Home › Blog › Electromechanical & Switchgear › Data Center Power & UPS › UPS battery stack materials
PORON, Mica, Kapton, and Graphite: Building the Material Stack in a Li-ion UPS Module
Lithium-ion UPS strings are replacing lead-acid across data-center tiers, and they bring the EV battery material kit with them, applied to a stationary cabinet. The stack reads from the cell outward: a compression pad that holds the cells in their preload window, a cell-to-cell fire barrier, a dielectric wrap, a thermal interface to the cooling plate, a module-level firewall, an inter-module thermal barrier, and the cabinet gaskets around all of it.
Each layer has one controlling property and one governing test method, and one sentence governs the whole assembly: UL 1973 and UL 9540A evaluate the system, the listing belongs to the tested assembly, and these materials support designs evaluated to those standards. This guide walks the stack the way the parent application page builds it, layer by layer, with values left on the maker TDS where they belong.
Request a quote for your project →
Layer 1: compression pads, specified by force window, not thickness
Li-ion cells need sustained, even compression as they swell and breathe through charge cycles, so the pad is a spring specified by its compression-force-deflection curve.
PORON industrial microcellular urethane (the 4701 series, with ShockSeal 4790-79 where the pad doubles as a seal) owns this layer because of its defining property, long-term compression-set resistance, which is what keeps the preload window valid years into service; methods are per ASTM D3574 on the TDS, and the 4701-40V0 grade adds a UL 94 V-0 class where the location demands a rating on the pad itself.
Get the cell maker's preload window in kPa and the swell allowance onto the drawing; firmness grade and thickness fall out of those two numbers, not the other way around.
Layers 2 and 3: fire barriers at three tiers, listings at the system
Thermal-runaway design layers containment by tier, and the parent page is blunt about the standards language. Cell-to-cell, the layer is mica fire-barrier sheet in the EV battery fire-barrier grade: thin, inorganic, die-cut to the cell footprint. Module-level, ProCell EV Firewall Barrier scales the same job to walls, lids, and dividers. Between modules and compartments, ArmaGel HT and HTL aerogel blankets buy the most temperature drop per millimeter (thermal methods per ASTM C177 and surface burning per ASTM E84 on the TDS).
The strategy as a whole is evaluated per UL 9540A on the tested assembly, with UL 1973 and UL 9540 governing the battery-system and ESS tiers and NFPA 855 the installation, all cited by designation. No die-cut sheet is "UL 9540 certified"; the materials are ingredients of a strategy whose result belongs to the tested system.
Layers 4 and 5: the dielectric wrap and the thermal path
The dielectric split is by mechanics, not voltage. Kapton HN polyimide film (the 100 through 500 gauge designations) wraps cells and lines busbar paths wherever the insulation bends; Nomex 410 and 414 aramid paper insulate the rack-mounted magnetics; and G10/FR4 glass-epoxy laminate (NEMA LI 1 grades) carries load as supports, standoffs, and barriers. On the thermal side, two different jobs hide in one word. Cell-to-cold-plate transfer wants thin, compliant graphite: eGRAF HITHERM graphite TIM, with thermal impedance per ASTM D5470 on the TDS.
Interfaces that must also insulate electrically, like SiC rectifiers to heat sinks on the conversion shelf, belong to the insulating TIM class: Rogers Protect 1500FG and Bergquist Sil-Pad TSP 900 class pads, whose TDSs carry D5470 thermal and D149 dielectric data on the same sheet. State the real mounting pressure on the drawing: TIM data is pressure-dependent, and the TDS curve only means something at the pressure the assembly actually applies.
Layer 6: cabinet gaskets and the room around the cabinet
The UPS cabinet's door and access-panel gaskets are specified like any enclosure (closure force, gap, compression class per ASTM D1056) but their material families answer to the room. RE-series EPDM foam carries the economical door-perimeter duty; where temperature endurance or a flame class drives the choice, the BISCO cellular silicones step in: HT-870 Soft, BF-1000 Extra Soft for ultra-conformable joints, the RS-series flame-retardant sponge, and kSil V-0, with UL 94 listings per the individual grade TDSs.
Behind the data hall, the generator room takes the mechanical set: 25# rebonded neoprene (and 27#) base pads under gensets sized by static bearing stress, SBE41VN vinyl nitrile isolating switchgear at gentler loads, and epichlorohydrin foam C41ECH sealing enclosures in the diesel haze, the fuel-resistant chemistry at foam closure forces (2 to 5 psi compression class per ASTM D1056 on its TDS).
Li-ion UPS Module Material Stack
| Layer | Family | Controlling property | Method / citation |
|---|---|---|---|
| Cell compression pad | PORON 4701 series | CFD window + set resistance | ASTM D3574; UL 94 V-0 on the 40V0 TDS |
| Cell-to-cell barrier | Mica fire-barrier grade | Inorganic barrier | Supports designs evaluated per UL 9540A (by designation) |
| Module firewall / compartment barrier | ProCell barrier; ArmaGel HT/HTL | Barrier tier | ASTM C177, E84 per TDS; system result belongs to the tested assembly |
| Dielectric wrap / supports | Kapton HN / Nomex 410/414 / G10-FR4 | Bend vs. load mechanics | Maker TDS (D149-class); NEMA LI 1; IEC 60664 context |
| Thermal interface | HITHERM graphite; Sil-Pad / Protect insulating pads | Impedance at real pressure | ASTM D5470; D149 where the TIM must insulate |
| Cabinet gaskets | RE-series EPDM; BISCO silicones | Compression class + flame track | ASTM D1056; UL 94 listings per grade TDSs |
Qualitative summary of the parent page's stack builder; per-grade values stay on the maker TDS, reviewed against your drawing during quoting.
