Preparation and properties of ODPA-ODA-SDA polyimide film and its application in corona resistance

• Published in: Progress in organic coatings Vol. 166; p. 106777
• Main Authors: Lang, Feng, Xiang, Yu, Xiao, Chunguang, Li, Duxin
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.05.2022; Elsevier BV
• Subjects: Aging; Aluminum oxide; Copolyimide; Corona ageing; Diamines; Dielectric loss; Dielectric properties; Electric equipment; Frequency analysis; Frequency spectrum; Insulation; Mechanical properties; Nanocomposites; Nanoparticles; Polyimide resins; Thermal stability; Copolyimide; Corona ageing; Nanocomposites; Dielectric properties
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/j.porgcoat.2022.106777

High-frequency trend of electrical equipment puts forward higher requirements on the dielectric properties of insulating materials, especially under corona ageing environment. Therefore, a facile and effective method for improved corona resistance is essential for the development of high-frequency power systems. In this article, 4,4′-Oxydiphthalic anhydride (ODPA) was chosen as the dianhydride while 4,4′-Diaminodiphenyl ether (ODA) and 4,4′-diaminodiphenyl sulphide (SDA) as diamines. Consequently, thermally imidized ODPA-ODA-SDA copolyimides were synthesized, and the influence of ODPA and SDA on the dielectric properties was discussed. High-frequency corona ageing test was also conducted to investigate the relationship between dielectric properties and the corona resistance. From dielectric frequency spectra analysis, the ODPA-ODA-SDA copolyimide was considered to exhibit the best dielectric properties when SDA accounted for 30% mole fraction of diamine, the dielectric loss of which was 24.03% lower than that of ODPA-ODA at 20 kHz. Meanwhile, the better corona resistance property and mechanical properties were obtained, especially the corona ageing lifetime was 2.26 times higher than that of ODPA-ODA. To further improve the corona resistance property, a series of modified-PI/Al2O3 nanocomposite films based on ODPA-ODA-SDA matrix were prepared by in-situ polymerization. When the content of Al2O3 nanoparticles reached 12 wt%, the thermal stability was improved and the corona ageing lifetime was 6.14 times longer than that of ODPA-ODA. This experiment provides new ideas and directions for reducing mechanical and thermal performance losses as well as achieving high-efficiency corona resistance, which is expected to promote the development of advanced insulating films. •Synthesized copolyimides show better mechanical properties and corona resistance.•The effect of copolyimide dielectric properties on corona resistance is discussed.•The anti-corona mechanism of PI/Al2O3 composite films is proposed.