The impact of halogen free phosphorus, inorganic and nitrogen flame retardants on the toxicity and density of smoke from 10 common polymers

The toxicity and density of smoke from 10 commonly used commercial polymer types was studied using the European railway standard EN 45545-2. This test method was chosen because it reflects the current state-of-the-art in assessing the hazards of smoke in bench-scale test scenarios (not because of a specific link to railway applications). The study involves 72 commercially relevant formulations provided by 12 industrial companies. Polymers studied include PE, PP, PC, PA6, PA66, u-PVC, p-PVC, PU, PIR, and epoxy resins. Reference samples as well as samples containing halogenated and Phosphorus, Inorganic or Nitrogen based Flame Retardants (PIN FRs) were tested according to the French tubular furnace method (NF X 70-100) to evaluate their smoke toxicity at 600°C and according to ISO 5659-2 at 50 kW m⁻² with Annex C of EN 45545-2 to evaluate their smoke density as well as toxicity at 4 and 8 min. This study highlights that the measured toxicity and calculated Conventional Indexes of Toxicity (CIT_NLP, CIT_{4 min}, CIT_{8 min}), as well as maximum smoke density (Ds_MAX) show generally no significant increase in the presence of PIN FRs in comparison to the neat polymers. The use of intumescent FRs or hydroxide based FRs generally allows considerable smoke reduction with little impact on smoke toxicity. Bromine based-FRs were found to be detrimental to both hazards in most matrices studied here.