FF series parts offer both Polypropylene & Polyester dielectrics. Polypropylene is ideal for higher operating voltages, (500 Vdc to 100 kVdc) and has a constant dielectric loss factor of 2 x 10-4 irrespective of temperature and frequency (up to 1 MHz). Polyester maximizes capacitance for lower operating voltages (75 Vdc to 400 Vdc), its capacitance is a function of both temperature and frequency. The dielectric loss factor of polyester is also a function of both temperature and frequency.