Semicrystalline Polymers with High Dielectric Constant, Melting Temperature, and Charge-Discharge Efficiency

The dielectric properties of semicrystalline poly(tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride) (THV) terpolymers with different compositions are investigated in a broad temperature range and under high voltage for potential applications in high energy density film capacitors with high thermal stability. It was found that the capacitor charge-discharge efficiency under high voltage (>200 MV/m) and the melting temperature can be significantly improved by increasing the tetrafluoroethylene (TFE) content. Melting temperature above 220 degrees C can be achieved in THV terpolymers with high TFE content. Although the THV terpolymers have lower dielectric constant than polyvinylidene fluoride (PVDF), their high melting temperature, low leakage current, and high charge-discharge efficiency represent significant advantages for capacitors operated under high charge-discharge repetition rate and at high ambient temperatures.