Environmental Engineering Reference
In-Depth Information
investigated the effect of black and white substrata on settlement. Both Ulva sp ., and
Spirorbis sp ., showed high settlement on black surfaces. Robson and co-workers [57]
suggested that the complex effect of colour on settlement of barnacles may be because
of the physico-chemical surface characteristics of the different pigments.
2.4.2 Effect of Fouling on Polymers
Microorganisms can damage the structure, integrity and function of polymers.
The changes may be physical, structural or chemical in nature. The main damage
comprises of:
(i)
Biological coating camoulaging surface properties,
(ii)
Discharge of additives and monomers that are eventually used as nutrients by
biofoulers,
(iii) Production of metabolites,
(iv) Enzymic degradation,
(v)
Physical penetration and disruption,
(vi) Accumulation of water leading to swelling, and
(vii) Secretion of pigments [58, 59].
It has been suggested that biodeterioration of PU polymers, occurs through enzymic
action of hydrolases, such as ureases, proteases, and esterases [59]. PU are products
of a polyol either from polyester or polyether and a di-isocyanate or a polyisocyanate.
Ocean currents and loating debris interact synergistically with the foulants to affect
the substrate.
Formation of conditioning ilms on polymer or solid surfaces is the irst step in
biofouling. A number of studies have indicated that conditioning ilms can change
the physicochemical properties of the polymer. Conditioning ilms change the surface
free energies of the substratum (γS) and of the adsorbing particle (γP) and therefore
indirectly inluence all the three thermodynamic parameters, namely the solid-particles
(γSP), the solid-liquid (γSL) and the particle-liquid (γPL) interfacial free energies.
These parameters are required for the calculation of the free energy of adhesion to a
substratum (Δ F adh), given by Equation 2.4 :
Δ F adh = γ SP - γ SL - γ PL
(2.4)
 
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