Anti Fouling Coating Based on CPs Report

8/10/2019 Anti Fouling Coating Based on CPs Report

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New

Anti

Fouling

Coatings

Based

on

Conductive

Polymers

Sze C. Yang, Richard Brown, Thomas Ramotowski, Wayne Tucker,

Lucie Maranda, Ryan Chena, Mae Shen

University of Rhode IslandOctober 2009

URITC PROJECT NO. 0001032

PREPARED FOR

UNIVERSITY OF RHODE ISLANDTRANSPORTATION CENTER

DISCLAIMER

This report, prepared in cooperation with the University of Rhode Island

Transportation Center, does not constitute a standard, specification, or

regulation. The contents of this report reflect the views of the author(s) whois (are) responsible for the facts and the accuracy of the data presented

herein. This document is disseminated under the sponsorship of theDepartment of Transportation, University Transportation Centers Program,

in the interest of information exchange. The U.S. Government assumes noliability for the contents or use thereof.


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New Anti Fouling Coating Based on Conductive Polymers

Sze C. Yanga, Richard Brown

b, Thomas Ramotowski

c, Wayne Tucker

c, Lucie Maranda

d,

Ryan Chena

, Mae Shena

a. University of Rhode Island, Chemistry Department, Kingston, RI

b. University of Rhode Island, Chemical Engineering Department, Kingston, RI

c. Naval Undersea Warfare Center, Newport, RI

d. University of Rhode Island, Graduate School of Oceanography, Narragansett, RI

Final Report to the URI Transportation Center for Project 1032

Introduction

Within the marine environment, any surface in contact with seawater suffers

from bio-fouling by marine organisms. When these organisms, such as algae and

barnacles, attach to the hull of a ship performance of the vessel is compromised.

Fouling on hulls increases fuel costs significantly, creates extra wear on engine

components due to extra power to move ships and can ultimately cause engine failure if

water intakes for cooling become blocked. Increased maintenance costs also occur as a

result of fouling as ships need to be dry docked more frequently for cleaning.

There are also unintended ecological effects when a bio-fouled ship moves

between ports. Fouling will transport non-indigenous species around. Greater

environmental inspections are required to detect any issues as soon as possible. This

requires more personnel, equipment and specific training.

Traditional antifouling paints were designed to release toxins from the surface of

the paint to prevent micro-organisms attaching to the surface1. The toxicity of the

released chemical species has been found to be damaging to the marine ecology and

poses problems for the environment. The previously banned tributyltin (TBT)

antifoulant was found to be extremely harmful to the environment. The current

commercial antifouling paint which contain large amounts (50% by weight) of copperbased antifoulants, is also harmful to the environment.

In this research, we explored the possibility for an alternative method for

reducing biofouling. We used an electronically conductive polymer as an additive to the

commercial paints such as polyurethane and epoxy. We set out to examine if the

additive is helpful for reducing fouling.


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Our proposal was motivated by the empirical data reported in the literature.

Medical researchers had found an unusually strong effect on cell growth in the presence

of a conducting polymer film2,3,4

. Cell growth was reported to be either strongly

suppressed or promoted depending upon environemental circumstances. In addition,

Wang et al reported an antifouling effect observed on paints containing single-strandpolyaniline

5. Previous researchers had reported a retardation in fouling by one to two

months relative to the same paint without polyaniline. These empirical results are

intriguing because it could be the first coated surface that prevents the attachment of

marine organisms without the release of any chemical agent.

For conducting polymer based antifouling paint5, the authors indicated that the

antifouling effect slowly decreased after immersion for one month. Their study

indicated that the decrease of effectiveness correlated with loss of electronic

conductivity of polyaniline. The reason for the loss of electronic conductivity is

dissolution of an anionic dopant (toluene sulfonate) in water. When the anionic dopant

is lost, the positive charge carrier on the polyaniline backbone becomes energetically

unfavorable and the conducting polymer is converted into the non-conductive form.

In this study we use a double-strand conducting polymer synthesized at URI6,7

to

replace the single-strand conducting polymer used in the previous study by Wang et al.

