Environmental Engineering Reference
In-Depth Information
characteristics, including surface roughness, topography and hydrophobicity have
been investigated for anti-fouling applications. Several surface modiication techniques
have also been developed to improve their properties in order to prevent fouling.
Non-sticking FRC tries to reduce or prevent fouling by providing low surface energy
and an ultra-smooth surface. This reduces the ability of the organism to form a
strong interfacial bond with the surface [2]. These non-sticky surfaces help with the
removal of foulers by shear and tensile stresses and by lowering the thermodynamic
properties of adhesion [52]. Although extensive research has been made in this area,
SPC is more eficient and cheaper, so the development of foul release systems was
initially poor. Fluoropolymer and silicone based polymer coatings are the two systems
used as FRC. The thickness of the silicone and luoropolymer coatings is 150 and
75 µm, respectively [82]. Fluoropolymers are non-porous, low surface-free energy
surfaces with non-stick characteristics. Silicon coatings which lead to weak adhesion
of barnacles, macroalgae and other macrofoulants is a commercial alternative to
biocide-based coatings [9].
A thicker coating is required with the silicone elastomers because less energy is required
to fracture the bond between the foulant and the coating. The release of the attached
organism takes place through a peeling fracture mechanism [52]. PDMS-based FRC
are the most commonly used ones. These coatings have low surface energy, low
roughness, low glass transition temperature and high elastic modulus [2]. However,
the accumulated fouling organisms are not removed easily [66] and recoating is also
dificult.
2.5.3.3 Non-toxic Polymer Surfaces with Anti-fouling Properties
The major approach in developing anti-fouling polymers involves using homogeneous
surfaces, heterogeneous surfaces and three-dimensional (3D) surfaces (
Figure 2.19
).
2.5.3.3.1 Homogeneous Surfaces
Homogeneous surfaces include surfaces that are amphiphilic, hydrophilic or
hydrophobic. The foul release hydrophobic surfaces include luorinated polymer
and PDMS polymer coatings. Polyethylene glycol (PEG) polymers are neutral, water-
soluble hydrophilic polymers with inherent anti-fouling properties. Their hydrophilic
nature and long, lexible chains coordinate with the surrounding water molecules,
thus enhancing their anti-fouling eficacy. PEG based copolymers have low protein
adsorption with a low elastomeric energy [10].
