Syensqo’s Ajedium™ PEEK Insulation Films: 44% PDIV Boost & 5X Longer Life Over PI Films for PTC Heaters

By: Nicolas Batailley, Carlos Abomailek, Victoria Lee, Elisa Piedimonte, Brian Baleno

Syensqo Materials

One of the main challenges of battery electric vehicles (BEV) or plug-in hybrid electric vehicles (PHEV) is finding effective ways to heat the cabin. Unlike internal combustion engine (ICE) vehicles, which use thermal energy from the engine to heat the interior, BEVs require a system to convert electrical energy into heat. Positive temperature coefficient (PTC) heaters and heat pumps (HP) are the combination of systems that offer fast cabin heating and window defrost, as well as enhanced energy efficiency for extended battery life.

High Voltage (HV) PTC heaters are the optimal solution for fast heating, as they eliminate the need for additional energy conversion systems such as DCDC converters, that reduce efficiency and unnecessarily increase the cost. 

A HV PTC heater introduces a range of new challenges for design engineers, including achieving a high thermal efficiency, balancing energy consumption and range, and maintaining proper levels of electrical insulation at high temperature throughout the vehicle’s lifespan. The type of insulation film used in the PTC heater is crucial for enhancing electrical insulation.

One of the key benefits for considering Ajedium™ PEEK insulation films over polyimide films is the improved electrical insulation. PTC heaters operate over a broad temperature range, from -40 ℃ to 180 ℃ and the electrical insulation films must consistently perform under these conditions. As illustrated in Figure 2, Ajedium™ PEEK films offer significantly higher reliability and safety compared to polyimide films.

The Ajedium™ PEEK film achieves 20% higher PDIV at 180 ℃. After 2,000 hours of heat aging, equivalent to 4 years of PTC heater life, it provides a 44% higher PDIV, offering engineers increased reliability. Notably PDIV levels below 1000V can pose a real danger of partial discharge inception in high-voltage architectures, such battery packs above 823V. 

Figure 1: PEEK vs. PI PDIV Comparison at temperature and time (Source: TAU Group)

In addition to higher PDIV and superior electrical insulation at high temperature, Ajedium™ PEEK film can be thinner (120 vs. 150 microns). This reduced thickness saves space, enhances heat dissipation and improves total cost of the solution.

Another crucial factor for PTC designers when selecting an insulation film is its ability  to withstand surface partial discharges. These discharges can potentially damage the electrical insulation, affecting the lifespan and durability of high-voltage heaters. This is especially relevant for insulation materials that degrade over time, such as the PI film shown in the example. Figure 2 below compares the lifetime of PEEK versus other materials under corona discharge conditions.

Figure 2: Ajedium™ PEEK film Corona Discharge Lifetime (ASTM D2275, 500 Hz, 2.5 kV, 23 C)

The data shows that Ajedium™ PEEK film has a lifespan 5X longer than PI laminates and aramid paper. 

In summary, Ajedium™ PEEK film provides PTC engineers significant improvements in electrical insulation and durability compared to polyimide films. With higher reliability, extended lifespan, and thinner Ajedium™ PEEK film, there is an improvement in heat dissipation while offering space savings and greater design flexibility. Please contact us to learn more about our HV PTC heater solutions.