Marine biofouling is the accumulation of organisms onto surfaces immersed
in sea water. Fouling of ships causes an increase in hydrodynamic drag which
leads to performance issues such as increased fuel consumption and a reduced
top operating speed. Fouling-release (FR) coatings are one way that paints have
been used in combating biofouling by allowing for the easy removal of settled
organisms. Traditional FR coatings are silicone elastomers which are soft, easily
damaged, and require a tie coat for adhesion to marine primers. Siloxanepolyurethane
FR coatings have shown promise as FR coatings, providing
enhanced durability and toughness, better adhesion to marine primers, and
comparable FR performance to commercial coatings. Preliminary studies were conducted to explore the use of PDMS macromers
in the preparation of siloxane-polyurethane FR coatings. Attachment and removal
of fouling organisms on the siloxane-polyurethane coatings based on PDMS
macromers was comparable to commercial FR coatings. Extended water aging
was also carried out to determine effects of extended water immersion on the
fouling-release performance of the coatings. At up to four weeks of aging, the FR
performance of the coatings was not affected. Static immersion marine field testing was performed to determine the
fouling-release performance of siloxane-polyurethane coatings prepared with
PDMS macromers. The performance was found to be comparable to commercial FR coatings for up to one year, including water jet removal of slimes, barnacle
push-off removal, and soft sponging. The coatings showed good fouling-release
performance until extremely heavy fouling was allowed to settle.
Underwater hull cleaning was conducted for one siloxane-polyurethane
composition identified as a top performer from static field testing. The coating was
easily cleaned of fouling with rotating brushes for six months. The cleaning
capability of the coating was reduced when large barnacles and other extremely
heavy fouling was present. A commercial FR coating became heavily damaged
with brush cleaning while the siloxane-polyurethane coating remained mostly
undamaged. With more frequent cleaning, it is suspected that siloxanepolyurethane
coatings would show cleaning capability for longer periods of time.
Pigmentation of siloxane-polyurethane coatings based on difunctional
PDMS and PDMS macromers was explored to investigate the effect on FR
performance. Pigmentation with titanium dioxide caused a slight decrease in FR
performance in some cases, but this was easily overcome by the addition of
slightly more PDMS in the coating binder, thus illustrating the feasibility of
siloxane-polyurethane coatings as effective, pigmented FR coatings.
Finally, the exploration of unique PDMS polymer architectures has been
explored for the development of additional, novel, fouling-release coatings. The
incorporation of end-functional PDMS homopolymer molecular brushes and
branched PDMS macromers into siloxane-polyurethane fouling-release coatings
shows promise for the development of unique coatings where improved FR
performance may be obtained. / Office of Naval Research (U.S.)
| Identifer | oai:union.ndltd.org:ndsu.edu/oai:library.ndsu.edu:10365/29313 |
| Date | January 2011 |
| Creators | Sommer, Stacy Ann |
| Publisher | North Dakota State University |
| Source Sets | North Dakota State University |
| Detected Language | English |
| Type | text/dissertation |
| Format | application/pdf |
| Rights | NDSU Policy 190.6.2 |
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