Dissertations / Theses on the topic 'Fouling-release'

Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2009.
Title from electronic title page (viewed Oct. 5, 2009). "... in partial fulfillment of the requirements for the degree of Doctorate of Philosophy in the Department of Chemistry." Discipline: Chemistry; Department/School: Chemistry.

The unwanted build up of fouling organisms on immersed structures has been a problem that has been addressed over the years in many different ways, from tar and pitch on the hulls of vessels to various toxin based ablative coatings and most recently, foul-release coatings that present a non stick surface to which organisms can not adhere strongly. These foul-release coatings have been relatively successful and further investigation into the formulation of siloxane based coatings is a environmentally acceptable and commercially viable concept. The significance of the hydrophilicity of a range of cured siloxane polymers upon the attachment of marine fouling species is presented. The polymers were synthesised from polymethylhydrosiloxane (PDHS) with the grafting of hydrophilic ethoxy based, linear chains of various lengths. Following cross linking, films of these materials were characterised by Nuclear magnetic resonance (NMR), Infrared (lR) spectroscopy, X-ray photoelectron spectroscopy (XPS), contact angle goniometry, topography, thermal analysis, sorption of water, force of adhesion and nano-indentation. The films were tested by bacterial growth and attachment studies, the growth and attachment of various algal propagules and also by static raft trials. Results suggest that there is a maximum hydrophilic content possible when investigating these coatings, due to the intake of water molecules, which causes swelling and subsequent degradation of the stability of the coating. The optimum hydrophilic content for achieving minimum adhesion of fouling organisms was unclear, however, trends in experimental data were identified. The bacterial attachment and growth studies conducted upon Fucus propagules indicated an increase in growth upon the PMHS polymers with the addition of3-{2-[2-(2-methoxy-ethoxy)-ethoxy]ethoxy}- propene groups, while the Sargassum propagules illustrated a reduction in growth during the same conditions. Ulva and Enteromorpha propagules showed no visible trends in growth upon the coatings tested. The surface energy and adhesion results illustrate that the PDMS with 3-{2-[2- (2-methoxy-ethoxy)-ethoxy]-ethoxy}-propene groups were the most adhesive of the coatings teste4 (14.9 oN in comparison to 3-9 oN) but possessed the lowest surface energy (22.46 mJ m2 ). In exposure trials over a 10 month period, the peroxide cured coatings out performed the other curing systems tested, however the colonisation of the range of polymers was inconclusive.

Marine biofouling is the accumulation of organisms onto surfaces immersed in sea water. Fouling of ships causes an increase in hydrodynamic drag which leads to performance issues such as increased fuel consumption and a reduced top operating speed. Fouling-release (FR) coatings are one way that paints have been used in combating biofouling by allowing for the easy removal of settled organisms. Traditional FR coatings are silicone elastomers which are soft, easily damaged, and require a tie coat for adhesion to marine primers. Siloxanepolyurethane FR coatings have shown promise as FR coatings, providing enhanced durability and toughness, better adhesion to marine primers, and comparable FR performance to commercial coatings. Preliminary studies were conducted to explore the use of PDMS macromers in the preparation of siloxane-polyurethane FR coatings. Attachment and removal of fouling organisms on the siloxane-polyurethane coatings based on PDMS macromers was comparable to commercial FR coatings. Extended water aging was also carried out to determine effects of extended water immersion on the fouling-release performance of the coatings. At up to four weeks of aging, the FR performance of the coatings was not affected. Static immersion marine field testing was performed to determine the fouling-release performance of siloxane-polyurethane coatings prepared with PDMS macromers. The performance was found to be comparable to commercial FR coatings for up to one year, including water jet removal of slimes, barnacle push-off removal, and soft sponging. The coatings showed good fouling-release performance until extremely heavy fouling was allowed to settle. Underwater hull cleaning was conducted for one siloxane-polyurethane composition identified as a top performer from static field testing. The coating was easily cleaned of fouling with rotating brushes for six months. The cleaning capability of the coating was reduced when large barnacles and other extremely heavy fouling was present. A commercial FR coating became heavily damaged with brush cleaning while the siloxane-polyurethane coating remained mostly undamaged. With more frequent cleaning, it is suspected that siloxanepolyurethane coatings would show cleaning capability for longer periods of time. Pigmentation of siloxane-polyurethane coatings based on difunctional PDMS and PDMS macromers was explored to investigate the effect on FR performance. Pigmentation with titanium dioxide caused a slight decrease in FR performance in some cases, but this was easily overcome by the addition of slightly more PDMS in the coating binder, thus illustrating the feasibility of siloxane-polyurethane coatings as effective, pigmented FR coatings. Finally, the exploration of unique PDMS polymer architectures has been explored for the development of additional, novel, fouling-release coatings. The incorporation of end-functional PDMS homopolymer molecular brushes and branched PDMS macromers into siloxane-polyurethane fouling-release coatings shows promise for the development of unique coatings where improved FR performance may be obtained.
Office of Naval Research (U.S.)

