advanced low-energy durable coatings

INVITED ARTICLE

Advanced low-energy durable coatingsAnna M. Wojdyla1,2,*,†, Geraldine G. Durand2, Alan Taylor2 and Ian W. Boyd1

1Brunel University, Uxbridge, Kingston Lane, Middlesex, Central Place, UB8 3PH, UK2TWI Ltd., Cambridge, Great Abington, CB21 6AL, UK

SUMMARY

The development of novel, durable, low-surface energy coatings with antifouling (ice, insects, biofouling etc.) and lowfriction properties is believed to be a promising direction for research with benefit to the transportation, construction andpower generation sectors. Conventional coatings and surface treatments have not been successful in this area because ofa lack of long-term durability and limited repellency of environmental fouling agents.

New nanostructured coatings, which can be deposited from the liquid state, offer a potential solution that can be easilyindustrially adopted. However, there is a lack of standardization regarding their characterization and performanceevaluation. The strategy selected by TWI and Brunel University to link the properties and structure of high-performancecoatings from the nano to macro scale is described and is illustrated by the presentation of some provisional results.Functionalised nanostructured silica species have been used to reinforce an acrylate matrix leading to retention of thehydrophobicity even after aggressive abrasive wear. Copyright © 2014 John Wiley & Sons, Ltd.

KEY WORDS

antifouling; nanostructure; durable; hybrid; low energy

Correspondence

* Anna M. Wojdyla, TWI Ltd., Cambridge, Great Abington, CB21 6AL, UK.†E-mail: [email protected]

Received 29 November 2013; Revised 14 April 2014; Accepted 19 April 2014

1. INTRODUCTION

The development of novel, durable, low-surface energycoatings with antifouling and low friction properties isbelieved to be a promising direction for research withbenefit to transportation, construction, and power gene-ration field. Fouling is a common problem across manyindustrial sectors. It is an accumulation of unwantedmaterial (ice, insects, algae etc.) on the solid surface,causing impairment in operational efficiency (Figure 1).For example, surface erosion of aircraft during routineflights has been claimed to increase fuel consumption andCO2 emission by 5% [1]. The increase in drag caused bybiofouling on hulls of ships results in them using 40%more fuel [2]. Ice build-up can affect wind turbineperformance, reducing power production and causingstructural failures in extreme situations [3]. Overall, windturbine stoppages due to the blade fouling are responsiblefor an estimated €72m in lost revenue across the EU everyyear [4].

The conventional antifouling coatings, such as fluoro-polymers, polysiloxanes do not meet market requirements.Low mechanical durability limits industrial adoption ofconventional antifouling coatings and provides the primarychallenge for new entrants into this market. Also, objective

comparison of antifouling ability after a long period ishampered by the lack of a standardized test procedure.

Industrial adoption of nanostructured coatings may be theway to solve the problems that currently exist. New, ad-vanced nanostructure coatings are generally believed to over-come some of the obstacles faced by the traditional ones [5].The remarkable feature of nanostructures is that theymay im-prove coating performance by linking things together, suchas mechanical robustness and antifouling properties, openingup the potential to wide variety of applications.

Nanostructure-based coatings have not yet changed thegeneral coatings market; however, they have been used formany niche applications, such as hearing aid protection,aircraft canopy protection, and for base plates of domesticsteam irons. It has been estimated that the global marketfor nanostructured coatings will reach the value of approx-imately $4bn at an average annual growth rate (AAGR) of32% through 2015 [6]. In this context, it is clear that im-portance of nanostructured coatings will increase over thenext few years. Nevertheless, some of the new excitingmaterials remain at the laboratory stage, because there isa lack of understanding of their behaviour. The characteri-zation of novel coating systems is therefore essential to un-derstand not only their potential benefit but also to assesstheir potential risks.

INTERNATIONAL JOURNAL OF ENERGY RESEARCHInt. J. Energy Res. (2014)

Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/er.3214

Copyright © 2014 John Wiley & Sons, Ltd.

One area where nanostructured coatings are hopedand expected to provide benefit is on wind turbineblades. These are readily damaged in use, which resultsin lower than desired efficiency due to the reduction inaerodynamic efficiency. The lack of coatings with a fullset of the desired performance capabilities and stan-dardized methods of testing means that expensive anddifficult manual inspection and maintenance must beregularly undertaken.

