Aerospace Electrical Insulation: Die-Cut Nomex Slot Liners, Kapton Winding Films, Mica Barriers & Busbar Supports
H-O Products die-cuts and converts aramid papers, polyimide films, mica, rigid laminates, and solid silicones into slot liners, phase separators, winding wraps, arc barriers, busbar supports, and dielectric interface parts for aircraft motors, generators, actuators, and power-distribution systems — built to your drawing. H-O is a materials converter: insulation system design and equipment qualification remain with the machine builder.
Built for: Stator slot liners and closures, phase and end-winding separators, transformer and coil wrap insulation, mica arc and barrier plies, G10 / FR4 busbar supports and standoffs, 270 VDC power-electronics barriers, terminal-board details, and compliant dielectric pads.
To insulate an aerospace machine or power system, pick by location and thermal class. For stator slot liners and phase separators, specify Nomex aramid paper: 410 as the baseline, 414 high-density for tight slots and automated insertion, 411 uncalendered where conformability matters more than thickness, and the Nomex NMN triplex laminate where a paper-film construction is called, with class behavior per the IEC 60085 framing on the DuPont data. For winding and coil wrap, use Kapton / Apical polyimide film. The remaining zones and duties are mapped in the When-to-spec list on this page. Values are per the TDS on file; see the material reference below for ordering details.
IEC 60085 (thermal classification of electrical insulation, by designation) · ASTM D149 (dielectric breakdown voltage and strength) · NEMA LI 1 (industrial laminate grades G-10 / FR-4 / G-11, by designation) · MIL-I-24768 (laminate military specification family, by designation) · MIL-STD-704 (aircraft electric power characteristics, incl. 270 VDC class, cited qualitatively) · RTCA DO-160 (environmental framing, cited qualitatively) · UL 94 (flammability listings per TDS) · vendor TDS for per-grade values.
- Stator slot liner / closure: Nomex 410 / 414 / 411 or NMN laminate
- Phase & end-winding separators: Nomex paper + Kapton film
- Winding / coil wrap insulation: Kapton / Apical film
- Arc & extreme-temperature barriers: Mica barrier sheet
- Busbar supports & standoffs: Norplex G10 / FR4 / G11
- Tracking-critical supports: Durostone composite
- 270 VDC-class barriers, thin: APTIV PEEK film
- Thermal ply inside coils: ManniGlas paper
- Low-friction separator plies: PTFE film (6113)
- Compliant dielectric pads: BISCO HT-12xx solid silicone
Where are you in the spec process?
This page serves rotating-machine and power-system engineers who already hold an insulation call-out and engineers still mapping thermal class, voltage, and forming constraints. Pick the path that matches where you are; you don’t have to read the rest.
Send a drawing, get a quote
Nomex 410 / 411 / 414 / 818 / NMN laminate, Kapton or Apical film, mica sheet, Norplex G10 / FR4 / G11, Durostone, APTIV PEEK, ManniGlas, PTFE film, or BISCO solid silicone on your drawing.
Skip to the quote form →Walk through the selection factors
Six selection factors (thermal class, dielectric duty, mechanical role, forming, environment, system voltage), a machine-insulation lookup by location and class, and nine material families with TDS-cited test methods.
Start with selection factors →
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1Send drawingUpload a DXF, STEP, or PDF, or describe the assembly. A sample part works too.
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2Material reviewEngineering reviews the part against the vendor TDS: thermal class at the machine’s hot spot, working voltage and test voltage, mechanical role and forming, environment and fluids, and how the part installs in the winding or assembly sequence.
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3PrototypeSamples typically ship in 3–5 business days for common die-cut configurations on materials we keep on hand. Made-to-order; MOQ varies by material and part.
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4ProductionStandard production runs ship about 2 weeks after drawing approval, including kiss-cut-on-liner and laminated configurations. Expedited service available. Ongoing parts run with material traceability and lot-code TDS records.
What are you insulating?
Application Zones
Five distinct material problems hide inside an aerospace electrical system: the stator slot, where liners and separators carry the machine’s dielectric life in fractions of a millimeter; the windings and coils, whose wrap insulation sets the thermal class; the busbar and distribution structure, where laminates do structural and dielectric duty at once; the higher-voltage DC electronics that more-electric architectures keep adding; and the terminal and interface details that finish every build.
Click a tab to see the duty, the constraint, and the material families H-O converts for that zone.
Stator slot liners, closures & separators
The slot is where an aerospace machine lives or dies: the liner separates winding from lamination stack across a gap measured in tenths of a millimeter, survives the insertion process, and then holds its dielectric and mechanical properties at the machine’s hot-spot temperature for the life of the equipment.
