Toughening of high performance tetrafunctional epoxy with poly(allyl amine) grafted graphene oxide

The mechanical and thermal properties of epoxy composites were improved by using poly (allyl amine) (PAA) grafted graphene oxide (GO) as a toughening agent. The GO was first converted to GO-COOH where all the hydroxyl groups on the basal plane were converted to COOH containing groups. GO-COOH was reacted with PAA to yield GO-g-PAA. The effect of PAA grafted GO nanosheets as fillers on mechanical and thermal properties of aerospace grade epoxy was studied. Epoxy nanocomposites containing graphene oxide (GO) and GO-g-PAA nanosheets were fabricated by incorporating 0.35 to 1.4 wt% of filler. GO-g-PAA modified epoxy nanocomposites showed excellent improvement in flexural, compression and fracture properties compared to neat epoxy and GO modified epoxy. Fracture toughness increased from 0.94 MPa m to 1/2 for neat epoxy to 1.75 MPa m-1/2 (87%) for epoxy nanocomposites modified with 0.7 wt% of GO-g-PAA nanosheets. The temperature for 5% weight loss showed drastic improvement of 24 degrees C for epoxy nanocomposites modified with 0.7 wt% of GO-g-PAA nanosheets. The examination of fractured surfaces of modified epoxy nanocomposites showed better interaction of GO-g-PAA nanosheets with epoxy compared to GO nanosheets.