Study of the addition of poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) thermoplastic to epoxy resin for use in self-healing composites
self-healing, thermoplastic-thermoset, DMA, FTIR, AFM.
Repair of damaged composite structural elements to restore pristine conditions and meet regulatory requirements can be a great challenge. Thus, materials capable of self-healing when damaged are of great interest. In one of the self-healing approaches studied in the literature, thermoplastic is added to a thermosetting matrix and the damaged material partially recovers its mechanical properties after a healing cycle. This technique employs heat to partially re-establish the mechanical properties of the composite material. In the present study, modification of epoxy resin with poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) (E-MA-GMA) termoplastic was evaluated. The influence of the employed type of hardener (anhydride and amine) on the properties of the material was also investigated. Dynamic mechanical analysis (DMA) was performed to evaluate changes in viscoelastic properties due to the thermoplastic addition. Fourier transform infrared (FTIR) spectroscopy was used to evaluate chemical alterations in thermoplastic-epoxy systems. Atomic force microscopy (AFM) was employed to examine the role of thermoplastic addition on epoxy network structure. Healing ability was assessed by comparing areas damaged by standard indentations on the surface of samples before and after healing cycle for materials with and without E-MA-GMA addition. Results suggest the presence of a E-MA-GMA second phase after curing, an increase in glass transition temperature (Tg) for all thermoplastic blended samples as compared to neat epoxy, the presence of one single Tg for epoxy anhydride hardened E-MA-GMA mixtures and chemical and structural alterations on epoxy network due to addition of E-MA-GMA. Further, the disappearance damage caused by indents on areas of the material modified with thermoplastic after a heating cycle supports the potential use of E-MA-GMA as healing agent.