Antifouling agent release from marine coatings-ion pair formation/dissolution for controlled release

In marine coatings, the ability to sustain constant release of antifouling agents (AFA(s)) over a long period of time has become increasingly important. One efficient approach to prevent that diffusion depletes the paint film's antifouling activity is to adsorb the AFA strongly to a specie with low translational mobility, such as a high molecular weight polymer. Therefore, the AFA, Medetomidine, was adsorbed onto a sulfonated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SDPS) generating a Medetomidine–SDPS ion pair in an organic solvent. The interaction was investigated by ¹H NMR in butanol (BuOH-d₁₀) and on solid surfaces by the quartz crystal microbalance with dissipation monitoring technique (QCM-D) in two different solvents, seawater and o-xylene. From the NMR studies in butanol (BuOH-d₁₀), a strong interaction between Medetomidine and SDPS was observed. From the QCM-D measurements, differences in affinity between Medetomidine and the SDPS was observed when changing from seawater to o-xylene. In seawater, the interaction was weak and displayed a large degree of reversibility compared to in o-xylene, where the interaction was strong and almost irreversible. Different swelling behaviour was also observed at the solid surfaces depending on the solvent used with o-xylene exhibiting the largest swelling of the polymer layer.     

Bioactive materials for antifouling coatings

Marine fouling is the result of the settling and subsequent growth of marine organisms on surfaces immersed in seawater. The most successful principle in use today for the protection of ship's hulls against this unwanted growth is the release of bioactive materials from antifouling coatings.

Antifouling coatings containing a mixture of cuprous oxide and triorganotin compounds in combination with sophisticated release mechanisms are considered to be today's most efficient systems. However, ever since the first biologically active materials were introduced into antifouling coatings, a search for alternatives has been continuing. Until the mid-1970s this research mainly involved the development of biocides which could simply prolong existing drydocking intervals, i.e. prolong the period in which the ship was fouling free. During the last decade, however, environmental aspects have become a top priority in the development of new biocides for antifouling coatings.     

Antifouling effect of hydrogen peroxide release from enzymatic marine coatings: Exposure testing under equatorial and Mediterranean conditions

Hydrogen peroxide (H₂O₂) may be considered an environmentally friendly antifouling alternative to common biocides such as Cu₂O and various organic compounds. In this work, the efficiency of antifouling coatings releasing hydrogen peroxide via enzyme-mediated conversion of starch, under Mediterranean and equatorial climatic conditions, is investigated. During seawater exposure of the coatings, starch is first converted to glucose by glucoamylase (rate-controlling step) and subsequently glucose is rapidly oxidised by hexose oxidase in a reaction producing hydrogen peroxide.     

Chitosan Nanocomposite Coatings Containing Chemically Resistant ZnO–SnOx Core–shell Nanoparticles for Photocatalytic Antifouling

Functional nanocomposites with biopolymers and zinc oxide (ZnO) nanoparticles is an emerging application of photocatalysis in antifouling coatings. The reduced chemical stability of ZnO in the acidic media in which chitosan is soluble affects the performance of chitosan nanocomposites in antifouling applications. In this study, a thin shell of amorphous tin dioxide (SnO_x) was grown on the surface of ZnO to form ZnO–SnO_x core–shell nanoparticles that improved the chemical stability of the photocatalyst nanoparticles, as examined at pH 3 and 6. The photocatalytic activity of ZnO–SnO_x in the degradation of methylene blue (MB) dye under visible light showed a higher efficiency than that of ZnO nanoparticles due to the passivation of electronic defects. Chitosan-based antifouling coatings with varying percentages of ZnO or ZnO–SnO_x nanoparticles, with or without the glutaraldehyde (GA) crosslinking of chitosan, were developed and studied. The incorporation of photocatalysts into the chitosan matrix enhanced the thermal stability of the coatings. Through a mesocosm study using running natural seawater, it was found that chitosan/ZnO–SnO_x/GA coatings enabled better inhibition of bacterial growth compared to chitosan coatings alone. This study demonstrates the antifouling potential of chitosan nanocomposite coatings containing core–shell nanoparticles as an effective solution for the prevention of biofouling.     

