What are intumescent polymers?

An intumescent is a substance that swells when exposed to heat, resulting in an increase in volume and a decrease in density. Intumescents are typically used to provide passive fire protection.

An intumescent polymer refers to a polymer that, when subjected to heat or fire, undergoes a chemical transformation that causes it to expand significantly, forming a charred, insulating layer. This charred layer serves to protect the underlying material by reducing the transfer of heat and acting as a barrier to flames.

When subjected to fire or high temperatures, the various components in the polymer matrix react, leading to the formation of a foam-like char layer that protects the material underneath.

Intumescent polymers are used in various applications, such as:

• Fire-resistant coatings: For steel beams in buildings, which can lose their load-bearing capacity when exposed to the high temperatures of a fire.

• Seals and gaskets: For doors, windows, and other openings to prevent the spread of fire.

• Cable coatings: To protect electrical and data cables in the event of a fire.

• Consumer goods: Such as electronics, to provide an added layer of fire safety.

Their ability to expand when heated and form a protective barrier makes these polymers invaluable in fire safety engineering and design.

How are intumescent polymers used in EVs?

Intumescent polymers are becoming increasingly vital in the design of battery packs, especially in electric vehicles (EVs) and energy storage systems, because of their unique fire-protection properties. Here’s why intumescent polymers make excellent fire barriers in battery packs:

Expansion Upon Heating:

As previously mentioned, these polymers expand significantly when exposed to heat; this expansion can be many times their original thickness. When used in battery packs, this expansion can effectively isolate individual cells or modules, preventing the spread of heat and fire from one cell or module to another.

Insulating Char Formation:

The char layer formed by intumescent polymers acts as an insulator, which reduces heat transfer. This is critical in battery packs because excessive heat can cause adjacent battery cells to go into thermal runaway—a chain reaction where a cell, once overheated, can cause neighboring cells to overheat and potentially ignite. By isolating and insulating cells, the char can prevent or slow down this chain reaction.

Containment of Flames and Gases:

The insulating layer formed by intumescent polymers can help contain flames and potentially harmful gases. This is particularly important if a cell vents or releases gases, which can be both toxic and flammable. By controlling the escape pathway of these gases, the risk of explosion or fire spreading is minimized.

Lightweight and Compact:

In applications like electric vehicles, weight and space are critical considerations. Intumescent polymers provide an efficient fire barrier without significantly increasing the weight or size of the battery pack.

Flexibility in Design:

Intumescent polymers can be applied as coatings, incorporated into casings, or used as separators, allowing for flexibility in battery design and optimization of fire protection measures.


Compared to other passive fire protection methods, intumescent polymers can be more cost-effective over the product’s life cycle due to their relatively inexpensive raw materials, simple application processes, minimal maintenance requirements, and ability to integrate seamlessly into existing manufacturing lines. Their efficiency in fire protection can also lead to savings from reduced collateral damage, regulatory compliance, and potential reductions in insurance premiums.

Compatibility with Manufacturing:

Intumescent materials can be integrated into current manufacturing processes without the need for substantial changes, making their adoption easier.

Given the increasing energy densities of modern batteries and the associated risks of thermal runaway and fires, integrating intumescent polymers into battery pack designs offers an added layer of safety, helping protect both the equipment and the users.

Explore Pyrophobic’s Innovative Fire Safety Solutions

The transformative power of intumescent polymers, including our industry-leading LithiumPrevent, is revolutionizing passive fire protection across numerous industries. At Pyrophobic, we are proud to spearhead this technological breakthrough, providing an array of certified products for building construction, energy storage, and electric vehicles.

We welcome you to browse our product range and discover how our proprietary intumescent polymer technologies can deliver superior fire protection tailored to your specific needs. Our experts are ready to collaborate with you to engineer custom safety solutions that address your unique challenges.

Feel free to reach out to us if you have any questions or require further assistance.