We previously developed a novel modified epoxy matrix for macrocomposites using reactive graphitic nanofibers (r-GNFs), which showed improved mechanical properties. This article is devoted to study the efficacy of the r-GNFs against the damage due to exposition of the matrix to hygrothermal environment and UV radiation. Moisture sorption characteristics of the pure epoxy and nanoepoxy were investigated and all kinds of matrices showed similar absorption behavior. Both diffusion and relaxation processes in sorption were observed. DSC curves of nonaged specimens of all concentrations confirmed that samples were not fully cured and r-GNFs lowered the curing degree. The effects of ageing were studied through the changes of molecular conformation by Fourier Transform infrared spectroscopy (FTIR). The results show that UV radiation assists in post-curing of the matrices. Hydroxyl unit, carbonyl unit, and epoxide unit were chosen to study the degradation. It is observed that the degradation due to UV radiation is more severe compared with that due to hygrothermal expose. It also reveals that r-GNFs resist the degradation of the epoxy resin; particularly, the nanoepoxy with 0.3 wt % of r-GNFs has the highest ageing resistance, which is in agreement with our previously tested results of mechanical properties. (c) 2007 Wiley Periodicals, Inc.