RP-HPLC optimization of econea by using artificial neural networks and its antifouling performance on the Turkish coastline

Coverage of artificial surfaces within seawater by fouling organisms is defined as biofouling. Although biofouling is a natural process, it has some disadvantages for shipping industry such as increased fuel consumption, and CO₂ emission. Therefore, the ships' hull must be covered by antifouling (AF) or fouling release type coatings to overcome biofouling. In general, the so-called self-polishing AF paints contain biocides for preventing fouling organisms. Their concentrations and release rates from AF coatings are of great importance and they definitely affect both quality and cost of the coating. In the present study, we aimed at applying a new robust method. In this method, we used a model biocide, i.e., econea, to obtain its RP-HPLC optimization through artificial neural networks (ANN) and to see its antifouling performance. Column temperature, mobile phase ratio, flow rate, concentration and wavelength as input parameters and retention time as an output parameter were used in the ANN modeling. In conclusion, the R&D groups in AF paint industry may use RP-HPLC method supported with ANN modeling in further studies.     

Improvement of interfacial adhesion between oxide ceramic nanoparticles and epoxy resin by wet-jet milling

Although ceramic/polymer composites are useful for various applications, such as sensors, electronics, automobiles, and aerospace, the aggregation of nanoparticles can lead to the degradation of the mechanical and functional properties of the composites. To mitigate this, the interfacial adhesion between epoxy resin and the oxide ceramic nanoparticles γ-aluminum oxide (Al₂O₃), silicon dioxide, and magnesium oxide was strengthened by wet-jet milling (WJM) treatment without a chemical modifier. The WJM treatment of the slurry containing nanoparticles and epoxy resin led to the good adsorption of epoxy resin onto the nanoparticle surface, which significantly improved the mechanical properties of the composites. Throughout this process, the amount of epoxy resin adsorbed on the nanoparticle surface and the composite mechanical properties increased with increasing WJM processing pressure, owing to the increased contact between the nanoparticles and epoxy resin droplets and the reduced droplet size. Furthermore, poor solvent was found to be effective for the dispersal of the nanoparticles because the epoxy resin droplets in the slurry were more stable on the nanoparticle surfaces than those in the solvent. When Al₂O₃ nanoparticles were used as a filler, the amount of epoxy resin adsorbed increased from 3.7 to 70.6 mg g⁻¹, and the composite tensile strength increased from 67.1 to 100.3 MPa in poor solvent and under high WJM processing pressure. This optimized WJM treatment will lead to improvements in the mechanical and functional properties of various composite materials.     

Inorganic precursor peroxides for antifouling coatings

Modern antifouling coatings are generally based on cuprous oxide (Cu₂O) and organic biocides as active ingredients. Cu₂O is prone to bioaccumulation, and should therefore be replaced by more environmentally benign compounds when technically possible. However, cuprous oxide does not only provide antifouling properties, it is also a vital ingredient for the antifouling coating to obtain its polishing and leaching mechanism. In this paper, peroxides of strontium, calcium, magnesium, and zinc are tested as pigments in antifouling coatings. The peroxides react with seawater to create hydrogen peroxide and highly seawater-soluble ions of the metal. The goals have been to establish the antifouling potency of an antifouling coating that releases hydrogen peroxide as biocide, and to investigate the potential use of peroxides as water-soluble polishing and leaching pigments. The investigations have shown that it is possible to identify particulates that, when applied as pigments in antifouling coatings, will provide polishing and leaching rates comparable to those of Cu₂O-based coatings. Furthermore, the combination of polishing and hydrogen peroxide leaching by a coating based on zinc peroxide in a suitable binder matrix provides antifouling properties exceeding those of a similar coating based entirely on zinc oxide.     

