Fabrication of conductive soybean protein fiber for electromagnetic interference shielding through electroless copper plating

We report on a simple but efficient strategy for the preparation of conductive soybean protein fiber (SBPF) by electroless copper plating method. The proposed method mainly composed of three procedures, namely, 3-aminopropyltrimethoxysilane (APTMS) modification, Cu⁰-seeding and Cu-coating deposition. Specifically, Cu⁰ activation procedure could be divided into two stages: Cu²⁺-absorption in cupric citrate solution and the subsequent in situ reduction to Cu⁰ with sodium borohydride. The elemental analysis of the samples in each step was carried out by using XPS measurement. In addition, the resultant SBPF-based Cu coating was subject to detailed analysis by SEM. It was found that a layer of fine Cu particles evenly distributed on the fiber surface with uniform grains and there were no obvious structural damages after the ultrasonic washing test. In contrast, the Cu coating obtained in absence of APTMS modification suffered a delamination, which confirmed the necessity of chemical modification on SBPF. Moreover, the resultant conductive soybean protein fibers were woven into plain weave in a single cylinder handloom, then corresponding shielding effectiveness values were measured by using a spectrum analyzer at frequency range of 30–1000 MHz.