Nomex aramid paper is the working family, 410 as the baseline, 414 high-density and calendered for tight slots and automated insertion, 411 the uncalendered, lower-density grade where conformability around coil ends matters more than thickness, the NMN triplex laminate (Nomex / polyester film / Nomex) for slot liners and phase separators that need a paper-film construction, and 818, a calendered aramid-mica paper, for high-voltage conductor and coil wrap, with class behavior framed per IEC 60085 on the DuPont data and breakdown per ASTM D149 per thickness.
Where the slot is tighter or hotter than paper alone serves, Kapton film and paper-film constructions carry the duty in less thickness. H-O die-cuts, slits, and creases liners, closures, and separators to the lamination drawing, in the quantities a winding line and a rewind shop actually consume. [8] [2]
Winding wrap, turn & layer insulation
Above the slot, insulation becomes a winding-room material: wraps, interlayers, and barriers that conform to coils, survive impregnation, and set the assembly’s thermal class. Kapton and Apical polyimide film are the high-class workhorses, thin, thermally stable, dielectric-dense, slit to wrap widths and die-cut into interlayer and barrier details. Nomex paper and the NMN laminate carry layer insulation, end fillers, and forming duty, and ManniGlas glass-fiber paper adds an inorganic thermal ply inside coils where the design calls one out.
Two converting details decide winding-room satisfaction: edge quality, because a nicked film edge becomes a dielectric weak point at impregnation, and slit-width consistency, because hand-wrap pace lives on it. Where coils meet arc-exposure or extreme local temperature, mica plies enter the stack, the mineral answer that holds integrity where organics char. Values per thickness stay on each TDS per ASTM D149.
Busbar supports, standoffs & phase barriers
Aircraft power distribution is mechanical engineering at dielectric stakes: busbar supports and standoffs position conductors against vibration and fault forces while insulating them, and phase barriers subdivide panels so a fault stays where it started. The material class is the glass-epoxy laminate family, Norplex G10 / FR4 / G11, graded under the NEMA LI 1 framing with military procurement under the MIL-I-24768 designations, machined and die-cut into supports, spacer blocks, barrier plates, and terminal boards.
Where the environment adds tracking exposure, contamination, condensation, altitude, the arc- and tracking-resistant Durostone composites (UPM-class grades among them) take over, per the maker’s comparative tracking data. The converting work is precision machining as much as cutting: hole patterns that match busbar drilling, edges that resist tracking initiation, and chamfers where creepage paths demand them. Per-grade mechanical and dielectric values stay on the laminate TDS.
Higher-voltage DC & power-electronics barriers
More-electric architectures moved aircraft power up the voltage ladder, and the 270 VDC class that MIL-STD-704 frames, with higher buses arriving behind it, tightened every insulation detail: creepage and clearance shrink-wrapped by power density, altitude derating that ground hardware never sees, and switching electronics whose barriers must be thin, stable, and mechanically serious.
The film families carry this zone. APTIV PEEK film brings dielectric strength with mechanical endurance, barriers, slot-style separators in compact machines, and formed details that survive assembly, per the Victrex TDS.
Kapton handles the thinnest barrier plies and wrap duty. Mica enters where local arc exposure or extreme temperature ends polymer candidacy, and laminate details (G10 / FR4) provide the structural insulation around modules. Altitude matters: dielectric margins that satisfy sea-level practice thin with pressure, which is why the system’s creepage / clearance design, owned by the equipment builder under its DO-160-framed environment, governs every converted part here.
Terminal boards, standoffs & compliant dielectric interfaces
Every machine and panel finishes with the small parts: terminal boards, insulating washers and standoffs, cover liners, and the compliant pads that sit between live hardware and structure. The laminates (G10 / FR4) carry the rigid duty, die-cut and machined boards, spacers, and washers with clean hole patterns.
The compliant duty belongs to BISCO HT-12xx solid silicone: dense, temperature-stable sheet die-cut into dielectric pads, terminal-cover liners, and conforming interfaces that take up tolerance while holding a defined thickness, with hardness and dielectric data per the Rogers TDS.
PTFE film (6113-class skived grades) adds low-friction separator duty where parts move across one another during assembly or thermal cycling. None of these parts is glamorous; all of them appear at every failure investigation, which is why edge quality, hole accuracy, and material traceability per lot are the actual specification. [14] [2]
Six decisions that drive your machine insulation spec
Electrical insulation for aerospace machines is a system spec: thermal class, dielectric duty, mechanical role, forming, environment, and system voltage all constrain each other, and a material that satisfies five of the six still fails the machine. The honest path is to fix the class and the role first, then let the families compete.
