Posted on 08/01/2021 in Transport Fire Safety 2020
Materials fire safety challenges and solutions

Franz Janson, TE Connectivity

TE Connectivity has been developing and supplying connectivity and sensing products for over 75 years, including for transport systems and vehicles, industry and communications installations and equipment.
Electric vehicles imply an increased need for fire safety, especially because of high voltages, both within the car and in charging mode. This leads to increasingly demanding fire test requirements:

  • UL94-V0, tending towards 0.8 mm and lower
  • CTI, moving from the standard 600V to higher requirements
  • GWFI for automotive interior materials
  • EN 60664-1 for HV product design

At the same time, manufacturers are defining increasingly performance and environmental specifications:

  • Halogen-Free materials, reflecting EHS and QA aspects
  • Sustainability, CO2 carbon footprint and recycling
  • Orange products with heat resistance up to max. 140°C
  • Resistance to humidity and water
  • Dimensional stability
  • Improved thermal conductivity
  • Low emissions
  • Flowability, to enable processing of complex product design
  • Laser marking requirements

Challenge: Ensure that materials for HV product design secures fire performance, mechanical and electrical properties as specified.

“TE Connectivity is a trademark licensed by the TE Connectivity Ltd. family of companies.” TE Connectivity electrical mobility

David Qi & Antonio Nerone,
RadiciGroup High Performance Polymers

RadiciGroup High Performance Polymers, a pinfa member company, formulates and supplies high performance polymer compounds, in particular polyamides. For sustainability reasons; all new developments at RadiciGroup High Performance Polymers are non-halogenated, non-ATO materials.
Data shows that e-vehicles contain (% weight) more polymers, especially polyamides, and less metals, than conventional vehicles. This can be explained by the push for light weight and use in the electric power chain, electronic control system and battery.
Recent developments for e-vehicles include developments of new materials combining electrical safety at high temperatures in harsh environments and high stiffness, for example to replace metals in battery housings (so reducing weight, improving corrosion resistance and avoiding electrical conductivity).

RadiciGroup High Performace Polymers sees five developing challenges for materials for e-vehicles. These are all relevant for internal combustion vehicles, but manufacturer specifications become more demanding or new standards set specific performance levels for e-vehicles.

  • Contact corrosion (galvanic): in use, including under temperature or elevated levels of humidity, materials must not release chemicals which can corrode metal connectors or impact electronics systems. In particular, halogenated materials or red phosphorus can generate corrosion during the vehicle life.
  • Constant colour including after heat and ageing. This is particularly important for EV safety orange used to signal high-voltage cables, both in charging installations and within the vehicle.
  • Electrical properties: volume resistance (the opposite of conductivity), dielectric strength (resistance to current travelling along the material surface). Such properties are critical for e-mobility, for both power transmission and electronic control systems. Again, these properties must be durable after heating and ageing.

New e-vehicle standards in China

China has taken the lead in implementing specific standards for e-vehicles, for example:

  • For charging stations, with GB/T 18487 – 2001 (220V plug-in charging), GB/T 20234 – 2015 (1000V high power charging) and GB/T 38775 – 2020 (cordless charging), with requirements such as fire performance and electrical characteristics (antistatic / electron accumulation, electromagnetic loss), mechanical properties, water resistance.
  • GB/T 31467 – 2015, for battery packs, including fire resistance, mechanical resistance (impact, vibration, simulated crash), heat, saltwater … Fire resistance is tested with a burning gasoline tank below the battery pack, and can be achieved with PIN FR polyamide 6 and 66 grades designed for this application.

Photos: Radici – polyamides. Galvanic contact corrosion. China GB/T 31467 battery fire test.

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