海洋船舶无毒、低毒防污涂料的研究进展

介绍了现代海洋船舶防污涂料的研究和应用情况,分别阐述了电化学防污涂料、化学活性物质释放型防污涂料和非化学活性物质释放型防污涂料的原理及其应用进展,并着重介绍了无毒低毒防污剂及防污涂料,指出长效、无毒的防污涂料将是未来涂料的发展方向。     

Analytical method for the release of isothiazolones from microtubules in artificial seawater

With restrictions on the use of metallic biocides in aquatic antifouling coatings, it is important to develop new methods to both contain and deliver these alternative compounds from marine coatings systems. Utilization of microencapsulation is one approach to the delivery of biocides that has not been utilized in the mainstream of antifouling paint formulations. When formulating next generation paints that utilize hydrophobic nonmetallic biocides, it is necessary to develop an understanding of the release kinetics of the compounds from model polymeric coatings in order to better develop methods for providing long-term efficacy. The biocide 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one is a nonmetallic and nonenvironmentally persistent biocide that has been registered in several countries for use as an antifouling agent and has gained approval by the U.S. Environmental Protection Agency. The release characteristics of this biocide from copper microtubules as well as polymeric films were determined by high performance liquid chromatography. Center for Biomolecular Science & Engineering, Code 6930, Washington, D.C. 20375-5348.     

主链降解型聚丙烯酸硅烷酯基自抛光防污涂料的研制

以新型主链降解聚丙烯酸硅烷酯树脂和松香作为基料树脂,通过防污剂复配筛选出防污效果较好的氧化亚铜/吡啶硫酮铜(Cu₂O/CPT)复配防污剂,运用正交试验设计方法,测定了防污剂渗出率和涂层附着力随浸泡时间的变化规律。研究发现:随着颜料体积浓度(PVC)增高,防污剂渗出率呈现增加的趋势;随着树脂/松香质量比的增高,渗出率呈现降低的趋势;随着渗出速率调节剂(R助剂)添加量增高,防污剂渗出率呈现降低的趋势。随着海水/淡水浸泡时间延长,防污涂层的附着力均降低,且淡水浸泡下涂层的附着力下降幅度更大。研究并得到PVC、树脂/松香质量比和R助剂用量的最佳值0.37、6∶1和1.4%,获得了新型主链降解聚丙烯酸硅烷酯防污涂料配方。所研制的防污涂料具有良好的防污性能,具有良好的产业化应用前景。     

Preparation and characterization of ZrO2/PES hybrid ultrafiltration membrane with uniform ZrO2 nanoparticles

In current or next-generation reuse systems, the development of new classes of antifouling membranes is needed before viable membrane-based approaches for wastewater reclamation can be achieved. In this study, ZrO₂/PES hybrid ultrafiltration membranes with uniform ZrO₂ nanoparticles were prepared by combining an ion-exchange process with a traditional immersion precipitation process. Hydrous ZrO₂ sol was synthesized by addition of anion-exchange resin in N,N-dimethylformamide solvent containing zirconyl chloride. Homogeneous ZrO₂/PES casting solution was then obtained by dissolving PES polymer in the ZrO₂ sol. The existence and dispersion states of ZrO₂ nanoparticles in the resultant membrane matrix were examined by X-ray photoelectron spectrometer, thermogravimetric analysis, scanning electron microscope and transmission electron microscope. The results indicate that the ZrO₂ nanoparticles were well dispersed throughout the PES matrix and the diameter of the formed nanoparticles was about 5–10 nm. The hydrophilicity of the membranes was determined by measuring the contact angles. The antifouling property was determined by antifouling experiments and atomic force microscopy. The results confirm that the existence of ZrO₂ nanoparticles improves the hydrophilicity and reduces protein adsorption of membranes.     

