European Coatings Congress — Poster Presentations
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MAY 2011 3
F O C U S O N P O W D E R C O A T I N G S
mathematically, and the resultsindicate that the amount ofpigment has only a limited effecton the short wave pattern of thepowder coated surface, althoughthe long wave roughness isstrongly affected. Above a criticalpigment concentration of 45 wt%,further pigment addition gives asignificant increase in the heightof the surface roughness. Theseresults demonstrate that for agiven pigment system the mosteffective way to improve the glossis by reducing the long waveroughness. This can be achievedby reducing the pigment loading.Good correlation of the resultswas obtained at both 60 and 20readings.
A two-scale model evaluation isessential in predicting the effect ofsurface topography on glossproperties.Article entitled A Mechanistic Study of theEffect of Pigment Loading on the Appearanceof Powder Coatings: The Effect of SurfaceTopography on the Optical Properties ofPowder Coatings: Modelling andExperimental Results by researchers at DSMResearch, published in Progress in OrganicCoatings, Apr 2011, 70 (4), 206-212
European Coatings Congress Poster Presentations
In addition to the Congresspapers, there were 14 posterpresentations given during theevening of the first day of theEuropean Coatings Show. Someinteresting items are abstractedhere. For further information seehttp://www.european-coatings-show.com/en or email@example.com.
1. Development of radiation andcorrosion resistant coatings forcentrifugal extractors
Centrifugal extractors driven byelectric motors are widely used inthe reprocessing of spent fuels ofFast Breeder Reactors. The rotorsand stators of the motors aremade from stampings of siliconesteel and are continuouslyexposed to radiation and nitricacid fumes. PEEK(polyetheretherketone) wasselected for the coating of rotors,
as a high performanceengineering plastic, with aradiation resistance of 109 radsand resistance to a wide range ofchemicals at elevated temperaturesin harsh environments. A 0.5micron film was applied to therotors and was assessed forhardness, electrical resistanceand testing in the corrosiveenvironment. It was confirmed togive suitable protection to therotor components. The stators,however, could not be protectedby the PEEK coating since thestator components could notwithstand the high stovingtemperature of 390C for PEEK.An epoxy powder coating wasapplied and found to give therequired chemical resistance tothe stators.
Felix Lawrence, Indira Gandhi Centre forAtomic Research, India
2. Coating comprising covalentlybound selenium preventing bio-fouling and corrosion
Hydraulic fracturing, involvessending high pressure fluidcontaining sand through a wellbore deep in an oil/gas bearingshale formation to cause fracture.This is followed by an injection ofsand or ceramic bead proppants,which are lodged inside the shaleto keep the fracture open. Thefractured shale allows free flow ofnatural gas and oil into thepipeline conveying them to thesurface for collection.Environmental problems areoccurring due to thecontamination of aquifers by theextensive use of conventionalbiocidal agents. Anaerobic iron-and sulfate-degrading bacteriarapidly proliferate in the fracturingfluids, causing corrosion of thepipes and clogging of theproppants. A biocidal solution tothe problem should beenvironmentally friendly and mustnot freely diffuse away from thebore hole. Covalently boundselenium is claimed to bepreferable to the use of copperand silver biocides because itremains permanently attached to
a surface while remainingbiologically active. It is FDAapproved and releases reactiveoxygen species such as hydrogenperoxide to kill the bacteria. Theeffect is short range and does notextend far from the coatedsurface. It is suggested thatcovalent selenium will findnumerous uses in the coatingsindustry in the future.Jonathan Matias, Poseidon Sciences Group,USA
3. Surface Chemistry of EpoxyCoatings & its Relationship to 21Pathogenical Microorganisms
Surgical devices are obviouslycleaned frequently to remove anymicroorganisms, but manycoatings patents have beenclaimed to offer protection.However, it has been shown thatsome of these formulations weremore prone to re-infection thanothers. Many of theseformulations were based on epoxychemistry, including liquids,powder coatings, pure epoxy,phenolic epoxy, and epoxypolyester.
A study was made of thesurface chemistry of each coatingusing an electron microscope.Some formulations were found toshow microscopic porosity largeenough to house some bacterialspores, viruses and prions. It wasalso found that different surfaceadditives produced differentdegrees of microporosity, and itwas concluded that spongiformemicroporosity should be avoided,while the formation of punctiformemicroscopy should be promoted.Micro sponge holes make itimpossible for chemical sterilantsto reach bacteria allowingmicroorganisms to remain hidden.Punctiforme microporosity appearsas open tiny craters, which makesthem more accessible tosterilants. This study showed thatthere are several significantdifferences in surface chemistryfrom one type of epoxy toanother, and this should be takeninto account when creatinghospital coatings, especially those