Wettttabiilliitty off Siilliica Gell Powder

1 E E E f f f f f f e e e c c c t t t o o o f f f M M M e e e c c c h h h a a a n n n i i i c c c a a a l l l d d d r r r y y y C C C o o o a a a t t t i i i n n n g g g o o o n n n t t t h h h e e e F F F l l l o o o w w w a a a b b b i i i l l l i i i t t t y y y a a a n n n d d d t t t h h h e e e W W W e e e t t t t t t a a a b b b i Abstract Dry particle coating has been used to create new-generation materials by combining different powders exhibiting different physical and/or chemical properties. Particles with relatively large particle size (host particles, 1-500 µm) can be mechanically coated with fine particles (guest particles, 0,1-50 µm) in order to create new functionality or to improve their initial characteristics. In this study the dry coating experiments were performed with two different mixing processes using Hybridizer (Nara) and Cyclomix (Hosokawa). Silica gel particles (d 50 = 55 µm) were coated with fine particles of magnesium stearate (d 50 = 4,6 µm) at two different mass ratios of magnesium stearate, 5% and 15%. Several methods of characterization were used to study the effect of dry coating on the flowability and the wettability of silica gel powder. The uncoated and coated silica gel particles were observed by environmental scanning electron microscopy (ESEM). The images showed that a more uniform coating was obtained in the case of Hybridizer. The flowability of the different samples obtained with Hybridizer and Cyclomix was characterized by measurements of the tapped and aerated densities. It has been shown that the flowability of silica gel treated in Hybridizer was not significantly affected whereas the flowability was reduced after treatment in the Cyclomix. The wettability of silica gel powder was determined by measurements of the contact angle between the water drop and the powder bed prepared …