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water-soluble section of the SPC polymer self-polishes by sloughing off, exposing a fresh paint
surface (Wells andSytsma 2009).
In general, only 10-20% of the biocide can be bonded to a copolymer, so the remaining biocides
are freely dispersed. The percentage of biocide bonded to a copolymer is not high enough to give
the paints effective antifouling properties. Therefore, the products on the market are usually a
mixture of SPC and free association paints (Watermann et al. 2004). The lifetime of these
coatings depend on its thickness, where thicker coatings tend to last longer. The coatings
gradually slough off every year, but a coating thickness of 375µmmay last 5 years (Brady 2005).
Examples:
A. InternationalMarineCoatings, IntersmoothEcoloflexSPC
Ecoloflex SPC is produced by International Marine Coatings. The self-polishing copolymer
technology is based on an acrylic matrix bearing copper salts of an organic moiety of unknown
composition. The coating has been reported to be active for 3 to 5 years (Yebra et al. 2003).
B. Kansai Paint, Exion
Exion is produced by Kansai Paint. It works through ion exchange, where a zinc-containing
pendant group is released from an acrylic backbone. There was no information about the
performance after a long immersion time (>30 days) (Yebra et al. 2003).
C. Jotun, SeaQuantum
SeaQuantum is produced by Jotun. It is based on silyl acrylate polymers, which control the
release of biocides. Tests of this paint did not show any erosion, but also did not exhibit
satisfactory antifouling properties (Yebra et al. 2003).
5.1.2.2.
Controlled depletion polymers (CDP)/free association paints
In these paints, the biocide is embedded in a soluble matrix. When the paint surface interacts
withwater, the paint dissolves, exposing and releasing the embedded biocides (Watermann et al.
2004,Wells and Sytsma 2009). Thematrix consists of a binder of rosin-derived compounds and
plasticizers or synthetic polymers in which the biocides are dispersed. Rosin is slightly soluble,
making it useful in antifouling paints. The polymers give the matrix mechanical strength and
film forming properties (Watermann et al. 2004).
The rate of dissolution of the binder is critical for the efficacy of this type of antifouling paint.
The soluble matrix facilitates biocide delivery and increases film integrity while it dissolves.
Over time, the biocides and the paint mixturewash away because of interactions with impurities
and inert molecules in the water, resulting in a leached layer. The leached layer reduces the
effectiveness of the paint by inhibiting biocide release which typically limits the lifespan of
CDPs to three years (Watermann et al. 2004).
Examples:
A.MilitaryStandardFormula 121/63
This coating has high loading of cuprous oxide andwater-soluble rosin. It controls biofouling by
continuous contact with copper. This coating is impractical for use in water because its service
life is only one to three years and the potential for copper toxicity in the surrounding
environments (Mussalli 1988).
