Study of hydrophobic-hydrophilic properties of high dispersed materials

Differential thermal effects of immersion of silica in water and decane vs time

An important characteristic of highly disperse materials is the ability to interact with water that allows one to distinguish hydrophilic and hydrophobic surfaces. The interaction with water plays an important role in many industrial processes, forecasting physical and chemical effects and in the final performance characteristics of the materials. For films and flat surfaces, the hydrophobicity is determined by  the water contact angle, but for powders a method of measurement of heats of immersion in polar and nonpolar liquids (e.g. water and n-decane) is more reliable, since the ratio of the corresponding heats of immersion gives the hydrophilicity index.

The studies of the hydrophobic -hydrophilic properties of highly disperse materials and evaluation of the hydrophilicity index can be carried out in a lab by measuring the heats of immersion of powders in water and decane using a Calvet microcalorimeter.

Study of  immersion heats

To study the heat of immersion, a sample is placed in a vial with a  thin curved tip, degassed at 150-200 °C to remove adsorbed moisture, and then the ampoule is sealed. It is placed in a calorimeter cell with a liquid. To interact with the liquid the vial tip is broken by pressing. The thermal effect of the interaction is recorded as an exothermic peak, integration of which allows estimating the heat of immersion.

Provider: Chuiko Institute of Surface Chemistry (CISC) of National Academy of Sciences of Ukraine

Kyiv, Ukraine: Tel.: + 38 (044) 422 96 43; Fax: 38 (044) 424 35 67; e-mail: [email protected]