Fouling Release Research Articles

Structure–property correlations of foul release coatings based on low hard segment content poly(dimethylsiloxane–urethane–urea)

We report the foul release characteristics of model poly(dimethylsiloxane–urethane–urea) (PDMSPU)-based coatings with a relatively lower hard segment content of 9 to 13.7 wt%. The PDMSPUs were prepared by facile moisture curing of isophorone diisocyanate-capped hydroxyalkyl-terminated PDMS. The surface free energies of the coatings were tuned (20–25 mJ/m2) by varying the hard segment content to be in the minimum adhesive regime (20–30 mJ/m2) of Baier’s curve pertaining to the relative amount of biofouling vs the critical surface tension of various chemical substrates. A series of complimentary analytical tools, namely 1H NMR spectroscopy, small-angle x-ray scattering (SAXS), FTIR-attenuated total reflectance spectroscopy (FTIR-ATR), contact angle goniometry, marine field tests, and quantitative biofouling adhesion in shear, have been employed to deduce several physicochemical parameters of importance to establish the structure property correlations. Further, the time-dependant changes in surface wettability and surface concentration of polar functional groups of the coatings (immersed in 3.5 wt% aqueous solution of NaCl) were investigated by FTIR-ATR and contact angle goniometry. The extent of surface restructuring was found to increase with increasing hard segment content of the PDMSPUs and consequently increasing attachment strengths of macrofoulants with the coatings, which were in the range 0.12–0.5 MPa.

Increasing Operational Efficiency of High Speed Ro-Ro Vessels Via New Hull Coating Technologies

In maritime economics, ships' fuel consumption accounts for the important part of operational expenses and it is straight forward that every ship owner would aim to run their fleet as optimum as possible in terms of fuel efficiency. IMO has developed the Energy Efficiency Operational Indicator (EEOI) that provides information concerning the efficiency of the ships in operation where fuel consumption is the main criteria for the calculation. The reduction of fuel consumption through decreased frictional resistance of hull is one of the most known method in maritime industry to increase operational efficiency of ships. Ship operators are generally making their decisions according to real-life experiences. It is clear that literature needs further studies regarding hull performances with the real-life data even if there will be higher uncertainties compared to laboratory test results. The purpose of this study is to review results of new hull coating technologies for high speed RO-RO vessels and analyze the potentials to decrease fuel consumption as well as speed loss. Actual field data of 8 high speed RO-RO vessels has been studied according to new standard ISO 19030 - Ships and marine technology, Measurement of changes in hull and propeller performance. Results indicate the importance of full blasting for hull performance and a significant fuel savings through decreased speed loss via new technology foul release silicone coatings.

Amphiphilic icephobic coatings

Abstract A series of amphiphilic siloxane polyurethane (AmSiPU) coatings were investigated for their icephobic properties. The use of coatings having amphiphilic surfaces for anti-icing applications has not been studied to a large extent although these types of coatings have more recently been studied for anti-fouling (AF)/foul release (FR) applications. Several polyurethane based amphiphilic coatings were prepared having variations in the composition as well as molecular weight of hydrophobic polydimethyl siloxane (PDMS), and hydrophilic polyethylene glycol (PEG). Surface characterizations of the coatings revealed the presence of both PDMS and PEG moieties, implying amphiphilic surface characteristics. The icephobic properties of these coatings were evaluated to investigate if amphiphilic formulations can deter ice adhesion. Water absorption and barrier behaviors of these coatings and their correlation to anti-icing properties were also studied.

Microfluidic accumulation assay probes attachment of biofilm forming diatom cells

Testing of fouling release (FR) technologies is of great relevance for discovery of the next generation of protective marine coatings. In this paper, an accumulation assay to test diatom interaction under laminar flow with the model organism Navicula perminuta is introduced. Using time lapse microscopy with large area sampling allows determination of the accumulation kinetics of the diatom on three model surfaces with different surface properties at different wall shear stresses. The hydrodynamic conditions within the flow cell are described and a suitable shear stress range to perform accumulation experiments is identified at which statistically significant discrimination of surfaces is possible. The observed trends compare well to published adhesion preferences of N. perminuta. Also, previously determined trends of critical wall shear stresses required for cell removal from the same set of functionalized interfaces shows consistent trends. Initial attachment mediated by extracellular polymeric substances (EPS) present outside the diatoms leads to the conclusion that the FR potential of the tested coating candidates can be deducted from dynamic accumulation experiments under well-defined hydrodynamic conditions. As well as testing new coating candidates for their FR properties, monitoring of the adhesion process under flow provides additional information on the mechanism and geometry of attachment and the population kinetics.

