Simultaneously improving the thermal stability, mechanical properties and flame retardancy of epoxy resin by a phosphorus/nitrogen/sulfur-containing reactive flame retardant

In order to broaden the application field of epoxy resin (EP), it is significant to heighten the fire safety without deteriorating the comprehensive performance. A high-efficiency reactive phosphorus/nitrogen/sulfur flame retardant (SAD) derived from 2-Thenaldehyde, 9,10-dihydro-9-oxa-10-phosphaphenanthrene10-oxide (DOPO) and 3-amino-1H-1,2,4-triazole (ATA) was designed, acting as the co-curing agent for DGEBA/DDM system. Fourier transform infrared (FTIR) spectra and nuclear magnetic resonance (NMR) were used to confirmed the chemical structure of SAD. Besides, the glass transition temperature (T g ) was gradually increased from 150.4 ℃ for EP to 156.9 ℃ for EP-7.5 and the maximum thermal decomposition rate was decreased after the introduction of SAD. The samples exhibited excellent thermal stability. Meanwhile, SAD promoted cross-linking reaction during curing process. Compared with EP, EP-5 (phosphorus content was 0.39 wt%) reached V-0 rating in vertical burning (UL-94) test and acquired a remarkable enhancement from 25.7% to 34.7% in the limited oxygen index (LOI) value, an obvious blowing out effect occurred when the samples burned. Furthermore, from the data of cone calorimeter (CC) tests, there was a reduction of 19.1% and 16.6% for EP-7.5′s the total heat release (THR) and the peak heat release rate (PHRR) compared with EP. And the analysis of char residue and incomplete combustion products indicated that SAD displayed bi-phase flame-retardant effect. It is very meaningful that the mechanical properties of materials were slightly enhanced after the introduction of SAD. The results showed that SAD has a broad prospect in practical application. • SAD significantly enhances the fire safety of EP with only 0.39 wt% of phosphorus. • The glass transition temperature gradually increases with the introduction of SAD. • SAD slightly improves the mechanical properties of epoxy resin.