Modelling characterisation of a fast curing silica nanoparticle modified epoxy

Abstract

Fast-curing epoxy polymers allow composite parts to be manufactured in minutes, but the curing reaction is highly exothermic with heat flows up to 20 times higher than conventional epoxies. The low thermal conductivity of the polymer causes the mechanical and kinetic properties of parts to vary through their thickness. In the present work, silica nanoparticles were used to reduce the exotherm, and hence improve the consistency of the manufactured parts. The kinetic properties were measured as a function of part thickness and it was noted that the exothermic heat of reaction can be significantly reduced with the addition of silica nanoparticles, which were well-dispersed in the epoxy. A model was developed to describe the increase in viscosity and degree of cure of the unmodified and the silica-modified epoxies. A heat transfer equation was used to predict the temperature and resulting properties through the thickness of a plate, as well as the effect of the addition of silica nanoparticles. No significant viscosity increase was found with the addition of up to 20 wt% of silica nanoparticles. The predictions were compared to the experimental data, and the agreement was found to be very good.