Epoxy resin nanocomposites containing graphite nanosheets (GNS) and unsaturated polyester resin (UPR) were prepared by incorporating GNS in semi interpenetrating network (semi-IPN) of epoxy resin and unsaturated polyester resin (E-UPR). GNS are prepared by thermal shock treatment of sulphuric acid-graphite intercalation compound (GIC) followed by ultra-sonication. The E-UPR-GNS semi-IPNs were further modified with aromatic amines such as benzidine (Bz) and diphenyl amine (DPA). All the samples were prepared by mixing Triethylenetetramine (TETA) as the curing agent at two different temperatures viz. room temperature (RT) and low temperature (LT; 5 °C). A transition is observed in the conducting properties of the samples: from an electrical insulator to an electrical semiconductor in case of nanocomposites especially on addition of GNS to E-UPR semi-IPNs. A sharp improvement is observed in conductivity after modification with diphenyl amine (DPA) cured at LT. The nanocomposites obtained at LT exhibit homogeneity with minimum anisotropy in conductivity. The morphology, mechanical, thermal and electrical properties were evaluated using various analytical techniques. Positron annihilation spectroscopy was carried out to correlate the measured properties with the free volume and free volume hole size distribution. The results are consistent with the reported studies. © 2016 Elsevier Ltd