Regulatory changes may have slowed electric vehicle adoption in the United States, but the global picture is quite different. EVs accounted for over 20% of new car sales in 2024, according to the International Energy Agency, which predicted an increase to 25% in 2025. In China, falling prices are expected to push that number to 60%.

Electric vehicles have far fewer parts, in total, than combustion cars. For the parts EV and combustion engine cars share in common, legacy automotive compounds often provide the strength, safety and durability required. But some EV parts encounter unique demands especially for insulation of high-power systems and dissipation of heat.

Faster Charging, Compact Modules, Changing Architectures

The EV transition is not only a dramatic change in platform but a shift from a stable technology to one that is very much still in ferment. Ongoing changes in EV design are placing new demands on plastic parts. Several OEMs are transitioning battery packs from 400 to 800 volts and their physical layout is changing as well. Cells are collected into fewer modules while being integrated into the floor, and components are altered to save weight and space. These changes push innovation in materials to provide the necessary thermal properties, electrical insulation, electromagnetic shielding and chemical resistance.

Electrical Properties at High Voltage

While most EVs on the road today have a standard 400-volt architecture, higher voltages are now widely available. Introduced into production with the Porsche Taycan in 2019, the 800-volt architecture has crossed over into mainstream vehicles like the 2025 Hyundai Ioniq 5 and Kia EV5, with several automakers planning to follow suit.

The move from 400 volts to 800 means faster charging (at high-power chargers), more efficient charging (due to a reduction in waste heat) and higher performance. It also means challenging material producers to meet more extreme specifications.

“Consumers’ biggest concern is range. Fast charging helps address that concern because instead of charging for hours at a time, you’re charging for minutes,” says Brian Baleno, SVP at Syensqo. “From a material perspective, it requires materials with high dielectric strength and high tracking index.”

Hyundai’s Ioniq 5 features 800-volt architecture that supports fast charging. Source: Hyundai Motor

At high voltage, an insulator can break down and become conductive, causing a short circuit. Dielectric strength is the maximum electric field strength that can be applied to an insulator before it will undergo such a breakdown. Comparative tracking index (CTI) is the material’s resistance to the formation of conductive, carbonized tracks on the surface.

Electrical failures can propagate through EV drivetrains, which can represent a fire and even explosion risk. Regulations require that insulation in EVs maintains its integrity even after exposure to extreme heat.

High-Voltage Motor Insulation

Higher voltage batteries translate, proportionally, to higher voltage across the drivetrain, including EV motors. Here, where all that voltage becomes motion, temperatures inside the copper windings can reach 180°C. Magnetic wires have insulation to prevent short circuits** **and additional lining in the slots in the motor stator to maintain separation from the metal.

For the electric motor in its new 800-volt electric vehicle platform, Volvo is using Syensqo Ketaspire PEEK (polyether ether ketone) for the magnet wire insulation and Ajedium PEEK film for the slot liners. Legacy materials for these applications would include polyimide or polyamide-imide (PAI) enamel, and aramid paper, respectively. The PEEK materials provide better stability at high temperatures. Motors of this kind are also liquid-cooled, and the PEEK material also provides chemical resistance and low moisture absorption. This same solution has been selected by Mavel Powertrain for use in an unnamed high-performance sports car.

Motor winding insulation and slot liners (visible just above where the wire enters the stator slot) made from Syensqo PEEK. Source: Syensqo

Thermal Shock Resistance

Busbars link the various elements of an EV drivetrain, providing a conductive path between, for example: the charging system and the battery, between battery components (individual cells or modules), between the battery and the power distribution unit, and between the inverter and the motor. The conductive material is overmolded with plastic to provide thermal conductivity and electrical insulation.

Busbars can be subjected to thermal shock during rapid charging or discharging or extreme weather. Copper has a relatively low coefficient of thermal expansion (CTE), so it doesn’t expand and shrink much when heated and cooled. If overmolded with a material that does have a higher higher CTE, thermal cycles cause stress in the insulation, leading to cracks that impair performance.

