Effect of silane modified nano zno on UV degradation of polyurethane coatings

c o m / l o c a t e / p o r g c o a t To Thi Xuan Hanga,∗, Ngo Thanh Dunga, Trinh Anh Truca, Nguyen Thuy Duonga, Bui Van Truoca, Pham Gia Vua, Thai Hoanga, Dinh Thi Mai Thanha, Marie-Geo

jou rn a l h om ep a ge :w w w e l s e v i e r c o m / l o c a t e / p o r g c o a t

To Thi Xuan Hanga,∗, Ngo Thanh Dunga, Trinh Anh Truca, Nguyen Thuy Duonga,

Bui Van Truoca, Pham Gia Vua, Thai Hoanga, Dinh Thi Mai Thanha,

Marie-Georges Olivierb

a Institute for Tropical Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanọ, Viet Nam

b Université de Mons (UMONS), Faculté Polytechnique, Service de Science des Matériaux, 20 Place du Parc, Mons, Belgium

Article history:

Received 8 May 2014

Received in revised form

25 September 2014

Accepted 10 November 2014

Keywords:

Polyurethane coatings

Silane modified nano ZnO

UV resistance

Electrochemical impedance spectroscopy

NanosizedZnOmodifiedby2-aminoethyl-3-aminopropyltrimethoxysilane(APS)waspreparedusingthe precipitationmethod.ModifiednanoZnObysilane(ZnO-APS)wascharacterizedbyXRD,SEM,TEMand UV–vismeasurements.Thedegradationofthepolyurethanecoating,thepolyurethanecoatings contain-ing0.1wt%nanoZnOandthepolyurethanecoatingscontainingnanoZnO-APSattwoconcentrations(0.1 and0.5wt%)duringQUVtestwasevaluatedbyglossmeasurementandelectrochemicalimpedance spec-troscopy.ThecoatingsurfaceafterQUVtestwasobservedwithSEM.TheresultsshowthatnanoZnO-APS hassphericalstructurewithparticlesizearound10–15nm.NanoZnOimprovedtheUVresistanceofthe

PUcoatingandsurfacetreatmentbyAPSenhancedtheeffectofnanoZnO.ThepresenceofnanoZnO-APS

at0.1wt%concentrationsignificantlyimprovedtheUVresistanceofpolyurethanecoating

©2014ElsevierB.V.Allrightsreserved

1 Introduction

Themainfactorsoftheenvironmentwhichcausetheweather

degradationoforganiccoatingsareultravioletradiation,oxygen

andwater.ToreducedamagesduetoUVradiation,UVabsorbers

areoftenincorporatedinorganiccoatings.Organicabsorbers

suf-ferfrom migration and degradation over time, so theydo not

exhibitlong-termstabilityincoatings.InorganicUVabsorbersdo

notmigratesotheycanprovidelong-termprotectionandaremore

andmorewidelyused.Duetotheirsmallsize,thenanoparticlescan

beusedatlowconcentrationwithoutdisturbingtheothercoating

properties

ZincoxideisaninorganicUVabsorberhavingawidebandgap

energyandusedasUVstabilizerinorganiccoatings[1–4].Thenano

ZnOwasinvestigatedasUVabsorberinapolyurethane/acrylicclear

topcoat.TheinfluenceofZnOconcentrationandfilmthicknesson

theUVprotectionwasinvestigatedandtheresultsshowthatthe

presenceofnanoZnO at2.0g/m2 can blockmorethan99% UV

radiation[1].ThenanoZnOandsilica-coatednanoZnOimproved

theexteriordurability and physic-mechanical propertiesof the

acrylicwaterbornecoatingsforwood[2,3].Thepresenceofnano

∗ Corresponding author Tel.: +84 0912178768; fax: +84 4 37564484.

E-mail address: ttxhang@itt.vast.vn (T.T.X Hang).

zincoxideparticlesreducesthephoto-degradationofthearomatic polyurethanecoating[4].TheeffectofnanoZnOonthe proper-tiesofpoly(styrenebutylacrylate)latex/nanoZnOcompositeswas alsopreviouslystudied.TheresultsshowthatincreasingnanoZnO contentanditsdispersibilitycouldenhancetheUVshielding prop-ertiesofthenanocompositesandthat60nmZnOparticlescould shieldUVraysmoreeffectivelythan100nmZnOparticles[5] NanoZnOatlow concentrationsimprovedcorrosion,scratch and abrasion resistances of coatingssuch as alkyd, epoxy and polyurethane coatings [6–8] However, the nanoparticles tend

to produce someagglomerates and migrate to coating bulk at highloadings[9–11].Theenhancement ofphysico-thermaland mechanicalpropertiesisstronglyconnectedwiththeinterfacial interactions with the binder and the dispersion degree of the nanoparticlesinnanocompositecoatings[3]

