SURFACE MODIFICATION AND CHARACTERIZATION OF PARTICULATE MINERAL FILLERS

The efficacy of the surface treatment of particulate fillers depends on the chemical character of the components, on the method and conditions of the treatment, and on the amount of treating agent. To achieve maximum efficacy the coupling agent must be chosen specifically for each polymer/filler pair. Because of its ionic character CaCO3 can be effectively treated with stearic acid, which forms a basic salt on the filler surface. One stearic acid molecule is attached to each Ca2+ ion and in the complete monolayer the molecules are vertically oriented to the surface. Maximum efficacy is expected at the monomolecular coverage of the surface, but the methods utilized to determine this concentration yielded different results. Stearic acid surface treatment of CaCO3 decreases its surface tension and the effect is more pronounced on the polar than on the dispersion component. The change in the surface characteristics of the filler influences also the properties of the composites in which they are used. © 1990.