Nomex is the brand name for meta-aramid, a heat-resistant aromatic polyamide developed by DuPont and owned by Arclin since April 2026. It is sold as fibre, as honeycomb and as electrical insulation paper. In motors and transformers, Nomex almost always means grade 410 paper: available in thicknesses from 50 to 760 µm, classified as a class H insulating material (180 °C), listed by UL with a temperature index of 220 °C and rated for 18 to 34 kV/mm short-term (SynFlex, Nomex 410 datasheet, to ASTM D-149). This article sets out grades 410, 411 and 414 and the laminates NMN and NKN, shows the properties per thickness, clarifies which of the two temperatures applies and says which grade to use where. Our range of aramid papers and laminates is listed under insulation materials.
Nomex from GOBA: supply forms, thicknesses and enquiry
GOBA supplies Nomex from a single piece, as material or as a finished part to your drawing.
- Supply forms
- Roll and slit roll, Sheet and board, Cut-to-size, Die-cut part to drawing, Formed part (folded, embossed or bent)
- Thicknesses
- To your specification. GOBA processes materials from 7 µm to 3 mm.
- Versions
- Nomex 410 as standard, also as NMN or NKN laminate. Other grades and aramid papers are sourced on customer request.
- Slit rolls
- Widths from 5 to 1,600 mm, tolerance ±0.1 mm, cores of 25, 55, 76 or 152 mm
- Die-cut and formed parts
- Material thickness 0.023 to 3.0 mm, dimensions up to 1,000 × 2,000 mm
- Quantity
- From 1 piece, from sample to series
- Lead time
- Two weeks at most when the material is in stock
What we need for your quotation
- Drawing or dimensions
- Quantity
- Material and thickness
For rolls also width, length, core diameter, core material (for example plastic) and tolerances.
Nomex is the brand, aramid paper the material
Chemically, Nomex is poly(m-phenylene isophthalamide), made from m-phenylenediamine and isophthaloyl chloride. DuPont developed the fibre in the early 1960s and launched it in 1967 under the name Nomex (Wikipedia, Nomex and Aramide). In April 2026 Arclin acquired DuPont's aramids business with the Nomex and Kevlar brands (Textile World), and Nomex datasheets have been published under Arclin since then. The paper is made from two forms of the same polymer, short floc and fibrids, which are laid into a web on the paper machine and, for grade 410, densified between rolls. This calendering is what separates the grades.
Anyone searching for Nomex often lands on firefighter jackets and racing suits. That is the same fibre as a fabric; for electrical insulation only the paper matters. What separates Nomex from Kevlar is the molecular geometry: Kevlar is a para-aramid with extended chains and high tensile strength, Nomex a meta-aramid whose chains cannot align and which in return stays heat and flame resistant (Wikipedia). Other manufacturers offer their own meta-aramid papers. What these papers have in common as a material group is described in the article on aramid paper.
Nomex grades: 410, 411, 414 and the laminating papers
The electrical insulation papers have been sold as the 400 series since the DuPont era. The grades differ in density, surface and filler; the polymer is the same in all of them.
| Grade | Construction | Thickness | Density | Typical location |
|---|---|---|---|---|
| Nomex 410 | calendered, high density | 0.05 to 0.76 mm | 0.72 to 1.13 g/cm³ | slot, layer, slot closure, transformer, almost any sheet insulation (DuPont, SynFlex) |
| Nomex 411 | uncalendered, absorbent | 0.13 to 0.58 mm | 0.30 to 0.31 g/cm³ | phase insulation, coil end filler in transformers (DuPont, SynFlex) |
| Nomex 414 | flexible, open surface | 0.18 to 0.38 mm | 0.9 to 1.0 g/cm³ | slots of hand-wound motors, wire wrap, dry-type transformers (DuPont) |
| Nomex 416 LAM, 464 LAM | laminating paper | 0.05 to 0.13 mm | not stated | outer plies of NM, NMN and NKN laminates (DuPont) |
| Nomex 418, 818 | mica filled | not stated | not stated | high voltage and corona exposure (SynFlex, CMC) |
| Nomex 410 creped | creped 410 | 0.856 mm from 0.08 mm | 0.15 g/cm³ | wrapping of leads, 110 % elongation instead of 11 % (DuPont) |
In practice two grades are enough. Nomex 410 is the standard for almost any sheet insulation and the grade we carry as standard. Nomex 411 is the exception for places where the paper should soak up resin and form a cushion. The other grades are special cases that should be named explicitly on the drawing.
