Influence of graphene nanoplatelets on curing and mechanical properties of graphene/epoxy nanocomposites

• Published in: Journal of thermal analysis and calorimetry 2016-08, Vol.125 (2), p.629-636
• Main Authors: Prolongo, M. G., Salom, C., Arribas, C., Sánchez-Cabezudo, M., Masegosa, R. M., Prolongo, S. G.
• Format: Article
• Language: English
• Subjects: Analysis; Analytical Chemistry; Chemistry; Chemistry and Materials Science; Epoxy resins; Graphene; Graphite; Inorganic Chemistry; Measurement Science and Instrumentation; Mechanical properties; Physical Chemistry; Polymer Sciences
• ISSN: 1388-6150; 1588-2926
• DOI: 10.1007/s10973-015-5162-3

The influence of graphene nanoplatelets (GNPs) on the curing of an epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) and cross-linked with 4,4′-diaminodiphenylmethane (DDM) was studied. Dynamic mechanical properties and tensile properties of the corresponding graphene/epoxy nanocomposites were obtained. Two compositions 1 and 5 mass% of GNPs were studied. The cross-linking reaction of the epoxy resin is accelerated in dispersions with 5 mass% GNPs. In the presence of GNPs, the curing reaction becomes less exothermic, obtaining less perfect epoxy networks compared to neat epoxy (DGEBA–DDM) thermoset. Accordingly, the glass transition temperatures ( T g ) of the nanocomposites are lower than that of the neat epoxy thermoset. This effect is not detected for low content of graphene (1 mass%). Protocol of curing having two isothermal steps leads to more perfect networks than the dynamic curing in the DSC. The T g reduction is minimized in the samples cured through two isothermal steps. The storage moduli of the nanocomposite containing 5 mass% graphene, both in the glassy ( T    T g ) states, are higher than the ones of neat epoxy thermoset, being most pronounced this effect at T  >  T g . Tensile tests confirmed the higher elastic moduli of the nanocomposites; however, a decrease in strain at break and tensile strength was observed for the nanocomposite containing 5 mass% of GNPs. This brittle behavior is consistent with the morphology of the samples studied by scanning electron microscopy.