Critical parameters in the determination of dielectric properties of synthetic polymers commonly used as insulators

It is well known that most synthetic polymers are poor conductors of electricity and heat. This observation confirms the fact that very few, if any, electrons capable of migrating under the influence of an externally applied electric or thermal gradient exist in these polymers. Consequently the determination of the dielectric properties of these materials represents a serious challenge to the investigator, since the detection of such small concentration of electrons or electric charges is extremely difficult. Not only must attention be given to the generation and transport mechanisms of electric charges in the material to be tested; the capabilities of the test equipment have to be matched to the requirements of the material and proper test methods selected. These aspects will be discussed in some detail in this paper and a few experimental results will be reviewed to illustrate these points.