Characterization of surface free energies of talc powders using the thin layer wicking technique

Thin layer wicking technique was used to determine the contact angles (Θ) of different liquids on powdered talc samples. The measured contact angles were used to calculate the surface free energies (γ _S) of talc and its components, which included dispersion (γ _S ^AB), acidic (γ _S ^d), basic (γ _S ⁺), and acid-base (γ _S ^AB) surface free energies, using the van Oss-Chaudhury-Good (OCG) equation. The surface free energy characterization was conducted on both the basal and edge surfaces. The results showed that talc is a low surface energy solid, and that its basal surfaces are basic, while its edge surfaces are acidic. It has also been found that the hydrophobicity of talc increases with decreasing particle size, indicating that fracture occurs preferentially along the basal surface of talc. As the particle size is reduced beyond a certain limit, however, talc becomes increasingly hydrophilic, indicating that talc begins to fracture along the edge surfaces, thereby exposing more hydrophilic surfaces.