Case Study Paints and Lacquers with Silica Nanoparticles - Safety of Nanomaterials along Their Lifecycle - page 383

detail, but they had nanomaterial characteristics such as high nanoporosity and high
specific surface areas (Edge et al. 2001) or by being described as colloidal silica
(Chmielewska et al. 2006). More detailed information on this type of nanosilica-
based biocidal nanocomposites was found in recent references.
In the first example, silica nanospheres doped (modified) with either 3.5 wt% Ag
or 4.5 wt% Cu nanoparticles were used in silicone acrylic emulsion paint intended
for architectural paints and impregnates (Zielecka et al. 2011). Only 0.5 and 0.1 wt%
of the Cu-doped silica nanoparticles (average dynamic light scattering zeta size =
132 nm) and 0.1 wt% of the Ag-doped silica nanoparticles (average dynamic light
scattering zeta size = 40 nm) were added to the different test paints. In the Ag-doped
nanosilica, the Ag is distributed as a homogeneous coating on the nanosilica sur-
faces. In the case of Cu-doped silica nanoparticles, small metallic Cu nanoparticles
were well-dispersed on the nanosilica surfaces. Cu-doped nanosilica was observed
to have greater antifungal capability than Ag-doped nanosilica, but both types had
highly efficient biocidal behavior.
In the second example, mesoporous microsilica was produced with 3-ioprop-2-
ynyl N -butylcarbamate biocide and used in an experimental water-based wood paint
(Sørensen et al. 2010). The results from this study indicated that the mesoporous
silica was able to prolong the release of the organic biocide. Efficient protection was
achieved at 0.05 wt% 3-ioprop-2-ynyl N -butylcarbamate biocide in the paint cor-
responding to addition of up to ca. 0.08 wt% doped mesoporous silica. At the same
time increased UV resistance was observed. Both observations indicate that addition
of the 3-ioprop-2-ynyl N -butylcarbamate biocide-doped mesoporous silica would
extend the in-service lifetime of the treated wood paint.
17.3 EXPOSURE TO NANOSILICA FROM MN PAINT INGREDIENTS
AND SANDING OF PAINTS AND LACQUERS
The manufacturing of paints and lacquers usually includes handling powders, dis-
persions, and slurries, whereas application of the coatings may be done by, for exam-
ple, brush, roller, dip coating, or spray. The direct risk of inhalation exposure can
generally be considered to be reduced during handling of MN dispersed in liquids
rather than powders. Dermal exposure, however, is expected to be the same as for
conventional paint formulations and dispersed additives. Finishing and renovation
may involve the use of polishing, sanding, and even high-pressure propellants (sand
blasting) of which the latter two processes are known to have high dust emission
potential consisting of paint/lacquer nanocomposite fragments and more or less lib-
erated fillers (Daniels et al. 2001; Koponen et al. 2011; Saber et al. 2012c). Figure 17.1
shows examples of such airborne particles generated during sanding of various paint
and lacquer products.
17.3.1 e xPosure to n anosiliCa in the P aint and l aCquer m anufaCturing
We did not find any published measurements on the occupational exposure to silica
MN in the paint and lacquer industry. One of our own studies submitted for publica-
tion investigates the airborne concentrations and exposure levels to dust at different