Elastomer/thermoplastic modified epoxy nanocomposites: The hybrid effect of ‘micro’ and ‘nano’ scale

The approach of simultaneously exploit the use of microscale elastomers/thermoplastics and nanoscale fillers for the modification of epoxy systems is presently an active research topic. Such hybrid modification of epoxy primarily helps to tailor multiple mechanical properties, without compromising other required properties. The current review reports about the development and properties of multicomponent epoxy systems modified with both elastomers/thermoplastics and nanofillers, on the basis of an updated literature survey. For a better understanding and comparison, the review initially provides a short discussion on key findings in binary blends of epoxy and elastomers/thermoplastic and binary epoxy nanocomposites. Successful studies dealing with multicomponent epoxy systems are also reported, where it is demonstrated that microscale modification individually, sometimes synergistically, enhances the fracture toughness of epoxy without affecting the properties optimized by nanoscale modification. The mutual role of microscale elastomer/thermoplastic and nanoscale filler on morphology, cure reaction, mechanical and thermal properties of epoxy multicomponent system is discussed. The complex interaction between the micro- and nano-phases determines phase separated morphologies in the multicomponent system, essentially related to the function of microscale modifiers in dispersion/intercalation/distribution of nanofillers and to the role of nanofillers in phase separation kinetics and mechanisms. The specific effect of nanofillers in phase separation mechanisms for epoxy blends, that place via nucleation and growth (NG) and spinodal decomposition, is analysed looking at the final morphology and hence performance of multicomponent system. Moreover, the fracture mechanism that operates in such multicomponent epoxy systems is discussed.