Possible selective physisorption of lower molecular mass of epoxy-vinyl ester chains on the montmorillonite nanoplatelets: A rheological approach

Abstract

Na+-montmorillonite nanoplatelets were surface functionalized by triethoxyvinylsilane through sol-gel reactions. The functionalized, and pristine nanoplatelets were then impregnated by Octadecyl-3-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionate, a primary phenolic antioxidant, to be used in an epoxy vinyl ester resin. The FTIR, Raman and, TGA results confirm that the functionalization reactions, and the antioxidant impregnation process have been successfully carried out. FE-SEM micrographs demonstrate that particle morphology significantly changed as a result of the processes. In the next step, three different concentrations of the obtained nanofillers were added to an epoxy vinyl ester resin, and the attained colloids underwent rheological assessment. Both steady-shear, and dynamic complex viscosity diagrams showed significantly increased values, by two orders of magnitude, for untreated Na+-montmorillonite compared to the other nanofillers, i.e. vinyl-functionalized, and antioxidant-loaded ones. It was then demonstrated that such an increase is most certainly attributed to a proposed theory as possible selective physisorption of lower molecular mass of epoxy vinyl ester chains on the untreated montmorillonite nanoplatelets.