The hot spot sets the class; the class gates the family. Insulation ages thermally: a material run above its class trades life for temperature on an unforgiving curve. Name the machine’s hot-spot class per the IEC 60085 framing before any material conversation starts.
Show all 6 selection factors tap to expand
Slot liners, turn wraps, and barrier plies do their work in fractions of a millimeter. At that scale, converting quality, edge condition, crease placement, hole accuracy, is dielectric performance: a nicked edge or off-pattern hole is a weak point the test voltage will find. Breakdown values are per thickness per ASTM D149 on each TDS.
Read the six factors below in order. Class first, dielectric duty second, mechanical role third; forming, environment, and system voltage then settle the grade and the converted format.
Thermal class at the real hot spot
IEC 60085 organizes insulation by thermal class (130 / 155 / 180 / 220 and beyond), and the assignment that matters is the machine’s hot spot, not its nameplate ambient.
Aerospace machines run hot by design, weight pays for temperature, so the class ladder climbs fast: aramid paper and polyimide film families earn high-class ratings on their TDS, laminates carry their own class data, and every grade’s assignment is per its maker’s documentation, not its family reputation. Put the hot-spot class on the drawing and the candidate list writes itself. [1]
Dielectric duty: working, test, and altitude
Three voltages matter: the working voltage the part sees daily, the test voltage it must survive at acceptance, and the altitude-derated margins aerospace adds, because dielectric withstand thins with pressure. Breakdown data per ASTM D149 is per thickness and per grade on each TDS; the system’s creepage and clearance design, owned by the equipment builder, converts those numbers into geometry. State working voltage, test voltage, and altitude condition, and the thickness conversation becomes engineering instead of habit. [2]
Mechanical role: liner, barrier, or structure
Insulation parts carry three different mechanical jobs. Liners and wraps conform and survive insertion (aramid paper, films). Barriers stand in fault paths and at arc exposure (mica, laminate plates, Durostone where tracking governs). Structural insulators, supports, standoffs, terminal boards, position conductors against vibration and fault forces (G10 / FR4 / G11 under NEMA LI 1 / MIL-I-24768 framing).
Materials migrate badly between roles: a structural laminate makes a terrible liner, and paper makes no standoff. Name the role on the drawing, then the family. [4]
Forming, creasing, and the winding room
Slot liners get creased and inserted, sometimes by machine at line rate; wraps get pulled to tension by hand; wedges drive into filled slots. The converting features that serve those processes, crease placement, cuff geometry, slit-width consistency, burr-free edges, are part of the part. A liner that fights the winding room gets “adjusted” on the bench, and bench adjustments are not lot-traceable. Specify forming features explicitly and send the lamination drawing; H-O cuts, creases, and kits to the winding sequence.
Environment: fluids, vibration, and contamination
Aerospace machines live wet: fuel-pump motors in fuel, actuator machines near hydraulics, generator terminals in condensation and de-icing chemistry, all of it vibrating per the DO-160-framed environment the equipment qualifies to.
Material behavior against the program’s fluid list is per-grade TDS and program data; tracking-exposed supports step from standard laminate to Durostone-class composites; and contamination-prone surfaces favor materials whose tracking and surface behavior are documented. List the fluids and the vibration framing on the drawing; environment edits the family list more often than voltage does. [6]
System voltage class and the more-electric trend
The 270 VDC class that MIL-STD-704 frames, and the higher buses behind it, compresses insulation geometry exactly while altitude thins margins: power density shrinks creepage paths as derating demands more of them. The film tier answers, PEEK and polyimide barriers in tenths of a millimeter, mica where arc exposure ends polymer candidacy, and the system-level creepage / clearance design governs every converted detail. State the bus class and altitude envelope; the converted parts inherit both. [5]
Specification Tools
Two tools to take you from “I have a machine insulation problem” to here’s what to put on the drawing: a machine-insulation lookup that maps part location and thermal class to a material family, and a side-by-side comparison matrix of every family on this page.
1. Machine insulation lookup by location and thermal class
Pick where the part lives in the machine and the thermal class at the hot spot. The lookup returns the material family the location-class pair maps to, with the forming note that usually decides satisfaction. Qualitative, per the H-O application research; per-grade class assignments and breakdown values stay on each TDS.
Pick a location and a thermal class
The result returns a material family for the location-class pair, the reasoning, and the forming note that matters at that location.
