Effects of Additives and Structure of Surfactants on Fire Retardancy of Polymer Nanocomposites

The focus of this research has been on fire retardancy of polymers, and this was achieved via nanocomposites formation, and by the combined effect of nanocomposites and conventional fire retardants like phosphates. Organic/inorganic fillers such as alumina trihydrate, zinc borate and layered hydroxy salts were also combined and their effects on flammability of vinyl ester resins evaluated. Chapter 1 gives a brief introduction on the methods currently employed to achieve flameretardancy of polymers and the test methods used to evaluate flammability and thermal stability of polymers and polymer nanocomposites. Chapter 2 addresses the possibility of synergy between nanocomposite formation and conventional fire retardants. The polymer nanocomposites were evaluated by X-ray diffraction, XRD, transmission electron microscopy, TEM, thermogravimetric analysis, TGA and cone calorimetry. Two approaches were used to introduce the additive into the polymer. In the first approach, clay and polymer POSS composites were prepared in the presence of phosphorus containing additives. The phosphorus additives used were screened using a high throughput technique developed in this laboratory. A reduction in flammability was observed for the polymer nanocomposites prepared in the presence of phosphorus additives. Some of the parameters measured at certain loadings showed more than an additive effect. In the second approach, a halogen-containing additive was chemically attached to the clay using dibromostyrene as part of the oligomeric ammonium salt used to modify clay. In this case, a significant reduction in both peak heat release rate and total heat released as observed at very low clay loa~ing and thus low bromine content, showing the additive and clay working together more effectively than when used independently. Generally very high bromine content is required to achieve flarne-retardancy and clay alone never shows a reduction in the total heat released, THR. In Chapters 3 polymer clay nanocomposites were prepared using different organically modified clays. The structure of the ammonium salt was changed by attaching different groups, like naphthenate and carbazole and varying the number of alkyl long chains attached to the clay. In this study it was shown that the structure of the ammonium cation affects the nanodisperdsion, thermal stability and flammability of polymer clay nanocomposites. In the last part of chapter 3, activation energy, Ea, for polystyrene and polystyrene nanocomposites was measured using the Flynn-Wall-Ozawa method and the nanocomposites were found to have higher activation energy compared to the virgin polymer. Chapter 4 gives a brief description of the possible future work