Fouling Release Research Articles

Amphiphilic Nitroxide-Bearing Siloxane-Based Block Copolymer Coatings for Enhanced Marine Fouling Release

The buildup of organic matter and organisms on surfaces exposed to marine environments, known as biofouling, is a disruptive and costly process affecting maritime operations. Previous research has identified some of the surface characteristics particularly suited to the creation of antifouling and fouling-release surfaces, but there remains room for improvement against both macrofouling and microfouling organisms. Characterization of their adhesives has shown that many rely on oxidative chemistries. In this work, we explore the incorporation of the stable radical 2,2,6,6-tetramethylpipiderin-1-oxyl (TEMPO) as a component in an amphiphilic block copolymer system to act as an inhibitor for marine cements, disrupting adhesion of macrofouling organisms. Using polystyrene-b-poly(dimethylsiloxane-r-vinylmethysiloxane) block copolymers, pendent vinyl groups were functionalized with TEMPO and poly(ethylene glycol) to construct an amphiphilic material with redox active character. The antifouling and fouling-release performance of these materials was investigated through settlement and removal assays of three model fouling organisms and correlated to surface structure and chemistry. Surfaces showed significant antifouling character and fouling-release performance was increased substantially toward barnacles by the incorporation of stable radicals, indicating their potential for marine antifouling applications.

Amphiphilic Zwitterionic Acrylate/Methacrylate Copolymers for Marine Fouling-Release Coatings.

Methacrylate and acrylate monomers are popular building blocks for antifouling (AF) and fouling-release (FR) coatings to counteract marine biofouling. They are used in various combinations and often combined into amphiphilic materials. This study investigated the FR properties of amphiphilic ethylene glycol dicyclopentenyl ether acrylate (DCPEA) and the corresponding methacrylate (DCPEMA) blended with 5 wt % zwitterionic carboxybetaine acrylate (CBA) and the corresponding methacrylate (CBMA). A series of (co)polymers with different acrylate/methacrylate compositions were synthesized and tested against the attachment of the diatom Navicula perminuta and in short-term dynamic field exposure experiments. The more hydrophobic methacrylate DCPEMA homopolymer outperformed its acrylate counterpart DCPEA. Incorporated zwitterionic functionality of both CBMA and CBA imparted ultralow fouling capability in the amphiphilic polymers toward diatom attachment, whereas in the real ocean environment, only the employment of CBMA reduced marine biofouling. Moreover, it was observed that CBA-containing coatings showed different surface morphologies and roughnesses compared to the CBMA analogues. Particularly, a high impact was found when acrylic CBA was mixed with methacrylic DCPEMA. While the wettability of the coatings was comparable, investigated methacrylates in general exhibited superior fouling resistance compared to the acrylates.

Antifouling Technology Trends in Marine Environmental Protection

Marine fouling is a worldwide problem, which is harmful to the global marine ecological environment and economic benefits. The traditional antifouling strategy usually uses toxic antifouling agents, which gradually exposes a serious environmental problem. Therefore, green, long-term, broad-spectrum and eco-friendly antifouling technologies have been the main target of engineers and researchers. In recent years, many eco-friendly antifouling technologies with broad application prospects have been developed based on the low toxicity and non-toxicity antifouling agents and materials. In this review, contemporary eco-friendly antifouling technologies and materials are summarized into bionic antifouling and non-bionic antifouling strategies (2000–2020). Non-bionic antifouling technologies mainly include protein resistant polymers, antifoulant releasing coatings, foul release coatings, conductive antifouling coatings and photodynamic antifouling technology. Bionic antifouling technologies mainly include the simulated shark skin, whale skin, dolphin skin, coral tentacles, lotus leaves and other biology structures. Brief future research directions and challenges are also discussed in the end, and we expect that this review would boost the development of marine antifouling technologies.

