Glass transition improvement in epoxy/graphene composites

Graphene oxide nanoplatelets (GO) were prepared from expanded graphite (EG) and functionalized with triethylenetetramine (GO-TETA). The GO-TETA consisted of a few layers of graphene (4-6 layers), as determined by atomic force microscopy and Raman spectroscopy. X-ray photoelectron spectroscopy showed that the TETA was covalently linked to the GO in the GO-TETA sample. Epoxy composites based on the diglycidyl ether of bisphenol A with TETA as a hardener and with 0.5-3.0 wt% additions of EG and GO-TETA were investigated. The results showed that the addition of the nanofillers led to an increase of 20 A degrees C in the glass transition temperature. A slight increase in the ratio of the elastic modulus/hardness of the nanocomposites was observed by nanoindentation tests carried out at a depth range of 300 nm-1.3 mu m; these tests indicated a tendency of increased fracture toughness. Microindentation had an enhancement of 40 % in hardness for the 1 wt% composite with GO-TETA relative to the corresponding value for the neat epoxy.