Inordertoimprovethedispersioninpolymermatrix,thesurface

ofnanoZnOcanbefunctionalizedbysilanecompounds[12,13] ModificationofnanoZnOsurfaceby3-aminopropyltriethoxysilane improveddispersionofnanoZnOparticlesinepoxycoatingandits anti-corrosionandanti-bacterialproperties.NanoZnO nanopar-ticlesmodifiedby3-(trimethoxysilyl)propylmethacrylatecanbe homogeneouslydispersedinthepolyurethaneacrylatematrix[13]

In this work nano ZnO modified by 2-aminoethyl-3-aminopropyltrimethoxy silane (ZnO-APS) as UV absorber for organiccoatings was prepared.The synthesized nano ZnO-APS

http://dx.doi.org/10.1016/j.porgcoat.2014.11.008

0300-9440/© 2014 Elsevier B.V All rights reserved.

thepolyurethanecoatingscontainingdifferentconcentrationsin

nanoZnO-APSwasevaluatedandcomparedtothepolyurethane

coatingandthepolyurethanecoatingscontainingnanoZnOafter

differentexposuretimestoQUVtestbyglossmeasurementand

electrochemicalimpedancespectroscopy.Thesurfaceofcoatings

afterQUVtestwasobservedbySEM

2 Experimental

2.1 Materials

Sodiumhydroxide, Zn(CH3COO)2,

2-aminoethyl-3-aminopro-pyltrimethoxysilane(APS)werepurchasedfromMerck

The used bicomponent polyurethane coating was based on

DesmophenA160withequivalentweightof1065andDesmodure

N75hardenerwiththeequivalentweightof255.Thetwo

compo-nentsweresuppliedbyBayer

2.2 PreparationofnanoZnO

NanoZnOwaspreparedbyusingtheprecipitationmethod[14]

Asolutioncontaining10mlofethanoland0.2gofNaOHwasslowly

addedundervigorouslystirringtoasolutionof30mlofethanol

and0.51gofZn(CH3COO)2.Theresultingsolutionwasmaintained

at70◦Cfor90min.Thenthesolutionwascooledbyusinganice

bathandstirredfor2hat0◦C.Theresultingwhiteprecipitatewas

agedfor12hat0◦C,andthenfilteredandwashedseveraltimes

withdistilledwaterandethanol.TheZnOprecipitatewasdriedat

50◦Cinavacuumovenfor24h

2.3 ModificationofnanoZnOby

2-aminoethyl-3-aminopropyltrimethoxysilane

ThefunctionalizationbyAPSwasperformedbymixingunder

vigorousstirringethanolsolutioncontaining0.15gofnanoZnOand

0.015gAPS.Thetemperaturewasmaintainedat60◦Cfor3h.The

whiteprecipitatewaswashedseveraltimeswithethanol.Silane

modifiednanoZnO(ZnO-APS)wasdriedat50◦Cinavacuumoven

for24h

2.4 Polyurethanecoatingpreparation

Carbonsteel sheets (150mm×10mm×2mm)were usedas

substrates.Sheetswerepolishedwithabrasivepapersfrom80to

600gradesandcleanedwithethanol

Polyuretane coating and polyuretane coatings containing

0.1wt%nanoZnOandnanoZnO-APSattwoconcentrations(0.1wt%

and0.5wt%)werepreparedandappliedoncarbonsteel.Thenano

ZnOandZnO-APSweredispersedbymagneticstirringandthen

sonicationwithultrasonicwavesat35kHzfrequencyfor20min

Theliquidpaintwasappliedbyspincoatingat600rpmfor1min

anddriedatambienttemperaturefor7days.Thedryfilm

thick-ness was30±3␮m (measured by Minitest 600Erichen digital

meter)

2.5 Analyticalcharacterizations

FouriertransforminfraredspectrawereobtainedusingtheKBr

methodonaNexus670Nicoletspectrometeroperatedat1cm−1

resolutioninthe400–4000cm−1region

X-ray diffraction measurements were performed with a

SiemensdiffractometerD5000withCuK␣X-raydiffraction

FE-SEMobservationswerecarriedoutusingaHitachi4800

spec-trometer

TEMobservationswerecarriedoutusingJEM1010transmission electronmicroscopyoperatingat80kV

