“Flame Retardants” and “Standard Testing”

The term “flame retardants” should be clearly understood to mean materials (additive or reactive) that deter or extinguish flame propagation under standard laboratory test conditions. The definition set forth by the relevant ASTM terminology subcommittee for a flame retardant chemical is “a chemical which, when added to a combustible material, delays ignition and reduced flame spread of the resulting material when exposed to flame impingement”. Note the relative rather than absolute language. Note also that terms such as “fireproof” or “flameproof” can be misleading and should not be used. It is also important for everyone working in this field as well as users of flame retardants to understand that tests run under standard small scale conditions do not necessarily predict the behavior of the materials under real fire conditions. Substantially all flame retardants can be defeated in a large enough fire. In these blog post, the use of terms such as “flame retardant” should in no way be construed as warranting performance in a large real fire.

Another important consideration is that flammability tests run on small, standard sized samples may not properly represent the performance of the final product containing the formulated plastic. Configuration, wall thickness, orientation, coatings, and adjacent materials can greatly affect flame retardant performance. The manufacturer should test the final product under use (and abuse) conditions. The relatively new European single-burning item test is a step in this direction. In the U.S., the Underwriters Laboratory and Factory Mutual have long recognized the importance of realistic testing. However, many tests called for in codes and purchase specifications still fall short of representing real fire conditions. Some of these methods, like the time-honored E-84 “Steiner 25-ft. tunnel,” and automotive MVSS 302 are considered by many fire experts to be in need of upgrading or replacing.

[E. Weil and S. Levchik, Flame Retardants for Plastics: Practical Applications (Hanser, 2016), p.1]

Next post we will dive into the most used flame retardant – Alumina Trihydrate.