Nomex® insulation
Nomex® insulation, cut to shape.
Nomex® aramid paper keeps its dielectric strength at temperatures that would char cellulose and soften polyester, which is why it lines the slots of motors and wraps the coils of transformers. We cut Nomex® paper from 0.05 to 0.76 mm into slot liners, phase barriers, wraps, washers and insulators to your drawing.
- Nomex® paper thicknesses we cut
- 0.05 to 0.76 mm
- Typical UL temperature index of Nomex® 410
- 220°C
What Nomex® is
What Nomex® paper is, and why it suits hot windings.
Nomex® is a meta-aramid, a polymer related to nylon whose ring structure gives it outstanding heat resistance. For electrical paper, short aramid fibres and binder particles are formed into a sheet on a paper machine and then calendered under heat and pressure into a dense, smooth paper. The most widely used type, Nomex® 410, has a high dielectric strength without any impregnation.
The paper does not melt, is self-extinguishing in air and carries a UL temperature index of 220°C, so it is used in Class H (180°C) systems and above. It is compatible with the varnishes, resins and adhesives used on windings, and with transformer fluids, lubricating oils and refrigerants, so it survives vacuum impregnation, oil-filled transformers and hermetic compressor motors. It is tough and flexible, and creases and folds without cracking.
It does have limits. Like any paper it takes up some moisture from humid air, although its dielectric strength falls only slightly. It costs more than presspaper or polyester film, so for cooler, lower-class duties those may be enough: our guide to electrical insulation materials compares them.
Insulation materials comparedProperties
Nomex® paper properties for insulation design.
These are typical published values for Nomex® 410 paper, for comparing materials at the design stage. The data sheet for the paper we supply applies to your part.
Two points stand out. Dielectric strength per millimetre peaks in the middle of the thickness range, so a thicker paper is not proportionally stronger. And the paper is markedly stronger along the machine direction than across it, which matters for folded and highly loaded parts.
Nomex® parts cut to your drawingNomex® 410: typical properties
General values, not a specification
| Property | Typical value |
|---|---|
| Dielectric strength by thickness (AC, rapid rise) | |
| 0.05 mm (2 mil) | 18 kV/mm |
| 0.08 mm (3 mil) | 22 kV/mm |
| 0.13 mm (5 mil) | 28 kV/mm |
| 0.25 mm (10 mil) | 33 kV/mm |
| 0.38 mm (15 mil) | 33 kV/mm |
| 0.51 mm (20 mil) | 32 kV/mm |
| 0.76 mm (30 mil) | 27 kV/mm |
| General | |
| Density | 0.72 g/cm³ at 0.05 mm, rising to about 1.1 g/cm³ at 0.76 mm |
| Relative permittivity (60 Hz) | 1.6 to 3.7, rising with density |
| Dielectric strength at 96% relative humidity (0.25 mm) | About 31 kV/mm, against 33 kV/mm dry |
| Thermal | |
| UL relative temperature index | 220°C |
| Shrinkage at 300°C | Below 2%; 0.2% or less from 0.25 mm up |
| Thermal conductivity | 0.10 to 0.18 W/m·K |
| Mechanical | |
| Tensile strength, machine direction | 43 N/cm at 0.05 mm to 816 N/cm at 0.76 mm |
| Tensile strength, cross direction | About 45% to 75% of the machine direction value |
| Elongation at break, machine direction | 10% to 23%, by thickness |
| Chemical | |
| Compatible with | Varnishes, resins, adhesives, transformer fluids, oils and refrigerants |
Dielectric strength by thickness (AC, rapid rise)
- 0.05 mm (2 mil)
- 18 kV/mm
- 0.08 mm (3 mil)
- 22 kV/mm
- 0.13 mm (5 mil)
- 28 kV/mm
- 0.25 mm (10 mil)
- 33 kV/mm
- 0.38 mm (15 mil)
- 33 kV/mm
- 0.51 mm (20 mil)
- 32 kV/mm
- 0.76 mm (30 mil)
- 27 kV/mm
General
- Density
- 0.72 g/cm³ at 0.05 mm, rising to about 1.1 g/cm³ at 0.76 mm
- Relative permittivity (60 Hz)
- 1.6 to 3.7, rising with density
- Dielectric strength at 96% relative humidity (0.25 mm)
- About 31 kV/mm, against 33 kV/mm dry
Thermal
- UL relative temperature index
- 220°C
- Shrinkage at 300°C
- Below 2%; 0.2% or less from 0.25 mm up
- Thermal conductivity
- 0.10 to 0.18 W/m·K
Mechanical
- Tensile strength, machine direction
- 43 N/cm at 0.05 mm to 816 N/cm at 0.76 mm
- Tensile strength, cross direction
- About 45% to 75% of the machine direction value
- Elongation at break, machine direction
- 10% to 23%, by thickness
Chemical
- Compatible with
- Varnishes, resins, adhesives, transformer fluids, oils and refrigerants
Typical published values for Nomex® 410. Ask for the data sheet of the paper we supply.