Dual approach of bimodality and nano-reinforcement towards toughened PDMS based foul release coatings

It is well established that crosslinked polydimethylsiloxane (PDMS) based coatings have efficacious foul release characteristics. However, a trade-off between mechanical integrity of filled and crosslinked PDMS based coatings and their foul release performance has been a bottleneck for producing efficient and durable coatings. In the present study, we report a dual approach of nano-reinforcement of a bimodal PDMS network as a strategy to produce simultaneously reinforced and toughened PDMS networks with facile release of macrofoulants from their surfaces. The nanocomposites of both unimodal and bimodal PDMS networks were prepared using oligomeric dihydroxyl functional PDMS precursor chains differing in their molecular weights by a factor of five and commercial Cloisite-20A nanoclay as the nanofiller. The clay layers were found to be mildly intercalated in the PDMS matrix, as revealed from investigations by scattering and imaging techniques at different length scales. While the unimodal PDMS networks did show nanoclay induced simultaneous reinforcement and toughening, at equivalent clay loadings, the bimodal PDMS nanocomposites seemed to stretch further with characteristic strain hardening before fracture. Dynamic mechanical analysis (DMA) and swelling studies of the nancomposites further confirmed the nanoclay induced reinforcement effect of the bimodal PDMS host matrix. The intrinsic low surface energy characteristics of PDMS were retained by bimodal blending of long and short chains and its subsequent nano-reinforcement. Macrofouling studies by panel immersion and release force measurements revealed that the macrofoulants could be dislodged from the nanocomposite coatings with a shear force < 0.05 MPa.

Antifouling and Removal Efficiency of Foul‐Release Polydimethylsiloxane‐based Coatings: Lab‐Scale and Seawater Immersion Fouling Test and Hydrodynamic Shearing Test

Antifouling is necessary to prevent the fouling of marine organisms on ship surfaces in seawater. Foul release (FR) coatings are considered an alternative to commercial antifouling coatings as eco‐friendly coating materials that can prevent toxic biocide emissions. However, the evaluation of FR coatings for antifouling is extremely complicated owing to their foul‐releasing mechanism with diverse surface properties. Therefore, a reliable laboratory simulation of the actual seawater immersion condition is required. Silicon‐based FR coatings with several additives were prepared to evaluate the reliability of a laboratory fouling test. To simulate the marine foulant removal efficiency of an FR coating surface based on the ship speed, a circulating seawater channel was applied. Laboratory test showed a similar tendency as the seawater immersion. From the results, laboratory‐scale microalgae fouling tests and circulating seawater channel tests are considered suitable for evaluating the antifouling performance of FR coatings.

Poly(oxazoline) for the design of amphiphilic silicone coatings

Fouling release coatings are known to be ecofriendly and to be a good alternative to the coatings containing biocides. To improve their efficiency and lifespan the incorporation of additives seems required. Amphiphilic system as PEG-silicone coatings have a lower impact on the environment. However, PEG oxidation in seawater impacts its lifespan. In this context, the development and incorporation of new hydrophilic additives offers great potentiel. The objective of this study is to design an amphiphilic fouling release coating containing poly(oxazoline) (POx) as additives. POx have similar physical properties as PEG and have already been used in biomedical applications.POx with a trimethoxysilane end-group has been synthesized to be crosslinked in a RTV silicone coating. The impact of its incorporation in a PDMS coating has been evaluated on surface properties and on coating organization. The results have been compared with a similar PEG-silicone coating. In addition, microbiologic assays have been carried out to evaluate the bacterial adhesion and the fouling properties of the coating. Two biomedicals bacteria and a marine bacterium were used to confirm the interest of POx.POx-silicone coating showed similar fouling efficiency against bacteria as PEG-silicone coating despite a bigger surface roughness and a lower compatibility with PDMS.

