Miscibility, morphology, mechanical, and thermodynamic properties of epoxy resins toughened with functionalized core-shell nanoparticles containing epoxy groups on the surface

Purpose - In order to obtain functionalized core-shell nanoparticles (CSNPs) as excellent toughening agents for epoxy resins. The paper aims to discuss these issues. Design/methodology/approach - Functionalized CSNPs containing epoxy groups on the surface were synthesized by emulsion polymerization with butyl acrylate as the core and methyl methacrylate copolymerizing with glycidyl methacrylate (GMA) as the shell. CSNPs were used as toughening agents for epoxy resins and their chemical structure was characterized by FT-IR. The morphology of modified epoxy networks (MEPN) was analyzed by SEM and TEM. Both the mechanical properties and thermodynamic properties were studied. Findings - The results show that nearly spherical CSNPs with the particle size of 50-100 nm are obtained. A certain amount of CSNPs are uniformly dispersed in epoxy resins by the grinding method and the MEPN shows the ductile fracture feature. The miscibility between CSNPs and epoxy matrix increases with the increase of GMA concentration which makes more bonds form between them. Epoxy resins toughened with 10 wt% CSNPs containing 10 wt% GMA show the best mechanical properties and the increase in tensile strength and impact strength of the MEPN is 13.5 and 59.7 percent, respectively, over the unmodified epoxy networks. And the improvement in impact strength is not accompanied with loss of thermal resistance. Practical implications - The MEPN can be used as high-performance materials such as adhesives, sealants and matrixes of composites. Originality/value - The functionalized CSNPs are novel and it can greatly increase the toughness of epoxy resins without loss of thermal resistance.