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ONLINE ISSN 2069-7430ISSN-L 1841-4737

PRO LIGNO Vol. 8 N 2 2012www.proligno.ro pp. 37-52

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O INTROSPECTIVA DEGRADRIILEMNULUI DE FAG (Fagus sylvatica L.)

EXPUS TIMP NDELUNGAT NEXTERIOR, DEASUPRA SOLULUI

Partea 1: Tipuri de degradare i influena

tratamentelor de suprafa, relevate prinevaluare nedistructivdupa 7 ani de

expunere

AN INSIGHT INTO BEECH WOOD (Fagussylvatica L.) DEGRADATION IN

OUTDOORS, ABOVE GROUND, LONG-TIME EXPOSURE

Part 1: Degradation and influence of

surface treatments revealed by non-destructive evaluation after 7 years

Maria Cristina TIMARProf.dr.eng. TRANSILVANIA University in Brasov Faculty of Wood Engineering

Adresa/Address: B-dul Eroilor nr. 29, 50036 Brasov, RomaniaE-mail: [email protected]

Emanuela BELDEANLect.dr.eng. TRANSILVANIA University in Brasov Faculty of Wood Engineering


Octavia ZELENIUCLect.dr.eng. TRANSILVANIA University in Brasov Faculty of Wood Engineering


Anca VARODIResearcher dr. eng.- TRANSILVANIA University in Brasov, ProDD Institute

Adresa/Address: Str. Institutului nr.10, Brasov, RomaniaE-mail: [email protected]

Rezumat:Fagul (Fagus sylvatica L.) este o specie

lemnoasimportantn Romnia, iar cercetrile carese refer la posibilittile de mbuntire aproprietilor lemnului de fag, n special durabilitateai stabilitatea dimensional n vederea extinderii idiversificrii utilizrii acestuia n aplicaii n exterior,deasupra solului, sunt de un deosebit interes. Inacest context este important sse studieze i sseneleag complexitatea fenomenelor de degradarecare se produc n timp, n aceste condiii i s setesteze eficiena tratamentelor de protecie prin testen teren corespunztoare.Cercetarea prezentat naceast lucrare a avut ca scop evaluarea degradriiprobelor de fag tratate i netratate, dup apte aniexpunere ntr-un test L-Joint modificat. S-a utilizat unsistem nedistructiv de evaluare i se prezintdiferitele aspecte privind degradarea complex a

lemnului i a peliculei de finisare, la nivel macro imicroscopic. S-a analizat de asemenea influenatratamentului de bio-protecie cu un produs dereferin urmat de finisarea cu o vopsea alchidicalb i o lazur alchidic semi-transparent deculoare maro. Discolorarea datorit ciupercilor demucegai i albstreal i crpturile au fostprincipalele fenomene de degradare care au aprutpe feele exterioare i n zona cepului. Putregaiul a

Abstract:Beech (Fagus sylvatica L.) is an important wood

species in Romania and research looking at thepossibilities of improving beech wood properties,especially durability and dimensional stability for anextension and diversification of utilisation towardsoutdoors, above ground applications (UC3) is of greatinterest. In this respect, it is important to study andunderstand the complex degradation phenomenaoccurring in time under these conditions and to testthe efficiency of the protective treatments inappropriate field tests. The research presented in thispaper aimed to evaluate the degradation of controland treated beech wood samples after seven yearsexposure in a modified L-Joint test. A non-destructiveevaluation system was employed and the differentaspects of the complex degradation of wood andcoatings, at macroscopic and microscopic level are

presented. The influence of a preservation treatmentwith a reference biocide product and further coatingwith an alkyd white paint and a brown alkyd semi-transparent lasure is also discussed. Discoloration bymould and staining fungi and cracks were the maindegradation phenomena occurring on the externalfaces and in the joint area (tenon). Decay was presenton some treated samples, but not in a large extent,being ranked up to maximum average values of 2 in

Autor corespondent / Corresponding author


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fost prezent numai pe unele probe tratate, dar nu pesuprafee mari, fiind evaluat la o valoare medie demaxim de 2 n cep i de 1.5 pe suprafeeleexterioare. Tratamentele superficiale aplicate au avutdoar un efect minor n reducerea degradrii lemnuluidup o perioad aa lung de timp. Cele mai bune

rezultate s-au obinut pentru probele tratate cuprodusul de bio-protecie i ulterior finisate cu vopseaalchidicalb. Variabilitatea proprietilor lemnului camaterial natural, coroborat cu numrul redus deprobe paralele (3) i posibile mici diferene ncondiiile efective de testare (variaia umiditii ntreprobe), trebuie luate n considerare la analizarearezultatelor experimentale.

Cuvinte cheie: fag; test L-joint modificat; putrezire;discolorare; crpare lemn; degradare pelicule; efectfactori de mediu.

INTRODUCERE

Lemnul de fag (Fagus sylvatica L.) este binecunoscut ca o specie de foioase cu coeficieni maride umflare i contragere i durabilitate naturalsczut (Molnar .a. 2001), motive pentru careutilizrile sale n condiii de exterior sunt foartelimitate (http://www.wood-database.com/lumber-identification/hardwoods/european-beech/). n acestcontext, cercetrile privind posibilitile dembuntire a proprietilor lemnului de fag, nspecial durabilitatea i stabilitatea dimensional, nvederea extinderii i diversificrii utilizrii acestuia nexterior, deasupra solului, corespunztor clasei deutilizare (UC) 3 definit de EN 335, sunt de interes.(http://www.erlauusa.com/Outdoor_Furniture.html).