Papers, pressboards and laminates
Nomex® papers, pressboards and laminates we cut.
Nomex® 410 is the standard calendered paper, and our 0.050 to 0.760 mm range spans its standard thicknesses. Other types exist for particular jobs: lower-density uncalendered paper, which soaks up resin for conformable wraps; papers containing mica, which resist corona discharge at higher voltages; and pressboard, a thicker, rigid board for spacers and barriers in transformers.
Laminates bond Nomex® to polyester insulation film, often as a paper, film and paper sandwich, or to Kapton® polyimide film. The film adds dielectric strength and the paper adds tear resistance and resin uptake, which makes laminates a common slot insulation for Class F and H motors.
Nomex® is a trademark of Arclin or its affiliates. Kapton® is a registered trademark of its owner. Other names are the trademarks of their owners.
Cut to your drawing
Slot liners, wedges, phase barriers, wraps and washers.
Matched to your class
We suggest the paper or laminate for your system's thermal class.
Nomex® from PSG
Forms and thicknesses
| Form | Available |
|---|---|
| Nomex® paper | 0.050 to 0.760 mm |
| Nomex® pressboard | On request |
| Nomex® and polyester film laminates | On request |
| Nomex® and Kapton® laminates | On request |
| Parts | Slot liners, phase barriers, wraps, washers, shims and insulators |
| Cutting | Die cut, or laser cut for complex parts and prototypes |
- Nomex® paper
- 0.050 to 0.760 mm
- Nomex® pressboard
- On request
- Nomex® and polyester film laminates
- On request
- Nomex® and Kapton® laminates
- On request
- Parts
- Slot liners, phase barriers, wraps, washers, shims and insulators
- Cutting
- Die cut, or laser cut for complex parts and prototypes
Other types and thicknesses on request.
Alternatives
Nomex® compared with presspaper, polyester and Kapton®.
Nomex® is not the only answer for slot and layer insulation. Choose what your insulation needs to see which materials qualify.
What does the insulation need?
Choose properties to find the right material. 5 materials compared.
| Requirement | Nomex® paper | Nomex®/polyester laminate | Presspaper | Polyester film | Kapton® film |
|---|---|---|---|---|---|
| Class H (180°C) and aboveLaminates are rated by system; many are used at Class F. | Yes | No | No | No | Yes |
| Class F (155°C) | Yes | Yes | No | No | Yes |
| Class B (130°C) | Yes | Yes | No | Yes | Yes |
| Highest dielectric strength for the thickness | No | Yes | No | Yes | Yes |
| Resists tearing during insertion | Yes | Yes | Yes | No | No |
| Takes up varnish and resinCalendered Nomex® 410 is dense; uncalendered types absorb more. | Yes | No | Yes | No | No |
| Oil-filled transformers | Yes | No | Yes | No | No |
| Lowest material cost | No | No | Yes | Yes | No |
General guidance; ratings depend on the grade and the approved insulation system. We confirm the materials available for your part with the quotation.
Applications
Where Nomex® insulation is used.
Nomex® earns its place where windings run hot, space is tight and a failure is expensive.
Motors
Motor slot liners and wedges
Slot liners, closures, wedges and phase separators for industrial and traction motors.
- Energy & Renewables
Transformers
Dry-type transformers
Layer, barrier and end insulation for dry-type transformers rated at Class H and above.
Oil-filled
Liquid-filled transformers
Paper and pressboard in oil, where hot spots run beyond what cellulose can take.
Generators
Wind turbine generators
Insulation for generators that run hot under a constantly changing load.
- Automotive
Vehicles
Electric and hybrid vehicles
Slot and phase insulation in compact traction motors and generators.
