Self-healing behaviors of metallized high-temperature dielectric films for capacitor applications

High-temperature metallized film capacitors (MFCs) are urgently desired in harsh application environments. Although there are a large number of research on polymer dielectrics with satisfactory energy storage property and excellent thermal resistance, it is not clear about the self-healing performance which is the key factor determining whether they can be applied in practice. In this paper, the self-healing behaviors of the metallized high-temperature dielectric films of poly (ethylene 2,6-naphthalate) (PEN), poly (ether ketone) (PEEK) and polyimide (PI) have been explored. Specifically, the influence of polymer chemistry, sheet resistance and interlayer pressure on self-healing process is analyzed in detail. It is found that the high carbon content in PI leads to the self-healing failure at low sheet resistance, though it displays small self-healing energy at high sheet resistance. The probability of successful self-healing of the metallized PEEK film is greatly reduced at high interlayer pressure. In addition, high self-healing energy which would lead to the fast ageing of MFC is obtained in PEEK. Fortunately, PEN with relatively low carbon content and the aliphatic-aromatic alternating structure shows brilliant self-healing ability at different sheet resistances and interlayer pressures with reasonable self-healing energy. Hence, PEN may be a promising candidate for high-temperature MFC from the perspective of self-healing.