Marine biofouling has troubled mankind, both environmentally and economically, since they set sail, resulting in many undesired consequences such as increased drag, reduced maneuverability, increased fuel consumption and greenhouse gas emissions, and heightened maintenance costs. This problem is highly complex as it involves more than 4000 marine organisms with varying modes of adhesion and surface preferences as well as many aquatic environments. The common state-of-the-art approaches to contend with marine biofouling on the submerged surfaces of ships in seawater has antifouling (AF) and fouling-release (FR) surfaces. As AF coating systems utilize biocides which are often toxic to the environment to prevent settlement of biofoulants, the endeavors have been shifted towards non-toxic FR marine system. Many FR systems take advantage of low surface energy and modulus polydimethylsiloxane (PDMS) on their surface, while the recent attempts explored the simultaneous effect of PDMS and hydrophilic moieties (i.e. polyethylene glycol (PEG) or zwitterionic polymers) on an FR surface, known as amphiphilic surfaces. Thus, the work in this dissertation focused on attaining amphiphilic surfaces with desirable FR performance. The studies in this dissertation were investigated to deliver two goals: 1) Enhancing the (FR) fouling-release performance of previously developed coating systems; 2) Introducing novel fouling-release marine coatings with set criteria. To address the former, a series of amphiphilic additives containing PDMS and hydrophilic polymers (zwitterionic-based or PEG) were prepared in chapters two-five. These additives were incorporated in several previously developed FR coating systems in order to modify their surfaces and enhance their FR performance. To address the latter, two amphiphilic marine coating systems were explored for accessing durable, non-toxic, and effective FR surfaces using epoxy-amine crosslinking chemistry. Overall, the studies in this dissertation not only demonstrated viable FR surfaces with desirable performance against several representative marine organisms such as N. incerta, U. linza, C. lytica, barnacles, and mussels but also contributed a deeper understanding about the effect of amphiphilicity concentration/balance on surface and FR properties.

Biofouling has been an economically and environmentally costly problem to mankind ever since they set sail. Biofouling causes frictional drag leading to slow vessel speeds, and increased fuel costs. Antifouling (AF) coatings containing biocides have been used for decades, however, since some biocides have shown undesired effects towards the environment, a non-toxic solution to combat fouling is desired. Subsequently, fouling release (FR) coatings quickly gained acceptance as a non-toxic approach to contend with biofouling. Unlike AF coatings, FR coatings not necessarily prevent settlement of organisms, they permit weak adhesion which is easily released by water shear or light grooming. The siloxane-polyurethane (SiPU) coatings based on the concept of self-stratification is a non-toxic and durable approach to prepare FR coatings. In this work, several approaches were considered to optimize surface properties of SiPU coatings. Incorporation of phenyl-methyl silicone oils led to improved FR properties towards several marine organisms in laboratory assays and in ocean field immersion. Enhancement in FR properties may be attributed to slowly exuding silicone oil providing surface lubricity, weakening the adhesion of marine organisms. Addition of diphenyldimethyl siloxane in to SiPU coatings at different ratios resulted in micro-scale surface topographical features which negatively affected microfouling-release while several coatings displayed good FR performance towards macrofouling organisms. In another study, decreasing the acid group content helped to improve FR performance towards barnacles, but FR performance towards diatoms were compromised. Novel amphiphilic siloxane-polyurethane (AmSiPU) coatings from polyisocyanate pre-polymers modified with polydimethyl siloxane and polyethylene glycol displayed excellent FR properties towards several marine organisms during laboratory assays. These AmSiPU coatings show promise as contenders to commercial FR standards. Initial development of SiPU coatings with hydrophilic surfaces showed promise, as the coatings showed rapidly rearranging surfaces with comparable FR performance to commercial standards which claim hydrophilic surface properties. During freshwater field immersion trials, SiPU coatings displayed excellent mussel FR performance up to 3 years. Surface analysis suggested that solvent content affected self-stratification and morphology of SiPU coatings. The SiPU coating system is a highly tunable, tough, environmentally friendly, and practical FR solution which can evolve along with non-toxic commercial marine coatings.
Office of Naval Research (Grant number N00014-12-1-0482)
SSPC
Valpar
American Coatings Association
North Dakota State University. College of Science and Mathematics

