NMN Insulation Paper (Nomex-Mylar-Nomex Composite) Class H
NMN insulation paper is a premium three-layer composite electrical insulation material consisting of a polyester film (Mylar) core laminated between two outer layers of Nomex aramid paper. This advanced structure delivers outstanding thermal endurance, superior dielectric strength, and excellent mechanical toughness — purpose-built for high-temperature transformer and motor insulation systems.
ACC Insulations manufactures high-quality NMN insulation materials for OEMs in transformer manufacturing, motor winding, traction systems, and high-performance electrical equipment production requiring Class H (180°C) thermal ratings.
What is NMN Insulation Paper?
NMN (Nomex-Mylar-Nomex) insulation is a three-layer flexible laminate where a polyester film (Mylar) acts as the high-dielectric core, and two layers of Nomex aramid paper on each face provide superior thermal resistance and mechanical toughness. It is the Class H upgrade to the standard DMD insulation system, engineered for electrical equipment that operates continuously at elevated temperatures up to 180°C.
The Nomex outer layers offer inherent flame resistance, chemical stability, and resistance to varnish and oil impregnation processes — making NMN the material of choice for dry-type transformers, traction motors, and aerospace-grade coils where thermal degradation cannot be tolerated.
NMN Layer Structure
Key Features
- Superior thermal endurance rated for Class H (180°C) operation
- Excellent dielectric strength from the Mylar polyester film core
- Inherent flame resistance from Nomex aramid outer layers
- Outstanding mechanical toughness — high tear and puncture resistance
- Fully compatible with varnish and resin impregnation systems
- Chemically stable in transformer oil environments
- Low moisture absorption for consistent performance in humid climates
- Good flexibility and conformability for precision winding applications
Technical Specifications
| Material | Nomex Aramid Paper + Polyester Film (Mylar) |
|---|---|
| Thermal Class | 180°C (Class H) |
| Thickness Range | 0.13 mm to 0.50 mm |
| Dielectric Strength | High (Mylar film core) |
| Flame Resistance | Inherent (Nomex aramid) |
| Color | Golden Yellow / Orange |
| Form | Rolls and Sheets |
| Impregnation Compatibility | Varnish, Resin, Transformer Oil |
NMN vs DMD — Which Should You Choose?
Both NMN and DMD are three-layer flexible composites sharing the same Mylar polyester film core. The critical difference lies in the outer facing material and the resulting thermal class:
| Property | NMN (Nomex-Mylar-Nomex) | DMD (Dacron-Mylar-Dacron) |
|---|---|---|
| Outer Layer | Nomex aramid paper | Dacron polyester nonwoven |
| Thermal Class | Class H (180°C) | Class F (155°C) |
| Flame Resistance | Inherent | Standard |
| Typical Color | Golden Yellow / Orange | White |
| Best For | Dry-type transformers, traction motors, high-temp coils | Standard motors, oil-type transformers, general coils |
Applications
- Dry-type transformer winding and slot insulation
- Traction motor insulation for railways and EVs
- High-temperature electrical coil insulation
- Generator and alternator winding systems
- Layer, phase, and turn insulation in Class H equipment
- Aerospace and military-grade electrical components
- Submersible motor and pump winding insulation
- Industrial drive motor slot liners
Types of NMN Insulation Available
- Standard NMN (Class H — 180°C)
- NMN with enhanced Mylar film thickness for higher dielectric rating
- Prepreg NMN (pre-impregnated with resin for fast winding)
- Roll form (standard and custom widths)
- Sheet form (custom cut-to-size)
Why Choose ACC Insulations for NMN?
- Consistent Nomex-to-Mylar lamination quality across every batch
- Custom thickness, roll width, and sheet sizes available
- Reliable and timely supply for high-volume OEM requirements
- Rigorous quality control with per-batch dielectric testing
- Expert technical support for material selection and application
- Competitive pricing with genuine Class H certified materials
Engineering Tools Suite
Not sure whether NMN (Class H) or DMD (Class F) is the right choice for your application? Use our smart insulation selector and thermal class calculator to make an informed decision.
Frequently Asked Questions
NMN stands for Nomex-Mylar-Nomex. It is a three-layer flexible composite electrical insulation material made of a polyester film (Mylar) core sandwiched between two layers of Nomex aramid paper. This construction delivers Class H thermal performance up to 180°C along with inherent flame resistance from the Nomex outer layers.
NMN insulation paper is rated for Class H insulation, allowing continuous operation at temperatures up to 180°C. This makes it the preferred choice over Class F DMD insulation for high-temperature motors, dry-type transformers, and traction systems where thermal margins are critical.
Both NMN and DMD share a polyester film (Mylar) dielectric core. The difference is in the outer facing layers. DMD uses Dacron polyester nonwoven fabric and is rated for Class F (155°C). NMN uses Nomex aramid paper and is rated for Class H (180°C). NMN also offers inherent flame resistance, which DMD does not. Choose NMN when your application demands higher temperature endurance or flame safety.
Yes. NMN insulation paper is chemically compatible with transformer oils and all standard varnish impregnation systems. The Nomex aramid outer layers provide excellent long-term oil resistance, making NMN suitable for both dry-type and oil-filled power transformer applications.