The purpose is to extend the duration of effectiveness of conducting polymers. The

double-strand polymer is a side-by-side complex of a conducting polymer with a

polymeric dopant and is shown schematically in figure1. Since the dopant is an integral

part of the conducting polymer, it is not susceptible to the problem of loss bydissolution. An additional advantage is that the double-strand conducting polymer is

much easier to blend with paint compared with the single-strand conducting polymer

used by the previous researchers.

Figure 1 A schematic of the URI double-strand conducting polymer.


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Synthesis of double-strand polyaniline

Double-strand polyaniline was synthesized by a template-guided synthesis8. A

typical small scale synthesis is described in the following: 0.25g Poly(acrylic acid)

powder (PAA) (M.W. 450,000, from Aldrich) was used as the template and was stirred

with 20 ml distilled water until all the powder was dissolved. Then 0.323 g aniline was

added into the PAA solution and was stirred for 24 hours to form PAA:An adduct. Next,

5 ml 1 M sulfuric acid was added into the PAA:An solution and was stirred for one hour

to acidify the adduct. At the end of this time, 5 ml 0.69 M ammonium persulfate

solution (0.79 g (NH4)2S2O8dissolved in 5 ml distilled water) was added ito the solution

and stirred for more than four hours. At this stage the product has a dark green color.

To obtain the final product this PAA:PAN complex was purified with a dialysis membrane

(35,000 M.W., Spectrum), first in hydrochloric acid then in distilled water.

Synthesis of organic/inorganic composite as a conducting polymer pigments forpaints.

A conducting polymer based pigment was previously developed at URI in

collaboration with Wayne Pigment Corporation.9 This conducting polymer pigment was

investigated as a non-chromate anticorrosive pigment for coatings on aluminum alloys.

In the present research work this type of pigment was used as an additive to epoxy or

polyurethane paints for its ease in blending with commercial paints, not because of the

need for its corrosion inhibition properties. The pigment was produced in a physical

adsorption process. An aqueous solution of the double-strand conducting polymer was

mixed with a slurry of inorganic pigments, such as SrHPO4, WO3, or CeO2. When the

condition of the mixture is properly adjusted, the organic conductive polymer

spontaneously and quantitatively adsorbs onto the inorganic pigment to form an

organic/inorganic composite suitable as a pigment for paints.

Figure 2 shows the adsorption of PAA:PAN on SrHPO4 particles, 1.00 g of SrHPO4

particles were mixed with 250 ml of 0.1528 g/l unpurified PAA:PAN solution then stirred

for two minutes. After stirring, when all the particles settled, the upper solution was

totally clear and the particles were green in color, which indicates that all the double-

strand polyaniline was adsorbed onto the SrHPO4particles.

By mechanically suspending inorganic particles in an aqueous solution of double-

strand polyaniline, a core-shell structure for the composite is expected with the polymer

coated on inorganic particles. Microscopic study, figure 3, shows that all the composites

have a uniform size within the range of 10 micrometer, while a bi-refringent


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phenomenon9under cross polarizer shows that the particles are really a composite

instead of a single amorphous polymer.

Figure 2.Physical adsorption of PAA:PAN on SrHPO4particles. In the left image,

PAA:PAN solution(green with white SrHPO4powder, and right image, particles settled

and clear upper solution.

(a) (b)

Figure 3.(a) Microscope image of the micron size (10 m) SrHPO4/ds-PAN composite

particles; (b) Bi-refringence phenomenon of the particles.

Paints containing conducting polymers as an additive.

The conducting polymer organic/inorganic composite was blended at 5% by

weight into a commercial polyurethane. The mixture is applied as a coating on glass or

onto procured polyurethane boards. The coatings show green color when the

conducting polymer is polyaniline. The coatings show a black color when polypyrrole

was used as the organic component of the composite.

In other tests, the conducting polymer pigments were blended at 1% to 5% by

weight into commercial epoxy resins. The paint was used to coat substrates of glass,

aluminum and steel.

Mix


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Fig. 4 Conducting polymer containing pigments.

Laboratory Evaluation of the conducting polymer coatings

Conducting polymer antifouling paint is not toxic to marine micro organisms.

In this section, laboratory experiments demonstrate that the conducting polymer

based antifouling paint is environmentally friendly. It is different from commercial

copper based antifouling paint, which leaches out chemicals that are toxic to algae and

marine micro-organisms. The experiments described in the followings showed that

although the conducting polymer paint inhibits the growth of algae directly on its

surface, it does not stop the growth of algae at the nearby surfaces. In contrast, the

commercial copper based antifouling paint not only inhibited the growth of algae on the

copper paint surface, but it also killed the algae in the surrounding sea water, and the

surrounding non-coated surfaces.