The main aim of this thesis was to investigate the potential of Elminius modestus (= Austrominius modestus) for evaluating the performance of fouling-release (FR) coatings. A secondary aim was to explore how the membranous-basis of this species influences the fracture mechanics and release from FR coatings in comparison to Balanus amphitrite (= Amphibalanus amphitrite), a barnacle with a calcareous-basis and widely adopted as a model for antifouling and FR studies. The critical removal stress (CRS) − the force required to remove fouling organisms, normalised by contact area − is a standard measure to evaluate FR coatings using either barnacles with calcareous-bases or metal studs (‘pseudobarnacles’). Testing FR coatings against a diverse range of fouling organisms is necessary to evaluate the global effectiveness of a coating. The percentage settlement of cyprids, growth rate, and CRS of laboratory-cultured barnacles were evaluated on polydimethylsiloxane (PDMS) standard coatings (Silastic T-2 and Sylgard 184). The percentage settlement on the PDMS coatings between the two species did not significantly differ, however, there were differences in the growth rate and CRS. When grown on Silastic T-2 and Sylgard 184 and fed Tetraselmis suecica algae, E. modestus grew at a faster rate than that of B. amphitrite. There was also a significant coating effect on the growth of E. modestus with barnacles on Sylgard 184 growing to larger size than those grown on Silastic T-2. The CRS of E. modestus was less than that for B. amphitrite but only for the coating Sylgard 184. Using high-speed photography, the separation processes of E. modestus and B amphitrite, from Silastic T-2 and Sylgard 184 coatings was observed. Four distinct separation patterns were characterised; lift, peel, adjacent peel and twist. These were based on the location of the initial separation and direction of propagating instabilities in respect to the direction of detachment force. The observed differences in the separation patterns between species may have more to do with the variations in shape and structure of the barnacle shell than to the type of basis. However, the flexibility of the membranous-basis of E. modestus was important for the propagation of the fracture as it hindered the formation of fingering instabilities as they progressed through the adhesive interface. The bulk properties of five polysiloxanes and three fluoropolymers were modified by changing the polymer chain length and cross-linker density, which provided coatings with a modulus ranging from 0.31 to 19.73 MPa. These were used to investigate whether laboratory assays were a good predictor of a coatings performance in the field, in terms of settlement/recruitment and CRS. Two field populations (Fairlie Quay and Burnham-on-Crouch) over two years (2010 and 2011) were compared to a laboratory culture of E. modestus barnacles. There were similarities between the laboratory settlement/field recruitment and CRS of E. modestus from the two field populations and the laboratory culture across the eight coatings. This made it possible to discriminate between the coatings. Although, the CRS measurements did significantly differ between locations and years, where the general pattern from highest to lowest in terms of CRS between the locations was Fairlie Quay > laboratory > Burnham-on-Crouch. These eight coatings were also used to investigate the degree in which the elastic modulus of a coating can influence the CRS of E. modestus, compared to the CRS of B. amphitrite. The regression analysis confirmed that as the modulus increases the CRS for both species increases. There were marked differences in the removal of barnacles from the high modulus fluoropolymers. B. amphitrite, unlike E. modestus, failed to detach and left the basis on the coating’s surface. As E. modestus can differentiate between the coatings in terms of FR efficacy and was amenable to laboratory culture with a comparable growth rate to B. amphitrite, this species is recommended as an additional model for FR studies.