2. Side-by-side: aerospace electrical insulation matrix
Every material family called out on this page, with its construction, class framing as reported on its TDS, and the role it fits. Click a column header to sort. Click any material name to jump to its accordion entry and full TDS reference.
| Material | Construction | Flame / FST data (TDS) | Key test methods | Form factor | Best for | |
|---|---|---|---|---|---|---|
| Papers & films | ||||||
| Nomex Aramid Paper410, 411, 414, 818 aramid-mica, NMN laminate | Aramid paper / board | Per DuPont TDS | ASTM D149; IEC 60085 | Slot liners, separators | ||
| Kapton / Apical Polyimide FilmHN general; FN bondable | Polyimide film | Per DuPont TDS | ASTM D149 | Winding wrap, thin liners | ||
| APTIV PEEK Film1000 / 2000 series; XPI tier | PEEK film | Per Victrex TDS | Per Victrex TDS | 270 VDC-class barriers | ||
| PTFE Film (6113 Series)Skived film grades | PTFE film | Per TDS | Per maker TDS | Low-friction separators | ||
| Laminates & composites | ||||||
| Norplex G10 / FR4 / G11NP500A G-10; NP510A FR-4; NP511 G-11 | Glass-epoxy laminate | NP510A UL-listed FR-4 (TDS); G-10 / G-11 not flame-rated | NEMA LI 1; ASTM D149 | Supports, terminal boards | ||
| Durostone CompositeUPM-class grades | Glass-reinforced composite | Per Röchling data | Tracking data per maker | Tracking-critical supports | ||
| Barriers & compliant interfaces | ||||||
| Mica Barrier SheetMuscovite; phlogopite high-temp | Mineral laminate | Inorganic; per TDS | Per maker TDS | Arc / fault barriers | ||
| ManniGlas Glass-Fiber Paper1200 / 1900 / 1902 / 2000 | Inorganic glass paper | Inorganic; per TDS | Per maker TDS | Thermal plies in coils | ||
| BISCO HT-12xx Solid SiliconeHT-1240 / HT-1250 / HT-1260 / HT-1270 | Solid silicone sheet | Per Rogers TDS | ASTM D2240, D149 (TDS) | Compliant dielectric pads | ||
Skip ahead and request your engineering review now
If your drawing already calls out a Nomex, Kapton, mica, Norplex, Durostone, APTIV, ManniGlas, PTFE, or BISCO grade, send it over for engineering review.
Machine insulation failures you can prevent at spec
Electrical insulation failures rarely announce themselves at acceptance test. The machine megs clean, survives its hi-pot, and ships. Then service hours accumulate and the weak points declare: a liner nicked at insertion, a class run past its hot spot, a support tracking across a contaminated surface. Five patterns cover most of what fails in this zone, and each one is a specification decision made before the first coil is wound.
Insulation failures are thermal history written in dielectric ink. Most in-service breakdowns trace back to temperature: a class exceeded, a hot spot mislocated, an aging curve traded for schedule. The class assignment is the spec’s most consequential line.
Show all 5 failure modes tap to expand
1. A liner nicked at insertion fails at the hi-pot, or worse, later
A slot liner arrives with edge burrs from a worn tool, the insertion process scuffs it, and the damage hides under the winding until test voltage, or two thousand service hours, finds it. The fix: treat converting quality as dielectric specification: burr-free edges, crease placement that survives insertion geometry, and incoming inspection that looks at edges, not just dimensions. Breakdown values per ASTM D149 assume intact material; the slot only ever contains the material as converted. [2]
2. The class was assigned to the ambient, not the hot spot
An insulation system specified to the housing temperature runs a winding hot spot a class higher, and thermal aging quietly halves and halves again the design life. Nothing fails at acceptance; everything ages on the wrong curve. The fix: assign the class per the IEC 60085 framing at the measured or modeled hot spot, derate honestly for altitude and duty, and pick grades whose class assignments per their TDS clear it with margin. The class line on the drawing is the life of the machine. [1]
3. A standard laminate tracks in a contaminated, condensing bay
A G10 support that serves perfectly in a dry panel goes into a bay with de-icing chemistry, condensation, and conductive dust. Surface leakage begins, carbonizes a path, and a phase-to-ground fault follows. The fix: match the support material to the surface environment: tracking-exposed locations step to the Durostone-class composites per the maker’s comparative tracking data, and creepage-path geometry, chamfers, ribs, distance, gets engineered with the material, not after it. [10]
4. A 270 VDC barrier specified by sea-level habit
A barrier thickness that satisfied decades of 115 VAC practice gets carried into a 270 VDC more-electric application, and the combination of higher stress, altitude derating, and compressed creepage paths erases the margin everyone assumed.
