There are a wide variety of composite applications being developed that require good fire-retardant performance. Many of these applications mandate the use of their own unique fire tests. An Ashland study published in 2012 demonstrated that there is little correlation between the various flame spread and smoke tests employed by code officials for approving FRP composites. It also showed that a resin system’s performance in one test may not guarantee that it will perform similarly in another test. The appropriate choice of fire-retardant (FR) resin technology will depend largely on what fire tests will be utilized and how the composites are fabricated.

Recently, ACMA published its “Guidelines and Recommended Practices for Fiber-Reinforced-Polymer (FRP) Architectural Products” to assist composite designers on selection of materials (resin, FR additives, reinforcements, etc.) and proper fabrication techniques (hand lay-up, infusion, pultrusion, etc.), as well as explain how these choices affect fire retardance. The guidelines also provide a helpful overview of important FR tests (such as NFPA 285, NFPA 286 and ASTM E84) and factors that contribute to successful test results. There is also a useful reference to adoption of the NFPA 285 test for the evaluation of floor-to-floor fire spread by the 2009 International Building Code, which was critical to the adoption of composite materials in building rain screens above four stories.

There are many FR resin systems available to construct fire-resistant FRP building panels. In horizontal fire tests like the ASTM E84 surface burning test, halogenated systems tend to be more efficient than aluminum trihydrate (ATH) filled resins in obtaining a low flame spread index. Some intumescent systems also work well in this test. Halogenated resin systems, however, are unlikely to meet the desired smoke index value (450 or less) unless the composite panel has a high glass content and a thickness less than 0.1 inches.

Non-halogenated FR epoxy options have been developed that produce less smoke in this test. There are broad offerings of flame-retardant epoxy systems, including non-halogenated options, for the reliability, protection and performance required for electrical laminates and other challenging composite applications. All U.S. epoxy producers have FR resin systems.

Phenolic resins are well known for meeting stringent flame/smoke/toxicity specifications and do not require specialty fillers. Benzoxazine thermoset resins combine good flammability resistance with outstanding thermal and mechanical properties.