Flame retardant (FR) chemicals are added to products to slow the rate of flame spread or the rate of ignition. FRs are a relatively inexpensive way to meet flammability requirements for items such as children’s car seats, fire-protective clothing, electronic devices and appliances, and the materials inside vehicles and airplanes.
FRs come in a wide variety of chemical structures. This guide provides an overview of polymeric FR, additive FR, and reactive FR.
General Definitions
Polymer = a very large molecule with a repeating unit called a monomer. Monomers link up to form polymer chains or networks. One polymer chain might have hundreds or thousands of monomers.
Oligomer = short polymer chain that might contain just a few monomers. Exact definitions vary.
Additive vs Reactive
Additive FRs are blended with or coated on the host material. They can be small or large molecules--even very large molecules, i.e. polymers.
Small molecule additive FRs: Can easily migrate out of host material and may transfer to dust, clothing, and skin.
Polymeric (and oligomeric) additive FRs: are less likely to migrate out of the host material due to the larger size of the molecule.
Reactive FRs become chemically bound to the host material during its formation. The finished material thus contains a built-in flame retardant that cannot easily migrate out like the more weakly bound additive FRs. Some product makers refer to materials containing reactive FR as “inherently flame retardant.”
Reactive FRs can be side-chain or backbone type, in which the FR chemical is attached either as an appendage along the polymer chain or as part of its “backbone,” respectively.
Schematics below illustrate the different types.
Simplified FR schematics
Gray = host polymer. Blue = FR.
Examples of products that may contain FRs
- airplane, train and bus seats (reactive or additive)
- children’s car seats (reactive or additive)
- children’s polyester pajamas (reactive)
- cotton or polyester safety garments (reactive or additive)
- electronic devices and appliances (reactive or additive)
- firefighter suits (reactive or additive)
- flight attendant uniforms (reactive or additive)
- foam board insulation (additive--polymeric or small molecule)
- hospital curtains (reactive or additive)
- mattresses (reactive or additive)
- outdoor gear such as tents (reactive or additive)