Case Study Paints and Lacquers with Silica Nanoparticles - Safety of Nanomaterials along Their Lifecycle - page 381

the 17 wt% nanosilica. Several advantageous phenomena including reduced total
environmental pollution load, high water and flame resistance, and surface hardness
were observed for the nanocomposite wall paint. The adhesion performance was,
however, lowered, but could be managed by use of appropriate primers. The higher
particle content and lower adhesion could be factors that possibly increase the risk of
exposure during abrasion of such paints.
In a third example, a hybrid material consisting of polystyrene-butyl acrylate-
acrylic acid-grafted silica was made from trimethoxysilane-functionalized fume
silica with an average primary particle size of ca. 25 nm. It was used to form a
nanosilica-doped latex nanocomposite for emulsion-type paints (Zhu et al. 2008).
The addition of 1.5 wt% of the functionalized hybrid silica nanoparticles signifi-
cantly improved the interfacial adhesion properties, UV shielding, water resistance,
and thermoresistance of the latex nanocomposite.
From 1 to 7 wt% of ca. 40 nm-size o -phenylenediamine-coated silica was added
to a nitrocellulose paint intended for corrosion-resistant coating on steel (Hegazy
et al. 2013). The starting material of the silica nanocomposite was not disclosed and
the functionalization was completed as part of the study and included further grind-
ing of the silica. It was found that the protection efficiency of the paint increased
significantly as well as its adhesion to the steel surface increased with an increase in
content of SiO 2 / o -phenylenediamine.
For application in both paints and lacquers, Bindzil ® CC30 (Akzo Nobel
Chemicals), NANOCRYL ® XP 21/0768, and Axilat™ Ultrafine LS5000 (Hexion
Specialty Chemicals B.V.) are examples of industrial products used in the Danish
NanoKem study (Mikkelsen et al. 2013; Saber et al. 2012a). Bindzil CC30 is a
7 nm-size organo-modified colloidal nanosilica (Figure 17.1a) intended for improv-
ing the hardness, adhesion, abrasive resistance, drying time, and sanding proper-
ties of latex coatings and water-based lacquers. In the work of Saber et al. (2012c),
11.63 wt% of the Bindzil CC30 was introduced into an experimental acrylic paint
produced by the Danish Coatings and Adhesives Association. NANOCRYL XP
21/0768 (HanseChemie; now EvonikHanse GmbH with trade name NANOCRYL
A 210) is a product belonging to a series of nanoparticle-modified acrylate mono-
mers. The NANOCRYL XP 21/0768 contains 50 wt% of 20 nm-size nanosilica
particles dispersed in 50 wt% 1,6-hexanediol diacrylate and is used a.o. for forma-
tion of transparent tear and abrasion resistant coatings (epoxy paints, lacquers, gel
coat formulations, and styrene-free vinyl ester resin systems) and stereolithography
formulations (Evonik, 2008). In the NanoKem study, ca. 5 wt% of the products
was applied in a nanosilica-enhanced UV-hard coat lacquer (Saber et al. 2012c).
Axilat Ultrafine LS5000 is an acrylate-modified colloidal nanosilica product with a
reported particle size smaller than 50 nm. Diluted in water, the hydrodynamic size
was 6.5 nm as determined by dynamic light scattering. Axilat Ultrafine LS5000 is
intended for latex-based coatings and water-based lacquers and improves impregna-
tion of the substrate, adhesion, and translucence of primers and paints. In the work of
Saber et al. (2012c), 28.5 wt% of the Axilat was used in a binder, also produced by
the Danish Coatings and Adhesives Association. In all cases, the formulations were
made for testing the potential hazards of paint- and lacquer-relevant nanomaterials
and sanding dust from surface coatings.