The influence of grinding on surface properties of talc

Talc, one of the most important industrial minerals, is commonly used as filler in paint, plastic & cosmetics and also used to give product extra properties due to its soft/plated, hydrophobic structure and high oil adsorption. In this study, effects of dry grinding on surface characteristics(contact angle & free surface energy), oil adsorption, and whiteness of talc were examined. Within this concept, the material was grinded by vibrated ball mill on different time periods(5-150 min.) by fixing the rest grinding parameters(ball charge, diameter of balls, material charge and vibration amplitude). After that, contact angles of each sample were measured in different media(water, formamid, diodomethan and ethylenglicol) with sessile drop method and free surface energies(mJ/m2) were calculated according to Zisman, Fowkes and Acid-Base methods by using measured contact angle data. Moreover, oil adsorption test and whiteness measurement were performed on each sample. According to results, contact angle of raw sample was measured as 63,80 and free surface energy was calculated as 37,37 mJ/m2 with Zisman method. Sudden increase was observed on the contact angle of 15 minutes grinded talc and then contact angle was stable after a slight decrease during longer grinding periods. Grinding period/Free surface energy curves and Grinding period/Contact angle curves of talc were found very similar. However, there were 4% to 25% differences between free surface energy values calculated with different methods(Zisman, Fowkes and Acid-Base). It was also seen that oil adsorption has been increased paralel to surface area increase and whiteness was determined after grinding.