UV–visspectrawereobtainedusingaGBCCintra40 spectrom-eter

2.6 QUVtestofcoatings The coatings were tested in the UV-condensation chamber ATLAS UVCON UC-327-2 with fluorescent UV lamps UVB 313 accordingtoASTMstandardG53-96(4hUVat70◦C+8hof con-densationat50◦C)

2.7 Glossmeasurements Theglossofcoatingswasmeasuredat60◦ witha Micro-TRI-glossfromBYK-Gardner

2.8 Electrochemicalimpedancemeasurements Theelectrochemicalimpedancemeasurementswereperformed usinganAutolabPGSTAT30overafrequencyrangeof100kHzto

10mHzwithsixpointsperdecadeusing30mVpeak-to-peak sinu-soidalvoltage

Theassessment of thecoating performancewasdetermined afterQUVtestbyEIS after1hofimmersionin3%Na2SO4 elec-trolytesolution.Theexposedareawas12.56cm2.Foreachsystem, threesamplesweretestedtoensurereproducibility

3 Resultsanddiscussion 3.1 CharacterizationofnanoZnO-APS Fouriertransformationinfraredspectroscopy(FT-IR)wasused

toconfirmthepresenceofAPSinmodifiedZnO.Fig.1shows

FT-IRspectraofAPS,nanoZnOandsilanemodifiedZnO(ZnO-APS) ThespectrumofAPSshowsabandat3370cm−1characteristicof

OHand NH2groups.Thebandsat2940cm−1and2840cm−1are

Wavenumber / cm-1

500 1000 1500 2000 2500 3000 3500 4000

(a)

(b)

(c)

Fig 1 FTIR spectra of (a) 2-aminoethyl-3-aminopropyltrimethoxysilane (APS); (b)

Fig 2 XRD patterns of (a) nano ZnO and (b) nano ZnO-APS.

attributedtothevibrationof CH3and CH2groups.Thebandat

1083cm−1isrelativetoSi Ovibrationandcharacteristicbandat

818cm−1originatesfromthesymmetricstretchofSi O CH3[15]

FT-IR spectrum of ZnO nanoparticles shows the peaks at

3451cm−1and1636cm−1duetothestretchingvibrationsofthe

OHgrouponthesurfaceofZnOnanoparticlesandahighintensity

broadbandaround455cm−1duetotheZn Ovibration[16]

FT-IRspectrumof ZnO-APSdisplaysthebands characteristic

of OHand NH2groupsandZn Oat3433cm−1and440cm−1

Thebandatabout1633cm−1canbeassignedtothedeformation

vibrationof OHgroup.Thebandat1041cm−1 isattributedto

Si O Si.Thedisappearanceofthepeakat818cm−1, characteris-ticofSi O CH3,andthepresenceofnewpeakat873cm−1which couldbeassignedtotheSi O Znbond,indicatethecomplete reac-tionbetweentheZnOnanoparticlesandthehydrolyzedAPS[15] Thebandsat2922cm−1and1384cm−1dueto CH2groupsofAPS TheseresultsindicatethatAPShasbeensuccessfullygraftedonto thesurfaceofZnOnanoparticles

3.1.1 XRDanalysis TheXRDpatternsofthenanoZnOandnanoZnO-APSare pre-sented in Fig 2 For nanoZnO the XRD pattern shows typical peaksat2=31.7◦,33.9◦,36.2◦,47.3◦,56.4◦,62.7◦and67.8◦ corre-spondingto(100),(002),(101),(102),(110),(103)and(112) respectively,whichcanbeindexedtohexagonalwurtziteZnOin thestandarddata(JCPDS,36-1451).ThepatternofnanoZnO-APS presentsthesamepeaksasnanoZnO.ThepatternofnanoZnOis shaperthanthatofnanoZnO-APS.Thisresultcanbeexplainedby thenanoZnOfunctionalizationsurfacebyAPS

3.1.2 SEMimages SEMimagesofnanoZnOandnanoZnO-APSareshowninFig.3

It canbeseen that theypresenta spherical shapewithsize in 10–15nmrange.AsobservedinFig.3a,thenanoZnOare agglom-eratedinclustershavingsizearound20–40nm

AlthoughthemorphologyofnanoZnO-APSissimilartonano ZnOwithasphericalshape,thecorrespondingnanoparticlesare wellseparatedwithoutformationofagglomerates

3.1.3 TEMimages Fig.4showstheTEMimageofnanoZnOandnanoZnO-APS TheseresultsconfirmtheZnOsphericalshapewithasizeinthe 10–15nmrange.ThemorphologyofnanoZnO-APSissimilarto nanoZnO

Fig 3 SEM images of (a) nano ZnO and (b) nano ZnO-APS.