Refrigeration
Hermetic compressor motors
Insulation that tolerates refrigerants and lubricating oils inside sealed compressors.
Cutting Nomex®
Cutting Nomex®: die cut and laser cut parts.
Nomex® cuts cleanly, and the right method depends on the shape, the tolerance and the quantity.
Die cutting for production
A cutting tool made to your drawing gives clean, repeatable parts at volume, with crease lines formed in the same stroke for liners that fold.
Laser cutting for complex parts
Laser cutting needs no tool, so it suits prototypes, short runs and intricate profiles where a die cannot hold the tolerance. Read more about laser and water jet cutting.
Grain direction
The paper is stronger along the machine direction, so parts are laid out so that folds and loads suit the grain. Mark any critical direction on your drawing.
Slot liners with cuffs
A cuffed slot liner needs a crease and a fold at each end. Tell us the slot dimensions, the cuff height and the stack length.
What to send us
A drawing or a sample, the thickness or type, the quantity and the thermal class of your system. Our custom shims page explains how we quote.
Nomex® FAQs
Nomex® questions, answered.
Can't find what you need? Our technical team is happy to help.
What is Nomex® paper?
Nomex® meta-aramid paper is an electrical insulation paper made from meta-aramid fibres, calendered into a dense, smooth sheet. It keeps its dielectric strength at high temperatures, does not melt and is self-extinguishing, so it is used to insulate motors, generators and transformers. Nomex® 410, the most common type, is made from about 0.05 to 0.76 mm thick.
What temperature class is Nomex®?
Nomex® 410 paper carries a UL relative temperature index of 220°C, and it is widely used in Class H (180°C) insulation systems and in systems rated at 200°C and 220°C. The class of a finished machine belongs to its whole insulation system as tested, so check that the paper is approved within yours.
Nomex® or presspaper?
Choose presspaper for economical insulation at Class A (105°C), especially in oil-filled transformers where the oil impregnates it. Choose Nomex® when the temperature is higher, when moisture or a fault could degrade cellulose, or when the insulation must not support a flame. Nomex® costs more per square metre, so the duty decides.
Can Nomex® be laminated with polyester film?
Yes. Nomex® paper bonded to polyester film, often as a paper, film and paper sandwich, is a common slot and phase insulation for Class F and H motors: the film adds dielectric strength and the paper adds tear resistance and resin uptake. Laminates with Kapton® are used for higher temperatures. Ask us which laminates we can supply for your part.
What thicknesses of Nomex® can you cut?
We cut Nomex® paper from 0.050 to 0.760 mm, which covers the standard range of Nomex® 410. Pressboard and laminates are available on request. Tell us the thickness on your drawing, or the voltage and thermal class, and we will suggest one.
Does Nomex® absorb moisture?
A little. Like any paper, Nomex® takes up some moisture in humid air and grows slightly, but its dielectric strength falls only modestly: typical data for 0.25 mm paper shows about 33 kV/mm dry and about 31 kV/mm at 96% relative humidity. Keep stock in its packaging, and dry parts before impregnation if your process calls for it.
Have a Nomex® insulator to specify?
Send us the drawing, the thickness and the thermal class of your system, and our technical team will recommend a paper or laminate and quote for the cut parts.
Gasket and shim materials
More materials and methods
Kapton® is a registered trademark of its owner. Gap Pad® is a trademark of Henkel. Sil-Pad® is a trademark of Henkel. Other names are the trademarks of their owners.
- Read more
Electrical insulation and thermal
Electrical insulation materials
Papers, films and sheet cut into insulators.
- Read more
Electrical insulation and thermal
Kapton® polyimide film
High-temperature film cut into insulators and shims.
- Read more
Electrical insulation and thermal
Thermal interface materials
Gap Pad® and Sil-Pad® cut to your component.
- Read more
Gasket and sealing materials
Rubber gaskets
Every common elastomer compared, plus insertion, natural and butyl rubber.
- Read more
Plastics and components
Engineering plastics
Nylon, acetal, polycarbonate and PVC parts to drawing.
- Read more
Cutting methods
Die cutting
Flatbed and rotary die cutting, prototype to volume.
- Read more
Reference
Types of shims
Shim materials, shapes and stacks, and how to specify one.
- Read more
Overview
Gasket and shim materials
Every material we cut, compared in one place.
Our customers
