AN ION TRANSFER MODEL FOR CONTACT CHARGING

The contact charge between a polymer containing ions and another polym er or metal is known to be affected by the type and concentration of t he ions in the sample. A model is presented to describe the observed c ontact charge. The model is based on the transfer of ions between the two surfaces and is for the case where one of the materials contains a known concentration of ions provided by either a molecular salt or an ionomer. The model considers that the sign and the magnitude of the c harge will depend on the ion content in the surface region of the poly mer, the relative mobilities of the two ions in the salt, and the rela tive stabilities of the two ions on each of the two surfaces in contac t. The model considers both the case where the charge is activated by many contacts, for example, roll-mixing an ion-containing polymeric po wder with beads of a different chemical composition, and the case wher e the charge is activated by single contacts as with two surfaces, pla nar or curved. From this model the relationships between charge and th e physical characteristics of the powder/bead mix, such as, the weight ratios and the size of the particles and beads, are derived. This rel ationship parallels those derived from the electron transfer model.