Effect of Anti-Hydrolysis AlN Microspheres on the Electrical Insulation and Thermal Conductivity of PMIA Paper

Poly-(meta-phenylene isophthal-amide) (PMIA) has been considered as an ideal insulating medium due to its excellent thermal stability and insulative strength. However, the poor thermal conductivity limits its application in complex electro-thermal environments. In this article, AlN microspheres were modified with $\text{H}_{{3}}$ PO4 and Al( $\text{H}_{{2}}$ PO $_{{4}}{)}_{{3}}$ to gain resistance of hydrolysis, and then, p-AlN/PMIA composite paper was prepared with a synergistic enhancement of the insulation and thermal conductivity. The results showed that, after doping with 10wt% of p-AlN, the paper was endowed with the breakdown strength of 35.0 kV/mm, which was 28.2% higher compared to the pure PMIA paper, while the thermal conductivity of PMIA paper was enhanced by only 22.3%. After doping with 40wt% of p-AlN, the thermal conductivity of sample was further improved to 0.277 W/( $\text{m}\cdot \text{K}$ ), which was 168.7% higher than that of pure PMIA paper, while the breakdown strength was maintained at 24.4 kV/mm.