Experimental details:

Laboratory storage of algae containing sea water:

Diatom and green algae from the Narragansett Bay sea water was collected and

incubated. The sea water was stored in a 20 gallon fish tank indoors with a moderate

level of exposure to sun light. The stored sea water was supplemented with daily

addition of low concentration mineral (ferric nitrate) and sodium phosphate nutrients.

The stored sea water in the fish tank showed moderate and controlled growth of algae.

Experimental design:

A small quantity of the algae containing sea water was transferred to three

incubator bottles which were sterilized prior to the experiment. Figure 5 shows the

three bottles employed for the investigation. Bottle A serves as a control. It contains

the algae in sea water with a small amount of sand and stone pebbles from the beach at


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the URI Graduate School Oceanography pier on Narragansett Bay in Rhode Island.

Bottle B contains a paint chip of 5% conducting polymer in commercial epoxy paint, in

the same sea water as Bottle A. Bottle C contains a paint chip of commercial copper

based antifouling marine paint in the initially the same sea water as that in Bottle A.

All three bottles were placed on a laboratory bench that receives relatively

uniform and indirect sun light. The same amount of low concentration nutrient

(mineral phosphate and nitrate) was fed to all bottles daily during weekdays. Figure 5

shows that there were observable differences after two weeks of the comparative test.

The green color from the algae in the salt water in Bottles A and B is maintained at

nearly the same intensity during the test period. There are about the same amount of

algae attachment and growth at the inside walls of Bottles A and B. In contrast, the

green color of the initially algae infested water in Bottle C disappeared within the first

week of the test. A closer examination showed that there was no algae attached to the

walls.

Figure 5. The conductive polymer containing paint (middle incubator flask) inhibits

fouling on the paint surface without decimating the algae activity on the surfaces of the

uncoated wall of the incubatior flask.

From this study, the toxicity of the presently used copper based antifouling paint

is clear. It rapidly kills all the algae that tries to attach to the paint surface, but it is also

toxic to algae in the near vicinity. To that extent it is non selective, it is toxic to all alge

independent of location as long as it is close to the paint. The conductive polymer


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containing paint on the other hand appears to be non toxic to algae that is not in direct

contact with it. Because no algae appeared to settle on the paint, it cannot be

determined whether it is toxic on contact or just that the conductive polymer has some

mechansim by which the polymer does not want to settle on the surface.

Laboratory tests for conducting polymer as additive in urethane

In this part of study, seawater was collected from Narragansett Bay, filtered with

a coarse mesh screen to remove any large particles and used as the test environment.

Conducting polymer painted glass slides immersed in the seawater tank were employed

for an initial study of submerged surfaces.

Before 30 gallon tanks were filled with the Narragansettt Bay filtered seawater,

sand and pebbles with visible algae growth on the surface were used to line the bottom

of clean tanks. An aerator was used to pump room air through the seawater. The tanks

were placed on a laboratory bench that receives indirect sun light. Small quantities of

nutrients (dilute sodium nitrate and phosphate solutions) were added periodically. All

tanks maintained a steady growth of algae. The side walls and the bottom of the tank

show accumulation of green algae coatings. A rack holding about 15 to 20 paint coated

slides were submerged in the algae containing seawater. Figure 6 shows an example of

an experiment at the initial stage of the test.

Figure 6. Initial stage of the laboratory test. A rack of test samples in an algae-

containing seawater in a laboratory glass tank. The bottom of the tank is lined with

pebbles from the Narragansett Bay.


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Figures 7a and 7b show an example of coated glass slides exposed in the algae-

containing seawater for 4 weeks. It can be seen that both the bare glass and the

polyurethane coated glass (in the middle) are infested with bio-fouling. The sample

with the same polyurethane coating with 5% conducting polymer (dark colored samples)

are relatively free from the adhesion of algae. Figure 7b shows a close up of the threesamples and the control in a different illumination.

Figure 7a. Photo of coated glass slides exposed in algae-containing laboratory tank for 4

weeks.

