Improved Plating Adhesion of Polyarylate Fibers via Supercritical CO2 and Impregnation of Slightly Soluble Oil on the Fiber Surface

Abstract

There is a growing demand for conductive fibers with high bending resistance, particularly for applications, such as smart textiles and robot arms. The amount of fiber for such applications can be reduced using high-performance fibers with high tensile properties, such as polyaramid and polyarylate Vectran®). However, because such fibers are crystalline with rigid molecular structures, they poorly adhere to plated films; thus, the plated fibers exhibit poor bending fatigue resistance. To solve this problem, in this study, we expanded polyarylate fiber using supercritical CO2 (ScCO2) and impregnated it with a metal complex (palladium acetate), which acts as a catalyst for electroless plating to induce an anchoring effect. However, because polyarylate fiber has an extremely low polarity, it is difficult to uniformly impregnate it with many metal complexes, even with ScCO2. Generally, an organic solvent is added to tune the polarity of supercritical CO2; however, the metal complex penetrates the fiber, thereby reducing the amount of metal complex near the fiber surface. Therefore, we tuned the polarity of the surface by applying various oils to the fiber surface. The sample electroplated in ScCO2 with oil applied to its surface showed the highest bending fatigue resistance, followed by that treated in ScCO2 without oil, and the sample treated in an aqueous solution showed the lowest. Furthermore, we measured the interfacial adhesion strength of the samples using the microdroplet method, and the same trend was observed.