Noile tehnologii, precum acetilarea sau tratamenteletermice, s-au dovedit eficiente (Militz i Hill 2005, VanAcker i Peek 2008), dar alte tehnologii mai simplebazate impregnarea cu rini (Pfeffer .a. 2012a,2012b) i acoperirea superficial i-ar putea gsi oaplicare mai larg.

n acest sens, este important sse studieze is se neleag fenomenele complexe de degradarecare apar n timp, n condiiile UC 3, ca rezultat alaciunii combinate a factorilor biotici i abiotici (Eatoni Hale 1993, Hon 2001) i sse evalueze eficienatratamentelor de protecie n teste n teren relevante(Van Acker i Stevens 2003, Raberg .a. 2005,Pfeffer .a. 2012a, 2012b).

n ultimele decenii au fost dezvoltate metodede testare n teren, pentru a evalua durabilitateanatural a lemnului i eficiena produselor deprotecie. Testele au fost concepute pentru utilizriale lemnului n contact cu solul (EN 252) i deasuprasolului (mbinri n L EN 330, mbinri suprapuseCEN/TS 12037). Evaluarea deasupra solului s-adovedit a fi mult mai dificildect n contact cu solul,din cauza variaiilor mari n severitatea expunerii.Aceasta include nu numai variaia condiiilor climaticen timp, ci i condiiile locale de expunere, careinflueneaz coninutul de umiditate, temperatura i

the tenon area and 1.5 on the external surfaces ofsome samples.The simple surface treatments applied had only aslight effect of reducing wood degradation over such along period of time. The best results were obtained forthe samples treated with biocide before finishing with

the alkyd white paint.In all cases the variability of wood as a naturalmaterial corroborated with the reduced number ofreplicate test samples (3) and possible smalldifferences in the actual testing conditions (moisturecontent variations between samples) should beconsidered when analysing the experimental results.

Key words: beech wood; modified L-joint; decay;discolouration; wood cracking; coatings degradation;weathering effect.

INTRODUCTION

Beech wood (Fagus sylvatica L.) is well knownas a hardwood species with high swelling andshrinking coefficients and low natural durability(Molnar et al 2001), reasons why its applications inoutdoor conditions are very limited (http://www.wood-database.com/lumber-identification/hardwoods/european-beech/). Researchlooking at the possibilities of improving beech woodproperties, especially durability and dimensionalstability for an extension and diversification ofutilisation towards outdoors, above groundapplications, corresponding to the use class (UC) 3defined by EN 335, is of interest(http://www.erlauusa.com/Outdoor_Furniture.html).

Novel technologies, such as acetylation or heattreatments proved their efficiency (Militz and Hill 2005,Van Acker and Peek 2008), but other simplertechnologies based on resins impregnation (Pfeffer etal 2012a, 2012b) and surface coating might find awider application.

In this respect, it is important to study andunderstand the complex degradation phenomenaoccurring in time under the conditions of UC 3 asresult of the combined action of biotic and non-bioticfactors (Eaton and Hale 1993, Hon 2001) and to testthe efficiency of the protective treatments inappropriate field tests (Van Acker and Stevens 2003,Raberg et al. 2005, Pfeffer et al 2012a, 2012b).

Field test methods have been developed overthe last decades to evaluate the wood naturaldurability and preservatives efficiency. The tests weredesigned for in ground contact (EN 252) and above -ground (L-joints -EN 330, lap-joints CEN/TS 12037)wood uses. Above-ground evaluation has proven tobe more difficult than in ground contact due to thewide variations in severity of exposure. This includesnot only the in-time climate variation but also the siteconditions that influence moisture content,temperature and UV exposure (Lebow 2010).

L-joint test, defined by EN 330 as standard


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expunerea la radiaii UV (Lebow 2010).Testul mbinrilor n L, definit de EN 330, ca

metoda standard pentru a evalua eficiena produselorde bio-protecie a lemnului folosite cu finisareulterioar, reprezint una dintre metodele cele maifolosite pentru a evalua apariia i extinderea

degradrii lemnului expus n exterior deasupra solului(Carey i Bravery 1986, Despot 1998, Clausen iLindnen 2011).

Epruvetele reproduc colul de jos al unei ramede fereastr cu o mbinare de slab calitate cefavorizeazptrunderea i reinerea apei n zona dembinare, ceea ce va duce la degradare fungic.

Design-ul mbinrilor L poate facilita iptrunderea apei de ploaie prin seciuneatransversal a capetelor (Highley 1993), accelerndastfel degradarea lemnului. Uzual, n acest testaceste seciuni se acopercu produse de etanare,ce au un efect important asupra degradrii lemnuluii a peliculelor de finisare (Boxall .a. 1992).

Un test L-joint accelerat a fost propus de VanAcker i Stevens n 1997 i utilizat cu succes pentruevaluarea durabilitii naturale a lemnului, n condiiileclasei de utilizare 3 (Van Acker i Stevens 1997,2003). Acelai test a fost apoi aplicat pentru a evaluaeficiena diferitelor tratamente ale lemnului pentruaplicaii in UC 3 (De Vetter i Van Acker 2010).