新型海洋防污涂料用防污剂及树脂的研究进展

防污剂和树脂是决定海洋防污涂料性能的关键成分。本文综述了近年来用于新型海洋防污涂料的天然产物防污剂和人工合成防污剂的研究进展;进一步从防污机理出发,总结了用于新型海洋防污涂料的基体树脂的种类,介绍了无锡自抛光树脂、生物可降解树脂、含杀菌官能团树脂、低表面能树脂和具有微相分离结构的树脂。此外,还展望了新型海洋防污涂料的未来发展方向,即环境友好的同时注重方式友好。     

Poly(arylene sulfide sulfone) hybrid ultrafiltration membrane with TiO2‐g‐PAA nanoparticles: Preparation and antifouling performance

Poly(arylene sulfide sulfone) (PASS) is a kind of newly developed polymeric membrane material which has excellent mechanical strength, thermal stability, and solvent resistance. And, it would be a potential material for high temperature ultrafiltration and organic solvent filtration. In this article, PASS hybrid ultrafiltration membrane with improved antifouling property was prepared by mixing TiO₂ nanoparticles which were grafted with polyacrylic acid (PAA). These membranes were prepared by a phase inversion technique and their separation performance and antifouling property of the prepared membranes were investigated in detail by SEM, FTIR, EDS, contact angle goniometry, filtration experiments of water, and BSA solution. The results shown that the TiO₂‐g‐PAA nanoparticles dispersed well in membrane matrix, the hydrophilicity of the membranes prepared within TiO₂‐g‐PAA nanoparticles have been improved and these membranes exhibited excellent water flux and antifouling performance in separation than that of the pure PASS membranes and PASS membranes with TiO₂ nanoparticles. More specifically, among membrane sample M0, M1.5, and MP1.5, MP1.5 which contained 1.5 wt% TiO₂‐g‐PAA exhibited the highest water permeation (190.4 L/m² h at 100 kPa), flux recovery ratio, and the lowest BSA adsorption amount. POLYM. ENG. SCI., 55:2829–2837, 2015. © 2015 Society of Plastics Engineers     

Polymer brush coatings for combating marine biofouling

A variety of functional polymer brushes and coatings have been developed for combating marine biofouling and biocorrosion with much less environmental impact than traditional biocides. This review summarizes recent developments in marine antifouling polymer brushes and coatings that are tethered to material surfaces and do not actively release biocides. Polymer brush coatings have been designed to inhibit molecular fouling, microfouling and macrofouling through incorporation or inclusion of multiple functionalities. Hydrophilic polymers, such as poly(ethylene glycol), hydrogels, zwitterionic polymers and polysaccharides, resist attachment of marine organisms effectively due to extensive hydration. Fouling release polymer coatings, based on fluoropolymers and poly(dimethylsiloxane) elastomers, minimize adhesion between marine organisms and material surfaces, leading to easy removal of biofoulants. Polycationic coatings are effective in reducing marine biofouling partly because of their good bactericidal properties. Recent advances in controlled radical polymerization and click chemistry have also allowed better molecular design and engineering of multifunctional brush coatings for improved antifouling efficacies.     

Antifouling activity of marine paints: Study of erosion

It is generally agreed that the prevention of marine fouling can be achieved by coatings from which a controlled release of toxic molecules prevents the growth of adhered organisms (bacteria, algae, molluscs). Since the end of 1990s, antifouling paints have been made by the blending of polyacrylic resins with biocides. The aim of this study was to use new polymers in order to obtain biodegradable antifouling paints with controlled release of biocide.     

Polypyrrole coatings for corrosion protection of Al alloy2024: influence of electrodeposition methods,solvents, and ZnO nanoparticle concentrations

Since ZnO nanoparticles increase the electrical conductivity of the polypyrrole (PPy) coatings, an investigation was carried out to evaluate the effect of ZnO nanoparticles loading on the corrosion protection performance of PPy coatings on AA2024 Al alloy in 3.5% NaCl solution. At first, some measurements were carried out to find the best experimental conditions containing the electrodeposition method, electrosynthesis solvent composition, and ZnO nanoparticles’ concentration for preparing the optimum PPy coating on Al alloy2024. Three different methods of electrodeposition, namely: cyclic voltammetry, galvanostatic, and potentiostatic techniques were analyzed. The anti-corrosion performance of the PPy coatings was evaluated by electrochemical impedance spectroscopy and Tafel polarization methods. The PPy prepared by potentiostatic method exhibited the best performance against corrosion of Al alloy2024 in 3.5% NaCl solution. Then, different mixtures of H₂O/ethanol were tested as electrosynthesis solvents for preparation of PPy coatings on the alloy by optimized electrodeposition mode (i.e., potentiostatic). In evaluation of the prepared coatings, the pure water was introduced as the optimum solvent in electrodeposition of PPy. The investigation of different ZnO nanoparticles’ concentrations proved that the PPy coating containing 0.025% ZnO nanoparticles was the optimum coating against the corrosion of Al alloy in NaCl solution. Finally, the long-term evaluation of the corrosion protection performance of the coatings revealed that the optimum coating provided suitable protection against corrosion up to 14 days after immersion.