Surfaces submerged in marine environments rapidly get colonized by marine organisms, a process known as biofouling. Fouling costs maritime industries billions of dollars annually. The most common methods of combating marine biofouling are toxin containing antifouling coatings which often have detrimental non-target environmental effects. These effects and proposed bans on harmful substances in antifouling coatings, mandates development of more environmentally friendly antifouling technologies. Of these, foul-release coatings, which minimize attachment and adhesion of fouling organisms (rather than killing them) are promising alternatives. Here I explored the utility of petroleum waxes as novel antifouling/foul-release coatings. I first investigated the responses of propagules (larvae or spores) of six common fouling organisms to wax coatings in the laboratory. A wide variation in the response of these different organisms, and in the different types of response (settlement, adhesion, etc.) by the same organism, was observed, but the most inhibitory coatings were those made from microcrystalline wax and silicone oil. However, in field trials in Sydney Harbour, paraffin waxes had the strongest antifouling performance, with activity up to one year (the trial duration). These waxes also had strong foul-release effects, with fouling that did attach mostly removed by a low pressure water jet. Composition of fouling communities on paraffin waxes differed significantly from other waxes or controls, with little or no hard fouling organisms (barnacles, bivalves) on paraffin. The mechanisms of antifouling and foul-release actions of paraffin waxes appear to be due to changes in surface properties. The surfaces of the paraffin waxes changed noticeably after 4 - 8 weeks immersion in the sea or in seawater aquaria. Antibiotic treatments showed that this change in surface appearance was due to biological (microbial) activity. Bacteria appear to remove the amorphous phase from the surface of the paraffin waxes, revealing an underlying crystalline phase, which is less affected by bacterial action. I suggest that these crystals form a microstructured ?bed of nails? of crystals of varying shapes and sizes which inhibit settlement and reduce adhesion strength of those organisms which do settle.

Biofouling, the attachment and growth of microorganisms and aquatic animals on submerged surfaces, poses many economic and environmental challenges like increase in frictional drag, fuel consumption, and cost of maintenance of ships. Coatings containing harmful biocides, called anti-fouling (AF) coatings, are used to combat fouling. But, the biocides proved toxic to the aquatic environment, which led to replacement of AF coatings by non-toxic fouling-release (FR) coatings. FR coatings do not contain toxic biocides and allow formation of a weak bond between the surface and the organisms, which can be easily broken through light grooming or hydrodynamic forces. Current research is aimed at developing robust coatings that can exhibit similar or superior FR performance as compared to commercial FR coatings. Previously, self-stratified FR coating systems were developed using siloxane and polyurethane (SiPU) in the Webster research group. Although the SiPU coatings exhibited comparable FR performance to the commercial standards, previous experiments did not show effect of surface grooming or cleaning on the FR performance. In the first part of the work, an SiPU formulation was abraded using two different Scotch Brite pads with varying roughness. Surface analysis experiments showed retention of hydrophobicity even after abrasions. The abraded coatings were characterized for FR performance against common fouling organisms. Improvement in FR performance of the abraded coatings compared to the smooth SiPU coating and the commercial standards against macrofoulants, like barnacles, was attributed to dimensions of the features formed on the coatings after abrasions. Recent concerns regarding hazards associated with using isocyanates to make polyurethanes necessitated the need to find “safer” alternatives in FR marine applications. Therefore, novel isocyanatefree glycidyl carbamate (GC) technologies were explored as potential substitutes for regular polyurethanes to make FR marine coatings. GC resins were modified using siloxanes and polyethylene glycols to make hydrophobic and amphiphilic coatings with varying surface chemistries. The resultant coatings were characterized for mechanical properties, thermal behavior, and finally, FR performance against common fouling organisms. Although GC coatings showed subpar overall FR performance as compared to the commercial standards, GC technologies show potential for use in marine applications.
Society for Protective Coatings (SSPC)
American Coatings Association (ACA)
North Dakota State University. College of Science and Mathematics