Fagul (Fagus sylvatica) reprezinto specie delemn important n Romnia(http://www.timberwood.ro/products.html,http://dfwm.ugent.be/woodlab/docs/gottingen/cristescu.pdf,http://www.alibaba.com/countrysearch/RO/beech-wood.html), astfel c cercetarile privind ameliorarea

lemnului de fag sunt de interes economic.n cadrul Facultii de Ingineria Lemnului dinBraov s-a realizat un amplu proiect de cercetarereferitor la posibilitile i limitele ameliorrii lemnuluide fag, prin tratamente superficiale simple utilizndrini, produse biocide i materiale peliculogene,menite s asigure o performan mbuntit nexterior, deasupra solului (UC3) (Timar .a. 2005,Timar i Beldean 2006, 2007a, Beldean 2009). nacest sens, pentru a studia fenomenele de degradarea lemnului care apar n timp i pentru a evaluaeficiena tratamentelor aplicate, s-a folosit un test L-joint modificat, adaptat dupcel propus de Van Ackeri Stevens (1997), (Timar i Beldean 2006, 2007b,Timar .a. 2008)

OBIECTIVEPartea din cercetare prezentat n aceast

lucrare a avut drept scop studierea degradriicomplexe a lemnului de fag i a materialelorpeliculogene de finisare, dup 7 ani expunere ncondiiile UC3, ca rezultat al aciunii combinate afactorilor biotici i abiotici activi n aceste condiii ievaluarea realista efectelor de protecie pe termenlung, a unui tratament de protecie cu un biocid dereferin i cu dou produse diferite de finisare.

method to evaluate the efficiency of woodpreservatives to be used under a coating, representsone of the most employed methods to evaluate theinitiation and progress of decay in wood exposedoutdoors, above ground (Carey and Bravery 1986,Despot 1998, Clausen and Lindnen 2011).

The test samples mimic the bottom corner of awiondow frame with a poor quality joint, whichfacilitates water ingress and retention in the joint area,leading to fungal degradation.

The L-joint design can also promote end-grainpenetration of rainwater (Highley 1993), thusaccelerating the wood degradation. End-grain sealersare usually employed and their effect on thedegradation of wood and coatings was foundimportant (Boxall et al. 1992).

An accelerated L-joint test was proposed by

Van Acker and Stevens in 1997 and successfullyemployed for evaluation of the natural durability ofwood in the conditions of use class 3 (Van Acker andStevens 1997, 2003). The same test was then appliedto evaluate the efficiency of different wood treatmentsfor applications in UC 3 (De Vetter and Van Acker2010).

Beech (Fagus sylvatica) is an important woodspecies in Romania(http://www.timberwood.ro/products.html,http://dfwm.ugent.be/woodlab/docs/gottingen/cristescu.pdf,http://www.alibaba.com/countrysearch/RO/beech-wood.html), so that research into beech wood

improvement is of economical interest.An extensive research project looking at thepossibilities and limits of improving beech wood bysimple surface treatments employing resins, biocideproducts and coatings, in order to impart a betterperformance in outdoors, above ground exposure(UC3), was undertaken within the Faculty of WoodEngineering in Braov (Timar et al. 2005, Timar andBeldean 2006, 2007a, Beldean 2009). With thisrespect a modified L-Joint, adapted from the oneproposed by Van Acker and Stevens (1997), wasemployed to study the wood degradation phenomenaoccurring in time under these conditions and to checkthe efficiency of the applied treatments (Timar andBeldean 2006, 2007b, Timar et al. 2008)

OBJECTIVESThe part of research presented in this paper

aimed at studying the complex degradation of beechwood and protective coatings after 7 years exposurein the conditions of UC3, as a result of the combinedaction of the biotic and non-biotic factors active inthose conditions and to realistically evaluate the long-term protective effects of a preservation treatmentwith a reference biocide and further coating with twodifferent coating materials.


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S-a efectuat o evaluare non-distructiv,macroscopici microscopic. Au fost evaluate attcolonizarea cu ciuperci i fenomenele asociate dedegradare (discolorare i putrezire) n zona mbinrii(cepul probelor) i pe suprafeele exterioare aleprobelor testate, ct i aspecte ale degradrii abiotice

(crparea lemnului, efectul factorilor de mediu,crparea peliculelor de finisare, exfolierea).

METOD, MATERIALE I APARATURn aceast cercetare au fost investigate probe

de fag (Fagus sylvatica L.), expuse timp de 7 ani ntr-un test tip L-joint (mbinare n L) modificat, adaptatdup cel propus de Van Acker i Stevens (1997),descris n publicaiile anterioare ale autorilor (Timar iBeldean 2006, Timar i Beldean 2007b, Timar .a.2008). Probele testate efectiv au fost elementeleorizontale (elemente cu cep) ale unor mbinari L la90, obinute prin montarea acestora n sistem cep iscobitur n elementele verticale lungi. Elementele

verticale au fost realizate din cele dou specii delemn nedurabile de referin: alburn de pin (Pinussylvestris) i fag (Fagus sylvatica L.), ncleiatempreun. Elementele verticale nu au fost tratate saufinisate n nici un fel n scopul de a permitecolonizarea rapid cu micro-organisme, dezvoltareaputregaiului i rspndirea acestuia la piesele realede testare (elementele orizontale cu cep), princontactul direct al acestora n zona mbinrii. Probeleau fost expuse pe un suport special, nclinate cu opant de 10 spre spate, astfel nct s ajute laptrunderea i reinerea apei n mbinare, pentruaccelerarea degradrii biologice n aceast zon(Fig. 1 a, b).

A non-destructive macroscopic and microscopicevaluation was performed. Fungal colonisation andassociated degradation phenomena (discolourationand decay) on both inner joint area (actual tenon oftest samples) and the external surfaces of the testsamples, alongside non-biotic degradation aspects

(wood cracking, weathering effect, coatings cracking,flaking, exfoliation) were evaluated.

METHOD, MATERIALS AND EQUIPMENTBeech wood (Fagus sylvatica L.) samples

exposed for 7 years in a modified L-joint test adaptedfrom that proposed by Van Acker and Stevens (1997),described in earlier publications of the authors (Timarand Beldean 2006, Timar and Beldean 2007b, Timaret al. 2008), were investigated in this research. Theactual test samples were the horizontal elements(tenon members) mounted in a longer mortisemembers of a 90 tenon and mortise L-joints. Themortise was made of the two perishable reference

wood species: sapwood of Pinus sylvestris and Fagussylvatica, glued together. The mortise members werenot treated or finished in any way in order to allow fastcolonisation by micro-organisms, development ofdecay and spreading of this attack to the actualtesting pieces (the tenon members) through theirdirect contact in the joint area. The samples wereexposed on a special rack at a 10 backwards slopeso that to promote ingress and retention of water inthe joint for accelerating biological degradation in thisarea (Fig. 1 a, b)

a bFig.1.

