When Battery Packs Go Into Thermal Runaway, Your Core Material Becomes the Last Line of Defense
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2026-07-27 20:33
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For eVTOL aircraft, battery enclosures, firewall bulkheads, and internal ducts face two extreme challenges — simultaneously.
On one side: temperatures that can exceed 500°C in thermal runaway events. On the other: complex 3D geometries where every millimeter of space is contested by batteries, cooling systems, and structural members.
Traditional rigid foams were never designed for this. Cold-bend them into tight radii, and the cell walls crack. Expose them to flame, and they continue burning — or worse, release dense, toxic smoke into the cabin.
Our XTylene® Zs Series PMI Foam was engineered specifically for this intersection of fire safety and complex geometry.
How Zs Series enables next-generation aerospace structures:
Self-Extinguishing Fire Protection — Built into the Polymer Chain
Unlike coated foams that lose their fire resistance when scratched or abraded, the Zs Series carries flame retardancy at the molecular level. Nitrogen- and phosphorus-containing functional groups are chemically bonded into the PMI backbone. Under heat, they decompose first — absorbing energy, forming a protective char layer, and releasing non-combustible gases that dilute oxygen at the surface.
The result: immediate self-extinguishing upon flame removal. Low smoke density. Low toxicity. Full compliance with FAR 25.853 FST requirements.
This matters for eVTOL because battery thermal runaway is not a single event. It's a cascade. A core material that self-extinguishes after the first cell vents buys precious seconds for the rest of the pack.
180–200°C Thermoformability — Complex Curves Without Cracking
When heated within its controlled thermal window, the Zs Series undergoes controlled plastic flow. The polymer network realigns without fracturing cell walls. Under vacuum or mold pressure, it drapes smoothly over tight radii and compound curves.
Once cooled, it locks into its final 3D geometry — negligible springback, 100% cellular integrity, and full retention of compressive and shear strength.
No cold-bending. No micro-cracks. No compromises.
One Material, Two Functions: Structural Core + Fire Barrier
Traditional fire protection adds weight: intumescent coatings, ceramic blankets, heavy insulation layers. The Zs Series eliminates this trade-off. It serves as both the structural sandwich core and the fire-resistant barrier — reducing part count, assembly labor, and total system mass.
Simplified Manufacturing: From Flat Sheets to 3D Parts
Flat Zs sheets can be thermoformed directly into curved geometries, replacing the wasteful alternative of 5-axis CNC machining from thick solid blocks. Material utilization improves 3–5x. Machine hours drop by over 60%. Total component cost falls accordingly.
Xintan PMI Core Matrix
Series | Key Advantage | Best For |
Tx | High specific shear modulus, Tg 210–235°C | 180°C autoclave co-cure, ultra-thin skins, eVTOL rotors, UAV spars |
Fm | Sub-0.1mm cell, minimal resin uptake | HP-RTM, mmWave radomes |
Zs | 3D Thermoformability + Self-Extinguishing FST | Curved firewalls, battery enclosures, cabin ducts |
Y | Cost-optimized PMI backbone | 120–150°C industrial oven cure, ass production |
In-House CNC & Thermoforming: Ready-to-Layup Core Kits
From flat pre-cut sheets optimized for thermoforming to fully heat-formed, 3D-milled core kits — Xintan delivers finished parts machined to your exact CAD tolerances. Zero MOQ for prototyping. Seamless scaling to production.
Developing next-generation eVTOL battery structures or aerospace fire-critical components?
DM us for Zs Series thermoforming process window guidelines and FAR 25.853 FST evaluation data.
Request a flat Zs test sheet to evaluate draping performance and flame retardancy on your own test rigs.
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