Long-term behavior of epoxy/graphene-based composites determined by dynamic mechanical analysis

Graphene oxide and reduced graphene oxide were obtained from graphite and reduction of graphene oxide, respectively, and functionalized with 4,4′-Methylenebis (phenyl isocyanate) isocyanate. Epoxy/graphene-based composites were prepared by dispersing the as-prepared carbon materials in epoxy resin based on diglycidyl ether of bisphenol A followed by curing with triethylenetetramine. The efficiency of the functionalization of the carbon materials was followed by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoeletronic spectroscopy, and atomic force microscopy. The epoxy-based composites were characterized by dynamic mechanical analysis at frequency and temperature sweeps in order to evaluate the long-term behavior of the composites by using the time temperature superposition principles and the master curves of multi frequency. All composites presented better working temperature range and durability as compared with the pure epoxy network. However, those prepared with graphene oxide and its reduced form functionalized with isocyanate groups presented better mechanical performance and long-term durability, probably because of the better filler-matrix interactions achieved in theses system. The results obtained suggest that the presence of isocyanate groups is the key role for achieving good mechanical performance, and the reduction step of graphene oxide is not of paramount importance for achieving good mechanical response.