Aspecte metodologice privind testul modificat L-Joint (mbinare n L) adaptat dupVan Acker andStevens (1997): a. forma i dimensiunile probelor (a se nota seciunea tangeniala feei superioare

expusa probelor); b. probe expuse pe suport/Methodological aspects of the modified L-joint test adapted from Van Acker and Stevens (1997): a.form and dimensions of test samples (note the tangential section of the upper exposed face of the

samples); b. test samples exposed on the rack.

Probele incluse n aceast cercetare au fost:probe martor netratate, codificate M, probe care au

The test samples included in this research were:untreated controls, coded M, samples that were


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fost tratate prin imersie de scurtdurat(15 minute la20C), ntr-o soluie a unui produs de protecie dereferin pe baza de sulfat de cupru, bicromat depotasiu i oxid de crom (compoziie n conformitatecu EN 330: CuSO45H2O-50% (m/m), K2Cr2O7 48%(m/m), CrO3- 2% (m/m), de concentraie 1%),

codificate R, i probe similare acoperite ulterior cuproduse de finisare codificate MS1, MS2 i RS1,RS2. Acestea au fost pregtite din probele martor Mi cele bio-protejate R, prin finisare cu doumateriale diferite: o lazur alchidic semi-transparent, maro, VILLA SUPRA (S1) i o vopseaalchidica alb SUPERPOLILAC, (S2), produse dePolicolor (www.Policolor ro). Finisarea s-a realizatprin pensulare n dou straturi succesive pesuprafeele exterioare ale probelor, montatetemporarn acest scopntr-un element vertical lung.Treiprobe paraleleau fostpregtite itestatepentrufiecarevariant.

Dei testul utilizat a fost dezvoltat pe bazatestului standard L-joint definit de EN 330, privindevaluarea eficienei relative a unui biocid careurmeazsa fie utilizat sub un strat de finisare, pentrucare sistemul de evaluare are n vedere i noteazexclusiv biodegradarea n zona de mbinare,combinnd discolorarea i putrezirea ntr-o cifrcumulativ(0 la 4), aceastcercetare a mers dincolode aceste obiective. Astfel, evaluarea non-distructiva probelor a luat n considerare att zona dembinare a cepului ct i ntreaga suprafaexterioar expus (feele de sus, laterale iinferioar), evalund individual discolorarea caurmare a atacului biologic (C, cu cotaii de la 1 la 3 nconformitate cu CEN/TS 12037:2003, Tabelul C1),putrezirea (D cu cotaii de la 0 la 4 n conformitate cuCEN/TS 12037:2003, Tabelul C2), i crpturile nlemn (CW cotate de la 0 la 4 - sistem original decotare). Mai mult dect att, n cazul probelorfinisate, peliculele de finisare au fost examinatepentru a evalua aderena lor la substrat (codificatdela 0 la 3 - sistem original de clasificare) i apariiafenomenelor specifice de degradare (crpturi, cojiri,exfolieri, degradri punctiforme), n timp ce pentrucele care nu au fost finisate, s-a observat aspectulgeneral i degradrile induse de radiaiile UV(culoare gri, asperizarea suprafeei sau detari defibre). Mai multe detalii despre sistemul complex deevaluare adaptat i original, n comparaie cu

sistemul de evaluare cumulativ al standardului EN330, au fost publicate anterior (Timar .a. 2008).

Evaluarea macroscopica fost completatprinexaminarea microscopic a suprafeelor n luminareflectat folosind un steremicroscop Optika SZM 2echipat cu o camer video-digital PRO3. Acestechipament a fost ales deoarece a permisinvestigarea direct a suprafeelor probelor dencercare fra fi necesarextragerea unui eantionmicroscopic care safecteze integritatea probelor.

treated by short time immersion (15 minutes at 20C)in a preservative reference solution based on coppersulphate, potassium dichromate and chromium oxide(composition according to EN 330: CuSO45H2O-50%(m/m), K2Cr2O7 48% (m/m), CrO3- 2% (m/m), 1%concentration), coded R, and corresponding coated

samples coded MS1, MS2 and RS1, RS2. Thesewere prepared from control M and bio-protected Rsamples by finishing with two different coatingmaterials: a semi-transparent, brown, alkyd lasureVILLA SUPRA (S1) and an alkyd white paintSUPERPOLILAC, (S2) by Policolor(www.Policolor.ro). Coating was achieved by brushingin two successive layers on the external surfaces ofthe test samples, temporarily mounted for thispurpose in a long mortise member. Three replicatesamples were prepared and tested for each variant.

Though the employed test was developedbased on the standard L-joint test defined by EN 330,referring to the evaluation of the relative efficiency of a

biocide to be used under a coating, so that theevaluation is looking to and rating exclusively thebiodegradation in the joint area combiningdisfigurement (discolouration) and decay ascumulative rate (0 to 4), this research went beyondthose goals. Thus, the non-destructive evaluation ofthe samples took into consideration both the innerjoint area (tenon) and the whole external exposedsurface (upper, lateral and lower faces), ratingindividually discolouration due to biological attack (Cgraded from 1 to 3 according to CEN/TS 12037:2003,Table C1), decay (D graded from 0 to 4 according toCEN/TS 12037:2003, Table C2) and cracks in wood(CW graded from 0 to 4 original grading system).

