In this study, we will present our recent work on filled polymer systems made from an optimized co-continuous mixture of Polyethylene terephthalate (PET) and polyvinylidene fluoride (PVDF) reinforced with highly conductive carbon additives composed of carbon black (CB) and synthetic graphite (GR). Multiwall carbon nanotubes (MWCNT) were functionalized then used to improve the electrical conductivity and mechanical properties of the developed systems, such as their flexural and impact strengths. It was observed that the best system was obtained using nitric acid (HNO3)-functionalized MWCNT. The latter led to the smothest samples surface, the lowest through-plane electrical resitivity (0.12 Ohm.cm) and the highest impact and flexural strengths. Theses results are attributed to the improved dispersion of the functionalized MWCNT, a result of their best compatibilization with the (PET/PVDF) polymeric phase.