Iron Compound

The polymer will produce a lot of smoke during the combustion process, and the smoke produced by the combustion of some polymers is toxic. Alfa Chemistry provides iron compounds for use as smoke suppressants, which is one of the more realistic ways to solve the problem of smoke suppression of polymer materials.

Typical Product

The main varieties are ferrocene, ferrocene 1,1-dicarboxylic acid, ferric oxide, potassium ferric oxalate, ferrous oxalate, etc., which are often used in combination with halides.

Smoke Suppression Mechanism

Ferrocene

Ferrocene can suppress fumes in the gas and condensed phases. The mechanism of smoke suppression is related to the structure of the polymer, especially the smoke suppression is related to whether the polymer contains halogen. For example, for ABS, ferrocene mainly suppresses fumes in the gas phase; in contrast, for chlorine-containing styrene-acrylonitrile-chloroprene terpolymers, it can suppress fumes in the condensed phase.

The effect of ferrocene and two other organoiron compounds in halogen-containing and halogen-free ABS polymers is shown in the table below.

Smoke suppression effect of organic iron additives [1]

Inorganic iron compounds

FeCl₃ is a catalyst for Friedel-Crafts-type reactions, which can couple with alkyl chlorides and aromatics remaining in the condensed phase to reduce smoke generation and increase coke yield. The activated carbon residue formed can also eliminate H· and ·OH radicals formed during the continuous combustion reaction. FeCl₃ is also used in a range of polymers, including polyesters, polyurethanes, and PS, to reduce material flammability and increase char yield.

Coupling Reaction of FeCl₃ with Alkyl Chloride [1]

Research Information

Fe₂O₃ as smoke suppressant for silicone rubber (SR)

Xilei Chen et al. proposed a method for the direct production of intumescent flame retardants and Fe₂O₃ filled silicones through a reaction process. The results show that Fe₂O₃ can improve the smoke suppression efficiency and thermal degradation temperature. In this work, Fe₂O₃ can promote the early cross-linking of polymers during decomposition, thereby increasing the formation of char. The integrity of the silica fume layer controls the efficiency of the diffusion barrier that limits the diffusion of fuel into the combustion zone and oxygen into the unburned fuel. [2]

Total smoke release curve (left) and TG curve (right) of SR composites [2]

References

1. Jianjun Li, et al. (2019). "7. The mechanism of smoke suppression". Theory of Flame Retardation of Polymeric Materials, pp. 195-210.
2. Xilei Chen, et al. (2015). "Influence of Fe₂O₃ on smoke suppression and thermal degradation properties in intumescent flame-retardant silicone rubber," Journal of Thermal Analysis and Calorimetry 123, 439–448.