Moreover, in the case of finished samples the coatingfilms were examined to evaluate their adherence tothe substrate (ranked from 0 to 3 original gradingsystem) and the occurrence of specific degradationphenomena (cracking, flaking, exfoliation, spot-wisedegradation), whilst for those not coated the generalaspect and evidence of UV induced degradations(grey colour, surface roughening or fibrous aspect)was noted. More details on the complex ratingscheme adapted and originally developed, incomparison with the standard EN 330 cumulativerating scheme, were previously published (Timar et al2008).

Macroscopic evaluation was completed bymicroscopic examination of the surfaces in reflectedlight using a stereomicroscope type Optika SZM 2fitted with a PRO3 digital video-camera. Thisequipment was chosen as it allowed the directinvestigation of the surfaces of the test pieces withoutbeing necessary to extract a microscopic sample andto affect the integrity of the test samples.


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REZULTATE EXPERIMENTALEFenomene de degradare - o prezentare calitativdup7 ani de expunere

Aspectul general probelor investigate poate fiobservat n Fig. 2, care aratdegradarea complex

EXPERIMENTAL RESULTSDegradation phenomena a qualitative approachafter 7 years exposure

The general aspect of the investigated testsamples can be observed in Fig. 2, showing that

a. b.Fig.2.

Probe de fag dup7 ani expunere n exterior, deasupra solului: aspectul general macroscopic alprobelor pe cele 3 fee investigate (a- faa superioarexpusdirect; b- falateral; c- fainferioar)i detalii ale degradrii cepului. Codul probelor: M- probe martor netratate; R- tratate cu un produs

biocid de referin; MS1- netratate, finisate cu S1; MS2- netratate, finisate cu S2; RS1- bioprotejate ifinisate cu S1; RS2- bioprotejate i finisate cu S2 /

Beech wood (Fagus sylvatica) after 7 years outdoors, above ground exposure: general macroscopicaspect of the test samples on the three investigated faces (a- upper, directly exposed face; b- lateral

face; c-lower face) and details of tenons degradation. Samples code: M- untreated control; R-bioprotected with a reference biocide product; MS1- untreated, finished with coating S1; MS -

untreated, finished with coating S2; RS1- bioprotected and finished with coating S1; RS2- bioprotectedand finished with coating S2.


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a lemnului i a peliculelor de finisare, dup7 ani deexpunere, ca rezultat al fenomenelor de degradarebiotice i abiotice. Cum era de ateptat, s-a observato degradare diferita zonelor ne-expuse direct (cepulmbinrii) i suprafaa exterioar expusa probelor.Referitor la suprafaa exterioar, degradarea maxim

i cea mai complex a fost nregistrat pe feelesuperioare, cele expuse direct la soare, ploaie i lacantitate maximde radiaie UV i ap(codificate an Fig. 2)

Degradarea biologic a constat n discolorridatorate ciupercilor de albstreal sau mucegire iputrezire provocat de ciupercile de tipBasidiomycetes, efecte care au aprut n timp, naceast ordine, aceasta fiind succesiunea comunde infestare relevat de cercetri similare (Despot1998, Pfeffer .a. 2012 a, b).

Discolorarea cauzat de ciupercile demucegire i albstreal, observat fie ca puncteizolate sau dungi sau pete, majoritar de culoare

albastru-gri pn la negru, a continuat sfie, dup7ani de expunere, fenomenul de bio-degradarepredominant. Aceasta a afectat nu numai probele defag netratate, dar i pe cele tratate cu produse deprotecie sau finisate, fiind prezent att n zonainterioar a mbinrii (cepul propriu-zis), ct i pefeele exterioare ale probelor, aa cum se poateobserva n Fig. 2.Trebuie remarcat totui, faptul c, pentru probelenefinisate, aciunea radiaiei UV i a apei adeterminat de asemenea, o schimbare a culorii n gri,care a concurat cu discolorrile biologice, att camomernt de apariie n timp ct i ca gamcoloristic, ceea ce a fcut destul de dificil

evaluarea discolorrii, n special pe faa superioarexpus. Aceast dificultate a crescut progresiv ntimp, n corelaie cu schimbarea de culoare n gridatorat efectului UV, tot mai accentuat, iasperizarea suprafaei. Acest lucru este n acord cudatele din literatura de specialitate cu privire lamecanismul degradrii lemnului sub influenafactorilor de mediu (Hon 2001) i cu alte dateexperimentale referitoare la ncercri n teren (Pfeffer.a. 2012a).

Examinarea microscopica zonelor de interesn lumina reflectat, a fost util pentru a verificaprezena ciupercilor de discolorare pe toatesuprafeele acestor probe, dup cum este ilustrat nimaginile din Fig. 3. S-au observat de asemenea,asperizarea suprafeei i detaarea fibrelordeterminate de aciunea factorilor de mediu, precumi existena crpturilor i a micro-fisurilor. Prezenaciupercilor de discolorare, pe feele laterale iinferioare, mai puin afectate de radiaiile UV i ap, aputut fi mult mai uor detectat.

degradation of wood and coatings, as a result of bothbiotic and non-biotic phenomena has occurred after 7years of exposure. As expectable, a differentdegradation was observed for the non-directlyexposed parts of the samples (the actual tenon of thejoint) and the external exposed surface of the

samples. Considering the external surface, themaximum and most complex degradation wasregistered on the upper faces, the ones directlyexposed to sun and rain and receiving the maximumamount of UV radiation and water (coded a in Fig. 2).

Biological degradation consisted in surfacediscolouration by stain or mould fungi and decay byrot fungi (Basidiomycetes), effects that appeared intime in this order, this being a common infestationsequence revealed by similar research (Despot 1998,Pfeffer et al 2012 a, b).