Barnacles are dominant hard–fouling organisms in marine waters. They attach to substrates by secreting a complex proteinaceous adhesive. Understanding the chemical composition of this multi–protein underwater adhesive and how it is affected by environmental variables, such as oceanic temperatures, is critical for developing nontoxic solutions to control biofouling. Previous experiments in our lab revealed an inverse relationship between critical removal stress (CRS) and temperatures at which barnacles were reared. Further investigations showed that this correlation is not attributed to differences in physical properties such as barnacle size or short–term changes in the viscosity of adhesive. Therefore, the observed effects may be influenced by a physiological response to temperature during initial growth and development. We hypothesized that rearing temperature affects the expression of proteins found in the adhesive matrix. To elucidate the underlying mechanisms responsible for the temperature effect, we analyzed uncured barnacle adhesive using two-dimensional gel electrophoresis (2DGE) and matrix-assisted laser desorption/ionization-tandem time-of-flight (MALDI-TOF/TOF) mass spectrometry (MS). In our analysis, we 1) detected differences in protein expression at two experimental temperatures (15°C and 25°C) and 2) identified several proteins that may serve functional roles in the process of adhesion. Our data are also consistent with a model that the curing process of barnacle adhesive may be analogous to the process of wound healing in animals.

Biological invasions are an important issue of global change and an increased understanding of invasion processes is of crucial importance for both conservation managers and international trade. In this thesis, I have studied the invasion of the brown seaweed Fucus evanescens, to investigate the fate and effect of a perennial, habitat-forming seaweed introduced to a coastal ecosystem. A long-term study of the spread of F. evanescens in Öresund (southern Sweden) showed that the species was able to expand its range quickly during the first 20 years after the introduction, but that the expansion has been slow during the subsequent 30 years. Both in Öresund and in Skagerrak, the species is largely restricted to sites where native fucoids are scarce. Laboratory experiments showed that the restricted spread of F. evanescens cannot be explained by the investigated abiotic factors (wave exposure and salinity), although salinity restricts the species from spreading into the Baltic Sea. Neither did I find evidence for that herbivores or epibiota provide biotic resistance to the invader. On the contrary, F. evanescens was less consumed by native herbivores, both compared to the native fucoids and to F. evanescens populations in its native range, and little overgrown by epiphytes. Instead, the restricted spread may be due to competition from native seaweeds, probably by pre-occupation of space, and the establishment has probably been facilitated by disturbance. The studies provided little support for a general enemy release in introduced seaweeds. The low herbivore consumption of F. evanescens in Sweden could not be explained by release from specialist herbivores. Instead, high levels of chemical anti-herbivore defence metabolites (phlorotannins) could explain the pattern of herbivore preference for different fucoids. Likewise, the low epibiotic colonisation of F. evanescens plants could be explained by high resistance to epibiotic survival. This shows that colonisation of invading seaweeds by native herbivores and epibionts depends on properties of the invading species. The large differences between fucoid species in their quality as food and habitat for epibionts and herbivores imply that invasions of such habitat-forming species may have a considerable effect on a number of other species in shallow coastal areas. However, since F. evanescens did not exclude other fucoids in its new range, its effect on the recipient biota is probably small.