Wavelength / nm

0.0

0.5

1.0

(a)

(b)

Fig 5 UV–vis spectra of (a) nano ZnO and (b) nano ZnO-APS.

3.1.4 UV–visanalysis

TheUVabsorptionpropertiesofnanoZnO-APSwereevaluated

andcompared tothoseofnanoZnO.UV–vis absorptionspectra

of0.01wt%nanoZnO-APSandnanoZnOethanolicsolutionsare

presented in Fig 5 For nanoZnO theabsorption in the range

of 360–230nm wasobserved This resultis in agreement with

literature[15,17].BycomparisonwithnanoZnO, nanoZnO-APS

absorbedinthesamerangeofwavelengthsbutthecorresponding

absorbanceislower.Theseresultsindicatethataftersilane

modi-fication,nanoZnO-APScanalsobeusedasUVabsorberinorganic

coatingstoblockUVradiation

3.2 QUVtestofcoatings

ThecoatingswereexposedinQUVtestchamberupto216h

and the degradation of coatings was evaluated by gloss

mea-surement and electrochemical impedance measurements after

differentexposuretimes,thesurfaceofcoatingsafterQUVtestwas

analyzedbySEM

3.2.1 Glossmeasurement

Coatingglosswasmeasuredafterdifferentexposuretimesto

QUVtest and thecoatingglossretentionis presentedin Fig.6

Glossretentionisdefinedasthepercentagechangeinthe

spec-imenglossduringQUVtestrelativetoitsinitialglossvalue.The

glossofcoatingsincreasedslightlyduringfirst96hofQUVtest

Thentheglossretentionofcoatingsdecreasedwhentheexposure

timeincreased.Theincreaseofcoatingsglossatthebeginningof

exposurecanbeexplainedbyinterchaincrosslinkingbetweenfree

radicalofadjacentchainsofresinsformedbyUVradiation[18]

Thelossofglossofcoatingsisrepresentativeofthedegradation

ofcoatingsduetoeffectsofultravioletradiation.TheUVradiation

causespolymerchainbreakdownandasaresultadecreaseof

coat-inggloss.After216hofQUVtest,glossretentionsofPUcoatings

containingnanoZnO-APSornanoZnOwerehigherthanoneofthe

Ucoating.Thehighestglossretentionwasobtainedwithcoatings

containing0.1wt%ofnanoZnO-APS(99.5%)after216hof

expo-sureincomparisonwiththeglossretentionofPUcoatingswhich

wasonly82.2%.After216hofexposuretheglossretentionsofPU

coatingscontaining0.1wt%ofnanoZnOwaslowerthanoneofthe

PUcoatingcontaining0.1wt%ofnanoZnO-APS,buthigherthan

oneofthePUcoatingcontaining0.5wt%ofnanoZnO-APS

TheseresultsshowthatnanoZnOimprovedtheUVresistance

ofPUcoatingsandsurfacetreatmentbyAPSenhancedtheeffectof

nanoZnO.TheeffectofnanoZnO-APSdependsonitsconcentration

80 85 90 95 100 105 110

QUV test time / h

Fig 6 Gloss retention versus exposure time to QUV test of () Pure PU coating; (△)

PU coating containing 0.1 wt% nano ZnO; (䊉) PU coating containing 0.1 wt% nano ZnO-APS; (♦) PU coating containing 0.5 wt% nano ZnO-APS.

inPUcoating.ThehighestefficiencywasobtainedwiththeZnO-APS concentrationof0.1wt%

3.2.2 SurfaceobservationbySEM Thecoatingssurfacebeforeandafter216hexposuretoQUVtest wereobservedbySEM.Fig.7presentstheSEMmicrographsofpure