Nomex 410: thicknesses and properties per gauge
The table shows typical values from the SynFlex datasheet, which is based on DuPont data. They are averages, not specification limits. Machine direction means along the roll.
| Nominal thickness | Basis weight | Density | Tensile MD / XD | Short-term breakdown |
|---|---|---|---|---|
| 50 µm | 41 g/m² | 0.72 g/cm³ | 43 / 19 N/cm | 18 kV/mm |
| 80 µm | 64 g/m² | 0.81 g/cm³ | 68 / 34 N/cm | 22 kV/mm |
| 130 µm | 115 g/m² | 0.88 g/cm³ | 141 / 71 N/cm | 28 kV/mm |
| 180 µm | 174 g/m² | 0.95 g/cm³ | 227 / 116 N/cm | 34 kV/mm |
| 250 µm | 249 g/m² | 0.96 g/cm³ | 296 / 161 N/cm | 33 kV/mm |
| 300 µm | 310 g/m² | 1.00 g/cm³ | 380 / 185 N/cm | 34 kV/mm |
| 380 µm | 395 g/m² | 1.02 g/cm³ | 462 / 252 N/cm | 33 kV/mm |
| 510 µm | 549 g/m² | 1.06 g/cm³ | 610 / 374 N/cm | 32 kV/mm |
| 610 µm | 692 g/m² | 1.13 g/cm³ | 728 / 500 N/cm | 32 kV/mm |
| 760 µm | 839 g/m² | 1.08 g/cm³ | 816 / 592 N/cm | 27 kV/mm |
Two things stand out. Thin papers hold less per millimetre because they are looser: 50 µm has a density of 0.72 and holds 18 kV/mm, from 180 µm the density is 0.95 and the strength around 33 kV/mm. And the paper is almost twice as strong along the roll as across it. The dielectric constant rises with density from 1.6 to 3.7 at 60 Hz, thermal conductivity from 0.103 to 0.175 W/(m·K). How dielectric strength is measured and why it depends on thickness is explained in the article on electrical dielectric strength.
180 °C or 220 °C: which temperature applies to Nomex
The same datasheet gives two temperatures, and both are correct. SynFlex lists Nomex 410 as a class H insulating material (180 °C) and at the same time as UL listed with a relative temperature index of 220 °C for mechanical and electrical properties. DuPont backs the 220 °C with ageing data: the paper keeps useful properties for at least ten years under continuous exposure to 220 °C, and up to 200 °C the electrical values barely change.
The 220 °C describe the material on its own. The 180 °C describe what a motor or transformer with Nomex, impregnating resin, enamelled wire and banding usually achieves as a system under the thermal classes. For design, the system class counts. A Nomex part in a class F machine (155 °C) has reserve; a Nomex part in a machine above 180 °C needs a UL-recognised insulation system in which exactly this combination has been tested. Where Nomex sits on the temperature ladder between polyester film, polyimide and mica is shown in the article on high-temperature insulation.
- Short-term, Nomex 410 still holds 12 kV/mm for several hours at 400 °C (DuPont).
- At 300 °C the paper shrinks along the roll by 1.8 % at 50 µm and by 0.2 % from 250 µm, and practically not at all across it (SynFlex).
- At the low end, Nomex is usable down to -196 °C, and at 77 K its tensile strength is even 30 to 60 % above the room-temperature value (DuPont).
- The paper is flame retardant to UL 94 V-0, its limiting oxygen index is 27 to 32 % and still 22 to 25 % at 220 °C (DuPont, SynFlex).
Continuous field strength: Nomex 410 holds 33 kV/mm briefly, 1.6 permanently
The short-term value in the table is a test value. For design, DuPont gives a different figure: the continuous stress on Nomex 410 should not exceed 1.6 kV/mm so that no partial dischargesdevelop and erode the paper over the years. For Nomex 411, SynFlex gives 1.2 kV/mm. Some distributors write 1.5 kV/mm; we work with the manufacturer's value.
A worked example shows the gap. A 250 µm paper with a typical thickness of 260 µm holds around 8.6 kV short-term (33 kV/mm times 0.26 mm). For continuous service you design it for 400 V (1.6 kV/mm times 0.25 mm). Between test value and operating value there is a factor of about 20. Anyone who sizes insulation by the short-term value builds in a source of partial discharge. You can check the relationship between voltage, thickness and field strength in the article on electric field strength, whose calculator has Nomex 410 as a preset.
