low stiffness of EPDM rubber, additional fixing points are required when it is used for longer piping. Therefore, in the cooling systems of traditional internal combustion engine vehicles, metal materials are generally chosen for longer piping, with EPDM rubber used only at the transition sections. In the combination of metal and rubber piping, there are numerous transition points, which not only significantly increase the number of parts but also raise the risk of leakage.

In contrast, PA12 piping has a higher stiffness and can be manufactured as a single-piece, integrated water pipe, effectively reducing the number of parts and enhancing system reliability. For example, a certain model of Guangzhou Automobile Group Co., Ltd. adopted a PA12 piping solution, reducing the number of parts in the piping system by 77% compared to traditional metal and rubber piping. Compared to metal and rubber piping, PA12 piping is lighter, more rigid, occupies less space, and is more reliable, making it highly valuable for promotion in new energy vehicles.

Furthermore, many researchers have conducted studies on PA12 piping to meet specific requirements for different scenarios. For example, Toray of Japan and Polyplastics-Evonik have jointly developed a three-layer extruded pipe. The outer layer of this extruded pipe is made of PA12 material, and the inner layer is made of polyphenylene sulfide (PPS) resin, bonded together with a special adhesive. This pipe can withstand high temperatures of up to 130°C and has excellent hydrolysis resistance and thermal stability, making it suitable for automotive cooling systems with higher temperature requirements.

Due to its excellent resistance to gasoline permeation, PA12 has been proven to be a safe and reliable material for fuel piping. However, with the emergence and use of blended fuels containing methanol or ethanol, higher requirements have been placed on the permeation resistance of fuel piping. Methanol or ethanol in blended fuels has strong permeation and solubility properties, which can easily cause hydrocarbons to seep out, failing to meet relevant environmental standards.

Researchers in China have carried out the development of low-permeation, low-exudation automotive fuel piping materials. By thoroughly analyzing the physical properties of various raw materials, they have developed materials suitable for fuel piping. They have also developed a PA12 symmetrical five-layer composite piping material that meets the low-permeation standards for fuel piping, as well as a complete fuel piping system composed of this composite material.

III. Typical Applications of PA66 in the Automotive Industry

Under the overarching trend of automotive lightweighting through “plastic-for-steel substitution,” PA66 has delivered significant value in both traditional internal combustion engine vehicles and new energy vehicles, directly or indirectly contributing to the societal goal of low-carbon emissions. During the manufacturing process of components, PA66, with a crystallization speed ten times faster than that of PA6, can quickly form in molds, thereby greatly improving production efficiency.

Compared to PA6, PA66 also boasts superior performance, including higher dimensional stability, lower water absorption, and a higher melting point. Widely used across various automotive systems, PA66 aims to enhance vehicle economy and reduce harmful gas emissions while maintaining or surpassing existing power output levels.

Taking the intake manifold as an example, early internal combustion engine vehicles primarily used PA6 for their intake manifolds. With the application of integrated turbochargers and the compact design of engines, the temperature resistance requirement for intake manifolds increased from 130°C to 200°C. As a result, original equipment manufacturers (OEMs) have gradually shifted towards using PA66 with a higher melting point to achieve performance upgrades.

Another typical application of PA66 is in engine mounts or drive motor mounts, which were traditionally made of steel or aluminum alloy. Since PA materials inherently possess damping and vibration-reducing properties, the use of PA66 reinforced with glass fibers in engine and drive motor mounts can effectively reduce the vibration and noise of the engine or drive motor.

In addition, since PA66 can withstand paint-baking temperatures of 160–180°C, integrating it into the automotive body-in-white not only enhances the mechanical properties of the vehicle body but also allows the PA66-reinforced material to effectively absorb impact energy during a collision. This protects both the occupants and the power battery to the greatest extent possible. Moreover, it can achieve a weight reduction of over 30% for the vehicle body, thereby improving the vehicle's handling and range.

In the research of new types of PA66 materials, many researchers have also developed PA66 materials suitable for specific automotive components. For example, the on-board charger, DC/DC controller, PTC heater, and high-voltage junction box in new energy vehicles are all high-voltage components. The high-voltage connectors between high-voltage components and high-voltage wiring harnesses often use halogen-free flame-retardant reinforced PA66, especially organophosphorus flame-retardant PA66.

Halogen-free flame-retardant reinforced PA66 has good flame-retardant and mechanical properties, but its price fluctuates significantly due to the supply of upstream raw materials. In contrast, PA6 has a sufficient supply and a relatively lower price. Therefore, the halogen-free flame-retardant reinforced PA66/PA6 alloy has become a promising alternative solution.

