Plastics make good dielectrics for the manufacture of capacitors. Polyethylene and polystyrene are commonly used. The method of manufacture is similar to that for paper capacitors. Stacking methods can be used if the plastic is rigid. The geometries can vary, and these capacitors are therefore found in various shapes.Capacitance values for plastic-film units range from about 50 pF to several tens of microfarads.
Most often they are in the range of 0.001 μF to 10 μF. Plastic capacitors are employed at AF and RF, and at low to moderate voltages. The efficiency is good, although not as high as that for micadielectric or air-dielectric units.