Freudenberg Sealing Technologies has introduced a material that it says withstands direct applied flames at up to 1,200°C for 25 minutes, with a 2mm-thick sample.
Quantix Ultra was designed to provide a flame protection barrier for lithium-ion battery cooling systems. It will be used for the first time by a car manufacturer in series production vehicles in February 2024.
Thermal runaway is an important consideration in the design of battery packs for BEVs and hybrid vehicles. One element of a multilayered approach to containing any thermal event is the use of fire-resistant materials within a pack. To date, most plastic materials have proved unsuitable for such applications.
Further tests to simulate the emission of hot particles under high pressure, which can occur if the gases in battery cells are abruptly discharged, showed that Quantix Ultra could withstand the stress test for 20 seconds. A similar thickness aluminum sample is destroyed in only two or three seconds.
For engineering plastics, temperature resistance is a key differentiating feature. This applies to both amorphous and semi-crystalline materials. All currently used polymers have one thing in common: once the so-called glass transition temperature is reached, their rigidity decreases noticeably and collapses abruptly when the melting point is exceeded. In such a case, flame protection stops.
“The new material doesn’t melt at high temperatures; instead, it exhibits elastic behavior that can be compared to elastomers,” explained Kira Truxius, material expert in thermoplastics at Freudenberg Sealing Technologies. “It also has a glass transition temperature that is 53 Kelvin higher, which means that it retains its rigidity and flame protection over a significantly longer period of time. When you add up its qualities, Quantix Ultra is at the very top of all currently known plastics.”
The base material is a thermoplastic that is already temperature resistant. The addition of fillers such as glass or carbon fibers reinforces the mechanical stability even under enormous heat. The additional cross-linking of the plastic molecular chains ensures that the component maintains its shape even under extreme conditions. The material properties can be adjusted with a focus on the specific application.
“Our patented know-how consists of the precise addition of suitable materials that create bridges between the molecular chains,” added fellow thermoplastics material expert at Freudenberg Sealing Technologies, Dr Björn Hellbach. “The patents are the result of successful teamwork.”
The material can be processed via injection molding and shares the same advantages as other thermoplastics, including the ability to produce complex geometries in short cycle times and thus in large quantities. The cross-linking also contributes toward economical production methods, as it is based on the introduction of a special cross-linking agent into the material while maintaining the standard injection molding process.
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