The European Commission funded project NATURALaims to provide testing methodologies to enable compari-son of a range of very different nanostructured coatingsand to specify methods of assessment relating nanoscalestructure to macroscale performance.

2. DESIGN STRATEGY—OVERVIEWOF THE PAPER

2.1. Surface energy and contact angle

Surface energy (γ) can be explained in two ways, in termsof force and in terms of energy. The force definitionoriginates from the thermodynamic equilibrium betweenthree different phases: liquid, solid, and vapour (Figure 2)[7]. The energy definition corresponds to the reversiblework required to extend a surface or to bring atoms fromthe interior to the surface region [8].

Quantitatively, surface tension acting on any surfacewill try to minimize the contact area, and its tendencycan be indirectly estimated by measuring the contact angle.The contact angle is formed, at the intersection between the

solid, liquid, and vapour. Surface energy and contact angleare linked by Young’s equation [9].

γSV ¼ γSL þ γLVcosθY (1)

γ is a surface energy of the interface and the letters L, S,and V are liquid, solid, and vapour phase, respectively,and θY is the contact angle. The force equilibrium inthis triple point is a trade-off between adhesive and co-hesive forces. Adhesive forces will seek to increase thesurface area between the droplet and solid, causing thedroplet to spread out, in contrast to cohesive forces,which will try to decrease the contact on the liquid/solidinterface. Shifting of this force balance gives a basis towetting classification.

2.2. Terminology of the wettability

In order to better understand the terminology of wettingclassification, definitions and terms are discussed in thisparagraph. The most commonly used words for wettabilityclassification are ‘hydrophobic’ (from Greek ‘water fear’)and ‘hydrophilic’ (‘water love’). Typically, a surface isdescribed as ‘hydrophilic’, when its Young’s contact anglewith water is less than 90° and wetting occurs on thesurface. Non-wettable surfaces with water contact angleshigher than 90° are called ‘hydrophobic’ (Figure 3). Never-theless, wettability process is much more complicated, andits terminology should be expanded. Marmur [10] hasproposed defining surfaces wetting based on levels ofroughness and all liquids, not solely water. Surfacescan be divided into three categories: smooth, rough,and very rough. Smooth surfaces most of the normallyused liquids have surface energy lower than the water(γwater = 71.97), hence, they will make with smoothsurface smaller contact angles than with water, and thesesurfaces are labelled and termed ‘hygrophilic’ (‘hygro’from Greek means liquid). Hygrophobic smooth surfaceshave not been discovered yet.

Nevertheless, in practice, we are dealing with roughsurfaces, where surface chemistry influences the observedcontact angle. It was proposed to use the prefix ‘para’,‘parahydrophilic(phobic)’, ‘parahygrophilic’ (from Greekmeaning beyond, past, by). In turn, the prefix ‘super’should be applied in situations when the surface showsextreme wetting behavior and we deal with completewetting or non-wetting. Marmur proposed calling thesesurfaces ‘superhydrophilic’ and ‘superhygrophilic’. Theterm ‘superhydrophobic’ should be reserved only for‘parahydrophobic’ surfaces with low contact angle hyster-esis. The terminology described earlier is summarized inTable I.

Superhydrophobic surfaces are often called low-energysurfaces. This means, that the energy of solid/vapourinterface is low and it is favorable in terms of minimizingenergy to extend this interface area and thus decrease theliquid/solid interface area [7].

Figure 1. Ice accumulation on high-voltage transmission lines.

Figure 2. Force balance in a three-phase system.

Advanced low-energy durable coatingsA. M. Wojdyla et al.

Int. J. Energy Res. (2014) © 2014 John Wiley & Sons, Ltd.DOI: 10.1002/er

2.3. Wetting regimes

Young’s equation describes the ideal situation at the triplepoint. The origin form of Young’s theory assumes that thesolid surface is homogenous, smooth, and hard. However,as mentioned in the previous paragraph, wetting in realityis much more complicated. This comes from the non-ideality of solid surfaces, which are affected by heteroge-neity and roughness.

The heterogeneity causes the liquid to move and someasurement of a single static contact angle is no longeradequate. If the three-phase contact line is in actual motion,we are dealing with contact angle hysteresis, in particular,the difference between advancing (θACA) and recedingcontact angle (θRCA) (Figure 4). The greater the difference,the more ‘sticky’ or ‘slippery’ the surface will be [11].Superhydrophobic surfaces typically exhibit a high

static water contact angle (>150°) and low hysteresis(Δθ< 10°).

