Breakdown Voltage of Thermoplastics with Clay Nanometer-Sized Fillers

The addition of fillers, such as talc, mica and carbon black, are used commonly in industry to improve physical properties of polymers, such as stiffness, hardness, wear, heat distortion temperature or electrical conductivity, or to reduce the overall raw material cost of a part. Not withstanding these opportunities, the addition of micron-sized fillers to a polymer may have detrimental effects on its dielectric characteristics, such as dielectric loss, breakdown strength and dielectric durability. Recently, the addition of nanometer-sized fillers, or nanofillers, has shown potential for improving the polymer's dielectric breakdown voltage in conjunction with augmentation of its mechanical properties. Five different sets of thermoplastics were tested between opposed cylindrical rod electrodes of 6.4 mm diameter with rounded edges of 0.8 mm radius. The applied voltages were at 60 Hz. All polymers in this study showed an increase in the average dielectric strength from five to fifty-six percent with the nanoscale dispersion of 1-5 wt% organically modified montmorillonite (nanoclay). Most of these increases exhibited statistically significant margins. The tested thermoplastic polymers include nylon-6, low-density polyethylene, low-density polyethylene/ethylene-vinyl acetate copolymer, and polyester. The percent composition of nanofiller was confirmed by thermogravimetric analysis and nanofiller distribution was analyzed using transmission electron microscopy.