Mechanism of metal removal from metal-coated plastics using pulsed power

Abstract

Recycling of electronic waste (E-waste) is an important subject from the viewpoint of resource conservation and environmental protection. Recently, application of pulsed power technology in the recycling field has attracted considerable attention. We have been investigating metal separation from CD-R as an example of metal-coated plastic, by applying pulsed power with concentric ring electrodes. We visualized discharges with an ultra-high-speed framing camera to clarify the mechanism of metal removal. During the first shot a fan-shape discharge was observed after the breakdown of a protective layer. It expanded until the current reached its peak value, and then gradually disappeared. The protective layer containing a metal layer was separated from the plastic substrate around the fan-shape discharge. Similar discharge pattern continued until the metal layer around the high voltage electrode was completely removed. Afterward, a surface discharge bridged between the high voltage electrode and the remaining metal layer, then continued with a fan shape. A similar discharge pattern lasted until complete removal of the metal layer. Precise observations revealed the characteristics of the fan-shape discharge, which was accompanied by the vaporization of the metal layer. Furthermore, the length and velocity of the discharge propagation were analyzed using an image processing software.