Enhancing the flame retardancy of polycarbonate through the synergistic effect of 1,3-Benzenedisulfonate acid dipotassium salt and phenyl polysiloxanes

As the application of polycarbonate (PC) in various fields continues to expand, the requirements for its flame retardancy are becoming increasingly stringent. To enhance the flame retardancy of PC, employing multi-element synergistic effects and developing novel flame retardants are considered as vital strategies. This work introduces a blend of 1,3-Benzenedisulfonic acid dipotassium salt (KSP) and three types of phenyl polysiloxanes, namely Octaphenylcyclotetrasiloxane (P4), Octaphenylsilsesquioxane (OPS), and ladder-like Polyphenylsesquioxane (L-PPSQ), into PC to create composites. The thermal stability and combustion properties of these composites were characterized using thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94 vertical burning, and cone calorimetry tests. Composites with phenyl polysiloxanes achieved a UL-94 V-0 flame retardant rating for 1.6 mm thickness sample and reduced the peak heat release rate by 30%–45%. PC composites with 3% OPS and 0.03% KSP achieved optimal performance, howing a LOI of 34.5%, a 45.4% reduction in peak heat release, and a 40.5% reduction in total smoke release. The flame-retardant mechanism was analyzed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS).