Over and the chemically cross-linked polyvinyl alcohol (PVA) gels

Over time; commercial ships, yachts and all other
floating platforms wet surfaces are covered with weeds, seashells such as
mussels, barnacles. This phenomenon called biofouling. Because of this
phenomenon, a new rough surface structure has been formed. Resulting from this
situation: friction coefficient of the vessel increases whereas maneuverability
decreases. It causes significant increases in the operating costs of the
vessel.1To prevent from that situation with the development of
chemical industry, antifouling paint contains Tributyltin (TBT) started to be
used since the 1960s.2 When the investigations have proven that TBT based
paints cause significant long-term damage to 
marine life, especially marine organisms endocrine system TBT based
antifouling paints has been banned since 1 January 2008 . Therefore, the new
generation antifouling paints containing zinc oxide started to use; which has
similar antifouling performance but has less harmful effect at marine life.3
But because of its harmful and long-standing effects on the marine environment;
the allowed amount of the zinc oxide that passes to water from the paint is
decreased from year to year in many countries. And in near future usage of zinc
oxide at marine paints will be completely banned.4 For this reason, a new
coating material must be developed to protect the wet surface as much as
possible from foreign organisms and keep it in a smooth structure.

There are many studies on antifouling properties of
hydrogels and other substances. On the basis of the idea of using hydrogels as
a new coating material: fouling organisms do not adhere to the skin of other
sea creatures (fish, algae etc.) but they settle down to rocks and similar
seashells and other hard surfaces such as metals. Hydrogels attract attention
with their similarity to the skin of sea creatures. 5 For example, Katsuyama
found that polyelectrolyte hydrogels avoid germination process against algae
zoospores 6. Rasmussen described toxic effects of some natural polymer gels
and the chemically cross-linked polyvinyl alcohol (PVA) gels to barnacle
cypris7. Cao founded resistance of polymer coatings of polysaccharides to the
adhesion of protein, algae, and barnacles 8

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Takayuki Murosaki et.al’s studies, various hydrogels have been investigated as
a surface coating material on the wet surfaces of vessels against fouling
organisms. The study of the laboratory and the field were mostly focused on the
effects on the barnacles. During the investigations, hydrogels with different
active groups having both single network structure and double network structure
were used. Examples are PAAm, PDMAAm, PHEMA, PHEA, PNAAMPS, PAMPS, PNaSS,
PDMAPAAQ, PAAc / PAAm and PAMPS / PAAM hydrogels. It is also used in hydrogels
having active groups -OH, -SO3, NH2, N (CH3) 2, CH3, N (CH3)  In the laboratory tests, test setups were
made by covering the floor with hydrogels such as PAMPS / PAAm in the test
pools produced from polystyrene and  the
settlement activities of the barnacle were observed 5 In the field tests,
PAMPS / PAAm double netted hydrogels and polyethylene plates as a control group
were fixed to the stainless surface and left in the sea. 9 In addition, the
swelling properties and the properties of the pores on the polyacrylamide-dextran
hydrogels were investigated according to the temperature of synthesis. In the
experiments, PAAm / Dx hydrogels were synthesized by crosslinking
copolymerization method at 3 different temperatures (+25, +5, -18). 10 Also
Various double-walled hydrogels (mostly hydrophilic) were obtained. The
strengths of these hydrogels against tensile forces and pressures were
investigated and compared with single-walled hydrogels. In addition, the
resistance of the obtained hydrogels to wear has been investigated. 11

From the experiments about using hydrogels as surface
protection materials showed that hydrogels with hydroxy and sulfonic groups
have been found to be a successful antifouling coating material. It has been
observed that the electric charges of hydrogels have no effect in protecting
the surface from living organisms. The longer the alkaline chain is, the
greater the antifouling effect of the hydrogel is observed. Negative results
were obtained when hydroxides and sulfonic acid groups were used together. 5


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