Materials ESPE Works With and Their Dielectric Properties

Using materials with insulative properties has become crucial due to the increasing need for energy conservation. These materials are often employed in various industrial applications — such as construction, transportation, and packaging — to enhance energy efficiency and reduce overall consumption. They are also crucial in maintaining indoor temperatures, reducing noise pollution, and preventing energy loss.

ESPE Manufacturing Co. is a trusted supplier of electrical insulators, including washers, gaskets, and fabricated plastic parts. We also specialize in the fabrication and conversion of non-metallic materials, allowing us to serve diverse markets and industries.

In this article, we will take a closer look at the materials we at ESPE work with and their respective dielectric properties.

What Are Dielectric Properties?

Dielectric properties are the electrical characteristics of a material that acts as an insulator, impeding the flow of electricity. These properties play a vital role in industries where electrical insulation is critical, such as telecommunications, electronics, and power transmission.

Here are three essential dielectric properties of a material:

  • Dielectric Constant: Also known as relative permittivity, this is the measure of how well a specific material can store electrical energy.
  • Dielectric Strength: This is the maximum electric field strength that a material can withstand before breaking down.
  • Loss Tangent: This is the energy lost as heat when a dielectric material is subjected to an alternating electric field.

Dielectric Materials and Their Properties

ESPE works with several electrical insulating materials to cater to diverse applications. Listed below are some of the materials we use and offer:


Formex is an insulating material recognized for its flame-retardant insulation and adaptability for various applications. It possesses excellent dielectric strength, with 0.010-inch Formex GK having 2200 V/mil strength. This makes it highly resistant to electrical surges. Additionally, it has a UL 94V-0 Flame Class Rating that meets global safety standards.

The exceptional dielectric properties of Formex are further enhanced by its non-hygroscopic quality, which means that it has an extremely low moisture absorption rate of less than 0.06%. This characteristic enables the material to retain its electrical insulation properties for an extended period.


ESPE specializes in the design, production, and distribution of Nomex materials, such as Nomex papers and Nomex pressboards. The formulation of these products involves incorporating meta-aramid polymers into their great, heat-resistant synthetic fibers. As a result, they possess outstanding electrical insulating properties and resistance to chemicals, heat, and radiation.

Nomex Type 410 is an insulation paper providing exceptional dielectric strength, mechanical toughness, flexibility, and resilience. It is available in 12 different thicknesses, ranging from 0.05 to 0.76 mm, for almost any electrical sheet insulation application. Specifically, the 0.010-inch Nomex paper has a dielectric strength of 815 V/mil, making it an excellent choice for high-voltage uses.

Fishpaper and Vulcanized Fiber

At ESPE, we offer a wide variety of vulcanized fiber and fishpaper products. Vulcanized fiber is a chemically pure cellulose material that is environmentally friendly as it contains no adhesives or resins. This low-pressure laminate is produced by reacting cotton or natural wood with various chemicals, including acids, bases, and zinc chloride.

Meanwhile, fishpaper is an insulating board or paper made from vulcanized cotton. It is a flexible material easily cut and shaped to fit around electrical components. As a result, it is commonly used to insulate electric motors, generators, and transformers.

A 0.015-inch vulcanized fiber boasts a moderate dielectric strength of 200 V/mil. It is useful for many electrical insulation applications and can provide adequate protection against electrical surges and breakdowns.

ESPE Manufacturing: Your Trusted Partner for High-Quality Electrical Insulation Materials

At ESPE Manufacturing, we have over 70 years of experience developing and distributing electrical insulators. Our expert team can also help you choose the best material for your requirements, as we cater to multiple markets and understand materials’ distinct properties.

Get in touch with us today to learn more about our products and services or to request a quote. Let ESPE be your trusted partner for all your electrical insulator needs!

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