The fix: rework the insulation details to the bus class per the MIL-STD-704 framing and the altitude envelope: film-tier barriers (PEEK, polyimide) with documented per-thickness breakdown, edges and spacing engineered to the derated case, and the system creepage / clearance design driving every converted dimension. [5]
5. The rewind shop cannot reproduce the OEM insulation kit
A machine comes in for rewind and the insulation arrives as improvisation: liners cut by hand, wraps substituted by availability, wedges shaved to fit. The rewound machine works, differently, and untraceably. The fix: kit the insulation system as a drawing-controlled product: every liner, separator, wrap width, wedge, and washer die-cut to the lamination drawing, labeled in winding order, lot-traceable, and repeatable across shops and years. H-O builds exactly these kits for OEM lines and rewind programs alike.
Material reference
Detailed reference for the nine material families on this page: the papers and films (Nomex aramid paper, Kapton / Apical polyimide film, APTIV PEEK film, PTFE film), the laminates and composites (Norplex G10 / FR4 / G11, Durostone), the barriers (mica sheet, ManniGlas glass-fiber paper), and the compliant dielectric family (BISCO HT-12xx solid silicone).
Dielectric breakdown is tested per ASTM D149 per thickness, thermal classes follow the IEC 60085 framing per grade, laminate grades follow NEMA LI 1 / MIL-I-24768 designations, and flammability listings per UL 94 appear as listed on each TDS.
H-O die-cuts, machines, and converts all of them to drawing; per-grade values are per the TDS on file, not headline numbers.
Nomex Aramid Paper (410 / 411 / 414 / 818 / NMN Laminate)Slot liners & separators · the machine-insulation baseline · per DuPont TDS
The baseline family of machine insulation: specify the grade to the slot and the process (414 for tight slots and automated insertion, 411 where conformability matters, NMN laminate where the slot needs a paper-film construction), and let converting quality, edges, creases, kits, carry the winding room. Values per the DuPont TDS on file.
Kapton HN / FN & Apical Polyimide FilmWinding wrap & thin liners · high-class film duty · ASTM D149 per TDS
The film that carries the hottest, tightest insulation duty on the aircraft: specify thickness from the per-thickness breakdown data, and hold edge quality, a nicked film edge is a weak point at impregnation. Values per the DuPont TDS on file.
APTIV PEEK Film (1000 / 2000 Series; XPI Tier)270 VDC-class barriers · mechanical endurance · per Victrex TDS
The film tier for the most demanding combination of dielectric, thermal, and mechanical duty: specify it where polyimide’s mechanics or the assembly process would compromise a thinner, softer film. Values per the Victrex TDS on file.
PTFE Film (6113 Series, Skived Grades)Low-friction dielectric separators · per maker TDS
A specialist: where motion and dielectric duty meet, PTFE film prevents the wear that would consume a paper or polyimide ply. Keep it to the locations that need it; values per the TDS on file.
Norplex G10 (NP500A) / FR4 (NP510A) / G11 (NP511) Glass-Epoxy LaminateSupports, standoffs & terminal boards · NEMA LI 1 framing · per Norplex TDS
The structural insulator of the aircraft electrical system: specify the grade to the class ladder (NP510A FR-4 baseline where a flame callout applies, NP511 G-11 hotter, NP500A G-10 where neither applies), and treat machining quality, holes, edges, chamfers, as part of the dielectric design. Values per the Norplex TDS on file.
Durostone Composite (UPM-Class Grades)Tracking-critical supports · arc-resistant composite · per Röchling data
The step you take when the environment, not the voltage, is the threat: tracking resistance is a surface property, and Durostone’s is documented. Pair the material with creepage geometry engineered to the same case. Values per the Röchling data on file.
Mica Barrier Sheet (Muscovite; Phlogopite High-Temperature)Arc & fault barriers · mineral-class integrity · per maker TDS
Mica answers the exposures nothing organic should see, and asks for converting discipline in return: clean cutting at holes and edges, careful handling, lamination where the stack needs support. Values per the maker TDS on file.
ManniGlas Glass-Fiber Paper (1200 / 1900 / 1902 / 2000)Thermal plies in coils & stacks · inorganic margin · per maker TDS
The light inorganic ply that buys thermal margin without mica thickness: position in the stack is part of the design, so convert to the drawing exactly. Values per the maker TDS on file.
BISCO HT-12xx Solid Silicone (HT-1240 / HT-1250 / HT-1260 / HT-1270)Compliant dielectric pads · dense solid silicone · per Rogers TDS
The compliant member of an otherwise rigid material set: it takes up tolerance and vibration while holding a defined dielectric thickness. Pick durometer from the closure force per the Rogers TDS on file.
Aerospace electrical insulation: engineer-grade FAQ
Twelve of the questions we hear most from machine, generator, and power-system engineers and from aerospace purchasing teams. If your question isn’t here, send a drawing or call, engineering picks up.
