Novel high glass transition polyamide-imide: Tg influence on electrical conductivity at high temperature

• Published in: IEEE transactions on dielectrics and electrical insulation Vol. 22; no. 5; pp. 3053 - 3058
• Main Authors: Diaham, S., Locatelli, M.-L
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.10.2015; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Conductivity; Dielectric properties; Dielectrics; Electrical conduction; Glass; High glass transition; PAI; Polyamide-imide; Temperature dependence; Temperature distribution; Temperature measurement
• ISSN: 1070-9878; 1558-4135
• DOI: 10.1109/TDEI.2015.004925

The dielectric properties of a novel high-glass transition polyamide-imide (hT g -PAI, T g =333°C) are investigated for its high temperature use as an insulating material in the range above 250°C in order to extend the limit of conventional PAI (c-PAI, T g =277°C). Four dielectric processes are identified between 50°C and 400°C. Among them, the electrical conduction (σ-conduction) is clearly reduced particularly in the range from 250°C to 320°C, i.e. T g (c-PAI)≤T≤ T g (hTg-PAI). The main reason explaining such an enhancement is the shift of ionic conduction contribution towards higher temperatures in hT g -PAI compared to c-PAI. In hT g -PAI, the higher-T g value allows better controlling the free volume expansion responsible of large ions motions in the bulk. In the range of potential applications (i.e. 250 to 320°C), the σ-conduction of hT g - PAI has an activation energy of 2.3 eV (~221.9 kJ mol-1).