Discolouration due to mould and stainingfungi, observed either as isolated spots or grouped instreaks or stains, mostly bluish-grey to black, was still

after 7 years of exposure the predominant bio-degradation phenomena. This affected not only theuntreated beech samples, but also the preservativetreated or coated ones, being present both in the innerjoint area (tongue of the tenon members) and on theexternal faces of the test samples as shown in Fig. 2.It has to be remarked however, that for the uncoatedsamples the action of UV radiation and water alsodetermined a colour change to grey, that actuallycompeted with biological discolouration both regardingwhen this started and the actual colour, hence makingthe rating of discolouration quite difficult, especially onthe upper exposed face. This difficulty increasedprogressively in time in correlation to the more

accentuated UV induced colour change and surfaceroughening. This is in accord with literature data onthe mechanism of weathering (Hon 2001) and otherexperimental data from field tests (Pfeffer et al.2012a).

The microscopic examination of the interestareas under a stereomicroscope in reflected light wasused to verify the presence of staining fungi on all thesurfaces of these samples, as illustrated in thepictures from Fig. 3. Surface roughening anddetached fibres due to weathering as well as cracksand micro-fissures could be also observed. Evenunder microscope, the presence of the discolourationfungi could be more easily detected on the lateral andlower faces less affected by UV radiation and water.


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a a

b b

c cBeech control M Beech Bio protected R

Fig.3.Aspectul microscopic al degradrii suprafeelor exterioare pentru probe nefinisate, observate la

stereomicroscop la mrire 40 x: a- fasuperioar; b- falateral; c- fainferioar: pete dediscolorare, crpaturi n lemn, asperizarea suprafeei, desprinderea fibrelor (bara de msur= 100 m)/Microscopic features of external surfaces degradation for uncoated samples observed under a stereo-microscope at magnification of 40 x: a- upper face; b- lateral face; c- lower face: discolouration spots,

wood cracking, surface roughening, fibres detachment (measuring bar = 100m).

Finisarea lemnului, cu cele dou tipuri demateriale peliculogene (S1, S2) a ntrziat doar iniialdiscolorrile biologice; formarea ciupercilor dealbstreal i mucegire sub pelicula de finisare ipenetrarea acestora n continuare prin pelicula fostevident pentru multe probe i, adesea, cauzadegradrii punctiforme i/sau a micro-fisurilor iexfolierii peliculei de finisare, n special pentruvopseaua alchidicalbS2.

Coating of wood with the two types of coatingmaterials (S1, S2) only delayed initially biologicaldiscolouration, the formation of staining and mouldfungi under the coating film and their furtherpenetration through the coating was obvious for manysamples and often the cause of the spot-wisedegradation and/or micro-fissuring and furtherexfoliation of the paint film, especially for the alkydwhite paint S2.


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a a

b b

c cBeech bio protected and coated RS1 Beech coated MS2

Fig.4.Aspectul microscopic al degradrii feelor exterioare pentru probele finisate, observate la stereo-

microscop la mrire de 40 x: a- fasuperioar; b- falateral: c- fainferioar: exfoliere, microfisuri

i crpturi n pelicula de finisare, dezvoltare ciuperci in zonele exfoliate, dezvoltare de mucegai subpelicula de finisare i modul de penetrare prin pelicul(bara de msur= 100 m)/

Microscopic features of external surfaces degradation for coated samples observed under a stereo-microscope at magnification of 40 x: a- upper face; b- lateral face; c- lower face: exfoliation,

microfissures and cracks of the coating film, fungal colonisation of exfoliated areas, development ofmould fungi under the coating film and penetration patterns through the coating film (measuring bar =

100m.


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Aceste aspecte ale colonizrii fungice aprobelor finisate, precum i alte fenomene dedegradare ale peliculelor de finisare (exfoliere,crpare, cojire), au fost de asemenea evideniate prininvestigarea microscopica probelor finisate (Fig. 4).Formele de degradare ale peliculelor de finisare

datorit dezvoltrii ciupercilor, prezentate n aceststudiu, sunt foarte similare cu cele raportate deSouza i Gaylarde (2002).

Putrezirea n zona mbinrii (cep) a fost adoua formde degradare biologica probelor (Fig. 2- detalii cep). Pentru probele prezentate n aceastlucrare, primele semne de putregai incipient, precumdiscolorri caracteristice i/sau nmuierea lemnului(cote de atac 1-2 ca valori individuale), au fostobservate prima dat dup 48 de luni de expunere,dar numai n mod excepional pentru unele probemartor i finisate (Timar .a. 2008). Acest tip dedegradare, dup 7 ani de expunere, a evoluat caseveritate (cote de atac 1-3+, ca valori individuale i

valoare medie maxim pe variant de tratare 2) irspndire, dar nc nu a reprezentat un fenomengeneral, existnd ncprobe individuale fr nici unsemn de putrezire la examinarea nedistructiv (deexemplu, MS1, RS1).

Putrezirea pe feele exterioarea putut fi clarobservat pe unele probe, dup 7 ani de expunere.Totui, numai feele superioare ale unor probe au fostafectate, i chiar i pentru acelai lot de 3 probe,apariia acestui tip de degradare a fost diferit. Seremarcfaptul c la examinarea precedent, dup5ani de expunere, unele semne incipiente de putregaipotenial s-au observat numai n mod excepional pefeele superioare pentru foarte puine probe.

