Sustainable Fire Safety for E-mobility

The automotive world is undergoing significant changes due to stringent climate targets, driving bans for diesel vehicles and major technological innovations. New practices are being put into action by manufacturers to provide more sustainable and more efficient solutions. One of the most popular change is the increased usage of electric vehicles in the last decade. During the last decade, electric vehicle sales increased by approximately 500% percent. In 2020, the number of EVs in Europe reached 1.4 million. Environmental concerns, governmental regulations and competition on E-mobility are the main driving forces acting on this increase.

Based on the estimated figures for 2021, it is foreseen that the use of electric vehicles will account for 38% of automotive sales in 2030. In September 2021, an electric vehicle model ranked at the top of motor vehicle sales in Europe for the first time.

The EV market share is growing dramatically every year. Safety is still a critical issue for EVs due to the exposure to high voltages and currents, short circuit, and leakage. For this reason, the new requirements that stand out for engineering plastics in the automotive industry are flame retardancy, good tracking resistance, maintenance of electrical properties at high temperatures, and excellent orange color stability. In the upcoming years, these requirements will be compulsory with the new standards introduced by OEMs.

eurotec^® challenges the safety issue on E-mobility with its tailored E-Mobility Concept. Flame retardant materials are becoming more important especially for battery systems. eurotec^® offers a wide range of products thanks to its vast experience in E&E, aviation, railway, and public life applications. Only basic flame test such as horizontal burning is stipulate for vehicles with internal combustion engines. EVs are not only subject to UL94 V0 requirements. Some additional flame retardancy requirements, such as heat release, limiting oxygen index and smoke toxicity, combined with good electrical properties are becoming critically important. Using its vast experience in this subject, eurotec^® developed a tailor-made flame retardant grade to overcome safety issues regarding EVs.

Tecomid^® NB40 GR30 NL XA68 (PA6 30% glass fiber reinforced, halogen free, flame retardant), Tecomid^® NA40 GR30 NL XA68 (PA66 30% glass fiber reinforced, halogen free, flame retardant) and Tecomid NC40 GR30 NL XA68 (PA6/PA66 30% glass fiber reinforced, halogen free, flame retardant) are graded V0 at 0.75 mm and have high heat resistance as well as high tracking resistance above 600V. As understood from the table below, these three grades have a very good LOI which is above 33%.

For heat release, flame spread should be decreased to delay flashover. There is no standard for heat release in the automotive industry yet. However, some OEMs began to inquire about heat release performance of materials, and this is still under discussion. eurotec^® is capable of assessing heat release performance thanks to its experience in the railway industry. If Mahre heat release values are below 60 and 90 kwm-2, this means that the material meets EN45545 R6 in railway transportation, which is a very challenging requirement. eurotec^® 's flame retardant products PA6, PA66 and PA6/PA66 have low heat release and smoke generation thanks to their special formulation. Heat release results are shown in the table below and are expected to meet OEM criteria for EVs.

TS ISO 5660-1 Plastics – Reaction to fire tests – Heat release, smoke production and mass loss rate Part 1: Heat release rate (cone calorimeter method)

40% glass fiber reinforced, halogen free and flame retardant PPA (Tecomid^® HT NT40 GD40 BK009 XA61) is used in the inverter housing system. It is graded V0 at 0.75 mm, with a CTI value of 600V. Additionally, it has exceptionally high dimensional stability compared to equivalent grades in the market thanks to its special formulation. Due to low moisture absorption in battery systems, it maintains electrical properties at high temperatures and provide safe use.

PBT flame retardant materials are becoming critically important for batteries due to their low moisture absorption properties. However, their CTI could be limited due to the nature of PBT. Tecodur® PB70 GR25 NL XA6Z (PBT 25% glass fiber reinforced, halogen free, flame retardant) is graded V0 at 0.75 mm and have high heat resistance and low moisture absorption. Thanks to its unique formulation, the CTI value of this material is 600V and challenge the CTI limitation caused by the inherent composition of PBT. This gives the material low heat release and makes it safe to use in the batteries of electric vehicles.