Biofouling has been an economically and environmentally costly problem to mankind ever since they set sail. Biofouling causes frictional drag leading to slow vessel speeds, and increased fuel costs. Antifouling (AF) coatings containing biocides have been used for decades, however, since some biocides have shown undesired effects towards the environment, a non-toxic solution to combat fouling is desired. Subsequently, fouling release (FR) coatings quickly gained acceptance as a non-toxic approach to contend with biofouling. Unlike AF coatings, FR coatings not necessarily prevent settlement of organisms, they permit weak adhesion which is easily released by water shear or light grooming. The siloxane-polyurethane (SiPU) coatings based on the concept of self-stratification is a nontoxic and durable approach to prepare FR coatings. In this work, several approaches were considered to optimize surface properties of SiPU coatings. Incorporation of phenyl-methyl silicone oils led to improved FR properties towards several marine organisms in laboratory assays and in ocean field immersion. Enhancement in FR properties may be attributed to slowly exuding silicone oil providing surface lubricity, weakening the adhesion of marine organisms. Addition of diphenyldimethyl siloxane in to SiPU coatings at different ratios resulted in micro-scale surface topographical features which negatively affected microfouling-release while several coatings displayed good FR performance towards macrofouling organisms. In another study, decreasing the acid group content helped to improve FR performance towards barnacles, but FR performance towards diatoms were compromised. Novel amphiphilic siloxane-polyurethane (AmSiPU) coatings from polyisocyanate pre-polymers modified with polydimethyl siloxane and polyethylene glycol displayed excellent FR properties towards several marine organisms during laboratory assays. These AmSiPU coatings show promise as contenders to commercial FR standards. Initial development of SiPU coatings with hydrophilic surfaces showed promise, as the coatings showed rapidly rearranging surfaces with comparable FR performance to commercial standards which claim hydrophilic surface properties. During freshwater field immersion trials, SiPU coatings displayed excellent mussel FR performance up to 3 years. Surface analysis suggested that solvent content affected self-stratification and morphology of SiPU coatings. The SiPU coating system is a highly tunable, tough, environmentally friendly, and practical FR solution which can evolve along with non-toxic commercial marine coatings.
Office of Naval Research (grant number N00014-12-1-0482)
SSPC
Valpar
American Coatings Association
North Dakota State University. College of Science and Mathematics
Coatings and Polymeric Materials
Coatings and Polymeric Materials
College of Science and Mathematics

abstract: With the application of reverse osmosis (RO) membranes in the wastewater treatment and seawater desalination, the limitation of flux and fouling problems of RO have gained more attention from researchers. Because of the tunable structure and physicochemical properties of nanomaterials, it is a suitable material that can be used to incorporate with RO to change the membrane performances. Silver is biocidal, which has been used in a variety of consumer products. Recent studies showed that fabricating silver nanoparticles (AgNPs) on membrane surfaces can mitigate the biofouling problem on the membrane. Studies have shown that Ag released from the membrane in the form of either Ag ions or AgNP will accelerate the antimicrobial activity of the membrane. However, the silver release from the membrane will lower the silver loading on the membrane, which will eventually shorten the antimicrobial activity lifetime of the membrane. Therefore, the silver leaching amount is a crucial parameter that needs to be determined for every type of Ag composite membrane. This study is attempting to compare four different silver leaching test methods, to study the silver leaching potential of the silver impregnated membranes, conducting the advantages and disadvantages of the leaching methods. An In-situ reduction Ag loaded RO membrane was examined in this study. A custom waterjet test was established to create a high-velocity water flow to test the silver leaching from the nanocomposite membrane in a relative extreme environment. The batch leaching test was examined as the most common leaching test method for the silver composite membrane. The cross-flow filtration and dead-end test were also examined to compare the silver leaching amounts. The silver coated membrane used in this experiment has an initial silver loading of 2.0± 0.51 ug/cm2. The mass balance was conducted for all of the leaching tests. For the batch test, water jet test, and dead-end filtration, the mass balances are all within 100±25%, which is acceptable in this experiment because of the variance of the initial silver loading on the membranes. A bad silver mass balance was observed at cross-flow filtration. Both of AgNP and Ag ions leached in the solution was examined in this experiment. The concentration of total silver leaching into solutions from the four leaching tests are all below the Secondary Drinking Water Standard for silver which is 100 ppb. The cross-flow test is the most aggressive leaching method, which has more than 80% of silver leached from the membrane after 50 hours of the test. The water jet (54 ± 6.9% of silver remaining) can cause higher silver leaching than batch test (85 ± 1.2% of silver remaining) in one-hour, and it can also cause both AgNP and Ag ions leaching from the membrane, which is closer to the leaching condition in the cross-flow test.
Dissertation/Thesis
Masters Thesis Civil, Environmental and Sustainable Engineering 2017