Blend nanocomposite film was prepared by loadings of irradiated ZnO in ratios of (5 wt%) inside the PVC/HDPE matrix using a hot-melt extruder technique. The physical and chemical properties of the irradiated and unirradiated ZnO samples are compared. The Vis–UV spectrum of ZnO shows an absorption peak at a wavelength of 373 nm that was slightly red-shifted to 375 nm for an irradiated sample of ZnO at a dose of 25 kGy due to the defect of crystal structure by the oxygen vacancy during gamma irradiations. This growth of the defect site leads to a decrease in energy gaps from 3.8 to 2.08 eV. AC conductivity of ZnO sample increased after the gamma irradiation process (25 kGy). The (PVC/HDPE)/ZnO nanocomposites were re-irradiated with γ rays at 25 kGy in the presence of four different media (silicon oil, sodium silicate, paraffin wax and water). FTIR and XRD were performed to monitor the changes in chemical composition. The new peak at 1723 cm−1 attributed to C=O groups was observed in irradiated (PVC/HDPE)ZnO samples at only sodium silicate and water media. This process induced new function groups on the surface of the (PVC/HDPE)/ZnO blend sample. This work aims to develop (PVC/HDPE)ZnO for oil/water separation. The highest oil adsorption capability was observed in samples functionalized by C=O groups based on the different tested oils. The results suggest that the surface characterization of the (PVC/HDPE)/ZnO can be modified to enhance the oil adsorption potential. Further, the gamma irradiation dose significantly enhanced the AC conductivity compared to the unirradiated sample. According to COMSOL Multiphysics, the irradiated sample (PVC/HDPE)ZnO in water shows perfect uniform electric field distribution in medium voltage cables (22.000 V).