Flame Retardant Properties of Polypropylene (Formex, Nomex, Fishpaper)

Flame retardancy is important in electronic and electrical equipment materials to comply with fire safety standards. Polypropylene is a versatile material with a flame retardant capability, making it popular in various manufacturing applications.

This article will explore the flame retardant properties of polypropylene, specifically Formex, Nomex, and Fishpaper — the three types used by ESPE Manufacturing Co. We will delve into the features behind their flame retardancy and their applications.

What Is Flame Retardancy?

Flame retardant properties are the capacity of a material to hinder the progression of flames or delay the onset of a fire. They are particularly important in industries prioritizing fire safety, such as construction, transportation, and electronics and electrical equipment.

The function of flame-resistant compounds is to inhibit the chemical reactions that occur during combustion. This reduces the material’s combustibility and contribution to the spread of fire.

Numerous techniques exist for applying flame resistance to materials. These include using chemicals, coatings, and flame retardant fibers or fillers within the substance.

Polypropylene Materials

ESPE Manufacturing Co. works with various electrical insulating materials to meet the needs of various applications. Here are some of the materials we employ and provide:


Formex is a type of electrical insulation material made from flame retardant polypropylene. It prevents electrically charged components from arcing and protects the users, equipment, and maintenance personnel. Its properties also ensure that the material will not melt or combust up to 115 °C (239 °F).

This material has received a UL 94V-0 rating, indicating that it meets specific flame resistance criteria and has undergone Underwriters Laboratories (UL) testing. This proves that they do not propagate flames and extinguish them on their own within a few seconds.


Nomex is a meta-aramid material renowned for its ability to resist flames, which can be attributed to its distinctive chemical composition. The material consists of polyamide molecules with long chains, making them highly heat-resistant and difficult to ignite. When exposed to high temperatures, the polymer chains within Nomex link together. This forms a protective layer of char that insulates the material and slows down the combustion process.

This polypropylene type has a wide temperature range from -196 °C (-320 °F) to 250 °C (482 °F) without significant degradation in its mechanical properties. This makes it suitable for high-temperature environments, such as aerospace, marine, electrical, and automotive industries. Furthermore, it has been extensively tested and has received the UL 94V-0 rating.

Fishpaper and Vulcanized Fiber

Fishpaper is an electrical insulation material composed of thin layers of paper that have been treated with a thermosetting resin. The resin acts as a binding agent, holding the layers of paper together and providing the material with its flame retardant properties. Due to this composition, fishpaper has a high flame resistance and is not prone to igniting or supporting combustion.

This material has moderate heat resistance and can withstand up to 120 °C (248 °F). This temperature range is ideal for electrical insulation applications with a moderate heat exposure risk. However, specialized grades can withstand higher temperatures of up to 155 °C (311 °F) or even 180 °C (356 °F). It has also received the UL 94V-0 rating.

Partner With ESPE Manufacturing Co. for Premium Electrical Insulation Materials

ESPE Manufacturing has been a trusted provider of electrical insulators for more than 70 years! We serve a wide range of markets and have a deep understanding of our materials’ unique properties. We also have an expert team that can assist you in selecting the most suitable material for your specific needs.

Contact us today to discover more about our top-quality products and services! You can also request a quote, and we will gladly help you with your needs.

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