How H-O Products helps
H-O Products is a precision die-cut converter, not a cell or battery-system manufacturer. We take sheet, roll, and blanket stock from the material makers and die-cut, kiss-cut, slit, waterjet-cut, laminate, and kit it to your drawing set: compression pads cut to the cell footprint, mica and ProCell barriers as drawn parts, Kapton pieces, TIM pads, and cabinet gaskets, shipped as kitted module sets with lot-code TDS records per material, under our ISO 9001:2015 certified quality management system in Winsted, Connecticut.
Every part is made to order. Kitting is how the documentation burden of battery programs gets manageable: every layer traces to its TDS and lot, which is exactly what a system-level evaluation wants to see. We do not mold or extrude in-house; profiles are coordinated through our partner network.
Frequently asked questions
Are these materials UL 9540 or UL 1973 certified?
No material is, and no honest supplier will claim otherwise: UL 1973 (batteries for stationary applications), UL 9540 (energy storage systems), and UL 9540A (the thermal-runaway fire-propagation test method) evaluate systems and assemblies, so the listing belongs to the tested system.
What the materials carry is their own documentation: material-level classes like UL 94 V-0 on the rated grade TDSs, the test methods behind their properties, and lot-code traceability. They support designs evaluated to the system standards; the system designer owns the evaluation.
How do I size PORON compression pads for battery cells?
Start from the cell maker's preload window (a force or pressure range, usually in kPa) and the expected swell over life. Pick the firmness grade whose compression-force-deflection curve (per ASTM D3574 on the TDS) delivers that pressure across the deflection span from fresh stack to fully swollen, then set thickness from the gap and the curve. The 4701 family's compression-set resistance is what keeps the window valid over years; the 40V0 grade covers locations that demand a UL 94 V-0 class on the pad itself.
Mica, ProCell, or aerogel: which fire barrier goes where?
By tier. Mica fire-barrier sheet is the cell-to-cell layer: thin, inorganic, die-cut to the cell footprint. ProCell EV Firewall Barrier is the module-level layer: walls, lids, and dividers that contain a module-scale event. ArmaGel aerogel blanket is the thermal-isolation layer between modules and compartments. A containment strategy usually layers two or three tiers, and the whole strategy is what gets evaluated per UL 9540A on the tested assembly.
What goes between a SiC rectifier and its heat sink?
An electrically insulating TIM: the Sil-Pad TSP class or Rogers Protect pads, whose TDSs carry thermal impedance per ASTM D5470 and dielectric data per D149 on the same sheet. Bare graphite is the wrong answer there because it conducts electrically; reserve HITHERM graphite for cell-to-cold-plate paths and heat spreading where isolation is handled elsewhere. Read every thermal number at your real mounting pressure.
Get a UPS material-stack recommendation
Send the module drawing set with the cell preload window, barrier-tier strategy, TIM mounting pressure, and cabinet closure details, and we will return a layer-by-layer material direction with the TDS citations and a quote.
Samples typically ship in 3 to 5 business days for common die-cut configurations; standard production runs about two weeks; special orders are quoted to the job. MOQ varies by material and part.
Family-owned in Winsted, Connecticut since 1971 · ISO 9001:2015 certified · OEMs worldwide send us a drawing — and get back their part.
Related reading
Request a quote for your data-center power & UPS part
Send H-O your drawing or describe the part—engineering reviews every RFQ and converts samples on your geometry.
Last updated · Reviewed by H-O Products engineering (ISO 9001:2015 certified converter, Winsted, CT).
References
- System-level, by designation (listing belongs to the tested system or assembly): UL 1973; UL 9540; UL 9540A; NFPA 855.
- Material-level, per the maker TDS: UL 94 (incl. V-0 on rated grades); ASTM D3574 (cellular urethane methods); ASTM D5470 (TIM thermal impedance); ASTM D149 / D150 (dielectric methods); ASTM C177 / E84 (aerogel thermal and surface-burning data); ASTM D1056 (cellular rubber classes); NEMA LI 1 (industrial laminates); IEC 60664 (insulation-coordination context).
- Maker technical data sheets: PORON 4701 series and ShockSeal; mica fire-barrier grade; ProCell EV Firewall Barrier; Kapton HN; Nomex 410/414; G10/FR4 (NP510/NP511); eGRAF HITHERM and SpreaderShield; Sil-Pad TSP series; Protect/Secure; ArmaGel HT/HTL; RE-series EPDM; BISCO HT/BF/RS and kSil V-0; rebonded neoprene; SBE vinyl nitrile; C41ECH.
This article summarizes the material stack for lithium-ion UPS and rack power equipment using the published standards and material families named above. System standards (UL 1973, UL 9540, UL 9540A, NFPA 855) are cited by designation only: they evaluate systems and installations, the listing belongs to the tested assembly, and the materials described support designs evaluated to them. Material classes (UL 94) belong to the listed grades per their TDSs; per-grade values must be confirmed on the maker's current technical data sheet.
H-O converts materials; it does not manufacture cells, design battery systems, or certify systems. All parts are custom manufactured to order; minimum production run quantities vary by material and part.