Wetting regimes on the rough surfaces and principles ofsuperhydrophobicity can be explained by two distincthypotheses. The first one (Wenzel state) describes the situ-ation when a liquid droplet penetrates the corrugation ofthe surface, roughness increases the contact area, but isnot able to build-up the air layer between solid and liquid(Figure 5) [12]. The observed contact angle—Wenzel con-tact angle (θW) is proportional to the Young contact angle(θY) by a roughness factor r.

cosθW ¼ rcosθY (2)

Cassie–Baxter state occurs when roughness traps the airin the valleys beneath the liquid and a droplet rests on thesurface. This results in the observed contact angle beingmuch bigger than the Young contact angle (Cassie contactangle (θC)) (Figure 5). Roughness has an impact on struc-ture designing. Micro structuring enhances hydrophilicityin hydrophilic surfaces and hydrophobicity in hydrophobicones. According to Eq. 2, the observed contact angle willincrease if θY> 90° and decrease when θY< 90°. In orderfor surface to display superhydrophobic properties, it isnecessary to provide a special microstructure to trap theair beneath the droplet.

Low energy surfaces have become very popular inrecent years because of their ‘sticky’ or ‘slippery’ models,which can be used in many applications. Such ‘slippery’surfaces can be beneficial in achieving self-cleaning,anti-icing, anticorrosion, anti-fogging, friction reduction

Figure 3. Surface types according their wetting behavior.

Table I. Wetting terminology proposed by marmur.

Roughness levelof the surface Wettability classification

Definition based on water CAin air, θsmooth = θY or θC Process

Smooth HydrophilicHydrophobicHygrophilic

0°≤ θsmooth≤ 90°θsmooth≥ 90° Wetting of the smooth surfaces

Rough ParahydrophilicParahydrophobicParahygrophilic

0°< θW< θsmooth θW or θC≥ θsmooth Wetting of the rough surfaces

Very rough SuperhydrophilicSuperhygrophilicSuperhydrophobic

θW=0°< θsmooth Complete wettingNon-wettablesurfacesVery low hysteresis on

parahydrophobic surfaces

Figure 4. Surface heterogeneity: contact angle hysteresis.

Advanced low-energy durable coatings A. M. Wojdyla et al.


surfaces. In turn, the ‘sticky’ model may bring advantagesin spraying, coating, liquid transportation processes.Superhydrophobic materials are therefore the backbonefor the design of effective antifouling coatings.

3. STATE OF THE ART

In general, there are three main categories of coatingsavailable on the antifouling market, which provide low-surface energy systems: fluoropolymers, polysiloxilanes,and inorganic–organic hybrid materials.

3.1. Fluoropolymers

The dominant low-energy coatings technology is based onfluoropolymers. However, it is likely to be limited in thefuture because of the concerns about their safety. Concernsabout the environmental and human health impact of long-chain fluoropolymers fundamental building blocks, such asperfluorooctane sulfonate and perfluorooctanoic acid, havebeen forcing manufacturers to search for replacements forthis family of materials [13].

Fluoropolymers offer chemically stable coatings but[14], unfortunately, their durability is often poor. Moreover,commercialization of fluoropolymer coatings has beenlimited by their high prices. The most well-known high-performance fluorinated coatings cost more than €1000/l.

3.2. Polysiloxanes

In recent years, the development and success of poly-siloxanes have originated from the market need for low vol-atile organic compounds (VOC) coatings. Siloxane-basedcoatings offer significant improvements in ultraviolet light,heat, chemical, and oxidation resistance because of thestrong silicon–oxygen bond [15]. These coatings are usedin many applications, such as construction, heavy dutyOEM, anti-graffiti, and most frequently in marine contexts.Nevertheless, their limitations can be summarized as achoice between hydrophobic but not abrasion resistantand mechanically stable but with being poor antifoulingcharacteristics.

3.3. Inorganic-organic hybrids

Interest in these coatings has continued to grow and coatingsmanufacturers and universities have placed an increasedemphasis on inorganic–organic hybrids research over the last

decade. The possibility of combining the characteristics ofinorganic and organic features has opened new directionsin technology. In general, these materials have been used toimprove surface energy properties as well as temperature sta-bility, chemical, and mechanical resistance [16]. However,their limitations lie in the high content of solvent, which isnecessary to prevent early gelation of the coating system.In addition, complex preparation routes impacts significantlyupon their price, making them unattractive for end users [17].

