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Flame Retardants
Published in Asim Kumar Roy Choudhury, Flame Retardants for Textile Materials, 2020
Melamine is mainly used in polyurethane foams, whereas melamine cyanurate is used in polyamides or in polypropylene intumescent formulations in conjunction with ammonium polyphosphate. The phosphate, polyphosphates,and pyrophosphates of melamine contain both nitrogen and phosphorus, and are used in polyamides. In some specific formulations, triazines, isocyanurates, urea, guanidine, and cyanuric acid derivatives are used as reactive compounds. (Pinfa, 2018).
Flame Retarded Polymer Foams for Construction Insulating Materials
Published in Yuan Hu, Xin Wang, Flame Retardant Polymeric Materials, 2019
Zhengzhou Wang, Xiaoyan Li, Lei Liu
Melamine (MEL) and its derivatives are widely used as flame retardant additives in polymers, including RPU foams. MEL and its derivatives usually exert their flame retardant action in both the gas phase and the condensed phase (Xu et al. 2015b). The effect of melamine polyphosphate (MPP) and melamine cyanurate (MC) (Figure 12.4) on the mechanical and flame retardant properties of RPU foams were studied, and it was found that the flame retardancy of MPP-filled RPU foams was better than that of the MC-filled foams (Thirumal et al. 2010). The flame retardancy of MC-filled RPU foams is mainly due to its endothermic decomposition that leads to the evolution of non-combustible gases (e.g., ammonia, N2) which dilute concentration of combustible gases in the gas phase. Despite the gas phase mechanism, MPP decomposes to form polyphosphoric acid, which promotes the formation of a carbonaceous char layer on the sample surface. In addition, the density and mechanical properties of MPP-filled RPU foams decrease, whereas the properties of MC-filled RPU foams improve at higher loadings which is possibly caused by different cellular structures of RPU foams. The addition of both MPP and MC has less effect on the thermal conductivity of RPU foams, especially in the range of loadings studied. Wang et al. (2017) reported synthesis of a phosphorous-nitrogen intumescent flame-retardant, 2,2-diethyl-1,3-propanediol phosphoryl melamine (DPPM), and found that the RPU foam with 25 phr DPPM achieved a UL-94 V-0 rating with a LOI of 29.5%. A novel nitrogen-phosphorus flame retardant, melamine amino trimethylene phosphate (MATMP, Figure 12.4) was synthesized, and the RPU foams containing 15 wt% MATMP passed the UL-94 V-0 test with a LOI of 25.5% and a 34% reduction of the peak HRR compared with untreated RPU foam. Furthermore, the compressive strength of the RPU foams filled with MATMP first increases and then slightly decreases with an increase in the MATMP content compared with those of the untreated foam (Liu et al. 2017a).
Effect of urinary pH upon the renal toxicity of melamine and cyanuric acid
Published in Journal of Environmental Science and Health, Part C, 2021
Linda S. Von Tungeln, Cristina C. Jacob, Greg R. Olson, Gonçalo Gamboa da Costa, Frederick A. Beland
Treating rats with a combination of melamine and cyanuric acid resulted in dose-dependent moribundity. This was associated with the formation of melamine cyanurate crystals and renal toxicity, which is similar to what has been observed in earlier studies.6,8,9,13–15 At the scheduled terminal sacrifice, histopathological analysis indicated that only one of 14 rats administered 40 mg melamine and 40 mg cyanuric acid per kg body weight had crystals, whereas seven of 11 rats treated with 100 mg melamine and 100 mg cyanuric acid per kg body weight had evidence of crystals (Table 2). The presence of crystals was associated with renal toxicity. In rats given 40 mg melamine and 40 mg cyanuric acid per kg body weight, only one rat presented evidence of renal lesions (renal tubule dilatation). In contrast, renal lesions were detected in seven of the terminal sacrifice rats administered 100 mg melamine and 100 mg cyanuric acid per kg body weight (Table 2). The dose-dependent increase in renal toxicity was also accompanied by increases in serum markers of kidney toxicity. Specifically, the maximum BUN level increased from 14 ± 4 mg/dL in the control rats to 27 ± 8 mg/dL in the 40 mg melamine and 40 mg cyanuric acid per kg body weight groups to 110 ± 23 mg/dL in the 100 mg melamine and 100 mg cyanuric acid per kg body weight groups.