Study of Tris-trimethylsilypropylcontaining Methacrylate Copolymers for Fouling Release Coating Applications

One environmentally friendly approach for the fouling release coating is to create coating surfaces that can resist colonization by fouling organisms or minimize adhesion between marine organisms and material surfaces, leading to easy removal of biofoulants. In this paper a series of tris(trimethylsiloxy)silyl (M3T) containing methacrylate copolymers with low surface energy were synthesized for fouling release coating application. The surface and mechanical properties of copolymer coatings were characterized. The amount of curing group TMOSPMA and hard component PMA has an effect on the surface and mechanical properties; more curing group and more hard component resulted in better mechanical property. The three component copolymer (M3T-co-PMA-co-TMOSPMA) with a molar ratio of 2/8/3 was shown to be a formulation that formed hydrophobic coating with good mechanical properties with respect to B hardness. More studies are still needed to meet the requirements for commercial fouling release coatings.

Preparation and Characterization of a Novel Hydrogel-Based Fouling Release Coating

With the rapid development of marine transportation industry, biological fouling not only affects the speed of navigation but also highly increases fuel consumption. In the paper, a novel hydrogel-based fouling release coating is developed to address the issue by a combination of non-stick property with a low surface tension of the coating. A hydrogel-based silicone fouling release coating was synthesized and two kinds of different intermediate coatings were studied to give a proper match as the tie layer between the substrate coated with primer and the hydrogel silicone on the surface. The adhesion strength, surface tension as well as surface topography of the fouling release coating were studied. The corrosion resistance and anti-fouling performance of the substrates sprayed with the coating were characterized by salt spray test and immersion test in a simulated marine system. The results show that the adhesion between the substrate and the fouling release coating is grade two measured by grid test. The water contact angle of the coating is 104.8o and Rz of the coating is 10.71μm. The specimen is intact after 1000 hours under salt spray test. No diatom was found settled on the specimens in a simulated static marine system while a little diatom was observed on the specimens in a simulated dynamic marine system. It has been found that the intermediate coating comprising of epoxy resin gives proper match between the primer and the fouling release coating consisting of PDMS resin. The coating exhibits superior anti-fouling performance under stationary state.

Effect of Variations in Micropatterns and Surface Modulus on Marine Fouling of Engineering Polymers

We report on the marine fouling and fouling release effects caused by variations of surface mechanical properties and microtopography of engineering polymers. Polymeric materials were covered with hierarchical micromolded topographical patterns inspired by the shell of the marine decapod crab Myomenippe hardwickii. These micropatterned surfaces were deployed in field static immersion tests. PDMS, polyurethane, and PMMA surfaces with higher elastic modulus and hardness were found to accumulate more fouling and exhibited poor fouling release properties. The results indicate interplay between surface mechanical properties and microtopography on antifouling performance.

Fouling release of UV-cured acrylic coatings: Set-up of an in vitro test with Rhodotorula mucilaginosa

Acrylic coatings were prepared by UV-induced crosslinking of two different diacrylates monomers having the same molecular weight but containing either a polyethyleneoxide chain or an alkylic chain. The fouling behavior of the UV-cured coatings was assessed by a simple set-up, monitoring the growth of Rhodotorula mucilaginosa and the adhesion of the film formed by the pigmented yeast. The effect of the monomers, the photoinitiator and the polymers on the microorganism growth was studied. The monomers partially inhibited the yeast growth, the coatings showed fouling release activity: yeast could grow on both coatings but with different morphology, they detached easily by washing depending on the type of coating. By examining the physico-chemical and mechanical properties of the polymers, the fouling release behavior was found mostly dependent on the surface tension and the water uptake of the coatings.

