Triboelectric series and charging properties of plastics using the designed vertical-reciprocation charger

A triboelectrostatic separation system consists of a tribo-charging of materials and a separation of the charged materials in an electric field. Selective charging and optimum charge density (charge-to-mass ratio: nC/g) of materials in tribo-charging are the most important parameters for separation efficiency. In this study, a new tribo-charger set was made by combining a vertical reciprocator and various charger materials, and then the triboelectric series and charging properties of the plastics was estimated. The charge density of particles was confirmed to depend on the relative humidity (<30%), the frequency (>250 Hz) and the retention time (>300s) in the vertical-reciprocation charger. In addition, the charge density of mixed samples (PMMA: PVC = 1:1) was experimentally validated to be higher than that of a single sample, because of contacting or colliding in combination with particle–particle and particle–charger surface. Triboelectric series and charging properties of plastics can be used to predict material separation for the recycling of waste plastic in triboelectrostatic separation.