As can be seen in Figure 9 biocides are very effective to suppress growth of organisms - no fouling is found in the left image
using the novel biocide in a marine paint. On the other hand not
using a biocide leads to the colonization of among other things
barnacles. It must be kept in mind that fouling and barnacles can
severely increase the cost and environmental impact for shipping
in terms of increased fuel consumption.
One major drawback with new molecules is a costly procedure for testing that must be conducted before application in Europe. Hence it might be of interest to use existing molecules in
smarter ways. At YKI, the Institute for Surface Chemistry a large
research effort is performed in order to control the release rate of
actives in various industrial areas. One example of a carrier/host
of actives such as biocides is the use of mesoporous particles. The
particles have a well-defined pore size that can be precisely controlled in the region 2-15 nm. Figure 10 shows transmission electron microscope (TEM) images of mesoporous particles produced
in a spray reactor at YKI. These particles can be loaded with actives that are released over longer periods of time.
different molds (Aspergillus Niger, Cladosporium sphaerospher-mum and Penicillium funiculosum). Figures 11-13 show the results of these experiments, showing a newly painted sample and
to the left a sample subjected to two weathering cycles.
As expected the paint with no biocide cannot withstand mold
growth even on a freshly painted surface. The state-of-the-art
formulation loses quickly its performance - probably due to too
fast leakage of the biocide from the paint. The paint with the biocide encapsulated in coated mesoporous particles show perfect
performance after two weathering cycles. The result indicates
that a slower release rate of the biocide into the coating can enhance the durability of paint against mold growth.
Concluding remarks
In a series of experiments we could correlate dirt pick-up with
surface hardness and tackiness. A silica particle-induced toughening of the paint surface showed decreased dirt pick-up in
three out of four commercial coatings and is thus seen as a
promising approach.
To meet new and/or upcoming legal restrictions on available
biocides to fight bio-fouling, we have successfully shown that
meso-porous silica particles can improve the long term performance of alternative biocide formulations. CW
Figure 10: TEM images of an uncoated mesoporous silica parti- cle (left) and a coated (9nm thick film) silica particle (right).
To evaluate the possibility to use those particles for sustained
release of biocides in coatings, we loaded encapsulated meso-porous particles with the commercially available biocide OIT.
Exterior acrylic emulsion paints were prepared from these particles and compared to standard formulations including OIT and
a reference formulation without the biocide. The paints were applied on filter paper and subjected to two weathering cycles in a
weatherometer. The coated filter paper samples were placed in
Petri dishes containing agar and tested against growth of three
Jens Voepel is project manager for polymeric materials and polymer synthesis at YKI, the Institute for Surface Chemistry in
Stockholm, Sweden. Jens holds has a PhD in Polymer Technology from the Royal Institute of Technology (KTH) in Stockholm
(June 2011) and a Bachelor of Science in Chemistry and Materials Science from The University of Applied Science in Rheinbach,
Germany. Jens joined YKI in March 2011 and is gaining experience with project related to coatings, controlled delivery and
pigments. He can be contacted at Jens.Voepel@yki.se.
Anders Larsson is responsible for Business Development of
Advance Materials and Area Manager Coatings at YKI, the Institute for Surface Chemistry in Stockholm, Sweden. Anders has
a PhD in Physical Chemistry from Gothenburg University (GU)
in Gothenburg (1999). After doing his postdoctoral studies at
the Max Planck Institute for Colloids and Interfaces (Germany)
he joined YKI during year 2000. He has led several projects related to coatings such as film formation studies, development of
cleaner surfaces, controlled delivery of biocides and much more.
He can be contacted at Anders.Larsson@yki.se.
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