Polypropylene(PP) is a permanently elastic plastic with high inherent damping, which is used as an insulating material in cabling, as a dielectric in power capacitors and in membranes of loudspeakers.
- In cabling, polypropylene is used for empty conduits and as an insulating material for cables. It carries the DIN/VDE designation 9Y. Polypropylene is thermoplastic and permanently temperature resistant. It can be used up to temperatures of over 100 °C. The permittivity or dielectric constant is between 2.3 and 2.5 at 50 Hz, and the dielectric strength is relatively high at 75 kV/mm.
- Polypropylene is used as a dielectric infilm capacitors and in power capacitors because of its high dielectric strength of over 600 V/µm. The volume resistivity of polypropylene is `6*10^18`. In addition, the wide temperature range of -55 °C to 85 °C makes it suitable for outdoor use in power electronics, heavy current systems and HVDC technology. Film capacitors with metal foil have the marking" MK".
- In acoustics, polypropylene is used in the diaphragms of midrange and woofers because of its high internal damping. The stiffness and hardness of the diaphragm is adjusted to the sound reproduction requirements by organic additives. The advantage of polypropylene diaphragms lies in the good technical production properties with a high reproducibility, it produces a good sound image in midrange drivers and has damping properties with which partial vibrations are damped. However, the pulse behavior is not as good as that of paper diaphragms.