Determination of Contract Angle and Surface Free Energy Components of the Small Particles by Thin-Layer Wicking Technique

Determination of contact angle on surface of magnesium hydroxide particlcs, surface-modified magnesium hydroxide and the surface free energy components of the particles by thin-layer wicking technique is studied. The wicking of magnesium hydroxide plates, in which there is almost no sub-pores, follows typical Washburn equation and consistent surface free energy components, nonpolar and polar, are obtained based on the wicking of different probe liquids. The surface-modified magnesium hydroxide shows lower surface free energy, the spontaneous penetration of many probe liquids used in this paper on the thin-layer plates become impossible, or a contact angle more than 90°appeared. Based on the spontaneous penetration of 1-bromonaphthalene, the nonpolar component of the surface free energy of modified magnesium hydroxide can be obtained, but to obtain the polar component, proper polar probe liquid with lower surface tension has to be found.