Two phosphorous-containing flame retardant form a novel intumescent flame-retardant system with polycarbonate

Hexakis(4-nitrophenoxy) cyclotriphosphazene (HNTP) and oligomeric bisphenol A bis(diphenyl phosphate) (BDP), phosphorous-containing flame retardant, were mixed into polycarbonate (PC) together as intumescent flame retardancy (IFR) system. The flame retardancy and thermal decomposition behavior of composites were studied with the limiting oxygen index(LOI), UL-94 vertical burning test, microscale combustion calorimeter(MCC) and thermogravimetric analysis(TGA). The results showed the LOI of IFR system increased by 1.68 times compared with pure PC. The addition of HNTP and BDP accelerated the first decomposition peak but weaken the second decomposition peak to improve the flame retardancy of PC. Furthermore, TGA coupled with fourier transform infrared(TGA/FTIR) was used to research the gaseous products. Scanning electron microscopy (SEM) analyses and FTIR spectroscopy were used to study the structure of residual char. The results showed that HNTP and BDP formed continuous bubbles on the surface of PC during burning and exhibited synergistic effects on thermal stability of PC.