The effect of adding different amounts (0.5-3 wt%) of nanosilica (NS) and organomodified montmorillonite (MMT) to diglycidyl ether bisphenol A (DGEBA) cured with isophorone diamine at different temperature on the viscoelastic, topographical and gelation properties of epoxy resin was studied. Gel time measurements revealed that both NS and MMT accelerated the curing reaction of DGEBA with IPDA. Both nanofillers were adequately dispersed in DGEBA. The particle size distribution depended on the amount of nanofiller. A broader distribution for NS than for MMT filled epoxy was obtained. On the other hand, an increase in the curing temperature was required to obtain the intercalation of the epoxy into the MMT tactoids. At room temperature, the addition of NS increased both the stiffness (high storage modulus) and the toughness (an increase in the area and height of the tan delta curve) of epoxy, but no significant differences were found by curing at higher temperature. Epoxy/MMT composites showed higher storage modulus in the rubbery region. The improved properties imparted by NS can be ascribed to the interactions between the silanol moieties on the nanosilica surface and the polar groups in the epoxy, whereas the improvement imparted by MMT organoclay was related to tactoid intercalation within the epoxy matrix. (C) Koninklijke Brill NV, Leiden, 2010