(412e) Superhydrophobic Surfaces Produced by Supercritical Fluid Technology

Supercritical carbon dioxide (scCO2) is a
non-toxic, easily recyclable fluid of low environmental impact. Superhydrophobic
self-cleaning surfaces have been produced by dissolving hydrophobic compounds
in scCO2, followed by spraying the solution through a pressure nozzle employing
the rapid expansion of supercritical solution (RESS) technique [1-3]. Research
has been conducted on the effect of different pre-expansion pressure and
temperature as well as distance between the nozzle and the treated surface,
with regard to particle morphology and size distribution. Laser diffraction
measurements have been conducted directly perpendicularly to the spraying cone from the
RESS system, providing information about the particle size distribution as a
function of spraying distance. Larger particles/agglomerates (10 – 25 mm) were produced at larger spraying
distance, whereas smaller particles (ca. 3 mm) more homogeneously covering the
surface were formed at shorter distance. Finally, results regarding solubility
determination of waxes and polymers in scCO2 will be described in the
presentation, as well as some alternative supercritical fluid techniques for producing
superhydrophobic surfaces.

1.     C. Quan,
O. Werner, L. Wagberg and C. Turner, Generation of superhydrophobic paper
surfaces by a rapidly expanding supercritical carbon dioxide-alkyl ketene dimer
solution, J. Supercrit. Fluids, 2009 (49) 117-124.

2.     O.
Werner, C. Quan, C. Turner, B. Pettersson, L. Wagberg, Properties of
superhydrophobic paper treated with rapid expansion of supercritical CO2
containing a crystallizing wax, Cellulose, 2010 (17) 187-198.

3.     International
patent application, WO 2009/0054465, O. Werner, C. Quan, C. Turner, L. Wagberg
and J.-C. Eriksson, "Method to prepare
superhydrophobic surfaces on solid bodies by rapid expansion solutions".