PUcoatingandPUcoatingscontainingnanoZnOandnano ZnO-APSatdifferentconcentrationsbeforeexposuretoQUVtest.Itcan

beseenthatthepurePUcoatingsurfaceissmoothand homoge-nous.ThePUcoatingcontaining0.1wt%ofnanoZnOshowsthe agglomerationofnanoZnO.ThePUcoatingcontaining0.1wt%nano ZnO-APShasuniformsurfacemorphologywithwelldispersednano ZnO-APS,whilethesurfaceofPUcoatingcontaining0.5wt%nano ZnO-APSshowstheagglomerationofnanoZnO-APS.Theseresults indicatethatthefunctionalizationsurfacebyAPSimprovedthe dispersionofnanoZnOinPUcoating,butthedispersiondegree decreasedwiththeincreaseofZnO-APSconcentration

Fig.8 shows thesurface micrographs of PUcoating and PU coatingscontainingnanoZnOandnanoZnO-APSafter216h expo-suretoQUV test ThepurePU coatingpresents largecracksof

100nmwidthatthesurface.Thisindicatesdrasticchangesof coat-ingduringexposuretoQUVtest.ForPUcoatingcontaining0.1wt% nanoZnOitisobservedasmallcrackonthesurface,butfailure degreewaslowerincomparisontopurePUcoating.ForPU coat-ingcontaining0.1wt%nanoZnO-APS,nocrackisobserved.With highernanoZnO-APSconcentrations(0.5wt%)itcanbeseenasmall crackonthesurface,butthefailuredegreewaslowerin compari-sontopurePUcoatingandPUcoatingcontaining0.1wt%nanoZnO ThisresultindicatestheimprovementinUVresistanceofthePU coatingswiththeincorporationofnanoZnOornanoZnO-APSin coatings.ThiscanbeattributedtotheUVblockingpropertyof nano-ZnO [4,5].ThesurfacetreatmentofnanoZnObyAPSenhanced itsefficiency TheefficiencynanoZnO-APS depends onits con-centrationand thebestUV resistantcoating wasobtainedwith concentrationof0.1wt%forwhichtheZnO-APSdispersionis ver-ified.TheincreaseofnanoZnO-APSconcentrationdidnotleadto highereffectonUVresistanceofPUcoating

3.2.3 Electrochemicalimpedancemeasurements

In ordertoassessthechangeofbarrierpropertyof coatings duringQUVtest,electrochemicalimpedancediagramsofcoatings weremeasuredbeforeandafterQUVtest.Figs.9and10presentthe

Fig 7 SEM images before QUV test of (a) Pure PU coating; (b) PU coating containing 0.1 wt% nano ZnO; (c) PU coating containing 0.1 wt% nano ZnO-APS; (d) PU coating containing 0.5 wt% nano ZnO-APS.

impedancediagramsofcoatingsbeforeandafter216hofexposure

toQUVtest,respectively

The impedance modulus at low frequencies were high and

superiorto108cm2.Thebarrierpropertiesincreasedwiththe

incorporationofnanoZnOornanoZnO-APScomparedtotheclear

polyurethanecoating.Forthissystem,theinitialbehaviorisclose

toapurecapacitivebehaviorwithaphaseanglecloseto−90◦in

wholefrequencyrange.ForpurePUcoating,aresistivebehavioris

observedatlowfrequenciesbeforeQUVtest

Theimprovementofbarrierpropertiesofcoatingsbythe pres-enceof nano ZnO and nano ZnO-APS can beexplained bythe enhancementofcoatingdensityduetotheadsorptionoftheepoxy resinonthenanoZnO andnanoZnO-APS therebyreducingthe transportpathsforthecorrosiveelectrolytetopassthroughthe coatingsystem[7–9]

After216hofQUVtest,theimpedancemodulusofallcoatings decreased.Theimpedancemodulusatlowfrequenciesofcoatings containingnanoZnOornanoZnO-APSweremuchhigherthanone

Fig 8 SEM images after 216 h of QUV test of (a) Pure PU coatings; (b) PU coating containing 0.1 wt% nano ZnO; (c) PU coating containing 0.1 wt% nano ZnO-APS; (d) PU

104

105

106

107

108

109

1010

1011

0 15 30 45 60 75 90

10-3 10-2 10-1 100 101 102 103 104 105

Frequency / Hz

Fig 9 Electrochemical impedance diagrams (bode presentation) obtained before

QUV test of () Pure PU coating; (△) PU coating containing 0.1 wt% nano ZnO; (䊉)

PU coating containing 0.1 wt% nano ZnO-APS; (♦) PU coating containing 0.5 wt%

nano ZnO-APS.

