One-component epoxy resin adhesive featured with high storage stability based on microencapsulation

Epoxy resin (EP) adhesive is an essential thermosetting polymer used in coating. A curing agent is typically added to the epoxy system during the curing process in order to obtain a three-dimensional network structure. Therefore, existing commercial adhesives are two-component systems containing EP and the curing agent separately. However, the curing agent is prone to oxidation in air, and two-component systems reveal rapid viscosity changes and poor storage stability. On the other hand, microcapsules possess special encapsulation properties that can isolate the curing agent from the air. Mixing EP and microencapsulated curing agent directly results in a one-component epoxy resin adhesive that is easy to store and use. In this paper, methyl ethyl disubstituted diamine (DMEDDM), namely a novel curing agent was microencapsulated adopting solvent evaporation method with thermoplastic resin polyetherimide (PEI) as the shell material. It is found that the microencapsulated DMEDDM (Mic-DMEDDM) reveals smooth and compact spherical appearance with mean particle size about 13.65 mu m. Moreover, the encapsulation efficiency of Mic-DMEDDM can reach up to 70%. After recycling the residual water phase seven times, the surface-regularized Mic-DMEDDM can still be obtained. Compared with two-component epoxy adhesive, the Mic-DMEDDM in one-component epoxy adhesive effectively extends the storage period to 43 days at 45 celcius. It is expected to find wide applications in coatings, electronic packaging materials and composite materials.