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6965816 
Journal Article 
Synthesis of a Novel Phosphorus-Containing Curing Agent and Its Effects on the Flame Retardancy, and Thermal Stability of Epoxy Resins 
Zhang, H; Gong, X; Li, Zan; Wang, Y 
2020 
1 
Russian Journal of Applied Chemistry
ISSN: 1070-4272
EISSN: 1608-3296 
93 
4 
611-623 
English 
WOS:000534889600017 
A novel curing agent containing phosphorus and carboxyl group compound diphenyl(2,3-dicarboxylpropyl)phosphine oxide (DPDCPPO) was synthesized and used as a curing and flame retarding agent for epoxy resins (EP). Its chemical structure was well characterized by Fourier transform infrared (FTIR) spectroscopy, H-1, C-13 and P-31 NMR. The DPDCPPO was mixed with phthalic anhydride (PA) by different weight ratios into epoxy resins to prepare flame retardant EP thermosets. The flame retardant properties, combusting performances, and thermal degradation behaviors of the EP thermosets were investigated by limiting oxygen index (LOI), vertical burning tests (UL-94), cone calorimeter measurement, and thermogravimetric analysis (TGA) tests. The surface morphologies and chemical compositions of the char residues for EP thermosets were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The water resistant properties were evaluated by placing the samples into distilled water at 70 degrees C for 168 h. The results revealed that the flame retardant EP thermosets passed V-0 flammability rating and the LOI value reached 33.2% when the weight ratio of DPDCPPO and PA was 20 : 80. The cone test results revealed that the combustion parameters of the flame retardant EP thermosets including heat release rate (HRR) and total heat release (THR) significantly decreased compared with pure EP thermosets. The TGA results indicated that the incorporation of DPDCPPO promoted the decomposition of epoxy resins matrix ahead of time compared with that of pure EP, and led to a higher char yield and thermal stability at high temperature. The morphological structures and analysis of the XPS of the char residues revealed that DPDCPPO benefited the formation of a sufficient, compact and homogeneous char layer, with rich flame retardant elements on the epoxy resin material surface during combustion. After completing the water resistance tests, the EP/20 wt % DPDCPPO/80 wt % PA thermosets retained excellent flame retardancy, and the moisture absorption of the EP thermosets decreased with the increase of DPDCPPO content in the thermosets, due to the existence of the P-C bonds and the rigid aromatic hydrophobic structure. 
flame retardant; curing agent; epoxy resin; synthesis