Page 130 - Handbook of Surface Improvement and Modification

8.1 Methods and mechanisms of surface cleaning 125

water treatment, air purification
such as photocatalytic decomposi-
tion of dioxins and VOC, and NO x
8
removal.
Self-cleaning glazing prod-
ucts utilized two technologies
based on photocatalytic hydro-
philic and hydrophobic capabil-
9
ity. The hydrophilic products are
installed on new products whereas
the hydrophobic products have to
9
be applied. The hydrophobic
coatings have life of 3-4 years. 9
Figure 8.3 shows photocatalytic
9
process of self-cleaning. More
Figure 8.5. Values of contact angle of a droplets of water on top of information on this subject can be
9
hydrophobic dyed cotton fabric using different anthraquinone found in the review paper.
dyes. [Adapted, by permission, from Salabert, J; Sebastian, RM; The PDMS/silica nanomate-
Vallribera, A, Chem. Commun., 51, 14251-4, 2015.]
rials improved robustness and
10
stain-resistance of limestone. The sol-gel treatment enhanced the properties of pure
10
limestone. It became hydrophobic, water-repellent, and stain-resistant. The addition of
polydimethylsiloxane to a silica oligomer associated with a neutral catalyst, in the pres-
ence of a surfactant, accelerated the gelling process and permitted to achieve effective
10
stone consolidation. Figure 8.4 shows that surface roughness increased with increased
10
addition of PDMS.
Large adhesion failures and decreased titanium amounts were recorded in durability
11
assessment of sol-gel coating on limestone. High surface roughness accounted for a bet-
ter adhesion of both crack-free and fissured films to the soft limestone, but some erosion
11
of the coated surface, compromised stone preservation. But, good self-cleaning perfor-
11
mance was still provided due to the retention of nanoparticles under the surface.
Anthraquinone reactive dyes were covalently grafted onto cotton fabric surfaces giv-
ing rise to breathable superhydrophobic textiles with self-cleaning properties [Figure
12
8.5]. Better performance has been observed for fabrics stained with polyfluorinated reac-
12
tive dyes.
Polyethylene glycol and vinyltriethoxysilane were used in different proportions to
13
produce a series of copolymers. The obtained surfactants had excellent surface proper-
13
ties, wetting power, and low foaming. Their application made cotton fabrics stain-resis-
13
tant.
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The water- and stain-resistant finishes to apparel have become very popular. In
one-step procedure to form highly hydrophobic surfaces on cotton and polyester fabrics a
modified silica sol was prepared by the reactions of a sol formed by alkaline hydrolysis of
tetraethoxysilane and alkyltrialkoxysilane in ammonia-ethanol solution or by the reactions
of a sol formed by the same method, followed by the addition of (3-glycidyloxypro-
14
pyl)trimethoxysilane and alkyltrialkoxysilanes. The treated cotton and polyester fabrics