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

POLY 567

James P. Lewicki,, David Hayward, John J. Liggat,, and Richard A. Pethrick. Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Thomas Graham Building, Glasgow, G1 1XL, United Kingdom
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.