In applications where fire performance is a concern, standard FRP resins can be modified to slow down flame spread and reduce smoke generation. These modified materials are often referred to as flame-retardant resin systems. They are not a single product, but rather a category of resin formulations designed to improve the fire behavior of fiberglass reinforced plastic components.

What are flame-retardant resin systems designed to do?

The primary goal of a flame-retardant resin is to reduce the rate at which flames travel across the surface of an FRP product and to limit the amount of smoke produced during combustion. In many industrial and public infrastructure projects, building codes or safety requirements call for materials that exhibit lower surface flame spread or lower smoke development than standard resins would provide.

It is important to understand that flame-retardant does not mean fireproof. FRP products made with these resin systems can still burn under certain conditions. The aim is to improve reaction-to-fire performance — how a material responds to an initial flame source — not to make the material non-combustible.

Common types of flame-retardant additives

Flame-retardant resin systems generally fall into two broad categories based on the chemical approach used:

  • Halogenated systems: These contain elements such as bromine or chlorine, which interfere with the combustion process in the gas phase. They are often effective at relatively low addition levels, but may produce dense smoke or corrosive by-products when burned.
  • Halogen-free systems: These rely on phosphorus, nitrogen, metal hydroxides, or other mechanisms to suppress fire. They are sometimes specified where smoke toxicity or corrosion of nearby equipment is a concern.

The exact choice between halogenated and halogen-free systems depends on the specific fire performance requirements, environmental regulations, and the conditions of the end-use application. This is a design decision, not a universal recommendation.

How fire performance is evaluated

Fire behavior of FRP materials is commonly evaluated using standardized test methods that measure surface flame spread and smoke development. Two widely referenced examples include:

  • ASTM E84 — a test method used primarily in North America to assess surface burning characteristics of building materials. It produces a Flame Spread Index and a Smoke Developed Index under specific test conditions.
  • EN 13501 — a European classification system for reaction to fire performance of construction products. It classifies materials based on their performance in a series of fire tests.

These standards are referenced here as examples of evaluation methods. Mentioning them does not imply that any particular HotFRP product has been tested to or meets the requirements of these standards. Project-specific fire testing and classification must be conducted on the actual product configuration being specified.

Why test results depend on more than just resin

The fire performance of an FRP product is not determined by the resin alone. Several design and manufacturing variables influence how the final component behaves when exposed to flame:

  • Laminate thickness: Thinner sections may behave differently from thicker ones when exposed to heat and flame.
  • Substrate and fiber content: The type and amount of glass fiber reinforcement affect how heat is absorbed and transferred through the laminate.
  • Surface finish: Grit-top or smooth surfaces may respond differently in a fire test.
  • Installation conditions: Ventilation, backing material, and orientation can all change how a material performs in a real fire scenario.

Because of these variables, fire performance claims must always be tied to a specific tested configuration. It is not appropriate to assume that one flame-retardant resin formulation will give the same test result across all product types, thicknesses, or installation conditions.

Related FRP products that may use flame-retardant resin

Certain product categories are more likely to require flame-retardant resin options because they are used in public access areas, industrial platforms, or enclosed spaces where fire safety is regulated. These may include:

If your project requires specific fire performance, the standard approach is to discuss the required test method, target index or classification, and the exact product configuration with the engineering team. Project-specific testing can often be arranged to evaluate a defined product against the applicable test method.

For more information on flame-retardant options or to request a technical discussion, contact the engineering team through the standard inquiry form.