Role of Backbone Chemistry and Monomer Sequence in Amphiphilic Oligopeptide- and Oligopeptoid-Functionalized PDMS- and PEO-Based Block Copolymers for Marine Antifouling and Fouling Release Coatings

Poly(dimethylsiloxane) (PDMS)- and poly(ethylene oxide) (PEO)-based block copolymer coatings functionalized with amphiphilic, surface-active, and sequence-controlled oligomer side chains were studied to directly compare the effects of hydrophilicity, hydrogen bonding, and monomer sequence on antifouling performance. Utilizing a modular coating architecture, structurally similar copolymers were used to make direct and meaningful comparisons. Amphiphilic character was imparted with non-natural oligopeptide and oligopeptoid pendant chains made from oligo-PEO and surface-segregating fluoroalkyl monomer units. Surface analysis revealed rearrangement for all surfaces when moved from vacuum to wet environments. X-ray photoelectron spectroscopy (XPS) spectra indicated that the polymer backbone and oligomer interactions play key roles in the surface presentation. Biofouling assays using the macroalga Ulva linza showed that the presence of peptoid side chains facilitated the removal of sporelings from the PDMS bloc...

Novel amphiphilic poly(dimethylsiloxane) based polyurethane networks tethered with carboxybetaine and their combined antibacterial and anti-adhesive property

The traditional nonfouling materials are powerless against bacterial cells attachment, while the hydrophobic bactericidal surfaces always suffer from nonspecific protein adsorption and dead bacterial cells accumulation. Here, amphiphilic polyurethane (PU) networks modified with poly(dimethylsiloxane) (PDMS) and cationic carboxybetaine diol through simple crosslinking reaction were developed, which had an antibacterial efficiency of 97.7%. Thereafter, the hydrolysis of carboxybetaine ester into zwitterionic groups brought about anti-adhesive properties against bacteria and proteins. The surface chemical composition and wettability performance of the PU network surfaces were investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle analysis. The surface distribution of PDMS and zwitterionic segments produced an obvious amphiphilic heterogeneous surface, which was demonstrated by atomic force microscopy (AFM). Enzyme-linked immunosorbent assays (ELISA) were used to test the nonspecific protein adsorption behaviors. With the advantages of the transition from excellent bactericidal performance to anti-adhesion and the combination of fouling resistance and fouling release property, the designed PDMS-based amphiphilic PU network shows great application potential in biomedical devices and marine facilities.

Synthesis of ultrahydrophobic and thermally stable inorganic–organic nanocomposites for self-cleaning foul release coatings

A conformal novel and low-cost series of elastomeric high-molecular weight polydimethylsiloxane (PDMS)/controlled SiO2-doped ZnO nanocomposites were accurately synthesized via hydrosilation curing. Different concentrations of doped nanospheres were inserted in the nanocomposite via in situ technique. The synergetic effect of micronanobinary scale roughness and controlled fouling on different kinds of substrates was determined. The hydrophobicity, roughness, and free-energy properties were investigated as self-cleaning and fouling release (FR) factors. The nanocomposites were also subjected to various tests on surface adhesion and mechanical properties, such as impact, T-bending, crosscut, and abrasion resistance. The anticorrosive features of nanocomposites were investigated through salt spray test. The mechanical tests and salt spray test exhibited the most profound effect by incorporation of 0.5% SiO2-doped ZnO nanospheres, indicating well distributed SiO2-doped ZnO nanofillers (0.5%). Results indicate that the nanocomposites retained the nanostructure characteristics under thermal and irradiation treatments. Furthermore, microfoulants of chosen bacterial progenies were applied on vinyl-ended PDMS/spherical SiO2-doped ZnO nanocomposites for about one month of laboratory assessments. These studies indicated the importance of good distribution of doped nanofillers on enhancing FR ability in the modeled nanocoatings. A particular increase in contact angle (CA, 167°±2) and the decrease in free energy of surface (9.24mN/m) and microroughness indicated the FR functionality of these nanocomposites. Our findings show evidence that the developed nanocomposites demonstrated inert and nonwettable properties, superior physical characteristics, surface innerness and lotus effect, long-term durability under UV radiation, and thermal stability and resistance against a wide range of pH solutions, making them promising as efficient environment-friendly self-cleaning for coating of ship hulls.

