Best Practices for Working with Nomex Sheet Material

Reliable electrical insulation depends on more than choosing a high-performance material. We also need to consider how the material is selected, cut, formed, installed, and integrated with the rest of the insulation system. Arclin (formerly DuPont) Nomex® sheet material is widely used for electrical insulation because it combines dielectric strength, mechanical toughness, flexibility, and thermal performance. At Sui On Insulating, we work with Nomex® insulation solutions for motors, transformers, generators, electronic equipment, and other demanding applications.

Start with the Right Nomex® Insulation Grade

Our first step is always to match the material to the application. Nomex® products are not a single universal material, and different grades can have different constructions and performance characteristics, for example, describes Nomex® 410 as an electrical insulation paper available in thicknesses from 0.05 mm to 0.76 mm. Its typical AC rapid-rise dielectric strength ranges from 18 to 34 kV/mm depending on thickness. These are typical material values rather than universal design limits.

We therefore consider the required dielectric performance, operating temperature, mechanical stress, available space, and processing method before selecting Nomex® sheet material. This prevents a common mistake: choosing insulation based only on thickness or temperature rating while overlooking the requirements of the complete electrical system.

Check Thickness and Dimensional Requirements

Thickness directly affects how insulation fits into a component. A sheet that is too thick can create assembly problems, while insufficient thickness may not provide the required electrical separation or mechanical protection.

We evaluate the available clearance and the required number of insulation layers before converting a sheet into a finished component. Nomex® 410 is available across ten nominal thicknesses from 0.05 mm to 0.76 mm, giving designers considerable flexibility for sheet insulation applications.

At Sui On Insulating, our Nomex® aromatic polyamide insulation product has a standard width of 914 mm. We also supply different Nomex® product forms, including insulation paper, aramid paper, tape, sleeve, adhesive tape, molded parts, felt, and binding tape.

Keep Nomex® Sheet Material Clean and Dry

Proper handling is another important best practice. Before processing, we keep insulation material clean and protect it from unnecessary contamination. Dust, oil, moisture, and other contaminants can affect processing consistency and may interfere with the surrounding insulation system.

Arclin reports that densified Nomex® papers retain approximately 90% of their bone-dry dielectric strength at equilibrium with 95% relative humidity. However, this does not mean storage conditions can be ignored.

We recommend maintaining controlled storage and handling procedures, especially when the material will be used in precision electrical equipment. Keeping sheets flat, clean, and protected before processing helps maintain predictable manufacturing quality.

Cut and Form the Sheet Carefully

Nomex® sheet material is often converted into shapes such as barriers, liners, slot insulation, separators, and other electrical components. Cutting accuracy matters because poorly controlled edges can create assembly difficulties or unwanted gaps.

We plan the cutting pattern around the component geometry and required coverage. During forming, we also avoid unnecessary damage, sharp folds, or excessive mechanical stress. The objective is to create a component that fits securely without compromising the intended insulation structure.

For higher-volume business production, repeatability is especially important. Consistent cutting and forming dimensions can help manufacturers reduce assembly variation and maintain stable production processes.

Consider the Complete Thermal Environment

Temperature is one of the main reasons engineers select Nomex® insulation for demanding electrical equipment. Sui On Insulating specifies its Nomex® aromatic polyamide insulation for continuous service at 220°C and identifies it as a Class H insulation material. The product information also states compatibility with common resins, varnishes, transformer oils, and cooling agents.

However, we never treat a temperature rating as permission to operate every component continuously at the same temperature. The actual insulation system also depends on the grade, thickness, surrounding materials, thermal profile, and equipment design.

Technical documentation explains that long-term thermal aging data are used to support the 220°C insulation recognition of Nomex® paper. This is why we evaluate the entire operating environment rather than relying on one specification.

Design Around Electrical Stress

Mechanical fit and thermal performance are only part of the equation. Electrical stress must also be considered carefully. Nomex® 410 provides high inherent dielectric strength, but DuPont specifically notes that its dielectric-strength figures are typical values and should not automatically be treated as design values.

We therefore consider voltage, geometry, layer arrangement, clearances, and the possibility of partial discharge when developing an insulation system. For transformer applications, DuPont recommends limiting continuous stresses in designs using Nomex® 410 to help minimize partial-discharge risk.

This approach is particularly relevant for engineers designing high-voltage motors, transformers, generators, and other electrical equipment where insulation failure can have significant consequences.

Nomex® for New Energy Vehicle Applications

As electric and hybrid vehicles place greater demands on motors, inverters, and other high-voltage components, insulation materials must combine electrical reliability with thermal and mechanical performance. Nomex® sheet material can be used in motor slot insulation, phase separation, barriers, and other areas where compact, dependable insulation is required.

For new energy vehicle drive systems, we consider the material together with motor design, voltage level, thermal conditions, and manufacturing process. This helps us select suitable Nomex® constructions for components that must operate reliably within space- and weight-conscious systems.

Build a Consistent Inspection Process

The final best practice is verification. We check dimensions, appearance, processing quality, and material identification before the insulation enters production. For critical applications, the inspection process should also correspond with the relevant technical requirements and equipment specifications.

At Sui On Insulating, our insulation portfolio supports industrial motors, high-voltage generators, dry-type transformers, oil-immersed transformers, new energy drive systems, and electronic products. Our management systems are certified to ISO 9001, ISO 14001, and IATF 16949, supporting consistent quality management across our operations.

Making Nomex® Sheet Material Work More Effectively

Using Nomex® sheet material effectively requires a complete process, from material selection and storage to cutting, forming, installation, and inspection. We focus on matching the Nomex® insulation grade and construction with the actual requirements of each electrical system rather than treating one material specification as suitable for every application.

For engineers and professional buyers, this approach can make material selection more predictable and production easier to control. At Sui On Insulating, we help customers to develop practical insulation structures for demanding electrical equipment while keeping material specifications and application requirements aligned.