A method to quantitatively assess the modes-of-action of flame-retardants

The assessment of the modes of action of flame retardants (FRs) and their quantification is a challenging issue. This study highlights that the condensed phase efficiency theta can be assessed by combining different flammability tests (pyrolysis-combustion flow calorimeter PCFC, Limiting Oxygen Index LOI, cone calorimeter). Relations were proposed to calculate LOI and pHRR in cone calorimeter from several parameters including theta. A satisfying agreement between experimental values and calculated ones were found for a set of several dozens of FR-free polymers assuming that theta = 1 (i.e. no action in condensed phase).Then, theta was evaluated for EVA/PE blends containing Aluminium TriHydroxyde (ATH) and/or Magnesium DiHydroxyde (MDH) and for ABS containing Ammonium PolyPhosphate (APP) and/or DecaBromoDiPhenylOxide (DBDPO) assuming that LOI and pHRR of flame-retardant compositions follow the same relationships as those of unfilled polymers. The evolution of theta (as well as chi, i.e. the combustion efficiency) highlights the modes of action of FRs and can contribute to the discussion about possible synergy or antagonism between FRs. Especially, an apparent synergism between APP/DBDPO is observed in cone calorimeter from a performance point of view. Nevertheless, the calculation of chi and theta challenges this conclusion. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study explores the assessment of the modes of action of flame retardants and their quantification. By combining different flammability tests, relations were proposed to calculate key parameters and evaluate flame retardant efficiency. The results suggest potential synergies or antagonisms between different flame retardants, challenging some previously held conclusions.