Fifty years of the Baier curve: progress in understanding antifouling coatings

Biofouling is an entirely natural process, but when it affects ship hulls, it adversely affects society through increased fuel consumption and production of carbon dioxide (CO2). Today, marine coatings include toxicants such as copper that prevent fouling but can themselves harm the environment. The societal choice then is either to burn more fuel or to release toxicant. Researchers today are looking for solutions that minimize or eliminate toxicants yet are efficient enough in antifouling performance that additional fuel consumption is not required. Understanding and controlling the physical structure of a coating surface that interacts with its environment may lead to effective toxicant-free or toxicant-reduced antifouling coatings. This commentary describes several current approaches in terms of the Baier curve, the relationship between fouling release and surface energy, the mechanical properties of the coating, the kinds of materials that presently show the most promise and recently developed strategies for antifouling coating design.

Marine anti-biofouling efficacy of amphiphilic poly(coacrylate) grafted PDMSe: effect of graft molecular weight

There is currently strong motivation due to ecological concerns to develop effective anti-biofouling coatings that are environmentally benign, durable, and stable for use by the maritime industry. The antifouling (AF) and fouling-release (FR) efficacy of amphiphilic, charged copolymers composed of ~52% acrylamide, ~34% acrylic acid, and ~14% methyl acrylate grafted to poly(dimethyl siloxane) (PDMSe) surfaces were tested against zoospores of the green alga Ulva linza and the diatom Navicula incerta. The biofouling response to molecular weight variation was analyzed for grafts ranging from ~100 to 1,400 kg mol−1, The amphiphilic coatings showed a marked improvement in the FR response, with a 55% increase in the percentage removal of diatoms and increased AF efficacy, with 92% reduction in initial attachment density of zoospores, compared to PDMSe controls. However, graft molecular weight, in the range tested, was statistically insignificant. Grafting copolymers to PDMSe embossed with the Sharklet™ microtopography did not produce enhanced AF efficacy.

An Experimental Study on the Effect of IS700 Coating on the Cavitation Inception and Development, and Noise Reduction of a Marine Propeller

In this paper, cavitation inception and development conditions are studied for five-blade propellers by experiments carried out in cavitation tunnel. Propeller noise is measured in different operating conditions for uncoated and coated propellers and also, the effects of silicone foul release (FR) coating, inter sleek 700 (IS700), are investigated on the cavitation delay and noise reduction of a marine propeller in cavitation tunnel. Finally, results are presented in low advance coefficients for cavitation inception and development, and noise reduction. These results can be applied as a reference for validating this propeller model in numerical simulations.

Preparation and properties of silicone fouling release coatings with long-life afterglow fluorescent

Based on polydimethylsiloxane, three-component coatings were prepared with different content of luminescence powder. The results showed that the illuminance of coatings increases with the content of luminescence powder, decays exponentially with the afterglow time, increases exponentially with the increase of exposure time. The afterglow illuminance augments with irradiated light illuminance. All coatings are hydrophobic and oleophilic. Surface free energy decreases with the increase of luminescence powder. They have highest impact-resistance and bend flexibility. The luminescence powder does not change obviously the shore hardness, tensile breaking strength, breaking elongation rate, elastic modular and roughness of coatings. The static test panels in sea generally could be covered obviously by biofouling including sponges, bryophytes and mussels, hydra, kelp, green algae after 2 months of immersion during growing season. But it never found that the barnacle attached on the coating surface during 4 years of immersion test. The static anti-fouling ability of the coatings is very limited. In addition, the sea creatures attached on the coating surface can be easily removed; even attached organisms will fall off and expose again the smooth coating surface. Consequently, all coatings with long-life afterglow fluorescent have a significant effect on preventing adhesion of barnacle and fouling-release performance.

Numerical Simulation of Frictional Resistance of Foul Release and Antifouling Coatings

Numerical Simulation of Frictional Resistance of Foul Release and Antifouling Coatings

Design of poly(vinylidene fluoride)-g-p(hydroxyethyl methacrylate-co-N-isopropylacrylamide) membrane via surface modification for enhanced fouling resistance and release property

