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Although no plastic can be rendered entirely fire proof, flame retardant thermoplastics can delay ignition and fire spread, which increases escape time, making them a critical part of product design for many devices and platforms, especially electric vehicles.

Electric Vehicles (EV) have been the hot topic in the automotive industry for the past several years. OEM’s are making significant investments into the electrification of their platforms and developing battery technology for today and the future. Safety, range, recharge time and recyclability are key elements of the success of the battery and thermal system; yet, the big challenge is the battery itself and its charging platform.

From a safety perspective, internal combustion engine (ICE) platforms have not had the electrical voltage requirements of that required with EV. Current EV battery systems range from 200 to 800 volts versus traditional ICE platforms at 12-14V. Controlling the electrical and thermal system of the battery has introduced flame retardant grades of thermoplastic to the automotive industry. These materials initialluy were not needed due to the lower voltage requirements; however, flammability and insulative characteristics of engineering grade thermoplastics are now critical to ensure shock and fire safety when used in high voltage connection points, encapsulating bus bar and electrical enclosure applications.  

There are several electrical properties and test methods that define a materials insulative, conductive and tracking resistance; however, we will focus on flammability characteristics.

How do you identify flame retardant characteristics? Classifications are obtained based on the specimen thickness and its reaction to an open flame. UL94, IEC 60695 are similar test methods for identifying flammability characteristics of thermoplastic materials. HB is the least stringent requirement where as 5VA is the most stringent. 

HB Horizontal Burn - Burn rate of < 3” minute or stop within 5” on a horizontal 3mm thick specimen.

V2 Vertical Burn - Burning stops within 60 sec. after 2 flame applications, dripping allowed.

V1 Vertical Burn - Burning stops within 60 sec. after 2 flame applications, dripping not allowed.

V0 Vertical Burn - Burning stops within 10 sec. after 2 flame applications, dripping not allowed.

5VB Surface Burn - Burning stops within 60 sec. after 5 flame applications, Specimen can have a burn through hole.

5VA Surface Burn - Burning stops within 60 sec. after 5 flame applications, Specimen can not have a burn through hole.

What other tests are available? IEC 60695 glow wire flammability index and ignition temperature are another standard for testing flammability using heat as the ignition source. This method identifies the maximum temperature a part material can withstand with no ignition, or self extinguish with no burning droplets of material over a 30-second timeframe. 

Both UL and IEC test methods provide directional guidance in selecting flammability characteristics of thermoplastic materials that meet or exceed the application requirements. Testing of the physical part is required as nominal wall section. The manufacturingprocess and geometry may also affect the materials performance.

Nexeo Plastics offers several FR material grades specifically developed to meet and exceed the requirements of these electrical applications. Material grades are compounded with different additive and filler formulations and specified for their stable mechanical properties and high operating temperature.

Lanxess Pocan PBT, Durethan PA6 and PA66

BASF Ultradur PBT, Ultramid PA6 and PA66

DSM ForTii PPA, Xytron PPS, Akulon PA6 and PA66

Solvay Ryton PPS, Amodel PPA

Sabic Valox PBT, Noryl PPE - Lexan FR PC, Cycoloy FR PC/ABS, Stamax FR PP, LNP FR compounds are also available offering flame retardant grades for enclosures, couplers and charging components.

Contact your Nexeo Plastics Account Manager and Technical Service Engineer to learn more about where and how flame retardant thermoplastic can solve your product development requirements.