Cure Index demonstrates curing of epoxy composites containing silica nanoparticles of variable morphology and porosity

Abstract

An image was taken by Cure Index on curability of epoxy with silica nanoparticles having variable morphology and porosity. Three kinds of silica nanoparticles with non-porous curved-rod, non-porous spherical, and mesoporous spherical microstructures were synthesized and characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM) and Brunauer–Emmett–Teller analyses. Epoxy nanocomposites containing 0.1, 0.3, 0.5 wt.% of nanoparticles cured nonisothermally in differential scanning calorimetry (DSC) at different heating rates and the glass transition temperature (Tg) for fully-cured samples was estimated. Cure Index unravelled the effect of nanoparticle morphology and porosity on epoxy crosslinking. Good cure was unconditionally the case for systems containing 0.3 wt.% of mesoporous spherical nanoparticles due to appropriate dispersion of porous nanoparticles, as captured by SEM. By contrast, dependency of curing on heating rate and nanoparticle loading in the case of non-porous spherical and curved-rod particles was evidenced by partially agglomerated domains. The state of nanoparticle-polymer interaction was also inferred in view of network formation in the presence of nanosilica particles of various morphology and porosity, which was nicely monitored by the use of Cure Index.