The separation of mixed plastics using a dry, triboelectric technique

A technique for the dry separation of mixed plastics has been developed. The process involves triboelectrically charging polymer particles by friction on the wall of an air-cyclone, followed by differential deflection in an electrostatic field. The effect of ambient relative humidity on the charge acquired by five commercial polymers has been investigated leading to the separation of a nylon-66 from artificial mixtures containing a polymethylmethacrylate, two kinds of polyethylene and polyvinylchloride (PVC) at room relative humidities and temperatures. Products with a purity above 96% have been achieved with recoveries ranging from 60 to 70%. Recoveries could be increased to about 90% on repassing the material through the apparatus. Such a dry separation process may find application in plastics recycling and recovery.