Synergistic Enhancement of Thermal Stability in Epoxy Nanocomposites via IPN Formation and GnPs/MWCNTs Hybrids

Abstract This study investigates the thermal properties and microhardness of epoxy/vinyl ester (EP/VE) interpenetrating polymer networks (IPNs) containing hybrid nanofillers comprising graphene nanosheets (GnPs) and multi-walled carbon nanotubes (MWCNTs). An equal weight ratio mixture of two compatible resins with similar chemical structures but different curing mechanisms, namely epoxy and vinyl ester resins, both based on bisphenol-A, was used to fabricate the IPN matrix. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were used to evaluate the effects of the type and amount of nanofillers based on carbon allotropes on the thermal degradation behavior of the resulting nanocomposites. The DTG thermogram of the IPN sample showed a single degradation peak, indicating the formation of a full interpenetrating polymer network and high compatibility between its constituent resin components, and the absence of detectable phase separation. Changes in TGA and DTG parameters of IPN samples containing hybrid nanofillers, compared to those without them, indicate that these nanofillers have improved the IPN's thermal stability. The nanocomposite containing 0.1 wt% GnPs/MWCNTs hybrid exhibits optimal performance and the highest fire retardancy, with a limiting oxygen index (LOI) of 20.17%. Microhardness measurements revealed that the IPN system exhibited hardness values comparable to those of the pure epoxy resin, indicating that mechanical integrity was maintained while also improving thermal properties.