Figure 7b. A close-up photo of the test panels in figure 7a.


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The same set of samples were photographed after 90 days of exposure in the

laboratory seawater. Figure 8 shows that algae has begun to coat the conducting

polymer containing polyurethane and the control samples.

Figure 8. The samples and controls from figure 7b after 90 days of exposure to algae-

containing laboratory seawater. The area with conducting polymer paint has less fouling

than the uncoated area (top) and the control sample of uncoated glass on the left hand

side of the image.

Field test in Narrangansett Bay, Rhode Island

In order to assess the antifouling properties of the conducting polymer coated

polyurethane panels in a marine environment, a series of field tests in collaboration

with Mr. Thomas Ramotowski and Dr. Wayne Tucker of NUWC, Newport were

performed. The objective was to compare the effectiveness for inhibiting biofouling of a

conducting polymer coated non-toxic paint with the commercial copper based

antifouling paints. A set of test panels were prepared in Aug. 2006 for immersion in

Narragansett Bay, Rhode Island, which is a nutrient-rich body of water. A recent

technical report10

published by the Narragansett Bay National Estuarine Research

Center analyzed the recent and historical data of the nutrients.


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Figure 9. Conducting polymer pigmented polyurethane coating on polyurenthane test

panels with dimension of 12x12x1 before the field test.

A typical test panel after coating is shown in figure 9. The four holes, one in each

corner, allowed these individual panels to be spaced out on tubes and to make a kite

for immersion. Several samples could then be tested on a single kite and the

environment would be similar for all the individual panels on the test kite. The panels

were in a horizontal position when immersed.

Figure 10. Test panels (1 ft x 1 ft) mounted on box kite type support structure.


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A typical kite of test samples is shown in figure 10 just prior to immersion. These

test panels were immersed 6 within the low-tide level at the side of a NUWC test site at

the Narragansett Bay of Rhode Island , figure 11. One set of tests started in Aug. 2006.

Another set of tests started in the spring of 2007.

Figure 11. Immersion of test panels at about 6 below the low-tide level, suspended

besides a dock area at NUWC test site in Narragansett Bay, RI.

These test panels were periodically pulled to the pier for photograph taking and

examination. Figure 12 shows a photograph of a box kite test assembly pulled out of

the Narragansett Bay during Aug. 2008 after 3 weeks of immersion. The front panel is a

coating with 5% conducting polymer pigment. The back panel is the same polyurethane

coating without conducting polymer pigment. It can be seen that the control panel has

much heavier bio-fouling comparing with that of the conducting polymer pigmented

panel. It can also be seen that the type of marine organisms attached to these two

panels are visually different. This impression was verified in panels examined by marine

biologists. This and other test results show that the conducting polymer pigmented

coatings can delay the bio-fouling in the field condition for about 1 month.

The field test results are consistent with the laboratory seawater tests described

in the previous section. The conducting polymer pigmented paints can delay the bio-

fouling but they eventually overcame by bio-fouling. Although this is an interesting

finding for a non-toxic antifouling paint, it is not competitive with the commercial

copper based antifouling paint. Figure 13 shows a set of test panels photographed after

2 months of field test. The front panel is a conducting polymer pigmented coating. The

back panel is a commercial copper based antifouling paint. The conducting polymer

pigmented coating is heavily fouled by the end of the second month, but the copper

based paint in the back is still relatively free from fouling.


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Figure 12. A photograph of test panels after 3-weeks of immersion in seawater. The

front panel is a conducting polymer pigmented coating. The back panel is a control

panel.

Figure 14 show the conducting polymer pigmented test panels after immersion

of about 6 months. At this point, there is no visual difference between the conducting

polymer pigmented panel and the control panel. It was noted that the initial surface

morphology (within the first 1 months) of marine organism growth on the paints with

conducting polymer additives was different from that of the control panels, see for

example figure 12. It appears that the conductive polymer was selective in allowingdeposition.

Figure 13. Test panels immersed for 2 months. Front: conducting polymer pigmented

polyurethane coating. Back: Commercial copper based antifouling paint.


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Figure 14. Test panels immersed for 6 months.

Conclusions:

A pigment was synthesized that consisted of a composite material of an

organic polyaniline electronic conducting polymer with an inorganic core. These

pigments were used to blend into commercial polyurethane and epoxy paints. These

paints were then coated on glass, metal and polyurethane substrates for tests of their

antifouling properties in the laboratory seawater tanks and in the field.