What material is used for slot liners in aerospace motors and generators?
Nomex aramid paper is the baseline: 410 general purpose, 414 high-density where the slot is tight or insertion stiffness helps, 411 uncalendered where conformability matters, and the NMN triplex laminate where a paper-film construction is called, with thermal-class behavior framed per IEC 60085 on the DuPont data and breakdown per thickness per ASTM D149. As slots tighten and hot spots climb, paper-film constructions and Kapton film carry the duty in less thickness, and PEEK film enters in the most compact machines. [8]
What do the thermal classes (130 / 155 / 180 / 220) actually mean?
They are the IEC 60085 framing for insulation thermal endurance: each class names the temperature an insulation system is assigned to live at, derived from thermal-aging behavior. The number that matters is the machine’s hot spot, not its ambient, and every grade’s class assignment lives on its maker’s TDS. Run insulation above its class and life shortens on an aging curve; specify the class to the real hot spot and the family list writes itself. [1]
When does Kapton film replace Nomex paper?
When space or temperature outruns paper. Polyimide film delivers its dielectric duty in a fraction of paper thickness, which buys slot fill in compact machines, and its thermal capability carries the hottest wrap and liner locations. The trade is mechanics and process: film demands edge quality and gentler handling, and paper-film laminated constructions often serve better than either alone. Per-thickness breakdown data per ASTM D149 on the TDS settles the thickness. [2]
What are G10 and FR4, and how do they differ from G11?
Grades of woven-glass epoxy laminate under the NEMA LI 1 framing, with military procurement under MIL-I-24768 designations: G-10 the classic glass-epoxy, FR-4 its flame-retardant sibling and the practical workhorse (Norplex NP510A here, UL listed), and G-11 the higher-temperature grade (NP511, 175 °C continuous, not flame-rated); NP500A is the G-10. In aircraft power hardware they are the structural insulators, supports, standoffs, barrier plates, terminal boards, machined and die-cut with the holes, chamfers, and edges treated as dielectric features. [4]
When is Durostone specified instead of a standard laminate?
When the surface environment, not the voltage, is the threat: contamination, condensation, de-icing chemistry, and altitude stress create tracking conditions a standard laminate surface may not survive. The Durostone composites carry documented comparative tracking performance per the maker’s data, which is why arc- and tracking-critical supports step to them while dry-panel hardware stays on FR4 economics. Creepage geometry gets engineered with the material, to the same environment. [10]
Where does mica still beat every polymer?
At arc exposure and extreme local temperature. Mica is a mineral: it neither chars nor tracks the way organics do, holds dielectric integrity through fault events, and serves arc chutes, fault barriers, and the hottest plies in coils and terminations. Muscovite covers most barrier duty; phlogopite carries the severest temperatures. The cost is mechanical: mica is brittle, so converting quality at holes and edges decides its service life. [12]
What changes at 270 VDC in more-electric aircraft?
Stress, margins, and geometry, simultaneously. The 270 VDC class that MIL-STD-704 frames raises working stress on every barrier; altitude derating thins dielectric margins exactly as power density compresses creepage paths. The insulation answers are film-tier: PEEK and polyimide barriers with per-thickness breakdown data, mica where arc exposure appears, and edges, spacing, and chamfers engineered to the derated case under the equipment’s DO-160-framed environment. Sea-level habits do not transfer. [5]
Why does converting quality matter as much as material choice?
Because machine insulation works in fractions of a millimeter, where a burr, a nick, or an off-pattern hole is a dielectric defect, not a cosmetic one. Breakdown values per ASTM D149 describe intact material; the slot contains the material as converted. Edge condition on films, crease placement on liners, hole accuracy on laminates, and slit-width consistency on wraps are specification items, and the drawing should say so. [2]
Can H-O kit complete insulation systems for OEM lines and rewind shops?
Yes, and the kit is the product: every liner, separator, wrap width, wedge, washer, and board die-cut or machined to the lamination drawing, labeled in winding order, lot-traceable, and reproducible across years and shops. That reproducibility is precisely what hand-cut rewind insulation cannot offer. H-O builds these kits across all nine families on this page as an ISO 9001:2015 certified organization in Winsted, Connecticut.
Does H-O design insulation systems or certify machines?
No. The insulation system design, class assignment, creepage / clearance geometry, qualification testing, belongs to the machine builder, framed by IEC 60085 and the program’s environment (DO-160 / MIL-STD-704 cited qualitatively). Material values belong to the makers’ TDS. H-O converts the documented materials to the qualified drawing, repeatably, with the lot-coded traceability the equipment’s paperwork expects. [6]
Why does this page frame values as “per the TDS on file”?
