Flame retardancy, thermal and mechanical properties of sulfonate-containing polyhedral oligomeric silsesquioxane (S-POSS)/polycarbonate composites

In this work, polycarbonate (PC) composites were prepared by incorporation of sulfonate-containing polyhedral oligomeric silsesquioxane (S-POSS) via direct melt blending. The S-POSS was synthesized using sulfonation of octaphenylsilsesquioxane by chlorosulfonic acid and potassium carbonate, and characterized by FTIR and ¹H NMR spectroscopy. The thermal and mechanical properties of composites with different S-POSS loadings were investigated by DSC, TGA and tensile tests. Micron-sized aggregates were observed in the PC composites by SEM. The present of S-POSS led to decrease the glass-transition and the initial thermal degradation temperatures of composites. The flame retardancy performance of composites was studied by LOI and UL-94 burning test. The composite had an LOI value of 33.3 and a UL-94 rating V-0 (3.2 and 1.6 mm) with the content of S-POSS was 0.25 wt.%.