Laboratory tests in seawater comparing conductive polymer containing paint

to copper containing antifouling paints showed that the conducting polymer based paint

does not release toxic chemicals unlike the copper containing paint which was toxic to

the surrounding environment.

Another laboratory test was performed to verify that the conducting polymer

has antifouling property. The 5% conducting polymer paints showed resistance to

biofouling relative to that of the control sample in a time window of 1 month before

both samples were fouled with algae growth.

Field tests of 12x12x1 coated panels were performed by immersion of test

panels in Narragansett Bay during the period of Nov. 2007 to June 2008. The field tests

showed that there is a moderate delay of fouling of 3 weeks to 1 month compared with

control panels with the same commercial paint without the conducting polymer

additive. The conducting polymers eventually fouled. Although the conducting polymer


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is a non-toxic antifoulants, the antifouling resistance faded faster than the control

panels containing copper paints. With a relative short period of antifouling activity of 1

month, it was concluded that the present formulation is not yet a viable replacement for

copper based antifouling paint.

In the field studies, it was noted that the initial surface morphology (within the

first 1 months) of marine organism growth on the paints with conducting polymer

additives was different from that of the control panels. From these limited number of

observations it can be speculated that the conducting polymer inhibits adhesion for

certain species of marine organism, but not all the species. The adhesion of the non-

inhibited species then form a bio-mass coated surface that facilitates further growth of

marine organisms and the eventual fouling. This leads to a recommendation on a

further study to validate this speculation. If validated, an understanding of the

mechanism for the physiological effect may be useful for further development of a

viable conducting polymer based antifouling paint.

References:

1. M. E. Callow and J. A. Callow, Marine biofouling: a sticky problem, Biologist 49, 1

(2002)

2. J.Y. Wong, et al.,Electrically conducting polymers can non-invasively control the shape

and growth of mammalian cells, Proc. Nat. Acad. Sci., 91, 1994, pp. 3201-3204.

3. B.E. Schmidt, et al., Stimulation of neurite outgrowth using an electrically conductive

polymer, Proc. Nat. Acad. Sci., 94, 1997, pp. 8948-8953.

4. A. Kotwal, et al., Electrical stimulation alters protein adsorption and nerve cell

interactions with electrically conducting biomaterials, Biomaterials, 22, 2001, pp. 1055-

1064.

5. Wang, X.-H.; Li, J.; Zhang, J.-Y.; Sun, Z.-C.; Yu, L.; Jing, X.-B.; Wang, F.-.S.; Sun, Z.-X.;

Ye, Z.-J. Polyaniline as marine antifouling and corrosion-prevention agent. Synthetic

Metals (1999), 102(1-3), 1377-1380.

6. L. Sun, H. Liu, R. Clark, S. C. Yang, Sun, Double-Strand Polyaniline, Syn Met 85,67

(1997)

7. J.-M. Liu and S. C. Yang, "Novel Colloidal Polyaniline Fibrils Made by Template Guided

Chemical Polymrization", J. Chem. Soc., Chem. Comm., 1529 (1991).


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8. L. Sun, S. C. Yang, J.-M. Liu, "Template-Guided Synthesis of Conducting Polymers:

Molecular Complex of Polyaniline and Polyelectrolyte.", American Chemical Society,

Polymer Preprints, 33, 379 (1992).

9. Conductive Polymer-Inorganic Hybrid composites, John Sinko, Sze C. Yang,

U.S. Patent 7125925 B2, Oct. 24, 2006.

10. Leanna Heffner, Nutrients in Mid-Narragansett Bay: A Spatial Comparison of Recent

and Historical Data Narragansett Bay Research Reserve, Technical Report, Jan., 2009,

http://www.nbnerr.org/.
http://www.nbnerr.org/http://www.nbnerr.org/http://www.nbnerr.org/


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AN ANALYSIS OF THE RELATIONSHIP BETWEEN ALGAE GROWTH RATES AND

THE TEXTURE OF THE ASSOCIATED MEDIUM.

