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Thermal and thermo-oxidative degradation of nanocomposites based on polyamide 11 (PA11) and organo-modified clay (Cloisite ® 30B) are studied in the melt state (T = 215 °C) via time-resolved mechanical spectroscopy (TRMS). The goal is assessing the potentiality of rheological analysis for studying polymer degradation in complex systems such as polymer nanocomposites, whose rheological response stems from the combination of the contributions of polymer and nanoparticles. We prove that a thorough analysis grounded on TRMS allows to isolate the effect of degradation of the polymer matrix, whose progress can be hence profitably monitored. Essentially the same degradation mechanisms as in neat PA11 are identified for the nanocomposite, but the kinetics of the thermo-oxidation processes are much faster in the presence of organo-clay. In particular, rheology promptly identifies cross-linking reactions since the early stage of the treatment in air. Matrix-assisted laser desorption/ionization and oxidative induction time measurements corroborate the conclusions drawn on the basis of rheological analyses, shedding light on the chemical aspects of PA11 degradation. Overall, rheological analysis confirms to be a valuable tool for monitoring polymer degradation even in case of inherently complex systems such as nanocomposites. In this case, however, the analysis can be difficult if the dynamics of the nanoparticles prevail over those of the polymer matrix, which is the case of nanocomposites at high filler contents. [ABSTRACT FROM AUTHOR]

Thermal and thermo-oxidative degradation of polyamide 11 (PA11) in the melt state ( T = 215 °C) are studied by resorting to time-resolved mechanical spectroscopy. Such an approach allows to elude the changes in the rheological properties occurring while testing, thus enabling the rigorous study of polymer degradation in the melt state. Different concurrent degradation reactions in oxidative (air) and non-oxidative (N 2 ) environment are promptly guessed by studying the time evolutions of rheological functions. In particular, changes in the zero–frequency complex viscosity reflects changes in the average molecular weight, while the appearance of a yield stress in the complex viscosity curve is identified as the rheological fingerprint of cross-linking reactions. Size exclusion chromatography corroborates the hypotheses based on rheological analyses, and matrix assisted laser desorption/ionization mass spectrometry sheds light on the chemical aspects of degradation. Specifically, post-condensation (in N 2 ), chain scission, hydrolysis and cross-linking reactions (in air) are identified as the dominant degradation mechanisms of PA11 in the melt state. Overall, our study demonstrates that rheology is a valuable tool to detect and discriminate among different degradation mechanisms in polymer melts. In particular, rheology promptly identifies cross-linking reactions, which can be difficult to be detected through common analytical techniques that envisage the solubilization of the polymer sample. [ABSTRACT FROM AUTHOR]