Effect of blending and nanoclay on dielectric properties of polypropylene

This paper investigates the effects of organomodified montmorillonite (clay) and styrene-(ethylene-co-butylene)-styrene triblock copolymer (SEBS) on the morphological and electrical properties of polypropylene (PP). A series of binary PP-clay nanocomposites along with nanocomposites having a blend matrix were prepared. The nanofillers were found to be well-embedded into the polymeric matrix with a high degree of dispersion. The microstructure of the blend matrix revealed a co-continuous structure for the equal proportion of the two polymers. This was shown to control the localization of nanofiller by triggering them to migrate into the SEBS phase, mostly accommodating in the interface and creating a strong network which eventually resulted in more exfoliation of clay platelets and comparable/superior electrical properties comparing to binary nanocomposites. The incorporation of clay resulted in a solid-like rheological behavior which was more enhanced in blend nanocomposites due to the stronger network of nanofiller. The dielectric spectra of the nanocomposites revealed two major relaxation processes aroused by the presence of clay. A new relaxation process was observed for the nanocomposites with the blend matrix, related to the SEBS phase. Both blending and nanofiller inclusion resulted in less accumulated space charge. A significant improvement in the AC breakdown strength of PP was witnessed upon addition of clay. Despite the less inherent breakdown strength of SEBS, the blend nanocomposites showed even more enhanced breakdown properties confirming the further improvement of nanofiller network structure.