Nanocomposite structure of polymer intercalated montmorillonites was formed in ethylene vinyl acetate copolymer/magnesium hydroxide flame retarded polymer system. Generally the presence of magnesium hydroxide flame retardant particles disturbs the structural analysis of such systems. Raman microscopic method was successfully applied for evaluating the distribution of components in presence of high concentration of flame retardant additives. The interphase formed around the nanoparticles influences the structure and the temperature dependency of the rheological characteristics, which was evaluated by thermal Scanning Rheometer. Surprisingly the combination of unmodified and modified rnontmorillonites provided the most advantageous rheology profile for improving the fire retardancy (reducing dripping and increasing the char-stability). (c) 2005 Elsevier B.V. All rights reserved.