A synthetic Li-fluorohectorite with typical aspect ratios around 1000 shows superior thermal, fire and mechanical properties. A comparison between Li-fluorohectorite and MMT underlines the crucial role of the aspect ratio in particular for flame retardancy. Furthermore, solution blending yields a better dispersion of the filler, as compared to melt compounding, which directly transforms into superior properties. Quite surprisingly, the homogenous clay surface layer built during burning of the PS fluorohectorite nanocomposite has such a high gas barrier that an intumescent-like behavior of the char is detectable. (C) 2011 Elsevier Ltd. All rights reserved.