1997 Volume 117 Issue 12 Pages 1449-1454
A mixture of plastic pellets or wasted plastic pieces are electrostatically separated. The mixture is charged by friction in a mixer and falls through horizontal electric field of 4kV/cm into three zones under the field. A mixture of two kinds of plastic pellets is separated with purity not less than 90%. A mixture of three kinds of pellets is separated to some extent in the zones at the extreme ends, in the first separation, according to locations of different kinds of pellets in the tribo-lectric charging sequence. This mixture will be separated in successive separations following the first one into respective pellets. A mixer made of a suitable plastic material and adapted to enhance the friction between different kinds of pellets makes easy and reliable the separation. Proper mixing time and high rotational speed of the mixer and low humidity increase the purity of separated pellets. Since the effect of blended additives of pellets on charging characteristics appears with good reproducibility, pellets and wasted plastics with such additives may be successively separated as well into respective plastics.