Investigating the aging behavior of polysiloxane nanocomposites with degradative thermal analysis and broadband dielectric spectroscopy

The physical and chemical aging of polysiloxane elastomers incorporating nano-scale particles of differing dimensions and aspect ratios is reported. A series of model polysiloxane nanocomposites have been prepared incorporating montmorillonite nanoclay and polyhedralsilsesquioxane (POSS). Broadband Dielectric Spectroscopy (BDS) has been employed to study the effects of aging on polymer-filler interactions within the nanocomposites by tracking changes in system ionic mobility and filler-induced Maxwell-Wagner-Sillars effects. TGA and DSC have been utilized to study the effects of aging on the non-oxidative stability of the nanocomposites. The complex evolution of volatiles that occurs during aging has been studied using Sub-Ambient Thermal Volatilization Analysis (SATVA). Results indicate that significant physical and chemical changes take place within the nanocomposites upon aging; acid catalyzed hydrolysis, chain backbiting and recombination reactions are re-structuring the polymer-filler network into a more thermodynamically stable form. The nature and magnitude of these processes is dependant on the nano-filler present.