High-Breakdown, Thermally Stable Ceramic Fiber–Reinforced Aramid/Polyphenylene Sulfide Composite Papers for High-Power Electrical Applications

The inherent porous defects in aramid insulating paper significantly compromise its insulation performance and thermal stability under high electric field strength and high-power-density operating conditions. In this study, two types of low-cost and readily available ceramic fibers were separately incorporated into aramid chopped fibers (ACFs)/poly(phenylene sulfide) (PPS) composite paper. The high-aspect-ratio ceramic fibers formed an intricate interwoven network within the composite, substantially reducing the porosity while reinforcing weak regions prone to electrical breakdown. At the same time, this dense fibrous architecture improved the mechanical properties through enhanced fiber interlocking. Test results show that, while maintaining improved mechanical properties, the ACFs/PPS composite papers incorporating mullite fibers and kyanite fibers exhibit breakdown strengths of 54.5 and 44.1 kV/mm, corresponding to 124 and 81% improvements over commercial aramid paper, respectively. Furthermore, the thermal endurance indices of these composite papers are 260.8 and 260.6 °C, substantially exceeding the 238.5 °C of commercial aramid paper, thereby demonstrating outstanding thermal resistance. After exposure to 200 °C and ultraviolet irradiation, the fabricated composite papers exhibited significantly less degradation than commercial aramid paper, confirming their exceptional structural stability in extreme environments.