Thin films of epoxy adhesives containing recycled polymers and graphene oxide nanoflakes for metal/polymer composite interface

Epoxy adhesives based on recycled poly(ethylene terephthalate) (PET), ground rubber tire (GTR), and graphene oxide (GO) nanoflakes were designed and their thermal and mechanical properties were discussed. By changing the amounts of the aforementioned components (recycled polymers and GO nanosheets), adhesive formulations were tested for tensile and single-lap shear strength applied at the interface between epoxy/carbon fiber and stainless steel. The best and the worst samples in regard to mechanical strength were specified and selected for thermal degradation analyses base on thermogravimetric analysis (TGA). The dispersion state of PET and GTR were also studied by the use of field-emission scanning electron microscopy (FE-SEM). It was found that addition of 10 phr of 75/25 (w/w) PET/GTR mixture to 100 parts by weight of epoxy together with 0.1 phr of GO could surprisingly enhance ca. 29, 260 and 585% the Young's modulus, tensile strength, and the toughness of epoxy, respectively. It was also proved that introduction of GO to the adhesive enhanced thermal stability of epoxy/(PET/GTR).