Bubbles and collapses: Fire phenomena of flame‐retarded flexible polyurethane foams

Abstract

Flexible polyurethane foams (FPUF) are easy to ignite and exhibit rapid flame spread. In this paper, the fire phenomena of two standard foam formulations containing tris(1,3‐dichloro‐2‐propyl) phosphate (FR‐2) and a halogen‐freepoly (ethyl ethylene phosphate) (PNX), respectively, as flame retardants are compared. A multi‐methodological approach is proposed which combines standard fire tests as well as new investigatory approaches. The thermophysical properties of the foams were determined by thermogravimetric analysis (TG), reaction to small flames was studied by means of the limiting oxygen index (LOI) and UL 94 HBF test, and the burning behavior was investigated with the cone calorimeter. Further, temperature development in burning cone calorimeter samples was monitored using thermocouples, and rheological measurements were performed on pyrolyzed material, delivering insight into the dripping behavior of the foams. This paper gives comprehensive insight into the fire phenomena of flame‐retarded FPUFs that are driven by the two‐step decomposition behavior of the foams. LOI and UL 94 HBF tests showed a reduced flammability and reduced tendency to drip for the flame‐retarded foams. TG and cone calorimeter measurements revealed that the two‐step decomposition behavior causes two stages during combustion, namely structural collapse and pool fire. The flame‐retardant mode of action was identified to take place primarily during the foam collapse and be based mainly on flame inhibition. However, some condensed‐phase action was been measured, leading to significantly increased melt viscosity and improved dripping behavior for foams containing PNX.

Composites of Semi-Rigid Polyurethane Foams with Keratin Fibers Derived from Poultry Feathers and Flame Retardant Additives

“…Similarly, the combination of Fyrol with ATH, MTH and ZO in most cases caused an increase in pCO and decrease in pCO 2 . Fyrol PNX, as a fire retardant with a high phosphorus content, works mainly in the gas phase but a small amount also remains in the condensed phase [ 61 ]. Therefore, for fire retardants acted in the condensed phase and exhibiting the ability to form char (GE, APP), a reduction in both parameters after Fyrol addition can be observed.…”

Moisture Resistance, Thermal Stability and Fire Behavior of Unsaturated Polyester Resin Modified with L-histidinium Dihydrogen Phosphate-Phosphoric Acid

“…Total heat release (THR) represents a measurement for the fire load of polymeric material [30]. In the case of investigated samples, a reduction from 159 MJ/m 2 for the unmodified resin to 95 MJ/m 2 for the samples containing the highest amount of FRs was noted.…”

“…In the case of investigated samples, a reduction from 159 MJ/m 2 for the unmodified resin to 95 MJ/m 2 for the samples containing the highest amount of FRs was noted. A decrease in THR indicates incomplete combustion due to char formation or lowered combustion efficiency [30]. Since all of the UP/FRs yielded a significant amount of residue, a THR reduction is related mainly to the char formation.…”

Development and Characterization of “Green Open-Cell Polyurethane Foams” with Reduced Flammability

“…In combustion, high energy OH and H radicals are created and scavenged by halogen radicals. Phosphorus-based compounds act in the condensed phase by changing the pyrolytic path of the polymers, also reducing the gaseous combustibles [9].…”

“…The use of halogen-containing flame retardants is highly restricted due to the release of large amounts of smoke and toxic gases during combustion [9,10]. However, flame retardants containing halogen are highly effective and still play a major role in reducing the flammability of rigid PUR foams.…”