Polypropylene film provides capacitor characteristics that are superior to those of polyester. Polypropylene capacitors have both high- and low-frequency applications. The plastic has properties that are similar to those of polystyrene, but capacitors made from it have higher AC current ratings. Polypropylene capacitors can operate at 105°C, and their volumetric efficiency is better than those made of polyester. Foil and polypropylene capacitors are used in CRT deflection, pulse-forming, and RF circuits. The capacitance tolerance for polypropylene capacitors is +-5 percent, and their temperature coefficients are linear.
Polystyrene film has characteristics that are similar to those of polypropylene. Capacitors made from the film exhibit a low dissipation factor, small capacitance change with temperature, and very good stability. But they are larger than comparably rated polypropylene units. Used in timing, integrating, and tuning circuits, their maximum operating temperature is 85°C.
Polycarbonate film capacitors offer dissipation factors and capacitance stability which approaches those of polystyrene capacitors. They also offer high insulation resistance stability. Operating temperatures are −55 to 125°C with capacitance tolerances of +-5 percent. These capacitors are widely used in military applications.
