Page 149 - Handbook of Surface Improvement and Modification

144 Water Repelling (Hydrophobization)

prepared by anchoring sol-gel
derived silica nanoparticles onto
alkali-treated polyester fabric sur-
faces and subsequently hydropho-
bilized with poly(isobutyl
methacrylate-co-3-methacryloxy-
propyltrimethoxysilane). 16 A n
excellent water-repellency was
obtained with water contact angle
o
of 154 and the sliding angle of
o 16
5 . Figure 9.8 shows anti-stain
properties of hydrophobized fab-
16
ric.
Highly hydrophobic cotton
fabrics were produced by modifi-
cation with bifunctional fluori-
nated silsesquioxanes in the sol-
17
gel process. The modifications
resulted in superhydrophobic
Figure 9.8. The anti-stain property of hydrophobized fabric surface.
[Adapted, by permission, from Shen, K; Yu, M; Li, Q; Sun, W; properties (contact angle of
o 17
Zhang, X; Quan, M; Liu, Z; Shi, S; Gong, Y, Appl. Surf. Sci., 426, 151 ). The textiles remained
694-703, 2017.]
hydrophobic after multiple wash-
17
ing process. Octaanions of silsesquioxane skeletons (cages) bind easily to both fibers
and functionalized silsesquioxane because of a considerable compatibility of the two
17
materials. This results in an increase of surface roughness and creation of a tight layer on
the fiber surface which enables a better exposure of fluoroalkyl groups on silsesquiox-
17
anes.
The mechanically durable superamphiphobic surfaces can be obtained via synergis-
18
tic hydrophobization and fluorination. Superhydrophobic poly(ethylene terephthalate)
fabrics were fabricated by one-pot in situ Stöber reaction of tetraethylorthosilicate and
dodecyltrimethoxysilane, in which the as-formed silica particles roughened the fiber sur-
18
faces and the hydrolyzed dodecyltrimethoxysilane hydrophobized the fabrics. The supe-
rhydrophobic fabrics were converted into superamphiphobic after modification with
o 18
perfluorodecyltrichlorosilane (water and oil contact angles higher than 150 ). The syner-
gistic hydrophobization of dodecyltrimethoxysilane, perfluorodecyltrichlorosilane and
polydimethylsiloxane made the roughened fabrics easy to be superamphiphobic using
18
very low concentration of perfluorodecyltrichlorosilane. The pristine PET fabrics have a
woven structure (Figure 9.9a) consisting of twisted yarns with microscale smooth and
18
round fibers (Figure 9.9b). After the Stöber treatment, the surface of PET fibers was cov-
ered with a layer of silica nanoparticles as well as their aggregates as shown in Figure
9.9c,d, making the fibrous materials with typical micro-nano hierarchical roughness which
18
was beneficial for superhydrophobicity or superamphiphobicity. The modification with
perfluorodecyltrichlorosilane and polydimethylsiloxane did not cause great changes in the
18
roughening morphology of fibers (Figure 9.9e,f). The wettability examination showed
that the contact angle for water on the perfluorodecyltrichlorosilane modified fabric was