Different kinds of additive and reactive flame retardants containing phosphorus are increasingly successful as halogen-free alternatives for various polymeric materials and applications. Phosphorus can act in the condensed phase by enhancing charring, yielding intumescence, or through inorganic glass formation; and in the gas phase through flame inhibition. Occurrence and efficiency depend, not only on the flame retardant itself, but also on its interaction with pyrolysing polymeric material and additives. Flame retardancy is sensitive to modification of the flame retardant, the use of synergists/adjuvants, and changes to the polymeric material. A detailed understanding facilitates the launch of tailored and targeted development.

https://www.mdpi.com/1996-1944/3/10/4710/pdf

Phosphorus-based Flame Retardancy Mechanisms-Old Hat or a Starting Point for Future Development?

Implementation of the NCN pathway of prompt-NO formation in the detailed reaction mechanism

Advances and challenges in laminar flame experiments and implications for combustion chemistry

The ubiquity of polymeric materials in daily life comes with an increased fire risk, and sustained research into efficient flame retardants is key to ensuring the safety of the populace and material goods from accidental fires. Phosphorus, a versatile and effective element for use in flame retardants, has the potential to supersede the halogenated variants that are still widely used today: current formulations employ a variety of modes of action and methods of implementation, as additives or as reactants, to solve the task of developing flame-retarding polymeric materials. Phosphorus-based flame retardants can act in both the gas and condensed phase during a fire. This Review investigates how current phosphorus chemistry helps in reducing the flammability of polymers, and addresses the future of sustainable, efficient, and safe phosphorus-based flame-retardants from renewable sources.

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Molecular Firefighting—How Modern Phosphorus Chemistry Can Help Solve the Challenge of Flame Retardancy

Combustion is directly related to energy conversion and the environment. Gas-phase chemical reactions such as thermal decomposition, oxidation and recombination play a critical role in combustion processes. Here we review six applications of synchrotron vacuum-ultraviolet (VUV) photoionization mass spectrometry (PIMS) in fundamental studies of combustion chemistry. These applications range from the use of flow reactors to probe elementary reaction kinetics, studies of pyrolysis in plug-flow reactors and oxidation in jet-stirred reactors, studies of spatial evolution of species concentrations in premixed and non-premixed flames, product distributions in pyrolysis of biomass, and analysis of polycyclic aromatic hydrocarbon (PAH) formation. These experiments provide valuable data for the development and validation of detailed chemical kinetic models. Furthermore, some additional potential applications are proposed.

Combustion chemistry probed by synchrotron VUV photoionization mass spectrometry

Flame Inhibition by Phosphorus-Containing Compounds over a Range of Equivalence Ratios

Fire suppression by low-volatile chemically active fire suppressants using aerosol technology

Studies of degradation enhancement of polystyrene by flame retardant additives

The mechanism of flame inhibition by phosphorus-containing species (PCSs) is known to involve their effect on the recombination of atoms and free radicals in flames. Chemical inhibition of laminar atmospheric methane/oxygen flames by trimethylphosphate over a range of equivalence ratio has been studied experimentally, using the heat flux method for measurement of burning velocity and molecular beam mass spectrometry for measurement of concentration profiles of both stable and labile species, and with numerical modeling using detailed chemical kinetic reaction mechanisms. Concentrations of H and OH in flames with and without the inhibitor were obtained by measurements and modeling. The addition of the inhibitor reduces the maximum concentrations of H and OH (in the reaction zone) in the lean and rich flame. This reduction is much larger in the rich flame than in the lean one. The concentration profiles of PCSs—PO, PO 2 , HOPO, HOPO 2 , and H 3 PO 4 were measured and simulated for rich and lean flames stabilized on a flat burner. According to flame speed measurements for inhibited CH 4 /air flames over a range of ϕ , the inhibition effectiveness E i increases in the range of ϕ  = 0.8–1.2 and then decreases with a further increase of ϕ . The increase in E i in the range ϕ  = 0.7–1.2 is attributed to a change of PCSs composition. The reduction in E i for ϕ  > 1.2 can be explained by a decrease in the concentration of active PCSs due to an increase in the concentration of inactive species, such as CH 3 PO 2 and other products of incomplete combustion of TMP. The inhibition effectiveness E i versus ϕ correlates with change of H and OH concentration at addition of TMP in flame. Validation of the previously developed model for inhibition by PCSs has shown that in spite of some discrepancies it adequately describes many experimental results.

Inhibition of atmospheric lean and rich CH4/O2/Ar flames by phosphorus-containing compound

Chemical inhibition of laminar propane flames by organophosphorus compounds has been studied experimentally and computationally using a detailed chemical kinetic reaction mechanism. Both fuel-lean and fuel-rich propane flames were studied to examine the role of equivalence ratio in flame inhibition. The experiments examined a wide variety of organophosphorus compounds. We report on experimental species flame profiles for tri-methyl phosphate (TMP) and compare them with modeled species flame profile results of TMP and di-methyl methyl phosphonate (DMMP). Both experiments and kinetic modeling indicate that inhibition efficiency is effectively the same for all of the organophosphorus compounds examined, independent of the molecular structure of the initial inhibitor molecule. Chemical inhibition is due to reactions involving small P-bearing species HOPO2 and HOPO produced by the organophosphorus compounds (OPCs). Ratios of HOPO2 and HOPO concentrations differ between lean and rich flames, with HOPO2 dominant in lean flames while HOPO dominates in rich flames. Resulting HOPO2 and HOPO species profiles do not significantly depend on the initial source of the HOPO2 and HOPO, and thus are relatively insensitive to the initial OPC inhibitor. A more generalized form of the Twarowski mechanism is developed to account for the results observed, and new theoretical values are determined for heats of formation of the important P-containing species, using the BAC-G2 method.

/pdf/flame-inhibition-by-phosphorus-containing-compounds-in-lean-3qmhci2c49.pdf

Andrey G. Shmakov

Papers

Flame Inhibition by Phosphorus-Containing Compounds over a Range of Equivalence Ratios

Fire suppression by low-volatile chemically active fire suppressants using aerosol technology

Studies of degradation enhancement of polystyrene by flame retardant additives

Inhibition of atmospheric lean and rich CH4/O2/Ar flames by phosphorus-containing compound

Flame inhibition by phosphorus-containing compounds in lean and rich propane flames