Importance of Dissociated Ions in Contact Charging

Abstract

Organic salts are known to affect the contact charge developed between two polymers. When ionomers are present, the charge often increases monotonically with the salt concentration and the charge has been ascribed to the transfer of ions. A model is presented which relates the charge with salt concentration in the polymer blend. In this model, only dissociated ions but not ion pair ions are proposed to transfer. The model incorporates ion pair dissociation (Kf) and ion pair aggregation (K) and shows that when ion pair aggregation is minimal, the concentration of dissociated ions scales near linearly with the square root of the concentration of salt in the blend. The linear relationship between the charge and [salt]1/2 is demonstrated. It is further shown that the equilibrated charge which is established is limited by the concentration of dissociated ions on the surface of the polymer and not by the surface provided by the second material. © 1992, American Chemical Society. All rights reserved.