Method of removal of the plastic insulator from waste cables by passing them between two rotating rolls that have different surface temperatures

Abstract

Recycling of cable waste, especially the complete separation of metal and insulating material for reuse has always been a problem. Especially this problem is relevant for small enterprises because present processes to recover insulating material consists of many stages and requires expensive equipment. The processes usually involve multistage grinding of the cables into smaller pieces and separating them into metal and plastic fractions. The problem can be solved by thermal methods based on the differences in coefficient of thermal expansion of the insulating material and conductor. By one of these methods the cable is passed between two rotating rolls, while surface of the one roll is heated below the melting temperature of thermoplastic insulator, surface of next roll stays cold. Thus the thermoplastic insulator of the cable breaks after the total impact of thermal deformation of insulator and metal conductor and softening of material of the insulator. Conductor remains undamaged and can be re-covered by new plastic insulating material layer. The experimental cable processing machine was designed and produced in the Laboratory of machines and technologies of the Vilnius Gediminas technical university, initial tests were performed. Such machine can be used by small cable manufacturing and waste management companies, electric devices repair and manufacturing workshops. Results of experimental research are presented as optimal peripheral speed of the rolls (or cable speed) versus diameter of the copper and aluminum conductor of the cable, when the temperature of the “hot” roll equals 160°C.