Cyclotriphosphazene hyperbranched P/N/Si prepared flame retardants improve mechanical properties and flame retardancy of epoxy resins

Abstract

In this study, a cyclotriphosphazene hyperbranched P/N/Si prepared flame retardant (HBPPSi) was synthesized, and the effects of different loadings of HBPPSi on the mechanical properties, thermal stability and flame retardancy of epoxy resin were investigated. The mechanical property studies showed that the addition of HBPPSi could effectively improve the strength and toughness of epoxy resin, in which the strength and toughness of 5% HBPPSi/EP composites were improved by 43% and 59%, respectively. Meanwhile, thermogravimetric analysis and combustion performance test analysis indicated that the loading of HBPPSi could significantly improve the carbon formation rate, flame retardancy, and smoke suppression performance of EP composites. 5% HBPPSi/EP composites achieved a V‐1 grade in the UL‐94 test, and the LOI value increased to 28.3%. Compared with the pure EP material, the maximum heat release rate (PHRR) and total smoke release (TSP) of the 5% HBPPSi/EP composite were reduced by 47% and 32%, respectively. In addition, the release of toxic smoke CO was also significantly reduced. More importantly, the mode of action of the effect of HBPPSi on the mechanical properties, flame retardant properties, and smoke suppression properties of EP materials was investigated.

In‐situ formation of macromolecule P/N/Si flame retardant for epoxy resin with low smoke toxicity and excellent flame‐retardancy

“…Also, the addition of EP/7‐KDC to the epoxy web resulted in a lesser FIGRA, an indication that KDC had a lesser fire spread rate. The av‐EHC and FIGRA values of EP/7‐KDC were all well below those of EP (29.95 MJ/kg and 5.88 kW/m 2 ·s, correspondingly), and this could be ascribed to the fact that KDC not only emits phosphorus‐containing radicals with extinguishing function and facilitates the forming of a powerful and stable carbon layer with many elements but also enhances the creation of noncombustible gases for combustion 34 …”

“…The residues of these carbons can serve as heat isolation barriers and inhibit the transport of heat and oxygen, thus exhibiting a certain condensed phase effect. This is advantageous to increasing the flame retardant performance of EP 34 …”

“…This is advantageous to increasing the flame retardant performance of EP. 34 The dynamic mechanical behavior of the cured EP was studied through dynamic mechanical analysis (DMA), and Figure 4 displays the relationship between the tanδ and temps. The glass transition temperature (T g ) was commonly obtained as a peak value from the tanδ curve.…”

“…The av-EHC and FIGRA values of EP/7-KDC were all well below of EP (29.95 MJ/kg and 5.88 kW/m 2 Ás, correspondingly), and this could be ascribed to the fact that KDC not only emits phosphorus-containing radicals with extinguishing function and facilitates the forming of a powerful and stable carbon layer with many elements but also enhances the creation of noncombustible gases for combustion. 34 Figure 6c,d and Table 4 display the results of the released smoke and toxic gases. At the beginning of combustion, the maximal smoke production of EP/5-KDC and EP/7-KDC decreased and was earlier than that of neat EP, while the maximal smoke release rate of EP/3-KDC was slightly raised than that of neat EP, because the gas phase flame retardation of DOPO played a big role in the early stage of combustion, releasing a lot of noncombustible gases, which resulted in the higher smoke release and also the earlier time to arrive at the maximal smoke release rate.…”

Solvent-Free Synthesis of a Hyperbranched Polyphosphoramide Cocuring Agent and Its Application in Fire-Safe, Mechanically Strong, and Tough Epoxy Resin

“…DMP, as a cocuring agent, endowed the modified EP composite with better fire safety performance and well-preserved mechanical properties than pure EP. In addition, Figure d and Table S6 exhibited the THR and TSP decline ratios of EP/8DMP and previous EP with P-containing HBPs (EP/P-containing HBPs). ,,,,− It could be found that EP/8DMP showed the highest THR and TSP decline ratios of 51.9 and 53.4%, respectively. Therefore, the as-designed EP/8DMP possessed the best fire safety performance among all EP/P-containing HBP composites listed in Table S6.…”