Crparea lemnului a fost un alt fenomen dedegradare major att pentru probe finisate ct inefinisate. Coeficienii mari de umflare i contragereai lemnului de fag i tensiunile interne asociate cuvariaia dimensional la schimbrile climaticecontinue explic aceast form de degradareprevizibil. De fapt, instabilitatea dimensional alemnului de fag conteaz mai mult pentru utilizareafoarte limitatn condiii de exterior a acestuia, dectdurabilitatea sa natural redus, care poate fi multmai uor corectat prin tratamente adecvate deimpregnare cu produse de protecie, avnd n vederegradul ridicat de impregnabilitate al acestei specii.(http://www.wolman.de/en/infocenter_wood/from_tree_to_wood/wood_species/beech/index.php). n plus,crparea extensiv n condiii de exterior vadetermina ptrunderea apei n interiorul materialuluilemnos i n consecinputrezirea acestuia.

Influena tratamentelor - o evaluare cantitativ,dup7 ani expunere

Graficele din Fig. 5, Fig. 6, Fig. 7 se refer lainfluena tratamentelor aplicate asupra apariiei iseveritii celor mai caracteristice fenomene dedegradare biotici abioticpentru probele nefinisate

These aspects of fungal colonisation of coatedsamples as well as other phenomena of coatingsdegradation (exfoliation of coatings, cracking, flaking)were also highlighted by the microscopic investigationof the coated wooden samples (Fig. 4). The patternsof coatings degradation due to fungal development

revealed by this study are very similar to thosereported by Souza and Gaylarde (2002).Decayin the joint area(tenon) was the second

form of biological degradation of the test samples (seeFig. 2 details of tenons). For the samples presentedin this paper, the first signs of incipient decay ascharacteristic discolouration and/or wood softening(individual rates 1-2) were firstly observed after 48months of exposure, but only exceptionally for somecontrol and coated samples (Timar et al. 2008). Thistype of degradation evolved after 7 years of exposureas severity (individual rates 1-3+, maximum averagerate for a trating variant 2)and spreading, but was stillnot a general phenomenon, meaning that there are

still individual samples without any sign of decay atnon-destructive evaluation (e.g. MS1, RS1).Decay on the external faces could be clearly

observed for some samples, after 7 years exposure.However, only the upper faces of some test sampleswere affected, and even for the same batch of 3replicate samples the occurrence of this type ofdegradation was different. It has to be remarked thatat the previous examination after 5 years of exposuresome incipient signs of potential decay were noticedonly exceptionally on the upper faces of a very fewsamples.

Wood crackingwas another major degradation

phenomenon for both uncoated and coated samples.The high swelling and shrinking coefficients of beechwood and inner tensions associated to thisdimensional variation in relation to the continuousclimate change explain this expectable form ofdegradation. Actually, the dimensional instability ofbeech wood counts more for its very limited exterioruse than its low natural durability that can be moreeasily corrected by adequate impregnation treatmentswith wood preservatives, considering the hightreatability of this species(http://www.wolman.de/en/infocenter_wood/from_tree_to_wood/wood_species/beech/index.php).Furthermore, the extensive cracking in outdoorsconditions will determine water ingress inside thewooden material and consequent decay.

Influence of treatments quantitative approachafter 7 years exposure

The graphs in Fig. 5, Fig. 6, Fig. 7 refer to theinfluence of the treatments applied on the occurrenceand severity of some of the most characteristic bioticand non-biotic degradation phenomena of theuncoated and coated beech test samples after 7 yearsof in-field exposure. The graphs are based on the


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i finisate dup7 ani de expunere n teren. Graficelese bazeaz pe valorile medii calculate pentru treiprobe paralele i se referexclusiv la faa superioara zonei exterioare i la cep (zona de mbinare), caresunt cele mai susceptibile la degradare. Trebuiemenionat, totui, faptul c s-a observat n unele

cazuri o mare variabilitate ntre cele 3 probe i, prinurmare, aceste rezultate ar trebui s fie consideratemai mult ca o bazde discuie, dect o bazpentruconcluzii finale. Un numr mai mare de probeparalele, precum i un sistem de monitorizare n timpreal a umiditii diferitelor probe de lemn ar fi fostnecesare pentru rezultate mai uniforme, aa cumprezintali autori (Despot 1998, Clausen i Lindner2011).

mean values calculated for three replicates and arereferring exclusively to the upper face of the externalarea and the tenon (inner joint area), which are themost susceptible to degradation. It has to bementioned, however, that a high variability betweenthe 3 replicate samples was noticed in some cases

and, therefore, these results should be consideredmore as a basis of discussionrather than a basis forfinal conclusions. More replicate specimens as well asa system of monitoring the actual level of moisturecontent in the different replicates would have beennecessary for more uniform results, as shown by otherauthors (Despot 1998, Clausen and Lindner 2011).

0

1

2

3

Discolorare/

Discolouration

C

Nefinisat/Uncoated Finisat/Coated S1 Finisat/Coated S2

FAG / BEECH

Fata superioara expusa/ Upper exposed face - 7 years

M

R

0

1

2

3

4

Putregai/DecayD


FAG / BEECH

Fata superioara expusa/ Upper exposed face - 7 years

M

R

a b

Fig.5.Influena tipului de tratament asupra degradrii biologice a feelor superioare ale probelor din testul L-

joint, dup7 ani expunere: discolorare (a) i putrezire (b).M- probe martor frbioprotecie, R- probe tratate cu produs biocid de referin/

Influence of type of treatment on the biological degradation of upper faces of the L-joint test samples

after 7 years exposure: /discolouration (a) and decay (b).M- control samples without bio-protection, R- samples treated with the reference biocide.

0

1

2

3

Discolorare/

Discolouration

C


FAG/ BEECH

Cep/ Tenon - 7 years M

R

0

1

2

3

4

Putregai/DecayD


FAG / BEECH

Cep/ Tenon - 7 years

M

R

a b

Fig.6.Influena tipului de tratament asupra degradrii biologice a cepurilor probelor din testul L-joint dup7

ani expunere: discolorare (a) i putrezire (b).M- probe martor frbioprotecie, R- probe tratate cu produs biocid de referin/

Influence of type of treatment on the biological degradation of tenons of the L-joint test samples after 7years exposure: discolouration (a) and decay (b).