Spray‐Painted Hydrogel Coating for Marine Antifouling

AbstractBiofouling is a longstanding problem for biomedical devices, food storage, and marine equipment. Traditional antifouling strategies involve the use of biocidal agents, low surface‐energy surface, and nanopatterned coatings. Recent studies show that hydrophilic surfaces are also promising for antifouling by directly reducing the adhesion of proteins and polysaccharides. However, it remains challenging to stably and conveniently coat nonadhesive hydrophilic polymers to various surfaces in high density. Especially, for marine antifouling, large‐area painting of hydrophilic polymer coatings is susceptible to low adhesion strength, inhomogeneous surface coverage, and short durability. Here, a paintable antifouling hydrogel coating is proposed to overcome these limitations. An epoxy midcoat layer is introduced to provide both strong noncovalent adhesion to various surfaces and covalent linkages to hydrogel layers. The 3D hydrogel layers provide homogenous, relatively low Young's modulus and dense surface coverage and therefore shows outstanding antifouling properties toward various proteins, polysaccharides, seaweeds, and oil. Moreover, this hydrogel coating degrades slowly in sea water and facilitates the release of fouling biomolecules and organisms. Considering the great antifouling and fouling release properties, convenient coating processes, and high adhesion strength, this novel paintable antifouling hydrogel coating is anticipated to be broadly applicable for marine antifouling and other relevant fields.

Synthesis and Characterization of Dendritic and Linear Glycol Methacrylates and Their Performance as Marine Antifouling Coatings.

Dendritic polyglycerol (PG) was covalently coupled to 2-hydroxyethyl methacrylate (HEMA) by an anionically catalyzed ring-opening polymerization generating a dendritic PG-HEMA with four PG repetition units (PG4MA). Coatings of the methacrylate monomer were prepared by grafting-through and compared against commercially available hydrophilic monomers of HEMA, poly(ethylene) glycol methacrylate (PEGMA), and poly(propylene) glycol methacrylate (PPGMA). The obtained coatings were characterized by modern surface analytical techniques, including water contact angle goniometry (sessile and captive bubble), attenuated total internal reflection Fourier transform infrared spectroscopy, and atomic force microscopy. The antifouling (AF) and fouling-release (FR) properties of the coatings were tested against the model organisms Cobetia marina and Navicula perminuta in laboratory-scale dynamic accumulation assays as well as in a dynamic short-term field exposure (DSFE) in the marine environment. In addition, the hydration of the coatings and their susceptibility toward silt uptake were evaluated, revealing a strong correlation between water uptake, silt incorporation, and field assay performance. While all glycol derivatives showed good resistance in laboratory settlement experiments, PPGMA turned out to be less susceptible to silt incorporation and outperformed PEGMA and PG4MA in the DSFE assay.

Polydimethylsiloxane Microdomains Formation at the Polythiourethane/Air Interface and Its Influence on Barnacle Release.

In this study, polydimethylsiloxane (PDMS)/polythiourethane (PTU) composite reinforced with tetrapodal shaped micro-nano ZnO particles (t-ZnO) was successfully produced by a versatile, industrially applicable polymer blending process. On the surface of this composite, PDMS is distributed in the form of microdomains embedded in a PTU matrix. The composite inherited not only good mechanical properties originating from PTU but also promising fouling-release (FR) properties due to the presence of PDMS on the surface. It was shown that the preferential segregation of PDMS domains at the polymer/air interface could be attributed to the difference in the surface free energy of PDMS and PTU. The PDMS microdomains at the PTU/air interface significantly reduced the barnacle adhesion strength on the composite. Both the pseudo- and natural barnacle adhesion strength on the composite was approximately 0.1 MPa, similar to that on pure PDMS. The pseudo-barnacle adhesion on reference surfaces AlMg3 and PTU reached approximately 4 and 6 MPa, respectively. Natural barnacles could not be removed intact from AlMg3 and PTU surfaces without breaking the shell, indicating that the adhesion strength was higher than the mechanical strength of a barnacle shell (approximately 0.4 MPa). The integrity of PDMS microdomains was maintained after 12 months of immersion in seawater and barnacle removal. No surface deteriorations were found. In short, the composite showed excellent potential as a long-term stable FR coating for marine applications.