Because insulation numbers are per-thickness, per-grade, per-condition facts: breakdown moves with thickness and temperature (ASTM D149), class assignments are grade-specific (IEC 60085 framing), and laminate properties vary by grade under NEMA LI 1. A single headline number flatters one condition and misleads the rest. This page names the governing framings and keeps per-grade values on the manufacturer TDS, which H-O reviews against your drawing during quoting. [2]
How do orders run for made-to-order insulation components?
Send a drawing, BOM, or sample part, the lamination drawing for slot work, the panel drawing for laminate work. Engineering reviews the parts against the TDS layer and your class, voltage, and environment, then quotes prototype and production. Everything is made-to-order against the drawing; MOQ varies by material and part.
Samples typically ship in 3–5 business days for common die-cut configurations on materials we keep on hand, and standard production runs ship about 2 weeks after drawing approval, with expedited service available. Lead-time details live in the process strip above and the quote form below.
Glossary: terms used on this page
Quick reference for the machine-insulation, laminate, and dielectric terminology used throughout. Each entry links to the relevant test method or section where applicable.
Slot liner
The insulation sheet lining a stator slot, separating windings from the lamination stack. Cut, creased, and inserted to the slot geometry; its converted edge and crease quality is dielectric performance.
Thermal class (IEC 60085)
The temperature assignment of an insulation system under the IEC 60085 [1] framing (130 / 155 / 180 / 220 and beyond), set at the machine’s hot spot. Each grade’s class behavior is per its maker’s TDS.
Phase / end-winding separator
Conforming insulation placed between phase groups and around coil ends, where windings of different potential approach each other outside the slot. Geometry follows the winding head, not the slot.
Creepage and clearance
The surface path (creepage) and air gap (clearance) between conductors. Altitude derates both, which is why aerospace insulation geometry, chamfers, ribs, spacing, is engineered to the derated case by the equipment builder.
Tracking
Progressive carbonized leakage paths across an insulation surface under contamination and voltage. A surface property: standard laminates serve dry panels, and tracking-exposed locations step to composites with documented tracking performance.
Dielectric breakdown (ASTM D149)
The voltage at which insulation fails under test, per ASTM D149 [2], reported per thickness on each TDS. Working margins, test voltages, and altitude derating are system design built on those numbers.
G-10 / FR-4 / G-11 (NEMA LI 1)
Industrial glass-epoxy laminate grades under the NEMA LI 1 [4] framing, with military designations under MIL-I-24768: the structural insulators of power hardware, machined and die-cut to drawing.
270 VDC class (MIL-STD-704)
The higher-voltage DC distribution class of more-electric aircraft, framed by MIL-STD-704 [5]. For insulation it means higher working stress, altitude-derated margins, and film-tier barrier details.
Slot wedge
The driven closure that retains windings in the slot, cut and formed from pressboard or laminate. Profile and lead-in geometry are drawing features; driven parts cannot be bench-adjusted traceably.
Impregnation (VPI / trickle)
The resin processes that consolidate a winding after insertion. Insulation materials must survive them, which is why edge quality and material-process compatibility per the TDS are selection inputs, not afterthoughts.
Rewind kit
The complete, drawing-controlled insulation set for rebuilding a machine: liners, separators, wraps, wedges, and boards, kitted in winding order with lot traceability, so the rebuilt machine matches the OEM build instead of approximating it.
Last updated · Reviewed by H-O Products engineering (ISO 9001:2015 certified converter, Winsted, CT).
Standards, test methods & technical references
The standards, test methods, and vendor technical data sheets cited throughout this page. Standards editions current as of June 2026; verify against the publishing body before final spec. H-O converts materials that are tested to these methods on the source manufacturer’s TDS; H-O does not independently certify materials, and flight qualification remains with the airframer or system integrator.