3.4. The era of nanostructure coatings

All previously described coatings provide high perfor-mance when new; however, they lack durability and canbe easily damaged. In practice, they cannot stand morethan one season in extreme environments. New approachesare required in order to produce a coating, which is anti-fouling and can retain performance over extended periodof time.

The development of nanostructured low-energy coat-ings with added functionalities shows promise in the indus-try. Nano advanced materials combined in the nanometerrange, derived from clearly dissimilar organic and inor-ganic components (Table II), offer the potential for signif-icant improvements in mechanical [18], optical, thermal[19], electronic, chemical, tribological [20], and engineer-ing properties.

There are two types of model design for nanostructuredcoatings. They can be generated by ‘top-down’ techniques,producing small pieces from the larger ones, for example,

Figure 5. Wetting regimes on the rough surface.

Table II. Typical properties of organic and inorganic materials.

Property Organic materials Inorganic materials

Bonding nature Covalent (C–C),Van der Waals,hydrogen

Ionic, covalent

Thermal stability Low HighDensity Low HighRefractive index Low HighMechanicalproperties

Elastic, flexible Hard, strong, brittle

Electronicproperties

Insulating toconductive non-magnetichydrophilicor hydrophobic atlow temperatureand pressure

Insulating tosemiconductorsmagnetichydrophilicor hydrophobic athigh temperatureand pressure

MagneticpropertiesPhysicalconsiderationsProcessability



etching or lithography. They can be also constructed by‘bottom up’ methods, using single molecules as buildingblocks to self-assemble the structure [6].

Scaling materials down into the nanoscale shows thatproperties vary from the ones observed in the macro range.It is also observed that it is not just the composition thatdetermines final properties. The functional performance isdirectly linked to structure. Differences in properties aremainly the result of changes in roughness level. However,there is a lack of standardization regarding nanostructuredcoatings characterization and performance evaluation.TWI together with Brunel University is investigating newcharacterization and measurement methods to developmeaningful structure property relationships, which linknanostructure characteristic, corresponding properties atnano level and their influence on the macro scale behavior.

A novel approach is addressed in the project NATURAL(www.natural-project.eu). Launched in March 2013, it is aSeventh Framework Programme, collaborative projectinvolving 10 industrial partners from across the EuropeanUnion. The technical focus of the project involves thedevelopment of new methodology and characterization ofnew advanced low-energy coating systems for antifoulingand low friction application in operating systems, like windturbine, and aerospace industry.

Adding different inorganic nanoparticles to an existingcoating is one possibility to tailor the coating architectureand achieve some of desired properties. As NATURAL isaiming to evaluate and characterize the effect of thenanostructures within the coating, we decided to incorpo-rate different types of nanoparticles into the current classleading organic polyurethane based coating and use anon-nanostructured one as a benchmark comparison.Polyurethane coatings are one of the best known and mostwidely used surface protection systems; however, eventhe class leading products are not durable enough forlong-term protection in aggressive environments and theaddition of nanoscale reinforcement is expected to en-hance robustness and improve antifouling characteristics[21]. In Table III, overviews of nanoparticles incorpo-rated into polyurethane matrix and its potential mecha-nisms were summarized.

Taking into account silver nanoparticles, we are lookingfor improvement in marine fouling due to the silver stronginhibitory, bactericidal, and antimicrobial effects [22]. Wealso believe that mixing them together with functionalizedclay nanoparticles, they will improve mechanical resis-tance of the coating. Significant consideration should alsobe given to the functionalized silsesquioxanes. They areable to enhance coating durability and lead to an easyincorporation into the polymeric materials.

There are a variety of nanoparticles that can be embeddedin organic matrices to enhance coating possibilities and func-tions. However, in order to provide a desired combination ofproperties, a careful selection of nanoparticle type andquantity is essential. Optimized selection of nanoparticlestype, loading level, and incorporation into target matrices isneeded to achieve optimized properties [23].

4. NEW APPROACH TO TESTING

In order to prove nanostructured coatings potential, anumber of key tests should be performed with respect tochemical analysis, surface energy, and morphologicalanalysis together with relevant mechanical, thermal, andtribological characteristic. Demonstration and validationrequires a range of characterization methodologies to as-sess fitness-for-purpose. Included in this is tribologicalcharacterization, which is not an intrinsic property, but isaffected by various parameters, including coating formula-tion, application, and environment (Figure 6) [24].