Long time super-hydrophobic fouling release coating with the incorporation of lubricant

Marine biofouling can be better governed by using super-hydrophobic and lubricant leaching behavior. It was prepared for a long time super-hydrophobic fouling release coating with the incorporation of phenylmethylsilicone oil as lubricant. With the reasonable control of the mass ratio of mixed nano-particles (hydroxylated multi-walled carbon nanotube and nano-magnetite), prepared reinforced coating has excellent super-hydrophobicity and lubricant leaching efficiency. Comparable studies with reported FR coating and commercial silicone coating, it exhibits excellent anti-biofilm adhesion performance with up to 98 % of biofilm adhesion removal rate. More beneficial, the isolation layer composed of the leached phenylmethylsilicone oil can make a good buffer effect for the reinforced coating surface, alleviating the deformation or damage caused by the friction between sand and the reinforced coating surface, effectively. This work is establishing new investments in environment-friendly fouling release coatings.

Effect of N-(2-Aminoethyl)-3-Aminopropyltrimethoxysilane on the Adhesion of the Modified Silicone Tie-Coating to Epoxy Primer

In this work, modified silicone tie-paints were prepared in a simple way for securing adhesion between the epoxy anticorrosive primer and silicone fouling release coating. Hydroxy-terminated polydimethylsiloxane (PDMS) mixture containing fillers and accessory ingredient was prepared as base component. N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane (DAMO) was mechanically mixed with other functional additives as curing component. ATR-FTIR, XPS, SEM and tensile tests were used to investigate the chemical structure, morphology and mechanical properties of the tie-coatings. It was focused on the effect of the DAMO content on the adhesion of the tie-coating to epoxy primer. Peel off and shear tests were carried out to evaluate the adhesion. The results showed that introducing DAMO can significantly improve the properties of the tie-coating. The adhesion between the tie-coating and the epoxy primer increases with the increase of DAMO content, but the excessive DAMO content will decrease the fracture strength of the tie-coating and decrease the quality of the coating. When the DAMO content in tie-coating is 1.97 wt.%, the tie-coating performs excellent in the interlaminar adhesion, shear strength and mechanical properties.

Self-healing, highly elastic and amphiphilic silicone-based polyurethane for antifouling coatings.

Silicone elastomer coatings have attracted increasing attention owing to their eco-friendly nature, excellent fouling release ability and drag-reducing property. However, the poor mechanical properties and lack of fouling resistance limit their applications. Herein, a silicone-based polyurethane with 2-ureido-4[1H]-pyrimidinone (UPy) and amphiphilic pendant chains is reported. The UPy groups and urethane can form hydrogen bonds with various substrates so that the coating has significantly improved adhesion strength (0.9-3.0 MPa) compared with the PDMS elastomer (0.3-0.4 MPa). Moreover, the quadruple hydrogen bonding between UPy moieties allows the polymer to have excellent self-healing ability and high elasticity. The modified polymeric coating has low surface energy (24 mJ m-2) and low elastic modulus (1.9 MPa), so it exhibits good fouling release performance. Besides, the amphiphilic side chains can effectively resist protein adsorption and adhesion of the marine bacteria Pseudomonas sp. and diatom Navicula incerta. The novel design can improve the resistance of silicone coating to biofouling and mechanical forces and is promising for high-performance antifouling coatings.

Eco-friendly foul release coatings based on a novel reduced graphene oxide/Ag nanocomposite prepared by a green synthesis approach

The purpose of making graphene/polydimethylsiloxane (PDMS)-based coatings is providing a suitable strategy to prevent fouling organism adhesion. In this study, graphene oxide (GO) reduced with Avicennia marina/Silver to achieve GOH@Ag nanocomposite. GOH@Ag, bare GO and multi-Wall Carbon nanotubes (MWCNTs) as nanofillers were individually incorporated into PDMS-based coatings with 0.01, 0.1, and 0.5 %wt. The surface characterization including pseudo-barnacle adhesion strength and water static contact angle and critical surface energy was performed for all samples. Evaluating field immersion was performed due to the samples in the natural seawater. The best results were observed for the sample with 0.5 wt% of GOH@Ag (RMS roughness = 103 nm, pseudo-barnacle adhesion strength =0.16 MPa, critical surface energy = 16 mN/m, static contact angle = 118.8°). The simultaneous presence of A. marina and silver element in the structure of graphene-based nanocomposite showed a synergistic effect on the performance of PDMS-based coatings which achieved outstanding result of antifouling efficiency (N = 18).

