Synergistic effects between silicon-containing flame retardant and DOPO on flame retardancy of epoxy resins

A novel flame retardant, containing silicon and nitrogen (PSiN), was synthesized, and it was used together with 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to prepare a flame-retardant system for epoxy resins (EP). Flammability and thermal behaviors of EP systems were estimated by limited oxygen index (LOI), vertical burning test (UL-94), microscale combustion calorimetry test and thermogravimetric analysis. The results showed that synergistic effects on the flame retardancy of EP composites existed between the DOPO and PSiN. When 3 % PSiN and 7 % DOPO were incorporated, the LOI value of EP was found to be 34 %, and the UL-94 test found to be class V-0. The microstructures observed by scanning electron microscopy and FTIR indicated that the surface of the char for EP/DOPO/PSiN system holds a more cohesive and denser char structure when compared to the pure EP and EP/DOPO systems.