Thermo-sensitive polymer poly(N-isopropylacrylamide) (PNIPAAm), hydrophilic polymer poly(hydroxyethyl methacrylate) (PHEMA) and copolymer p(hydroxyethyl methacrylate-co-N-isopropylacrylamide) [P(HEMA-co-NIPAAm)] were synthesized onto poly(vinylidene fluoride) (PVDF) membrane via atom transfer radical polymerization (ATRP) in order to improve not only fouling resistance but also fouling release property. The physicochemical properties of membranes including hydrophilicity, morphology and roughness were examined by contact angle analyzer, scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. The antifouling property of membranes was improved remarkably after surface modification according to protein and bacterial adhesion testing, and filtration experiment. Minimum protein adsorption and bacterial adhesion were both obtained on PVDF-g-P(HEMA-co-NIPAAm) membrane, with reduction by 44% and 71% respectively compared to the pristine membrane. The minimum bacterial cells after detachment at 25°C were observed on the PVDF-g-P(HEMA-co-NIPAAm) membrane with the detachment rate of 77%, indicating high fouling release property. The filtration testing indicated that the copolymer modified membrane exhibited high resistance to protein fouling and the foulant on the surface was released and removed easily by washing, suggesting high fouling release and easy-cleaning capacity. This study provides useful insight in the combined “fouling resistance” and “fouling release” property of P(HEMA-co-NIPAAm) for PVDF membrane modification, even for other types of the membrane in wide application.

Influence of hydrodynamic stress on the frictional drag of biofouling communities

The role of hydrodynamic wall shear stresses on the development of the fouling community structure and resulting frictional drag were examined using a commercially available fouling release coating. Immersed test panels were exposed to three different hydrodynamic treatments, one static and two dynamic (corresponding to an estimated wall shear stress of 7.0 and 25.5 Pa). The drag of the panels was measured in a hydrodynamic test chamber at discrete time intervals over 35 days. The fouling community composition on the static panels was significantly different from the organisms observed on the dynamic panels. Despite different fouling community composition, the drag forces measured on the panels were very similar. This suggests that the frictional drag of low form and soft fouling communities are similar and that there may be a stepwise increase in frictional drag associated with the presence of mature calcareous organisms.

Managing Redox Chemistry To Deter Marine Biological Adhesion

With global shipping accounting for 3.5% of annual fossil fuel use, we have incentive to keep hulls clean from encrusting foulers including barnacles, oysters, and mussels. Current antifouling coatings function by releasing biocidal copper into the surrounding waters. Rather than poisoning the oceans, environmentally benign approaches to defeating biological adhesion are in great demand. Recent chemical characterization insights have found that oxidative cross-linking of proteins plays a potentially key role in the formation of several bioadhesives. Here, antioxidant compounds were placed into coatings in order to quench oxidative chemistry and inhibit glue formation. Antioxidant-containing surfaces decreased mussel adhesion relative to controls. Attacking the mechanisms of biological adhesion may provide us with a new strategy for foul release coatings and minimize the environmental impacts of shipping.

Bubbles versus biofilms: a novel method for the removal of marine biofilms attached on antifouling coatings using an ultrasonically activated water stream

The accumulation of marine organisms on a range of manmade surfaces, termed biofouling, has proven to be the Achilles’ heel of the shipping industry. Current antifouling coatings, such as foul release coatings (FRCs), only partially inhibit biofouling, since biofilms remain a major issue. Mechanical ship hull cleaning is commonly employed to remove biofilms, but these methods tend to damage the antifouling coating and often do not result in full removal. Here, we report the effectiveness of biofilm removal from FRCs through a novel cleaning device that uses an ultrasonically activated stream (UAS). In this device, ultrasound enhances the cleaning properties of microbubbles in a freely flowing stream of water. The UAS was applied on two types of commercial FRCs which were covered with biofilm growth following twelve days immersion in the marine environment. Biofilm removal was quantified in terms of reduction in biovolume and surface roughness, both measured using an optical profilometer, which were then compared with similar measurements after cleaning with a non-ultrasonically activated water stream. It was found that the UAS significantly improves the cleaning capabilities of a water flow, up to the point where no detectable biofilm remained on the coating surfaces. Overall biofilm surface coverage was significantly lower on the FRC coatings cleaned with the UAS system when compared to the coatings cleaned with water or not cleaned at all. When biofilm biomass removal was investigated, the UAS system resulted in significantly lower biovolume values even when compared to the water cleaning treatment with biovolume values close to zero. Remarkably, the surface roughness of the coatings after cleaning with the UAS was found to be comparable to that of the blank, non-immersed coatings, illustrating that the UAS did not damage the coatings in the process.The data supporting this study are openly available from the University of Southampton repository at http://dx.doi.org/10.5258/SOTON/399420.