Long-term biofouling formation mediated by extracellular proteins in Nannochloropsis gaditana microalga cultures at different medium N/P ratios.

Biofouling represents an important limitation in photobioreactor cultures. The biofouling propensity of different materials (polystyrene, borosilicate glass, polymethyl methacrylate, and polyethylene terephthalate glycol-modified) and coatings (two spray-applied and nanoparticle-based superhydrophobic coatings and a hydrogel-based fouling release coating) was evaluated by means of a short-term protein test, using bovine serum albumin (BSA) as a model protein, and by the long-term culture of the marine microalga Nannochloropsis gaditana under practical conditions. The results from both methods were similar, confirming that the BSA test predicts microalgal biofouling on surfaces exposed to microalgae cultures whose cells secrete macromolecules, such as proteins, with a high capacity for forming a conditioning film before cell adhesion. The hydrogel-based coating showed significantly reduced BSA and N. gaditana adhesion, whereas the other surfaces failed to control biofouling. Microalgal biofouling was associated with an increased concentration of sticky extracellular proteins at low N/P ratios (below 15).

A novel approach for the evaluation of ice release performance of coatings using static friction measurements

Atmospheric icing on structures and equipment represents a challenge for operation and safety. Passive ice removal by ice-phobic coatings has received much attention over the last decades. The current state-of-the-art methods for quantifying the ice-release properties of such coatings suffer from a range of drawbacks, including poor reproducibility and high complexity test setups. Here, a facile rotational tribometer approach for measuring the static friction between polymeric coatings and ice is presented. The torque necessary to initiate motion at the coating-ice interphase was used as a measure of ice release. For a polydimethylsiloxane-based coating (Sylgard 184), the effects of ice-temperature, normal force, coating thickness, and dwell time (contact time between coating and ice at rest with fully applied normal force prior to applying torque) were established along with the conditions resulting in least data variation. With these conditions, tribology-based friction measurements were carried out on two additional coatings; a two-component polyurethane, and a commercial foul release coating. The outcome of the method, i.e., grading of the coatings in terms of antiicing effect, matched those obtained with a widely used ice adhesion test method based on ice shear adhesion testing. The same trends are revealed by the two methods. However, the findings from the proposed tribology-based method result in consistently lower variation in outcomes and offer more detail on the ice adhesion and friction mechanisms.

Influence of Phenylmethylsilicone Oil on Anti-Fouling and Drag-Reduction Performance of Silicone Composite Coatings

In this study, we explore the effect of phenylmethylsilicone oil (PSO) addition amount and viscosity in a fouling release coating based on polydimethylsiloxane (PDMS). The surface properties, mechanical properties, anti-fouling and drag-reduction performance of the coating were studied. Meanwhile the influence of the basic properties of the coating on the anti-fouling and drag-reduction performance was also studied. Subsequently, the antifouling performance of the coating was investigated by the Navicula Tenera and bacteria adhesion test. As a result, the high content of PSO paint has a high foul removal rate. The incorporation of PSO into paint can reduce the elastic modulus and surface energy of the coating to reduce its relative adhesion factor (RAF). The lower the RAF, the better the antifouling effect of the coating. The drag-reduction performance of the coating was verified by the torque selection experiment, and the results showed that incorporation of PSO into paint can enhance the elongation and hydrophobicity of the coating, thereby increasing the drag reduction rate of the coating.

Using encrusting bryozoan adhesion to evaluate the efficacy of fouling-release marine coatings

Biofouling communities are spatiotemporally diverse, underscoring the need to assess fouling-release (FR) coating performance against common biofouling taxa at multiple field sites. Adhesion strength assessments of FR coatings incorporate few taxa into standardized protocols. This study tested the feasibility of incorporating existing ASTM barnacle protocols on tubeworms and encrusting bryozoans (EB). Additionally, trends in adhesion strength among these taxa were compared at two field sites. EB adhesion at both field sites showed consistent results and adhesion strength followed the same trend: tubeworms > barnacles >EB. Testing EB adhesion was feasible and enhanced assessments of FR coatings by increasing the diversity of assessed taxa.

