A triboelectric series orders a set of materials by the sign of the charge of each material when one is rubbed against the other. This can be done for toners by placing two toners of interest in a small vial, mixing them vigorously, and then sampling the mixture in a charge spectrograph. Almost invariably the toners charge against one another, and some separation is observed in the charge spectra. If the toners differ only in pigment, the relative charge of the toners should indicate the relative charge of the pigments. This has been done for a set of typical pigments melt blended into a polyester resin. Mixing all possible combinations of two toners leads to a self consistent ordering of the pigments. When the process is repeated after a silica surface additive has been blended onto the individual toners, a self consistent triboelectric series can again be generated; however, the ordering is different from that generated from the unblended toners. Ordering the toners by the charge level generated when each is mixed with a polymethylmethacrylate coated carrier generates yet another ordering of the pigments. Possible reasons for the variation in triboelectric ordering will be discussed.
Paul C. Julien, "The Use of Toner-Toner Charge Spectra to Generate a Pigment Triboelectric Series" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP16), 2000, pp 588 - 590, https://doi.org/10.2352/ISSN.2169-4451.2000.16.1.art00043_2