Researchers in China have studied the changes in flame-retardant properties, electrical properties, mechanical properties, and thermal resistance of the PA66/PA6 alloy when the ratio of PA66 to PA6 varies. They found that as the proportion of PA6 increases, the toughness of the alloy slightly improves, while its flame-retardant properties and mechanical strength slightly decrease. Conversely, as the proportion of PA6 decreases, the tensile strength is reduced, but the toughness is significantly enhanced.

PA66 is also used in the battery box of new energy vehicles. Researchers in China have conducted studies on the mechanical properties of short carbon fiber-reinforced PA66 with different fiber contents and have evaluated and simulated the performance of this material when applied to lightweight battery boxes. The results show that compared to metal battery boxes, the short carbon fiber-reinforced PA66 material reduces the weight of the box by 84%. Under rough road and sharp turning conditions, the maximum stress on the box is reduced by 30%–50%. It was also found that the carbon fiber content has a significant impact on the maximum displacement of the battery box. An increase in carbon fiber content under rough road and sharp turning conditions can significantly reduce the box displacement.

Currently, in the automotive industry, PA66 is widely used for strapping materials longer than 30 cm. However, PA66 exhibits relatively poor toughness at low temperatures and requires cold-resistant toughening modifications. Researchers in China have adopted a twin-screw compounding method, selecting different types of toughening agents and PA66 materials with varying viscosities to develop cold-resistant and toughened PA66 materials suitable for automotive strapping.

PA66 possesses excellent thermal resistance, corrosion resistance, and toughness, making it a potential alternative to long-chain PA for automotive water pipes. However, due to the presence of strongly polar amide groups in the PA66 molecular chain, it is prone to deformation and hydrolysis when in contact with coolant. To address this issue, researchers in China first modified the PA66 material by adding toughening and hydrolysis-resistant agents through compounding, enhancing its hydrolysis resistance and toughness. Subsequently, they successfully developed automotive cooling hoses primarily composed of PA66 using conventional hose extrusion processes. The modified PA66 hoses achieved a burst strength greater than 2.6 MPa, with a 40% reduction in material costs, effectively resolving the complex manufacturing processes and high costs associated with long-chain PA hoses.

Overall, the amount of plastic used in vehicles can be considered one of the indicators of the level of automotive design and manufacturing. Currently, developed countries use approximately 150 kg of plastic per internal combustion engine (ICE) vehicle, with PA accounting for about 20% of this total. In China, the average PA usage per ICE vehicle is currently around 8 kg, projected to reach 15 kg by 2025 and potentially increase to 30 kg by 2030. For new energy vehicles (NEVs), referencing models like the Tesla Model 3, it is estimated that by 2030, the PA usage per NEV could reach 50 kg.

Data from the China Passenger Car Market Information Association shows that in 2022, the sales volume of ICE vehicles in China was 14.868 million units, a decrease of 2.302 million units compared to the previous year. ICE vehicles are losing market share at an alarming rate. Both domestic and international automakers have announced plans to cease the development of ICE vehicles around 2030, after which ICE vehicles are expected to gradually exit the market.

In contrast, the NEV market is experiencing rapid growth. At the China EV 100 Summit, researchers estimated that by 2025, the annual sales volume of NEVs in China could reach 7–9 million units, and by 2030, it could reach 17–19 million units. According to relevant research institute statistics, the total usage of PA materials in vehicles is projected to reach 1.44 million tons by 2030.

In summary, advancements in engine technology, the transition to new energy vehicles, and the trend towards automotive lightweighting are not only effectively promoting reductions in emissions and improvements in social operational efficiency but also creating a significant incremental market for engineering plastics like PA. In the foreseeable future, the demand for PA materials in the automotive industry is expected to continue to grow, and the PA materials industry has entered a period of rapid development.

The automotive industry is rapidly adopting engineering plastics like PA6, PA66, and PA12 to meet the demands of lightweighting, improved fuel efficiency, and enhanced performance. These materials are increasingly replacing traditional metals in various applications, including engine components, fuel systems, and structural parts. However, as the industry transitions towards new energy vehicles (NEVs) and higher performance standards, the need for flame-retardant solutions has become more critical.

YINSU Flame Retardant Company, a leading flame-retardant solutions provider, offers a range of halogen-free flame retardant specifically designed for nylon materials. These flame retardant not only meet the stringent safety and environmental standards required by the automotive industry but also enhance the mechanical properties and durability of nylon components. By integrating YINSU Flame Retardant Company's flame-retardant technology, manufacturers can develop advanced materials that support the growing demand for sustainable and high-performance automotive applications, contributing to the ongoing evolution of the automotive materials market.