Thermoplastic composite by Envalior passes thermal runaway tests at low thickness

Envalior offers a new thermoplastic composite under its Tepex brand, which passes the standard thermal runaway tests for electrical vehicle (EV) battery housings, even with very low test specimen thickness.

Fibers reinforced for high resistance on fire and temperature

The high resistance feature of composite is attributed to the non-flammable, long and continuous fibers that reinforce the material in a multi-layer structure.

With test specimen thickness of just 2mm or even less, the composite can pass the standard tests covering thermal runaway and thermal propagation events, such as the battery enclosure thermal runaway (BETR) test to UL 2596.

The material easily meets the requirements of the battery stress test involving particle bombardment. The component did not undergo burnthrough even in exposure to particle bombardment, when temperature reaches as high as 1400°C at the end, or for another 20 seconds after.

Experts from Envalior inspect a Tepex test specimen that successfully withstood a battery stress test involving particle bombardment without undergoing burnthrough.

Even following exposure to particle bombardment and temperatures of as high as 1400°C, the test specimen did not undergo burnthrough.

In addition, the composite also acts as an effective barrier against external fire sources. In the fire pan test, which is based on UN regulation 180, 6.2.4, and simulates highly realistic battery fire scenarios in accident situations, burning fuel did not create holes in the material, and the fibers did not ignite.

Lightweight feature facilitates mass production

The lightweight benefit of the material facilitates its mass production. The density of the exclusively glass fiber-reinforced material variant is around 70% less than that of steel.

If the core layer of the composite is reinforced with carbon fibers, this difference in density is even greater. Thus, compared with aluminum, the composite can be significantly more than one third lighter.

Flexible on choices of fiber and matrix materials, including recycled ones

The composite comprises several layers of long and continuous fibers. Depending on the requirements, each layer can be reinforced with special fiber textiles.

The total fiber content in the composite is more than 50% by weight. Polyamides or other engineering plastics can be used as matrix materials. Composite with variant containing recycled carbon fibers is also available, with a proportion of recycled material in the composite at around 36% by weight.

High electrically insulation and tracking resistance

Carbon fibers in the composite delivers electromagnetically shielding for battery housing. This shielding ensures that any equipment in or near the battery is not exposed to electrical or electromagnetic interference.

The fibers of the outer layer are completely impregnated with matrix plastic, which creates a closed plastic surface. This ensures the material exhibits outstanding electrical properties such as high dielectric strength and surface resistance, as well as outstanding tracking resistance.

Resistant to immersion cooling fluids

The composite is also resistant to immersion cooling fluids. Entire battery housings are often submerged in these electrically non-conductive and highly flame-retardant fluids as a means of direct cooling (immersion cooling).

Long-term storage in standard dielectric immersion cooling fluids showed that even after 1,500 hours, the composite does not undergo any changes to its mechanical properties or start to swell, nor does it release any substances into the cooling fluid.

Creating sustainable material cycles

Like other products in the Tepex brand, the thermoplastic material can be easily recycled. Production waste such as offcuts can be easily shredded and then reused as quality assured recycled compounds for injection molding.

Components can also be recycled in this way. Composites and components can also be recycled by means of solvolysis and depolymerization, creating sustainable material cycles.