Preparation and Improvement of Thermal Stability and Interfacial Strength of PI / PEEK Composite Film by Atmospheric Pressure Plasma Treatment

ABSTRACT In order to meet the requirements for the use of high‐temperature‐resistant electromagnetic wires, the surface hydrophilicity and surface energy of PI films were improved by plasma modification, and polyether ether ketone (PEEK) emulsion was coated on the surface of PI films. High‐performance PI/PEEK composite films were successfully prepared, and the interfacial strength between the PI film and Cu foil was significantly improved. The effects of sintering temperature on the melt swelling effect of PEEK on the surface of PI films were systematically studied and the optimal sintering process parameters were determined to be 334°C and 20 min. The thermal stability, durability, and interfacial bonding strength of the composite films were thoroughly investigated through thermogravimetric analysis, aging experiments, and interfacial property tests. The results show that the modified composite films have excellent thermal stability at 400°C and remain structurally stable after aging at 350°C for 12 h. Especially after aging treatment at 300°C, the grooves on the surface of the composite film completely disappeared, and the coating showed good swelling characteristics and a significant increase in tensile strength. By optimizing the plasma treatment parameters (800 W, 6 mm/s), the room temperature peel strength of the PI/PEEK composite film reached 9.55 N/cm, which was 77.84% higher than that of the untreated composite film. At the same time, the plasma treatment significantly enhanced the interfacial bond strength between the composite film@Cu up to 5.61 N/cm.