Dielectric and thermoanalytical behavior and spectroscopic and kinetic evaluation of water in heat-resistant electrical insulating films

Nowadays, along with requirements for developing heat-resistant electrical insulating materials, various kinds of high polymers with polar structures are used, which are characterized by high heat-stability, good electrical properties, hydrophilic nature, etc. While their heat-stability is beneficial to their uses, their hydrophilic nature is sometimes detrimental, since the existence of water in electrical insulation is apt to deteriorate their electrical properties and dimensional stability. How water interacts with the polymer molecules in electrical insulating materials is an important issue to be solved; how inadequately the water can be classified into its free and bound forms in the materials has always been an interesting question. Heat resistant electrical insulating materials to be studied were selected and specimens conditioned by exposing them to moisture or immersing in water. The materials chosen were the following high polymeric films: Aramid, polyamide, biaxially oriented polyethylene terephthalate (PET), and biaxially-oriented polyethylene naphthalate (PEN); and an aromatic polyamide (Aramid) paper.