Innovative antifouling technologies: microtexture and metal

Vučko, Matthew John (2014) Innovative antifouling technologies: microtexture and metal. PhD thesis, James Cook University.

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Fouling causes negative economic impacts to the major marine industries of shipping, aquaculture and geophysical exploration. Currently, the most widely used method to prevent the accumulation of fouling is copper-based biocidal antifouling paints. However, their deleterious impact on the marine environment and non-target organisms is driving the need to develop environmentally-sustainable antifouling technologies. Innovative antifouling technologies employing microtexture, photocatalysts and cold spray metal embedment are promising alternatives to current antifouling paints. This thesis investigates these alternative technologies to identify their efficacy across both niche and broad spectrum antifouling applications.

In Chapter 2, a series of 18 textured (0.4–1,000 μm) and non-textured (0 μm) polydimethylsiloxane (PDMS) surfaces with round- and square-wave linear grating profiles were tested for their antifouling potential against the settlement of fouling organisms in the laboratory and in the field against the recruitment of a multi-species fouling community. In laboratory assays, Nitzschia closterium and Amphora sp. were deterred by all surface topographies regardless of texture periodicity. Settlement of Ulva sp. was lower on texture sizes less than propagule size, and settlement of Saccostrea glomerata and Bugula neritina was lower on texture sizes closest to, but less than, larval sizes. After the six month field trials, all textured surfaces lost their deterrent effect, however, the foul-release capabilities of textures were still present. High initial attachment was correlated with more fouling remaining after removal trials, indicating that fouling recruited in higher numbers to surfaces upon which they attached most strongly.

In Chapter 3, the potential for a photocatalyst to enhance the antifouling properties of microtexture was examined. PDMS surfaces, textured with a square-wave linear grating profile (0, 20, 200, 300 and 600 μm), were embedded with a range of photocatalytic titanium dioxide (TiO₂) nanoparticle loadings (3.75, 7.5, 11.25 and 15 wt%). The resulting surfaces were used to test the combined efficacy of these technologies as antifouling materials in the laboratory and in the field against the common fouling bryozoan, B. neritina. Settlement of B. neritina was quantified in the laboratory under two intensities of ultraviolet light. The lowest settlement rates were observed on 20 μm surfaces. However, texture effects were not as critical to larval settlement as the presence of TiO₂. TiO₂, in conjunction with ultraviolet light, completely inhibited larval metamorphosis even at the lowest loading (3.75 wt%) and the lowest intensity of ultraviolet light (24 W m⁻²). Recruitment of B. neritina during field trials showed similar results to laboratory assays. The lowest recruitment occurred on 20 and 200 μm surfaces, with recruitment being significantly lower on all surfaces containing TiO₂. Therefore for B. neritina, although all TiO₂ loadings were effective, 3.75 wt% can be used as a minimum inhibitory concentration to deter larval settlement and the addition of a 20 μm texture further increases the deterrent effect.

In Chapter 4, the use of cold spray technology to give antifouling properties to thermoplastic polymers (polymers) by embedding metals known to prevent fouling was investigated. Two polymers, high-density polyethylene (HDPE) and nylon were metallised with copper powder using cold spray technology. After 250 days in the field, copper-embedded HDPE and copper plate controls were completely free of hard foulers compared to copper-embedded nylon and polymer controls which were heavily fouled with both soft and hard fouling. The success of copper-embedded polymers is related to the interaction between the properties of the polymers (elastic modulus and hardness) and the cold spray process which affect particle embedment depth, and subsequently, the release of copper ions as determined by analytical techniques. This chapter demonstrates that embedding metal particles using cold spray equipment is an effective antifouling technology for polymers, in particular those that are difficult to treat with standard copper-based biocide paints. Furthermore, efficacy is a function of the interaction between the cold spray metal and the polymer recipient.

In Chapter 5, cold spray metal embedment was used to determine the effects of loading densities of metal particles on fouling. Antifouling efficacy under field conditions was quantified for low (22.1 ± 4.8 g m⁻²) and high (101.1 ± 10.8 g m⁻²) densities of copper particles embedded into polyurethane seismic streamer skins, which are used in geophysical exploration. Failure of each copper-embedded treatment was defined as settlement of hard foulers. Low-density streamers failed after 42 days while high-density streamers failed after 210 days. Most importantly, the high-density streamers were completely free of hard foulers including the barnacle Amphibalanus reticulatus during this time. In conclusion, cold spray metal embedment is an effective antifouling technology for polyurethane seismic streamer skins, under intense fouling conditions. Higher copper particle densities enhance antifouling longevity and the effect of density provides a tool to extend efficacy and enhance antifouling performance for specific polymers.