Roughness plays a crucial role in tribology. Besidesthe ability to control wetting, modification of topogra-phy has been considered as a potential way of enhanc-ing wear and friction resistance due to reducing thereal area of contact [8]. Linking coating mechanicalresistance with its roughness is a key to understandinfluence of the nanostructure on the macroscopic be-havior. Nevertheless, the conventional approach tovalidation of the abrasion resistance of low-surfaceenergy coatings is not suitable. Current methods arebased on measurements of water contact angle whencoating is fresh. These methods do not consider surfaceenergy changes after abrasion testing.

In response to the need for new testing approach, thesecond aim of the NATURAL project is to develop astandardized method that will allow novel nanostructuredcoating to be evaluated in a manner that allows nanoscalecharacteristic to be correlated with their effects on macroscale behavior.

Table III. Advancedcoatingsystemswith their potentialmechanisms.

Nanoparticle addition/structuring Mechanisms/hypothesis

Silver (Ag) nanoparticles+functionalized clay particles

Functional biocide toprevent algaeImproved mechanicalproperties

Surface active clay particles Anti-fouling and improvedmechanical properties

Silica nanoparticles�SiO2 Superhydrophobic coatings�anti-icingproperties

Titania nanoparticles�TiO2, Mixed nano-oxideof ZnO/Ag, functionalizednanoclays

Anti-fouling properties

ZrO2 and/or Al2O3 Anti-erosion effects/anti-icing properties

Functionalized silsesquioxanes,Stöber spheres,Functionalized silsesquioxanes+Stöber spheres

High abrasion resistanceand low surface energy



http://www.natural-project.eu

5. PRELIMINARY RESULTS

One of the first examples of this technological approachwas carried out. In this initial study, the influence of thesilsesquioxanes on coating durability was evaluated byassessing the retention of antifouling coating propertiesunder abrasion conditions. These nanoparticles incorpo-rated in organic matrix are believed to meet the marketchallenge of producing a coating, which is both antifoulingand durable.

Silsesquioxanes, prepared with TWI’s patented Vitolane®technology [25], embedded into acrylic matrix werecompared with commercially available low-energy coat-ings. All coatings were deposited onto steel substrateand cured for 1 h. Linear abrasion testing was performed

(100, 250, 500, and 1000 rubs with 0000 wire wool).The number of rubs required to achieve ‘breakthroughpoint’ were compared (Figure 7). ‘Breakthrough point’indicates the point, at which the measured surface energyis the same as the substrate material.

The data highlighted in Figure 7 illustrates significantlyenhanced abrasion resistance associated with the additionof nanoparticles to coating formulation. Moreover, 1000rubs is not the final value for Vitolane® coating, becausewe stopped testing at this point.

The preliminary results obtained in this study providesome overall idea on the possibilities of the advanced nano-structured coatings. It is recognized that in a wind turbineenvironment, erosive as well as abrasive wear is important.Erosion testing is planned as a later step in this project.

Figure 6. Effect on various parameters on tribological performance.

Figure 7. Comparison of ‘breakthrough value’.



6. CONCLUSION

The commercially available low-surface energy coatingstend to be not durable in harsh operating conditions. Theindustrial need for multifunctional coatings, such as anti-fouling and mechanically durable, is significant. It wasfound that producing low-surface energy coating with in-corporated nanoparticles may contribute to a potentially in-teresting strategy for improving durability. However, toenhance the quality of nanostructured coatings, better un-derstanding of the structure at nano level is necessary. Itis essential to link surface energy and surface roughnesswith mechanical robustness.

A novel testing routine that allows evaluation of corre-lation is being developed by TWI and Brunel University.This new technique will help to better understand mechan-ical, chemical, and morphological variations in coatingsand help to select the right coatings for right applications.

Furthermore, retention of surface finish above and be-yond the formal ability to repel foulants is a key compo-nent for long term durability.

ACKNOWLEDGEMENTS

Authors would like to acknowledge the interest and supportof colleagues of TWI and Brunel University. Financialsupport is kindly acknowledged from EPSRC and TWILtd. Also, funding from the EU via FP7 is kindly acknowl-edged for the NATURAL project with Grant No. 310397.

