Synthesis of a silicon-containing flame retardant and its synergistic effect with potassium-4-(phenylsulfonyl)benzenesulfonate (KSS) in polycarbonate (PC)

A novel flame retardant (DAPSiO), containing silicon and nitrogen, was synthesized by using dichlorodiphenylsilane, γ-chloropropyl methyl dimethoxysilane and 1,2-ethanediamine. DAPSiO was used together with potassium-4-(phenylsulfonyl)benzenesulfonate (KSS) to prepare a flame-retardant system for polycarbonate (PC). The structure of DAPSiO was characterized by Fourier transform infrared spectroscopy (FTIR), and ¹H-NMR tests. Flammability and thermal behaviors of PC/KSS/DAPSiO systems were estimated by limited oxygen index (LOI), vertical burning test (UL-94) and thermogravimetric analysis (TGA) tests. The results showed that the flame retardancy and thermal stability of PC/KSS system were improved with the addition of DAPSiO. When 1 wt% DAPSiO and 0.5 wt% KSS were incorporated, the LOI value of PC was found to be 44, and class V-0 of UL-94 test was passed. The scanning electron microscopy (SEM) and FTIR indicated that PC/KSS/DAPSiO system held a more cohesive and denser char structure when compared with pure PC and PC/KSS system.