I. Introduction
Nowadays, polypropylene (PP) nonwovens are used in many fields: energy [1, 2]., packaging, medicine and aviation industries. By using polyimide (PI), the application area of nonwovens can be extended due to its cryogenic and high temperature resistance. This paper presents the results of studying the electrical properties and the stability of the electret state of nonwovens made from «spunbond» PP [3] and PI by electroforming [4]. The electret state in the studied samples was created in corona discharge. The stability of the electret potential difference was studied in isothermal mode and by thermoactivation spectroscopy. Thermostimulated depolarization currents (TSDC) were measured in open circuit. The temperature dependence of conductivity and the value of activation energy were calculated from the TSD currents. It was found that the electret state in PI nonwovens is more stable than that of PP at temperatures up to 130 degrees. Recommendations are given, taking into account the cost of nonwoven materials and their electrophysical properties for their application. It is also worth noting that polyimide nonwoven material is stable up to 200 degrees Celsius, when polypropylene can no longer be used.