KCl nanoparticles-loaded octaphenylsilsesquioxane as an efficient flame retardant for polycarbonate

In this work, potassium chloride loaded octaphenylsilsesquioxane (OPS-K) was synthesized by pre-dispersing the solution of potassium chloride (KCl) in solvent. The micro-nano structure of OPS-K not only achieves the good dispersion of KCl nanoparticles in OPS, but also helps improve its thermal stability. Furthermore, the flame retardancy of OPS and OPS-K on polycarbonate (PC) was studied by oxygen index (LOI), vertical combustion (UL-94) and cone calorimeter (CONE) tests. Compared with OPS, OPS-K confers better flame retardancy upon PC matrix. With the loading amount of 4 wt%, OPS-K is able to increase the LOI value from 28.1% to 34.5% and can reach the V-0 rating easily. Furthermore, the peak heat release rate (PHRR) was decreased by 35%. Studies on the fire properties of flame retardant PC demonstrate that OPS-K contributes to the formation of a compact and uniform char during combustion. The formation of a continuous and homogeneous surface shielding over the PC matrix protects the underlying polymer and inhibits the transfer of heat and mass, thereby improving the flame retardant performance of PC.