Particle adsorption in evaporating droplets of polymer latex dispersions on hydrophilic and hydrophobic surfaces |
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Authors: | K Uno K Hayashi T Hayashi K Ito H Kitano |
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Institution: | (1) Sankyo Aluminium Industry Co. Ltd 70 Hayakawa, Takaoka city Toyama 933-8610 Japan, JP;(2) Department of Chemical and Biochemical Engineering Toyama University 3190 Gofuku Toyama 930-8555 Japan, JP |
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Abstract: | Stain patterns formed by drying up of droplets of polymer latex dispersion on hydrophilic and hydrophobic surfaces were examined
in light of the mechanism of particle adsorption in evaporating droplets. On hydrophilic surfaces, the volume of droplets
decreased with time, keeping the initial outline of contact area, and circular stain patterns were formed after the dry-up
of droplets. By the microscopic observation of particles in the droplets, it was found that a large portion of the particles
were forced to adsorb on the outline of the contact area where a microscopic thin water layer was formed because of hydrophilicity
of the surface. On hydrophobic surfaces, on the other hand, the contact area of droplets decreased as evaporation proceeded,
while no particle was adsorbed on the surface at the early stages. The particles in the droplets started to aggregate when
the concentration of particles reached a critical value, and the aggregates adsorbed on the surface forming tiny spots after
the dry-up. Time evolutions of contact angle, contact area and volume of the droplets were analyzed in light of differences
in the adsorption mechanisms between hydrophilic and hydrophobic surfaces.
Received: 14 January 1998 Accepted: 1 May 1998 |
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Keywords: | Contact angle hydrophobicity droplet of latex dispersion adsorption pattern of particles |
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