Finally, in Chapter 6, loading density gradients of metal particles were investigated. Particles of copper, bronze and zinc metal were embedded into a polymer using cold spray technology to produce loading density gradients. The gradients were used to identify the species with the highest tolerance to the release of copper and zinc ions. The gradients also established the minimum effective release rates (MERRs) of copper and zinc ions needed to prevent the recruitment of fouling under field conditions. Watersipora sp. and Simplaria pseudomilitaris had the highest tolerance to the release of metal ions. Copper and bronze gradient tubes were similar in their MERRs of copper ions against Watersipora sp. (0.058 g m⁻² h⁻¹ and 0.054 g m⁻² h⁻¹, respectively) and against S. pseudomilitaris (0.030 g m⁻² h⁻¹ and 0.025 g m⁻² h⁻¹, respectively). Zinc was not an effective antifouling material with failure within two weeks. The cold spray gradients were effective in determining MERRs and these outcomes provide the basis for the development of cold spray surfaces with pre-determined life-spans using controlled MERRs.

In summary, the research presented throughout this thesis describes innovative antifouling technologies that can be used as alternatives to current antifouling paints. In addition, this thesis identifies the efficacy of these technologies across niche and broad spectrum antifouling applications, while highlighting the importance of field-based trials. The incorporation of microtexture and a photocatalyst to already successful foul-release coatings, allows for further improvement of those materials. In addition, the use of cold spray technology as an innovative method to give antifouling properties to thermoplastic polymers has been thoroughly investigated and provides a promising avenue for future research and commercialisation. In conclusion, this thesis provides a significant contribution to the relatively new field of environmentally-sustainable antifouling technologies and provides an innovative method to give antifouling properties to materials that previously, could not be protected against fouling.

Item ID: 41025
Item Type: Thesis (PhD)
Keywords: antifouling; biofouling; bronze; bryozoan; Bugula neritina; cold spray metals; copper; environmental protection; HDPE; Hydroides elegans; marine environments; metal clusters; metal ion tolerance; metal spraying; minimum effective release rate; nylon; PDMS; photocatalysis; polydimethylsiloxane; polymers; silicone; texture; thermoplastic polymers; titanium dioxide; topography; Watersipora sp.
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Publications arising from this thesis are available from the Related URLs field. The publications are:

Chapter 2: Vucko, M.J., Poole, A.J., Carl, C., Sexton, B.A., Glenn, F.L., Whalan, S., and de Nys, R. (2014) Using textured PDMS to prevent settlement and enhance release of marine fouling organisms. Biofouling, 30 (1). pp. 1-16.

Chapter 3: Vucko, M.J., Poole , A.J., Sexton , B.A., Glenn, F.L., Carl, C., Whalan, S., and de Nys, R. (2013) Combining a photocatalyst with microtopography to develop effective antifouling materials. Biofouling, 29 (7). pp. 751-762.

Chapter 4: Vucko, M.V., King, P.C., Poole, A.J., Carl, C., Jahedi, M.Z., and de Nys, R. (2012) Cold spray metal embedment: an innovative antifouling technology. Biofouling, 28 (3). pp. 239-248.

Chapter 5: Vucko, M.J., King, P.C, Poole, A.J., Jahedi, M.Z, and De Nys, R. (2013) Polyurethane seismic streamer skins: an application of cold spray metal embedment. Biofouling, 29 (1). pp. 1-9.

Chapter 6: Vucko, M.J., King, P.C., Poole, A.J., Hu, Yi, Jahedi, M.Z., and de Nys, R. (2014) Assessing the antifouling properties of cold-spray metal embedment using loading density gradients of metal particles. Biofouling, 30 (6). pp. 651-666.

Date Deposited: 29 Oct 2015 04:06
FoR Codes: 09 ENGINEERING > 0912 Materials Engineering > 091207 Metals and Alloy Materials @ 40%
09 ENGINEERING > 0912 Materials Engineering > 091209 Polymers and Plastics @ 40%
06 BIOLOGICAL SCIENCES > 0608 Zoology > 060808 Invertebrate Biology @ 20%
SEO Codes: 96 ENVIRONMENT > 9604 Control of Pests, Diseases and Exotic Species > 960407 Control of Pests, Diseases and Exotic Species in Marine Environments @ 50%
96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 50%
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