Methyl‐DOPO—a new flame retardant for flexible polyurethane foam

Abstract

Flexible polyurethane foams are widely used in many industrial applications, such as upholstered furniture and mattresses, automotive applications, etc. The chemical nature of the polyurethane, the low density, the high air permeability, and the open cell structure cause this material to be highly flammable. In this study, the influencing variables on the burning behavior of flexible polyurethane foams are investigated. Additionally the synthesis, formulation, characterization, and testing of a new phosphorus flame retardant (FR) methyl-DOPO 9,10-dihydro-9oxa-methylphosphaphenthrene-10-oxide in flexible polyurethane foam with low density is performed. The new FR shows an excellent flame retarding behavior by acting mainly in the gas phase. Here the vaporization of methyl-DOPO occurs in the same temperature region as the depolymerization of the urethane and the bisubstituted urea groups during pyrolysis of the foam. Furthermore TG-MS measurements revealed the release of high concentrations of low molecular weight species like HPO, CH 3 PO, or PO 2 in the mentioned temperature region. These species are able to scavenge the H-and OH-radicals in the radical chain reactions of the flame leading to a significant increase of the CO/CO 2 ratio during cone calorimeter experiments.

Effect of Meltable Triazine-DOPO Additive on Rheological, Mechanical, and Flammability Properties of PA6

“…Thus, the value of T 5 was of about 386˝C, the decomposition process registered a single stage with a reduction of 20˝C in the value of T max (430˝C), while the char yield had a value of 0.9 wt %. Similar data, regarding the influence of the additive on thermal stability, were obtained for different polymers and FR based on DOPO derivatives [26][27][28]. The incorporation of various DOPO-based FR additives led to a decrease in thermal stability of the corresponding polymers.…”

“…The flame-retardant efficiency of the new DTE-DOPO-based FR in PA6 might be also facilitated by the release of melamine derivatives through the decomposition of FR additive resulting in a dilution of fuel, as implied by the TGA analysis. It is known that an efficient gas-phase flame-retardant activity is determined by the release in the same temperature range of both FR additive and the decomposition products of the polymer [26]. Therefore, the slight reduction of thermal stability of the triazine-DOPO-based FR compared to neat PA6 may support a gas-phase fire inhibition mechanism.…”

“…In general, an effective flame retardant additive should decompose and release active species in the gas phase at a temperature close to the degradation temperature of the polymer matrix [26]. Thus, to further analyze the flame retardant behavior of the additives, direct insertion probe mass spectrometry measurements were performed to identify the volatile products released during the thermal decomposition of PA6 formulations.…”

“…Melamine also destabilizes PA6 and increases the dripping behavior of the polymer; therefore, the fuel source is removed from the combustion zone [22]. Concerning the phosphorous-containing flame retardants, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and its derivatives could be an attractive FR solution for PA6 due to their relatively higher thermal stability [25][26][27][28]. DOPO and its derivatives are known to predominantly act by a gas-phase mechanism, through the formation of PO¨radicals, which might also be assisted by a condensed-phase activity via the incorporation of specific functionalities at the DOPO moiety [25,29].…”

An Overview of Mode of Action and Analytical Methods for Evaluation of Gas Phase Activities of Flame Retardants

“…It is very difficult to monitor and identify the decomposition pathways of flame-retardants in gas phase. Some methods have recently been developed in order to analyze and quantify the decomposition products of a flame retardant in a polymeric matrix [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. With emerging analytical techniques, it has become possible to get a better understanding of the mode of action of flame-retardants.…”