Flame-retardant and UV-resistant polycarbonate composites with well-preserved mechanical properties enabled by silsesquioxane/sulfonate-functionalized nano carbon black

A sulfonate/silsesquioxane-functionalized nano carbon black (CBSP) was synthesized by grafting polyhedral oligomeric silsesquioxane (POSS) and sulfonate groups onto carbon black (CB) surface, aiming to meet practical requirements of outdoor-used polycarbonate (PC). Upon adding 1 wt% CBSP, PC/1.0CBSP composite displayed a limiting oxygen index (LOI) of 31.3 % with a vertical burning (UL-94) V-0 classification. Its peak heat release rate (PHRR) and total smoke release (TSR) were decreased by 39 % and 21 % relative to PC. The superior fire retardancy can be attributed to the triple reinforced effect from CB, sulfonates and POSS by promoting the formation of denser and more resilient char layers. CBSP well preserved mechanical performances of PC due to its reinforced interfacial compatibility and improved UV shielding through the absorption of UV photons by CB. This work provides a feasible strategy for fabricating fire-retardant PC composites with superior mechanical robustness and UV-resistant properties, expecting to increase applicability and lifespan. • A silsesquioxane/sulfonate-functionalized nano carbon black (CBSP) was synthesized. • CBSP endowed PC composites with superior UV-shielding and fire-retardant properties. • CBSP effectively maintained the mechanical properties of PC composites.