Influence of structural effects of halogen and phosphorus polyol mixtures on flame retardancy of flexible polyurethane foams

Abstract

synopsisThe role of mixtures of reactive bromine and phosphorus flameretardant polyol intermediates as well as the individual bromine and phosphorus reagents in suppressing combustion of flexible polyurethane foams was investigated by means of the oxygen index flame test and charring techniques. Bromine alone appears to contribute to flame retardancy in the solid as well as the vapor phase. A substantid portion of the bromine from both aliphatic and aromatic bromide flame retardants w q accounted for in the char, and this is also true when phosphorus is preseqt. Ionic bromine appears to be the most effective elemental form. Like phosphorus, bromine alone in foams is also observed to increase the yield of char. Aliphatic bromide in mixture with phosphonate or phosphate gave enhanced flame retardancy, whereas, mixtures with phosphite are not beneficial. Maximum flame retardancy and char yields correlate well for bromine mixed with phosphate and phosphonate, whereas' the relationship does not hold with phosphites. Charring experiments at 500°C with foams containing both phosphorus and bromine generdy afforded a constant P/Br ratio, suggesting a specific chemical interaction for flame retardancy. Phosphate flame-retardant efficiency was sensitive to concentration of phosphorus in the foams. On the other hand, phosphonate and phosphite exhibited a constant level of fire resistance at phosphorus levels greater than 0.3%.

A Comparative Study of the Effect of Phosphorus and Chlorine in Urethane and Isocyanurate-Urethane Foams

“…Polyols based on phosphates were found to be more effective as flame retardants in urethane and isocyanurate-urethane foams than polyols based on phosphonates. Similar results were reported for flexible urethane foams by Papa and Proops [76] and for cotton by Arney [77]. At phate-based polyols decompose faster than phosphonate into catalytically active species, which catalyze char formation.…”

“…It was found that results of other authors obtained for flexible foams [76] and cotton [77] can be linearized by the same method ( Figure 3) and thus the effect of the phosphorus on the oxygen index values can generally be correlated by the following equation:…”

Preparation and characterization of novel flame retardant (aliphatic phosphate)cyclotriphosphazene‐containing polyurethanes

“…Generally, polyurethanes do not exhibit sufficient flame retardancy and are easily burned. Therefore, emphasis on the development of technologies to promote flame retardancy and create flame‐retardant materials has recently increased 2–4. Among these materials, organophosphorus compounds, which generate negligible amounts of toxic gas and smoke, have demonstrated high efficiency as flame retardants for polyurethane.…”

Possible phosphorus/halogen synergism in flame retardant textile backcoatings

“…6,7 Some authors consider two modes of interaction, the first being a physical interaction observed in the combination of ammonium polyphosphate and hexabromocyclododecane within polyacrylonitrile. 8 An alternative physical interaction is suggested to occur in flexible polyurethane formed from bromine and phosphorus-containing polyols, 9 where it has been observed that the bromine system does not act in the gas phase as a radical trap (as would typically be expected) but as a blowing agent thus producing a foamed char. A second postulated mode suggests some form of chemical interaction of phosphorus and bromine when present either in the same or separate molecules.…”