Nomex® seals

Nomex® is a registered trademark or brand of DuPont and is characterized in particular by its excellent dielectric, thermal, chemical and mechanical properties, which are based on the stable molecular structure of the synthetic aromatic polyamide polymer (aramid). Therefore, the Nomex® material available from us as a sealing paper is used in a wide range of applications, such as transformers, generators and other electrical equipment. The Nomex® paper used as electrical insulation material is available in various product lines, which differ in terms of their areas of application.

We, Rehm Dichtungen Ehlers GmbH, manufacture your individual flat gaskets from the various Nomex® papers.   

Available Nomex® grades at Rehm Dichtungen Ehlers GmbH

As already described, the various qualities are differentiated into diverse product series. We, Rehm Dichtungen Ehlers GmbH, offer products from the 400 and 900 series of the manufacturer DuPont.
The 400 series contains the original Nomex® paper type 410. Basically all products of the 400 series show excellent thermal, mechanical and chemical resistances. In addition, gaskets from the 400 range are flame retardant and do not melt.
The 900 range, on the other hand, is an insulating solution specially developed for liquid-filled transformers and are resistant, for example, to transformer oils, dielectric fluids and high-temperature fluids (silicone oils).

Nomex® qualities

Nomex® 410
Type Nomex® 410 is the standard type of Nomex® grades, which is suitable for various insulation applications. The aramid paper is characterized in particular by its thermal, mechanical and chemical insulating properties. The Nomex® 410 grade is temperature or heat resistant in a temperature range of up to 220° C without losing its electrical or mechanical properties. At the same time, this insulation material has excellent dielectric properties. In this context, Nomex® 410 prevents the transfer of heat as well as electrical energy and increases the lifetime and reliability of electric motors and generators. In conclusion, the standard grade is flame retardant and non-flammable.
Nomex® 411
The Nomex® 411 grade has a lower density (0.3) than Nomex® 410, which results in lower mechanical and electrical properties of this aramid paper. The insulating material is available in thicknesses from 0.13 to 0.58mm. Known applications of this material are in motor phase insulation and in applications where thermal insulation is required.
Nomex® 993
The material Nomex® 993 is a pressboard that belongs to the 900 product range and has thus been specially developed for liquid-filled transformers. This ideal insulation solution is available in thicknesses of 1.0-4.0 mm and is characterized by its stability combined with deformability.
Nomex® 994
Compared to Nomex® 993, Nomex® 994 pressboard has a higher density, resulting in a higher compressive load as well as increased resistance. However, the weight of this material is higher than that of Nomex® 993. Gaskets made of this pressboard are excellent as insulation material in high dielectric and thermal environments, such as spacers in liquid-filled transformers.

The properties of Nomex® paper as a sealing material

Nomex® paper is a high-strength and heat-resistant high-performance polymer insulation material made from meta-aramid fibers. The material is produced in a complex papermaking process from two different fiber types (flakes and fibrids) of the aramid polymer. Depending on the type, production takes place in a two-stage manufacturing process, using a high-temperature calender to achieve high densification of the material. For example, Nomex® Type 410 is produced in this way.

The surface insulating material has excellent mechanical properties or stabilities, which are reflected in high tensile and abrasion resistance. With regard to the thermal properties of the material, high and low temperature resistance can be determined. Thanks to the polymer structure of the material, seals or blanks made of this sheet insulation material can be used in applications with low temperatures. This polymer structure also means that the Nomex® paper does not lose its mechanical and electrical properties, even at high temperatures of up to 200 °C. The material is also resistant to high and low temperatures. The high temperature resistance is also complemented by the material's flame resistance. Nomex® papers do not melt, which means that they are considered flame retardant and thus meet the requirements of the UL94-V0 fire safety standard. For this reason, Nomex® gaskets are considered by us, Rehm Dichtungen Ehlers Gmbh, to be a sealing material for fire protection. In addition to the mechanical and thermal properties already described, gaskets made of this sheet insulation material also have excellent chemical resistance. For example, Nomex® paper is resistant to solvents, acids and bases as well as transformer fluids, lubricating oils and refrigerants. Another advantage of this gasket material is its insensitivity to moisture.

The advantages and material properties of Nomex® paper at a glance

Flat gaskets, blanks and sheets made of this material are characterized by the following advantages in summary:

  • Excellent mechanical properties or stabilities in terms of dielectric strength, tensile strength and abrasion resistance.
  • High temperature resistance - use in low and high temperature applications possible.
  • Excellent chemical resistance to solvents, acids, lubricating oils, transformer fluids, etc.
  • Nomex® paper is flame retardant (UL94-V0) and is therefore suitable as a fire protection seal.
  • Insensitive to moisture

Applications of Nomex® paper

The excellent thermal, mechanical and chemical properties of the aramide papers from the 400 product series and the pressboards from the 900 product series are the reason for the wide range of possible applications in the most diverse industries, such as the electronics industry, rail vehicle industry and renewable energies.

Aramid papers Types 410 and 411 are used, for example, in electric motors and generators to extend service life as well as to increase reliability. The high temperature resistance, resistance to oil and flame retardant properties of Nomex® Type 410 and 411 favor the use of seals made of this material for insulating transformers. We are also aware of applications in the electronics industry. As a high-performance insulating material, aramid papers are used in medium and high voltage applications (e.g. ballasts and switchgear) as well as in data centers, with the aim of ensuring an uninterrupted power supply.

As already described, types 993 and 994 belong to DuPont's 900 product series and have been specially developed for liquid-filled transformers. For this reason, gaskets made from these pressboards are used in a wide variety of applications in liquid-filled transformers, depending on the density required. For example, flat gaskets or spacers made of Nomex® 993 and 994 are used in mobile transformers, traction transformers, wind turbine, rail or furnace transformers.  

We will be happy to answer whether Nomex® papers are also suitable for your purposes. Please contact our customer service for comprehensive advice.