Polymer nano-clay composites have generated a great deal of interest due to their improved flammability resistance as observed in reduced heat release rates, and char formation during cone calorimetry. This paper presents industrial test results on the fire performance of various nano-clay filled extruded polystyrene (XPS) foams. It shows the nano-clay dramatically changes the burning characteristics of XPS foams from melting and dripping typical of thermoplastics to char formation, a frequently observed characteristic of thermoset resins. This behavioral change is frequently identified with improved fire resistance during a real fire exposure since the carbonaceous char "protects" the underlying polymer from direct exposure to the flame.However, in this work, it's been discovered that the organic surfactants typically used to modify nano-clay surface for improved processability, can adversely impact other characteristics of the foam, i.e., oxygen index, and spread of flame which are also important to it's performance in fires. In this study, we found that some types of nano-clays, produced commercially, can cause polystyrene-nanocomposite foams to be more flammable to the point where product specifications related to building fire codes are compromised. A method of producing and using modifier-free nano-clay in polystyrene foam processing has been developed to eliminate this adverse effect.
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