“Depending on the expansion/shrinkage of the thermoplastic insulation during thermal exposure, relative to the metal conductor, a certain strain reserve is needed as well,” explains Joachim Flöck, automotive marketing manager at Celanese.

Busbars overmolded with Celanese’s Zytel HTN, formulated to withstand rapid temperature changes. Source: Celanese

Celanese has investigated thermal shock resistance by subjecting busbars to cycles of temperature swings and recording how long it takes for cracks to appear. Celanese is supplying new glass-filled polyamide Zytel HTN grades, FE130008 and FE130009, for this application. In addition to material selection, the design of the metal inlay, flow length and insulation thickness are also important factors.

Busbar designs and materials that resist thermal shock are important for vehicle safety, as insulation can prevent arcs and shorts, and can reduce the risk of thermal runaway.

Trends in EV design will likely make materials science even more important. “We see a trend towards more compact designs; as a result, electrical insulation properties will play a more important role than they did in the past,” says Flöck. “Furthermore, the increase of temperatures leads to the need for materials with an improved thermal conductivity.”

Platform Changes Necessitate Complex Parts

For better flexibility in designing the rest of the car, automakers are also working to make battery packs more compact and integrating them with the floor of the vehicle. They are tightening the cell packing and lightweighting wherever possible.

The low-profile design of the Cadillac Celestiq required a custom battery pack design completely different from the module configuration in other GM EVs. In addition to providing structural support, electrical isolation and maintaining low risk of thermal runaway, the module cover needed to provide a cooling pathway to the module enclosure. A glass- and mineral-filled polyamide compound from SABIC, Konduit PX11311U, is used by Sun Microstampings to mold this part, which was a finalist in Society of Plastics Engineers’ Automotive Innovation Awards.

To achieve higher thermal conductivity, the battery module cover for the Cadillac Celestiq is molded with a specialized filled polyamide compound. Source: Society of Plastics Engineers

The compound has a much higher thermal conductivity than typical for a polyamide, which enables it to safely transfer heat away from the cells while maintaining electrical isolation. The high conductivity makes it possible to eliminate a stamped metal component.

Fast-and-Ready Charging Systems

Faster charging helps quell range anxiety by speeding turnover at charging stations, but for motorists to experience the advantage on the road, they need not just a capable vehicle but also access to a capable charging system. Less than 3% of publicly accessible stations operate at 350 kW or above, according to Department of Energy data. Convenient super-fast charging will require greater numbers of weather-proof, durable, safe and stable charging systems. And that means plastics engineering.

Charging connectors are exposed to the elements and uptime is key, so the materials they are made of have to offer not only robust electrical and thermal properties but also high durability and impact resistance. Nylons PA 6 and PA 66 have good tracking properties and elongation at break, but they lack dimensional stability.

“The main challenge in developing an insulative material suitable for diverse applications lies in balancing a combination of properties that can sometimes conflict,” says Marc Marbach, global business director, polybutylene terephthalate (PBT), at Envalior.

The company has introduced a new PBT grade, Pocan BFN4232ZHR, designed for this application.

This diagram illustrates how the new Pocan grade was developed to balance the best properties of PBT and PA for demanding insulation applications like EV charging stations. Source: Envalior

The new Pocan grade has flammability rating of V0 at 0.75 mm, high hydrolysis resistance and maintains elongation at break above 70% — even after 1,000 hours of storage at 85ºC and 85% relative humidity. According to Marbach, the mechanical properties enable the careful design of snap fittings, where dimensional stability is key.

Driving Plastics Forward

Super-fast charging could remove a barrier to entry for many would-be EV adopters. That could lead more OEMs into 800-volt systems and even beyond. Already, the Lucid Air has a 924-volt architecture.

The consolidation of battery modules continues; Volkswagen and Stellantis are introducing battery packs called cell to pack, with no modules at all.

EV designs may stabilize in the future, with brands offering variations on a winning configuration, a design that will do for cars what the 6-in. glass rectangular slab did for phones. But for now, the EV market remains a dynamic space. The handful of polymer applications listed here, along with dozens of others, will remain fertile ground for material innovation for years to come.