Influence of Different Concentrations of Glycidylisobutyl-POSS on the Glass Transition of Cured Epoxy Resin

In this study, polyhedral oligomeric silsesquioxane glycidylisobutyl-POSS was dispersed in epoxy resin by ultrasound, and the parameters of a phantom model, the Williams-Landel-Ferry (WLF) and Vogel-Fulcher-Tammann (VFT) equations were modeled using dynamic mechanical analysis (DMA) to evaluate their influence on the glass transition state. The relaxation and retardation time distributions were estimated using a nonlinear regularization method, and the estimated physical parameters were discussed based on the results obtained from transmission electron microscopy (TEM). The TEM analysis indicated higher POSS dispersion with a spherical shape. The POSS dispersion was associated with the formation of micelles due to their hybrid character. The micelles favored the interconnections of the nodular microstructure of the epoxy thermosetting, which led to an increase in their Tg values. These interconnections increased the structure's percolation, promoted a reduction in the thermal expansion coefficient and resulted in a more homogeneous glass transition, in terms of a cooperative distribution in the relaxation times at the time scale measured. (C) 2014 Wiley Periodicals, Inc.