The separation of post-consumer plastics of different polymeric compositions is becoming an important topic for the reduction of waste and promotion of recycling. The comminution of plastics creates variable particle shapes which cause difficulties in the separation by a cyclone. To study the influence of particle shape, tests have been performed to determine how the partition curve changes with particle shape in cylindrical cyclones. The test results give a complete picture on the influence of particle shape and size on the cut density d(50) and the probable error E-p. Coupled with a mathematical description of the partition curve, these parameters can assist in process simulation, selection and design of dense medium separation (DMS) systems devoted to plastic recycling. (C) 2000