Rheology, curing and time‐dependent behavior of epoxy/carbon nanoparticles systems

Abstract

This study delved into the characterization of epoxy nanocomposites containing diglycidyl ether of bisphenol‐A (DGBEA), graphene nanoplates (GN), and carbon nanotubes (CNT) across a range of weight percentages (0.05% to 2%). The nanocomposites were produced through a process involving mechanical stirring and ultrasonication. To assess compatibility, three‐dimensional solubility parameters (3DSP) were employed. CNT demonstrated superior compatibility with epoxy and triethylenetetramine (TETA), due to its higher amount of oxygenated species in nanoparticle surface compared to GN. A rheological percolation phenomenon occurred in CNT systems at concentrations above 0.2%, while GN did not display percolation even at 2% concentration. Incorporating nanoparticles led to increased curing enthalpy due to surface functional groups. As the percolation network formed, viscosity rose, and a reduced glass transition temperature (Tg) indicated restricted molecular mobility. Surprisingly, Tg consistently increased by approximately 27°C during composite annealing, regardless of nanoparticle type or concentration. This was attributed to forming a three‐dimensional network structure potentially originating from reactions between nanoparticle‐oxygenated groups and the epoxy matrix. This phenomenon was crucial in heightened creep and irreversible deformations, setting these nanocomposites apart from pure resin behavior.