REFERENCES

1. Market research report. Royal Aeronautical Society,2011–2012.

2. Calllow JA.Advanced nanostructured surfaces for the con-trol of biofouling. Project No. NMP4-CT-2005-011827.

3. Dalili N, Edrisy A, Carriveau R. A review of surfaceengineering issues critical to wind turbine perfor-mance. Renewable and Sustainable Energy Reviews2009; 13:428–438. doi:10.1016/j.rser.2012.09.013.

4. Corten GP, Veldkamp HF. Nature 2001; 412:42–43.5. Sanchez C, Belleville P, Popall M, Nicole L. Applications

of advanced hybrid organic – inorganic nanomaterials:from laboratory to market. Chemical Society Reviews2011; 40:696–753. doi:10.1039/c0cs00136h.

6. Research and markets: the global market report fornanostructured coatings. E-resource http://www.businesswire.com/news/home/20101101006971/en/Research-Markets-Global-Market-Report-Nanostruc-tured-Coatings. 2010

7. Hobæk TC. Lessons from nature. NanotechnologySpecialization Project, 2010.

8. Castro Lobato EM. Determination of surface freeenergies and aspect ratio of talc. Master thesis, 2004.

9. Yarnold GD, Mason BJ. A theory of the angle ofcontact. Proceedings of the Physical Society SectionB 1949; B62:121–125.

10. Marmur A. Hydro- hygro- oleo- omni-phobic? Termi-nology of wettability classification. Soft Matter 2012;8:6867–6870. doi:10.1039/C2SM25443C.

11. Roach P, Shirtcliffe NJ, Newton MI. Progress insuperhydrophobic surface development. Soft Matter2007; 7:224–240. doi:10.1039/b712575p.

12. WenzelRN.Resistance of solid surfaces towetting bywater.Industrial and Engineering Chemistry 1936; 28:988–994.

13. United States Environmental Protection Agency(USEPA). Long-chain perfluorinated chemicals (PFCs)action plan, 2009. E-resource: http://www.epa.gov/oppt/existingchemicals/pubs/pfcs_action_plan1230_09.pdf

14. Ebnesajjad S. Introduction to fluoropolymers, 2011;49–60.

15. Mowrer NR. US patent 5618860, 1997.16. Keijman JM. Inorganic-organic hybrid coatings in the

protective coatings industry, SSPC 2002 ConferenceProceedings.

17. Wienhold U, Westerwelle U. New routes to sol-gel sys-tems. European Coatings Journal 2006; 7(8):40–45.

18. Mammeri F, Bourhis Le E, Rozes L, Sanchez C.Mechanical properties of hybrid organic-inorganicmaterials. Journal of Materials Chemistry 2005;15:3787–3811. doi:10.1039/B507309J.

19. Chiang C-L, Chang R-C, Chiu Y-C. Thermal stabilityand degradation kinetics of novel organic/inorganicepoxy hybrid containing nitrogen/silicon/phosphorusby sol–gel method. Thermochimica Acta 2007; 453(2):97–104. doi: 10.1016/j.tca.2012.11.010.

20. Pham DC, Na K, Piao S, Cho IJ, Jhang KY, Yoon ES.Wetting behavior and nanotribological properties ofsilicon nanopatterns combined with diamond-like carbonand perfluoropolyether films. Nanotechnology 2011; 22(39):395303. doi:10.1088/0957-4484/22/39/395303.

21. Jonschker G, Pahnke J, Friedrich R, Schütz-WidoniakJ. Matched to the medium: core-shell process enhancesnanoparticle compatibility and performance. EuropeanCoating Journal 2008; 10:46–51.

22. Dash A, Singh AP, Chaudhary BR, Singh SK, Dash D.Effect of silver nanoparticles on growth of eukaryoticgreen algae. Nano-Micro Letters 2012; 4(3):158–165.doi:10.3786/nml.v4i3.

23. Chaharmahali AR. The effect of TiO2 nanoparticles onthe surface chemistry, Structure and Fouling Perfor-mance of Polymeric Membranes, PhD Thesis, 2012.

24. Luo DB, Fridrici V, Kapsa P. A systematic approach forthe selection of tribological coatings. Wear 2011; 271(9–10):2132–2143. doi:10.1016/j.wear.2010.11.049.

25. Taylor A, Barrett L. TWI industrial member report no.1007, 2011.



http://www.epa.gov/oppt/existingchemicals/pubs/pfcs_action_plan1230_09.pdf

http://www.epa.gov/oppt/existingchemicals/pubs/pfcs_action_plan1230_09.pdf

advanced low-energy durable coatings

Documents