ofthePUcoating.Theimpedancemodulusatlowfrequenciesof

coatingscontaining0.1wt%nanoZnO-APSwashigherthanoneof

thePUcoatingscontaining0.1wt%nanoZnO.Forcoatings

contain-ingZnO-APS,thePUcoatingcontaining0.1wt%nanoZnO-APSkept

aquitehighimpedancemodulusatlowfrequencies.Theincreaseof

concentrationofZnO-APSinPUcoatingsdecreasedtheimpedance

modulusofcoatings

It wasproposed byKittel et al [19] and the groupof

Bier-wagen[20–22]thattheimpedancemodulusatlow frequencies

measuredversusexposuretimecouldserveasanestimationof

thecorrosionprotectionofapaintedmetal.Fig.11plots|Z|100 mHz

versusQUVtesttime.Itisobservedthatthe|Z|100mHzvaluesofall

coatingsdecreasedrapidlyduringfirst72hofQUVtest.Thisresult

indicatesarapidlossoftheprotectivepropertiesofthefilm.The

fallof|Z|100mHz duringthefirst72hofQUVtestwasattributed

tothedegradationofcoatingsduetotheUVradiation.Afterthis

0 15 30 45 60 75 90

Fig 10 Electrochemical impedance diagrams obtained after 216 h of QUV test of

() Pure PU coating; (△) PU coating containing 0.1 wt% nano ZnO; (䊉) PU coating

QUV test time / h

l10

Fig 11 |Z| 100 mHz versus QUV test time of () Pure PU coating; (△) PU coating con-taining 0.1 wt% nano ZnO; (䊉) PU coating containing 0.1 wt% nano ZnO-APS; (♦) PU coating containing 0.5 wt% nano ZnO-APS.

exposuretimetoQUVtest,the|Z|100mHzvalueofpurePUcoating,

PUcoatingscontaining0.1wt%nanoZnOandPUcoating contain-ing0.5wt%nanoZnO-APScontinuedtodecrease.ForthePUcoating containing0.1wt%nanoZnO-APSthe|Z|100mHzvalueremained rel-ativelystableathighvalues.After216hofQUVtestthe|Z|100mHz valueofPUcoatingscontainingnanoZnOandZnO-APSweremuch higherthanoneofthepurePUcoating.The|Z|100mHzvalueofPU coatingcontaining0.1wt%nanoZnO-APSwashigherthanoneof thePUcoatingcontaining0.1wt%nanoZnO.AmongPUcoatings containing nanoZnO-APS, thecoating with 0.1wt% nano ZnO-APShasthehigher|Z|100mHz value.Theseresultsshowthat the presenceofnanoZnO-APSimprovedtheUVresistanceofPU coat-ingandthebestcoatingsperformancewasobtainedwith0.1wt% nanoZnO-APS.Theresultsobtainedbyimpedancemeasurements areinagreementwiththeglossmeasurementsandSEM observa-tions

Thedecreaseof|Z|100mHzvaluesinthecaseofpurePUcoating,

PUcoatingcontaining0.1wt%nanoZnOandPUcoatingcontaining 0.5wt%nanoZnO-APScanbeexplainedbythepresenceofcracks

inthecoatingsafterexposuretoQUVtest.Forcoatingcontaining 0.1wt%nanoZnO-APS,nocrackappeared,sothatthecoatinghas thehighestglossretentionand|Z|100mHzvalueafter216hexposure

toQUVtest

4 Conclusion Nano ZnO modified by 2-aminoethyl-3-aminopropyl-trimethoxysilane (ZnO-APS)was successfully synthesized ZnO-APShassphericalstructureanditsparticlesizeisabout10–15nm ThedegradationofPUcoatingscontaining0.1wt%nanoZnOand nanoZnO-APSattwoconcentrations(0.1wt%and0.5wt%)dueto exposureinQUVtestwasstudied.ThepresenceofnanoZnOand ZnO-APSimprovedtheUVresistanceofPUcoatings.Thesurface modificationofnanoZnObyAPSenhanceditsefficiencyandthe efficiencyof nanoZnO-APSdepends onitsconcentration.Nano ZnO-APSat lowconcentrationof0.1wt%enhancedsignificantly

UVresistanceofPUcoating.TheincreaseofZnO-APSconcentration didnot improvevery much theUV resistanceofPUcoating It willbenecessarytoimprovethedispersionofnanoZnO-APSand optimizeitsconcentrationinthecoating

TheauthorsgratefullyacknowledgethesupportofMinistryof

ScienceandTechnologyofVietnamthroughproject

132/2013/HÐ-NÐT and Wallonie-Bruxelles International (WBI) of Belgium

throughproject28

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