Effect of functionalized TiO2 nanoparticles on dielectric properties of PVC nanocomposites used in electrical insulating cables

The tendency to enhance the dielectric properties of insulating materials used in cables has become necessary in order to design new insulation systems that can withstand higher voltage levels. The current study is to investigate the improvement in dielectric properties of Polyvinyl Chloride (PVC) due to the insertion of chemically functionalized titanium oxide (TiO₂) nanoparticles. The functionalization of TiO₂ nanoparticles was performed using vinyl silane coupling agent. The PVC/TiO₂ nanocomposites, with different weight fractions of nanoparticles up to 5 %, were fabricated using solution casting of PVC with the aid of nanoparticles dispersion within the molten polymeric matrix. The surface morphology of synthesized PVC/TiO₂ nanocomposites was characterized by field emission scanning electron microscopy (FE-SEM). Then, their dielectric properties were studied by measuring and simulating the AC dielectric breakdown strength under quazi-uniform electric fields. The relative permittivity (ε_r) and dielectric loss (tan δ) were also measured in the frequency range 20 Hz to 1 MHz at room temperature. It is found that the dielectric breakdown strength of PVC was increased with incorporating functionalized TiO₂ into their matrix compared to that with un-functionalized TiO₂ or that of unfilled PVC. Furthermore, ε_r and tan δ were decreased by about 43% and 41%, respectively, over the unfilled PVC at 50 Hz. 3 % was found the optimal loading fraction of functionalized TiO₂. This reveals that PVC/TiO₂ nanocomposites with functionalized TiO₂ had better dielectric properties. This may be attributed to the low surface energy of the functionalized TiO₂ nanoparticles that prevented the agglomeration of nanoparticles and restricted the mobility of polymeric chains, and in turn, suppressed the free space charges resulting in a decrease in the capacitance and losses inside the nanocomposites.