Patrick Fullera, David Keach

aand Richard Brown

b

a. Bishop Hendricken High School, Warwick, RI.

b. University of Rhode Island, Chemical Engineering Department, Kingston, RI

Final report to the URI Transportation Center for Project 1032

Introduction

Marine biologists have empirically observed a distinct variation in algae growth

rates on different types of shells. A proposed theory for this anomaly is that the texture

of a seashell may inhibit or promote algae growth. This theory may be applied to the

hulls of seafaring vessels. Many ships, especially cargo vessels, constantly have to deal

with algae growth on their hulls. Present solutions to this problem are few, and include

simply accelerating to wash off the algae on the hull. However, algae adheres to thehulls of the ships, costing many companies millions of dollars in operating, maintenance

and failures. Assuming the aforementioned theory is valid, it logically follows that that a

properly textured hull could be resistant or immune to sea algae growth. If one could

devise a more precise correlation between algae growth and the texture of the growth

medium, the results could be applied to create algae-resistant textured hulls.

In order to test the validity of the theory relating shell texture to algae growth,

images were taken different types of shells. In this study, none of the shells had algae

growth on them, so it was hoped to find a surface feature that would be consistent

between the shells and lead to a non-fouling surface texture. A scanning electron

microscope (SEM) was used to image the surface features of shells at 250, 500, 1000,

2000, and 4000 times standard magnification. Twelve different types of shells, collected

from different areas on the east coast, were examined. The varying SEM magnifications

permitted observation of regularities and irregularities in shell texture, with the aim of

the ability to categorizing shells based on texture.


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Results

Although characteristics between the 12 seashells were distinct and different from each

other, there seemed to be some notable similarities. All of the shells observed can be

grouped into one of three categories. The few shells contained in category one had long

grooves, much like canyons, that ran parallel to each other. Henceforth, these will be

referred to as refer to as the canyon group.

Figure 1.1 Shell 6 at 250 magnification

The texture of shell 6, figure 1.1, was smooth to the touch. When imaged in

the SEM, one could make out small linear ridges. The scale of these ridges was on theorder of one to two microns in width.



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These concave grooves were the foundation of microscopic islands which

scattered themselves across the surface of shell 6.A second shell with the canyon

configuration is shown in figure 1.2. The features in this case are quite coarse, on the

scale of tens of microns in width and uneven in comparison to the earlier shell in figure

1.1.

The next category is slightly broader. The shells in group two appeared to haveno canyons of any kind. For the shells in this category a consistent surface roughness

apparent, figure 2.1 and figure 2.2. This was roughness raised above the surface.




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For this second category of shell, the surfaces are always uneven. Unlike the

canyon group, there is really no easy smooth place for algae to settle on the surface.

The scale of the roughness was of the order of 5 to 10 microns.

The third category of shells was actually a combination of two other surfaces.

Rather than a surface roughness, these shells had flat surfaces with depressions like

craters in the surface and these were part of a coarser ridge type structure, figure 3.1.


This distinct combination was most prominent on shell 23, figure 3.2. In

addition to craters and flat areas contained within ridges cracks were present on this

surface shown by the white area in the micrograph where gold coating used to provideconductivity to the shell did not penetrate down into the cracks.



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A slightly smoother surface but with overall the same characteristics is shown

in figure 3.2. For this shell the ridges were not as sharp and the background surface was

not as rough. For the shells of this category, there were large smooth area where algae

would be able to settle.

There was one particular specimen that did not fall into any of the threecategories. However, it should be noted that this was not a shell but a plaster of Paris

mold of a shell. Needles were present on the surface and it is suspected that this is from

the calcium based crystals and does not reflect the shell surface but the surface of

plaster of Paris. This materials therefore should not be used to copy the surface of shells

to mimic them.

Figure 4.1 Shell sculpture at 1000 magnification

Conclusion

There did not seem to be one overriding feature of the shells surface that

pointed to an control of the fouling behavior. Shells had coarse ridges in quite large

scales down to microscopic features that would probably be disruptive to marine

growth such as algae. However the large ridge or canyon structures have rather largeflat areas, by comparison, which would allow easy settlement of algae and adhesion to

the surface. It would then appear that there may be other factors, such as a biological

agent on the surface that may control adhesion of algae. It would appear from this study

that surface texture is not a method to pursue for algae growth suppression.


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Anti Fouling Coating Based on CPs Report

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