Preparation and antifouling performance evaluation of fluorine-containing amphiphilic silica nanoparticles

Ocean-going ships, deep-sea equipment, coastal facilities, and other underwater surfaces are often attached to and fouled by marine microorganisms, animals, and plants, leading to damage, equipment failure or major economic losses in severe cases. Therefore, it is of great significance to take measures to prevent marine biofouling. To date, no single eco-friendly technology has been developed to achieve good antifouling effects. Therefore, the combination of multiple antifouling factors is still one of the main strategies to strengthen antibiofouling performance. In this paper, amphiphilic block copolymer (PTFEMA-co-PSBMA) functionalized silica (SiO2) nanoparticles of SiO2-g-(PTFEMA-co-PSBMA) were prepared by surface initiated atom transfer radical polymerization (SI-ATRP), and then they were physically blended with polydimethylsiloxane (PDMS) matrix to prepare one kind of novel antifouling coating. Compared with control silicone rubber coating and bare SiO2-dopped silicone rubber coating, the experiment results show that the diatom density on the surface of the copolymer functionalized silica nanoparticle-dopped coating is reduced by approximately 30 % and 50 %, respectively. Furthermore, upon employing washing process, it is found that the highest removal rate of diatoms on the surface of the copolymer functionalized silica nanoparticle coating is 50 %, which is approximately twice the removal rate of the unmodified SiO2 silicone rubber coating. Finally, it is found that the surface of the copolymer functionalized silica nanoparticle coating still has good antifouling and fouling release properties upon encountering wear test. These above results prove that the coatings with functionalized nanosilica nanoparticles have better antifouling performance. Current strategy in this work provides a new route for developing environmentally friendly fouling-releasing antifouling coatings.

Porous silicone substrates inhibit permanent barnacle attachment under natural conditions.

Barnacles are able to effectively adhere to most surfaces underwater. Dewetting of the corresponding surface prior to the release of their permanent adhesive plays an important role in the attachment process. Possibly, a surface that is able to interfere with this process may have exceptional fouling repellence and fouling release abilities. Therefore, open-pored foams made from polydimethylsiloxane (PDMS) were tested together with flat PDMS samples as controls in a 13-week-long field experiment in the Baltic Sea. On a weekly basis, both settlement and fouling density development of the bay barnacle Balanus (=Amphibalanus) improvisus were monitored. The overall settlement was close to zero on PDMS foams and the few attached barnacles were not able to stay on the PDMS foams longer than 1 week after initial settlement. Changes in the stiffness of the PDMS foams did not affect these results. Open-pored PDMS foam systems may be a promising tool in the development of new, innovative antifouling strategies.

Toward the Application of Graphene for Combating Marine Biofouling

AbstractThe discovery of graphene has brought great innovations to materials science. Since tributyltin antifouling coatings were banned worldwide in 2008, the development of green antifouling coatings has become necessary. Recently, novel graphene‐related antifouling coatings have been the focus of many studies due to their enhanced mechanical strength, excellent antifouling capabilities, and environmental friendliness. This review starts by introducing the basic antifouling mechanisms of graphene nanosheets and the possible antifouling mechanisms when graphene is incorporated into coatings. Subsequently, the progress and existing problems regarding the application of graphene in the prevention of marine biofouling are discussed. Specifically, this review focuses on six graphene‐related antifouling coatings, including pure graphene film, nanohybrids, foul release coatings, photocatalytic nanocomposites, desalination membranes, and materials for uranium enrichment. The fabrication, antifouling properties, working mechanisms, and future development of graphene‐related antifouling coatings are highlighted. In addition, the potential environmental risk of using graphene materials in preventing marine biofouling is explained, and the basic requirements for designing an environmentally friendly graphene‐related antifouling coating are discussed. Finally, the prospect of applying graphene materials for combating marine biofouling is presented. This review aims to aid in improving the design of graphene‐related green antifouling coatings.