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Abstract: The thermal degradation of three Polyhedral Oligomeric Silsesquioxane/Polystyrene (POSS/PS) nanocomposites of formula R7 R′1 (SiO1.5)8/PS (where R = Cyclopentyl and R′ = Phenyl), at various (3%, 5% and 10%) POSS concentration, was studied in both inert (flowing nitrogen) and oxidative (static air) atmospheres. Compounds were prepared by the polymerization of styrene in the presence of POSS. Degradation was carried out in a thermobalance, in the scanning mode, at various heating rates, and the obtained thermogravimetric (TG) curves are discussed and interpreted. The temperature at 5% mass loss (T 5%) and the activation energy (E a) of degradation of various nanocomposites were determined and compared with each other and with those of unfilled polystyrene (PS). The T 5% and degradation E a values of nanocomposites were higher than those of neat PS, thus indicating a better heat resistance and lower degradation rate, and then a better overall thermal stability. On the basis of the obtained thermal parameters the nanocomposite at 5% of molecular filler appears the most thermally stable. The results are also compared with literature data on similar PS based nanocomposites. [Copyright &y& Elsevier]

Abstract: The kinetics of the isothermal degradation in static air atmosphere of four well known polymers, polyethylene (PE), polystyrene (PS), polycarbonate (PC) and poly(methyl methacrylate) (PMMA) was studied by both a long-term (more than three years) experiment at relatively low temperature (423 K) and a set of short-term experiments at higher temperatures. The activation energy (E a) values of degradation were determined by both the MacCallum and Wilkinson literature methods, and were compared with those obtained through a new very simple method we set up, based on the direct regression of TG mass loss data. About two years ago we published the results concerning PE and PS because their mass losses during long-term experiments were sufficiently high. The long-term degradation experiments were continued until now and in this second part we report the results concerning PC and PMMA. The degradation E a values calculated from short-term experimental data through the three different methods were in good agreement with each other for both PC and PMMA, thus confirming the general applicability of our simple method for the determination of E a. The experimental data at lower temperature of PC were not in agreement with those at higher temperatures, thus confirming the low reliability of the kinetic parameters (and then of lifetime predictions) at low temperature determined by experiments at higher temperatures. Partially disagreeing results were obtained for PMMA, which were discussed and interpreted. [Copyright &y& Elsevier]