IEC 60085
Electrical insulation – Thermal evaluation and designation: the thermal-class framing (130 / 155 / 180 / 220 and beyond) cited qualitatively throughout this page. Class assignments per grade are on each maker’s TDS. webstore.iec.ch (IEC 60085)
ASTM D149
Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies: the per-thickness breakdown framing on every dielectric TDS cited here. astm.org/d0149
UL 94
Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances: flammability listings cited per grade and thickness on the polymer-material TDS. shopulstandards.com (UL 94)
NEMA LI 1
Industrial Laminating Thermosetting Products: the grade framing (G-10, FR-4, G-11, and siblings) behind the structural laminates on this page, cited by designation. nema.org
MIL-STD-704
Aircraft Electric Power Characteristics: the power-quality and voltage-class framing (including 270 VDC) cited qualitatively for more-electric insulation context. quicksearch.dla.mil
RTCA DO-160
Environmental Conditions and Test Procedures for Airborne Equipment: the environmental qualification framing for the equipment these insulation parts serve, cited qualitatively. rtca.org
MIL-I-24768
Insulation, Plastics, Laminated, Thermosetting: the military designation family for procurement of the glass-epoxy laminate grades, cited by designation. quicksearch.dla.mil
DuPont Nomex / Kapton technical data
Manufacturer data for Nomex aramid papers (410 / 411 / 414 / 818) and the NMN laminate, and Kapton films: thermal-class behavior, per-thickness breakdown per ASTM D149-class methods, and forming guidance per grade. dupont.com
Norplex-Micarta laminate technical data
Manufacturer data for the NP500A (G-10), NP510A (FR-4) and NP511 (G-11) laminates: mechanical, thermal, and dielectric properties per grade under the NEMA LI 1 framing. norplex-micarta.com
Röchling Durostone technical data
Manufacturer data for the Durostone composite grades: comparative tracking performance, mechanical properties, and electrical-grade documentation. roechling.com
Victrex APTIV PEEK film technical data
Manufacturer data for APTIV standard and XPI films: dielectric, thermal, and mechanical endurance properties per grade. victrex.com
Mica sheet technical data (muscovite / phlogopite)
Maker TDS for rigid and flexible mica barrier sheet: temperature capability, dielectric data, and forming limits per grade. cogebi.com
Lydall (Alkegen) ManniGlas technical data
Manufacturer data for ManniGlas glass-fiber papers: basis weight, thickness, and high-temperature stability per grade. alkegen.com
Rogers BISCO solid silicone technical data
Manufacturer TDS for the HT-12xx solid silicone series: hardness ladder, dielectric data, and temperature capability per grade. rogerscorp.com
Updated . Standards editions and links current at publication; verify against the publishing body before final spec. H-O converts materials tested to the methods cited; lot-specific documentation available on request.
Get a machine insulation engineering quote
Send a drawing, BOM, or spec sheet, the lamination drawing for slot work, the panel drawing for laminate work. We typically respond within one business day with a material-family recommendation, prototype lead time, and TDS verification against your thermal class, voltage, and environment.
Prefer to talk it through first? Contact the engineering team or call (860) 469-1144.
See also: related H-O application pages
Engineering content for the adjacent aerospace application categories, all under the aerospace, defense & space industry hub and the energy, power & high voltage overview.
Application page
Avionics thermal management & interface materials
The thermal side of the same electronics: graphite spreaders, TIM pads, and dielectric boundaries for conduction-cooled boxes.
Read the page
Application page
EMI shielding gaskets for aerospace & defense
Conductive elastomer gaskets for the enclosures these machines and panels feed.
Read the page
Application page
Arc flash & fire protection
The fault-energy side of electrical materials: arc barriers, flash protection, and fire-rated layers in power equipment.
Read the page
Application page
Busbar, transformer & motor insulation (industrial)
The industrial sibling of this page: the same material science applied to switchgear and ground-based machines.
Read the page
Application page
Fuel, hydraulic & chemical-zone sealing
The fluid-exposure chemistry for the wet machines these insulation systems serve: fuel pumps, actuators, hydraulics.
Read the page
Industry hub
Aerospace, defense & space materials
The full industry directory: every aerospace sub-application H-O converts for, from thermal insulation to EMI shielding.
Open the hub
Material data & standards. All material properties and ratings referenced on this page are taken from the source manufacturer’s technical data sheets and the cited standards: dielectric breakdown per ASTM D149 per thickness, thermal classes per the IEC 60085 framing per grade, laminate grades per NEMA LI 1 with MIL-I-24768 designations by procurement, flammability listings per UL 94 as listed, and MIL-STD-704 / RTCA DO-160 cited qualitatively as system and environmental framing.
This page frames performance qualitatively and keeps per-grade values on the TDS, where they belong. H-O converts materials tested to these methods; H-O does not design insulation systems, does not certify machines, and makes no airworthiness claims. Verify against the vendor TDS and your equipment’s qualification basis for your specific application.
Conversion scope. H-O die-cuts, machines, and converts paper, film, laminate, mica, and elastomer stock to drawing in Winsted, Connecticut: slot liners and closures with creases and cuffs, separators, slit wrap widths, wedges, machined supports and terminal boards, barrier plies, and winding-order insulation kits, with material traceability and lot-code TDS records, as an ISO 9001:2015 certified organization.
H-O does not manufacture raw material in-house; extruded or molded profiles are coordinated through a partner network. Lead-time and MOQ details are on the process strip and in the quote form above.