Charging agent

DIELECTRIC PROPERTY OF NON-AQUEOUS SYSTEMS WITH CHARGING AGENT 

---

In dry coating processes the frit is ground dry with or without additives to the required fineness. For powder coating no further additives are necessary. Powders for electrostatic coating have to be hydrophobized to adjust the specific resistivity of the powder surface to lO to 10 Clem. This is achieved by adding charging agents to the mill. Special silicones are especially suitable therefor. 

Figure 4 Schematic illustration of how a particle is charged in the presence of an amphoteric (and zwitterionic) charging agent.

Figure 14 Commonly used charging agents or dispersants in nonaqueous system.

Since most ER suspensions don t contain the charging agent, the electrode polarization can be ruled out as contributing to the ER effect. The next question that arises is whether the Debye or the interfacial polarization would control the ER effect or if they would jointly control the ER effect. As is known, the Debye polarization is generated due to the dipole orientation in an electric field. For most solid materials, the dipole is almost unable to reorient because the solidification usually fixes the molecule with such rigidity in the solid lattice that there is little or no orientation of the dipoles even in an extremely strong electric field [34]. If the ER effect stems from the polarization of the solid particulate material, it seems unlikely that the Debye polarization would make any contribution, and the interfacial polarization will probably be responsible for the effect. Hao experimentally clarified this issue by measuring the ER response time [26] and temperature dependence of the dielectric property 35, as the ER response time and the... 

Considering that most ER suspensions arc non-aqueous systems that do not contain any charging agent, the contribution from the electrode polarization could be negligible, too. Eq. (47) can be further simplified as ... 

---