Nomex 410 or 411: the choice depends on where the part sits
At the same nominal thickness of 250 µm the two grades are worlds apart. Uncalendered 411 weighs a third, carries an eighth of the tensile load and a quarter of the short-term field strength.
| Property at 250 µm | Nomex 410 | Nomex 411 |
|---|---|---|
| Density | 0.96 g/cm³ | 0.31 g/cm³ |
| Basis weight | 249 g/m² | 82 g/m² |
| Tensile strength MD | 296 N/cm | 35 N/cm |
| Elongation MD | 22 % | 3.4 % |
| Short-term breakdown | 33 kV/mm | 9 kV/mm |
| Maximum continuous field strength | 1.6 kV/mm | 1.2 kV/mm |
| Dielectric constant at 60 Hz | 2.9 | 1.2 |
For its location 411 is still the right paper: it soaks up impregnating resin like a sponge and fills voids that a dense paper leaves open. Our assignment by location, based on DuPont's application data:
- Slot insulation, slot closures and layer insulation: Nomex 410, because tensile strength during insertion and dielectric strength per millimetre count here. The designs are described in the articles on slot insulation and slot closures.
- Hand-wound motors and impregnated dry-type transformers: Nomex 414, electrically like 410 but softer and with an open surface.
- Phase insulation in the end winding and coil end fillers: Nomex 411, when the part should form a cushion after impregnation. Which other materials are used there is covered in the article on phase insulation.
- Windings under corona stress, for example on inverter drives or in high-voltage coils: a mica-filled grade such as 418 or 818, or mica itself.
- Thin slot at high voltage: NMN or NKN laminate, because the film in the core carries the field.
NMN and NKN: Nomex as a laminate
Pure aramid paper is porous. It absorbs resin well but holds less per micrometre than a closed film. The laminates combine both: NMN places a polyester film between two plies of Nomex, NKN a polyimide film. DuPont states UL insulation systems typically up to 180 °C for NMN, used for slots, wedges and phases in class H and large class F machines. NKN is part of UL systems up to and including 220 °C and thus of machines above class H. The film sets the limit: polyester caps NMN, polyimide lifts NKN. Construction and variants of the polyester composite are described in the article on NMN laminate, the lower-cost composite with polyester nonwoven instead of aramid in the article on DMD laminate.
Processing Nomex: machine direction, folding, storage
Nomex 410 can be slit, punched, folded and embossed, and it behaves like a tough paper while doing so. Three points belong on the drawing or in the conversation before ordering.
- Machine direction: at 250 µm the paper holds 296 N/cm along the roll and 161 N/cm across it (SynFlex). DuPont recommends orienting the paper to suit the application. For slot closures and slot liners the machine direction therefore belongs on the drawing.
- Folding and embossing: angles, edges and shapes are made with our embossing and folding tools.
- Humidity and solvents: moisture slightly lowers tensile strength and improves elongation and tear strength. Alcohols, ketones, acetone, toluene and xylene cause slight, mostly reversible swelling (DuPont). At 20 °C and 50 % relative humidity the paper keeps indefinitely (Seipp).
Master rolls come in 457 or 914 mm width (SynFlex). In contract slitting we cut strips of 5 to 1,600 mm from them with a width tolerance of ±0.1 mm. In stamping and forming we process material thicknesses from 0.023 to 3.0 mm up to a part size of 1,000 x 2,000 mm, with steel rule dies for samples and solid steel tools for series and tight tolerances.
Nomex, Kapton, pressboard, micanite: which material when
The most common objection to Nomex is the price. For a class A or B machine it is justified: electrical pressboard carries 105 °C, polyester film 130 °C, and both cost less. From class F the calculation flips, because pressboard is hygroscopic and absorbs moisture, while Nomex according to DuPont is insensitive to moisture and still lasts ten years at 220 °C.
Our recommendation for the range from 155 to 220 °C is Nomex 410 or a Nomex laminate. There are two exceptions. Where the slot leaves only 50 µm of insulation height, Kapton wins through its higher field strength per millimetre, and it carries 240 °C. Where heating conductors or arcs act above 250 °C, only mica remains, that is micanite.
How GOBA processes Nomex
Nomex 410 is our standard. We process it as roll material, blanks and punched parts and use it in the laminates NMN and NKN. Other Nomex grades and aramid papers from other manufacturers we source on customer request, for instance when a specification prescribes a particular grade or a customer wants to test an alternative. The paper becomes slot liners, slot closures, phase insulation, layer insulation for transformers and folded insulation and molded parts to drawing.
For an enquiry we need three things: the thermal class or continuous temperature of the machine, the operating voltage at the part and the drawing with thickness, grade and machine direction. If the grade is missing, we propose one based on where the part sits.
