ABSTRACT
Polyolen nanocomposites are largely synthesized by using melt intercalation method of nanocomposite synthesis where the polymer melt at high temperature is compounded with the organically modied inorganic ller under the action of shear. The compounding temperatures as well as mixing time are two parameters that generally in©uence the mixing efciency. To achieve optimal mixing, high compounding temperature as well as long compounding protocols may be required, which, however, can lead to the thermal degradation of the organic modication of the ller. As an example, polypropylene is a material of choice for a wide variety of applications. It is also conventionally incorporated with inorganic llers to further enhance its properties [1-3] and subsequently its applications. However, the high melt temperatures required along with the high mechanical shear used in the melt intercalation and processing operations poses a concern for the thermal stability of the ammonium modication. Temperatures more than 200°C are generally employed for such processes, which are almost equal or higher than the initial onset of degradation of the alkyl ammonium groups of the surface modications. It has been observed that the conventionally used alkyl ammonium cations have an onset of
CONTENTS
10.1 Introduction...................................................................................................................... 265 10.2 Imidazolium Salt and Thermal Stability ..................................................................... 266 10.3 Nanocomposites Morphology ....................................................................................... 268 10.4 Oxygen Barrier Properties ............................................................................................. 269 10.5 Tensile Properties ............................................................................................................ 270 10.6 Calorimetric and Thermal Properties .......................................................................... 271 10.7 Mechanical Modeling of Nanocomposites .................................................................. 272 10.8 Role of Compatibilizer .................................................................................................... 275 10.9 Conclusions ...................................................................................................................... 281 Acknowledgments ...................................................................................................................... 282 References ..................................................................................................................................... 282
degradation as low as 180°C by TGA studies [4]. The thermal degradation was observed to follow the Hoffmann degradation path involving the early breakage of weaker C-N bond in the ammonium modication. As the rupture of the C-N bonds would knock off the whole alkyl chains bound to the ler surface, thus, breakage of even a small number of such bonds may be enough to signicantly change the thermodynamics of the system. This changes the interfacial interactions between the organic and inorganic phases of the composite because of the changes in the structure of the surfactant. The production of low-molecular-weight species during such degradation reactions can consequently affect the physical and mechanical properties of the polymer in the composite like viscosity, molecular weight, glass transition temperature and ©ammability, etc. [5-10]. Furthermore, the fundamental theoretical investigations on the thermodynamics and kinetics of polymer melt intercalation and hybrid formation have never undertaken the considerations of the thermal degradation of the organic ammonium ions at higher temperatures in account and have assumed the perfect stability of the organic modication even at high temperatures [11,12].
