The development of materials for electric vehicles -- take PCU materials as the center

- Jul 17, 2019-

1. Introduction

The automobile industry is undergoing a once-in-a-century revolution, and CASE(networking, autonomous driving, sharing, electrification) has become an important keyword.Among them, electrification is against the background of environmental issues on earth. In order to meet the needs of countries mainly in Europe and China to replace petroleum fuels, ICE is accelerating the transition to electric vehicles (HEV, PHEV, EV, FCV).Britain and France will ban the sale of ICE from 2040, while Norway, the Netherlands, India and China have also proposed future sales of EV and HEV only.In this wave of electrification, the company is also working hard to develop resin products to contribute to the electrification of cars.

2. Car parts revolutionized by electrification

In contrast to ICE, which USES a fuel engine, evs use a battery-powered electric motor, which requires a large-capacity battery, a drive motor, a charging gun to charge the battery, a socket, and a power control unit (PCU) to adjust the power output of the drive motor.These parts are driven and controlled by much higher voltages and currents than conventional cars.

3. Resin required for PCU parts

To drive the motor, the PCU needs to convert the dc voltage supplied by the battery to three-phase ac voltage, and to charge the battery, it needs to be able to convert the ac voltage generated by the generator to dc voltage.Resin as insulation parts, has been used in reactors, inverter housing, current sensors, DC-DC converters and so on.In addition, because the PCU has high current and voltage, the resin with high insulation characteristics is required in the operating environment.In addition, with the development of miniaturization and lightweight in recent years, the heat resistance of the resin impact and welding heat resistance also began to have some requirements.

Since automotive parts are used in very harsh environments (for example, -40 ~ 150℃, ~ 95%RH), the resin needs to be tolerant in such environments.Especially for high voltage parts represented by PCU, the insulation characteristic reduction caused by water absorption is listed as one of the risk points.Our products, DURANEX® PBT and DURAFIDE® PPS, have a low water absorption rate and have the advantage of maintaining insulation characteristics in harsh automotive environment. They are widely used in high-voltage parts.The following for you to introduce a customer has been adopted by the company's products.

3-1. DURANEX® PBT CG7030 with excellent creepage resistance

Under the influence of the environment, car sales since the end of last year showed a downward trend, the industry also has some concerns.Poly is still optimistic about the overall growth momentum, the group will increase production into the plan to further expand the market.Technical departments also focus on new energy, low emission (VOC), 5G communication and other difficult hot topics to tackle.

In the key project of green material list led by China automotive technology research center authorized by the ministry of industry and information technology of China, POM product "chenggang DURACON M90LV" was selected as the only engineering plastics in the first batch of "green plastics for vehicle use (low VOCs)".

※ about resistance to creepage

The general test method for creepage resistance is shown in the picture below. In the presence of aqueous electrolyte solution, ac voltage is applied to evaluate the difficulty of breakdown of insulation.CTI(relative to creepage index) refers to the maximum voltage without creepage and is used as an indicator of creepage resistance.If water or salt seeps into high-voltage parts, the phenomenon of electric leakage and trace may lead to fire accidents, so the insulator of high-voltage parts needs to choose the material with high CTI value.

3-2. DURAFIDE® PPS 6150T73 with excellent shock resistance

In recent years, in order to meet the requirements of miniaturization and lightweight parts, resin and metal integrated molding (insert molding) has become the mainstream.Insert molding, because the metal part and resin part of the linear expansion rate is different, resin temperature change may be cracked, so the resin needs to have a high heat resistance impact to prevent cracking.At the same time, due to the need to keep the metal parts in the proper position, this also requires a high dimensional accuracy.To meet these market demands, the company developed DURAFIDE 6150T73.On the basis of high heat and chemical resistance PPS, this grade is endowed with excellent heat shock resistance, machinability and high dimensional accuracy.One problem with conventional techniques is that increasing the formability (fluidity) reduces the resistance to heat shock.By optimizing PPS matrix polymers, various filling materials and additives, and improving the modification technology, we have created this high molding and impact resistance grade.Now, we are expanding the market in electric car parts, and the sales volume is increasing steadily.

The principle of ◯ thermal shock fracture

◯ the improvement of the performance of the heat shock

4. Future-oriented material development

Although the PCU USES resin for insulation, the shell itself is metal.The resinization of the shell may become a trend in the future.The benefits of resinization include, for example, energy savings (lightweight) and increased productivity.But there is a big hurdle.Generally speaking, the problem of metal resinization lies in the strength and dimensional accuracy. However, the electrical parts represented by PCU need a more metal-like resin, so how to achieve electromagnetic wave shielding and high thermal conductivity has also become a topic.In view of this kind of electric parts subject, the company is promoting the research and development of materials.

◯ next-generation vehicle requirements for resin

4-1. Development materials: electromagnetic wave shielding materials

With the development of electric vehicle, various parts need to take measures to prevent electromagnetic noise (EMC※).If electromagnetic noise causes the car's electronic control unit (ECU) to misoperate, it can cause huge problems.Metals are highly shielded from electromagnetic noise.On the other hand, because the ordinary resin almost no electromagnetic shielding, so it is difficult to directly replace.The company is exploring the market demand while developing materials with electromagnetic wave shielding characteristics.

◯ electromagnetic shielding material (development) of the shielding performance

EMC(electromagnetic compatibility) refers to solving both EMI(electromagnetic interference) and EMS(electromagnetic sensitivity) problems at the same time.

5. Conclusion

This time we mainly introduce PCU oriented materials.At present, electric drive is the key word in the market of various parts are being developed, representative of the motor and battery parts.We will look for another opportunity to introduce the trend of components materials other than PCU.In the future, we will continue to be a professional engineering plastics manufacturer, and strive to develop materials that meet the market demand.