     

Measurement of the adhesion strength of metal oxide and metal nitride thin films sputtered onto glass by the direct pull-off method

We have measured the adhesion strengths of metal oxide and metal nitride thin films reactively sputtered onto glass substrates using a specially devised direct pull-off test. For double-layer coatings such as metal nitride (CrN_x, TiN_x)/metal oxide (Al₂O₃, SnO₂, Ta₂O₅, TiO₂, ZnO, ZrO₂)/glass, separation usually took place at the nitride/oxide interface. The adhesion strength at the interface was found to depend on the strength of chemical bonding in the films concerned: for the same nitride top layer, the adhesion strength increased as the strength of the metal-oxygen (M-O) bond in the oxide underlayer decreased. X-ray photoelectron spectroscopy (XPS) measurements showed that a mixed layer was created at the nitride/oxide interface and that the adhesion strength at the interface increased with increasing thickness of the mixed layer. For single-layer coatings such as metal nitride (CrN_x, TaN_x, TiN_x, ZrN_x)/glass, the adhesion strength of the film to the glass substrate was found to increase with increasing strength of the M-O bond between the metal atom (M) in the nitride film and an oxygen atom (O). These adhesion behaviors could be explained by adhesion models based on chemical bonds at the interfaces.     

Dispersion of calcite by poly(sodium acrylate) prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization

Calcite is dispersed into nanoparticles with the use of polysodium acrylate, PAANa. The molecular weight distribution of PAANa greatly influences the characteristics of the dispersion. Near-monodisperse PAANa adsorbs irreversibly and totally onto the CaCO₃ surface, but for polydisperse PAANa, a mass segregation occurs, where only chains with a selected molecular weight are adsorbed. With polydisperse samples, small spherical CaCO₃ particles are generated in addition to calcite crystals. This bimodal dispersion is less viscous than the dispersion containing only calcite crystals.     

防污剂对海洋环境的影响探讨

防污涂料中防污剂的使用对海洋环境造成的影响越来越引起人们的关注,各种法律法规相继建立来限制防污剂的使用。探讨了几种比较常用的海洋防污剂的渗出行为、降解行为以及对海洋环境的影响,为实现防污涂料的环保化提供借鉴。     

Electrophoretic deposition of hydroxyapatite-chitosan-CNTs nanocomposite coatings

Three component suspensions of hydroxyapatite (HA), chitosan and CNTs were prepared in ethanol base solution (15 vol% water and 0.05 vol% acetic acid). The adsorption of HA nanoparticles on CNTs was investigated by FTIR and SEM analysis. It was found that HA nanoparticles are adsorbed on CNTs via chemical bonding between -NH₂ groups of chitosan (adsorbed on their surface) and -COOH groups of CNTs. Current density as well as kinetics of EPD was studied at 60 V. It was found that current density increases or remains nearly constant during EPD due to the rise in water electrolysis as deposit grows on the substrate. Deposition weight against EPD time showed a linear trend due to the absence of any voltage drop over the deposit during EPD. The incorporation of chitosan and CNTs in the microstructure of coatings was confirmed by TG/DTA and SEM analysis. CNTs exhibited high efficiency in reinforcing the microstructure of coatings and preventing from their cracking. CNTs incorporation in the coatings improved their mechanical properties (adhesion strength, hardness and elastic modulus) and corrosion resistance.