The dielectric losses in some representative insulating materials

A detailed study is made of the permittivity and power factor of a number of insulating materials over the whole range of conditions encountered in electrical practice, including frequencies from 10 c/s to 24 000 Mc/s and temperatures from ¿35° C to +240° C in appropriate cases. The materials fall into the following groups: (a) Silicones and other silicon-oxygen structures including mica and glass. (b) Non-polar plastics including polystyrene, polyethylene, polytetrafluorethylene, etc. (c) Pure synthetic resins of the phenol-formaldehyde and anilineformaldehyde classes. (d) The polar plastic Kel F, a chlorinated derivative of the nonpolar polytetrafluorethylene. The main features of the dielectric behaviour of these groups are explained in terms of known features of their structures.