Low-loss polypropylene for electrical purposes

The results of dielectric-loss measurements on groups of experimental and plant-scale polypropylene samples have been used to select materials which have low losses over a wide frequency range at room temperature, and in which conduction, which shows up as a runaway loss increase with increasing temperature at power frequencies, has been reduced to a low level. Data on a propylene-ethylene copolymer with similar properties are also presented. Comparisons with results for low-loss polythene and polytetrafluoroethylene indicate that polypropylene has the lowest losses of the group in the microwave region. The electrical applications of these low-loss materials are dicussed.