M- control samples without bio-protection, R- samples treated with the reference biocide.


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De asemenea, crparea i/sau detaareapeliculei epoxi de sigilare aplicat iniial pe captulopus cepului, a avut probabil o influenmare asupradegradrii mai rapide i extinderii acesteia pe uneleprobe comparativ cu probele similare reprezentndaceeai variant de tratare, aa cum a demonstrat

Boxall .a.(1992).Datele referitoare la discolorarea datoratciupercilor de mucegire i albstreal (Fig. 5a, Fig.6a), arat n mod clar c tratamentul probelor prinimersie de scurt durat n produsul biocid dereferin pe baza de cupru i crom, a euat nasigurarea unei mai bune rezistene pe termen lunglemnului de fag, la acest tip de degradare. Finisareasuprafeelor nu a mpiedicat atacul ciupercilor dediscolorare, care se dezvolt foarte bine sub peliculade finisare, mai ales n cazul vopselei alchidice albeS2, aa cum s-a prezentat n Fig.4. Acest lucru esten bun concordan cu cercetrile efectuate deSouza i Gaylarde (2002), care au demonstrat ntr-un

test accelerat de laborator, c o bio-deteriorare maisever a panourilor finisate a avut loc pentrupanourile inoculate cu un amestec de ciuperci sub unlac non-biocid, fa de cele inoculate peste peliculade finisare. Cu toate acestea, o discolorare maiextins a fost observat pentru probele bio-protejatei finisate n comparaie cu cele finisate frun pre-tratament de bio-protecie (RS1, RS2, comparativ cuMS1 i MS2 n Fig. 6), ceea ce reprezintun rezultatdestul de ciudat i nu ar trebui sconduccititorul lao concluzie greit din punct de vedere al practiciicurente n tratarea lemnului. n general, un tratamentde protecie nainte de finisare, mbunteterezistena la biodegradare i ar trebui s fie o

practiccomercialcomunpentru produse finite dinlemn n UC 3, cum este cazul ferestrelor (Cookson2010).

Situaia a fost similar i n ceea ce priveteeficiena tratamentelor superficiale de bio-protecieasupra rezistenei la putrezire (Fig. 5b, Fig. 6b). ncele mai multe cazuri, cele mai mari grade dedegradare prin putrezire, n cep i pe suprafaaexterioarsuperioar, au rezultat pentru probele pre-tratate cu produsul biocid, din nou, un rezultat carepoate induce n eroare. Aplicarea produsului biociddoar superficial prin imersie de scurt durat (15min/20C), nu a putut conferi rezisten la putrezire,acesta fiind un fenomen ce se produce nprofunzime. De obicei, un tratament prin impregnaren vid este recomandat pentru lemnul utilizat n UC 3(de exemplu, ferestre), dei chiar i un tratament prinimersie ntr-un produs de protecie corespunztor,nainte de finisare, ar trebui sofere o rezistenmaibunla putrezire, n comparaie numai cu tratamentulde finisare, aa cum arat Cookson (2010), peferestre model, dup un test de 8 ani expunere nexterior. Putrezirea i discolorarea sunt n mare parteinfluenate de coninutul de umiditate din lemn(Raberg .a. 2005), iar infiltraiile de ap ar putea fiaccentuate de crpturile din lemn sau de fixarea

Also, the cracking and/or detachment of epoxyend-sealer applied initially on the cross-cut endopposite to the tenon, might have had a big influenceon a more rapid or extended deterioration of sometest replicates compared to the similar replicates, asshown by Boxall et al.(1992)

The data referring to the discolouration due tomould and staining fungi (Fig. 5a, Fig. 6a) clearlyshow that the treatment of the test samples by shorttime immersion in the reference biocide product basedon copper and chromium failed in ensuring a betterlong term resistance of beech wood to this type ofdegradation. Coating of surfaces did not prevent theattack of the discolouration fungi as they develop verywell under the coating film, especially in the case ofthe white alkyd paint S2, as it was presented in Fig.4.This is in good accordance to research of Souza andGaylarde (2002) who demonstrated in an acceleratedlaboratory test, that a more severe bio deterioration ofcoated wooden panels occurred for the panels

inoculated with a fungal mixture below a non-biocide-containing varnish compared to the ones inoculatedabove the coating. However, a more extensivediscolouration was observed for the bio-protected andcoated samples compared to those coated withoutany biocide pre-treatment (RS1, RS2 compared toMS1 and MS2 in Fig. 6), which is quite a strangeresult and should not mislead the reader to a wrongconclusion for common practice. Generally, apreservative treatment before coating improvesresistance to biodegradation and should be commoncommercial practice for commodities in UC 3, such aswindows (Cookson 2010).

The situation was quite similar when looking at

the efficiency of the applied surface bio-protectiontreatment on the resistance to decay (Fig. 5b, Fig. 6b).In most cases higher degradation rates of decay intenon and on the upper external surface resulted forthe samples pre-treated with the biocide product,again a misleading result. The application of thebiocide product just on the surface by a short-timeimmersion (15 min/20C) could not impart resistanceto decay which is a bulk phenomenon. Usually avacuum impregnation treatment is recommended forwood application in UC 3 (e.g. windows), though evena treatment by dipping in an appropriate preservativebefore further coating should impart a better decayresistance compared to just coating, as shown byCookson (2010) on model windows after a test of 8years exposure.Decay and discolouration are mostly influenced by themoisture content in wood (Raberg et al 2005) andwater ingress could be promoted by cracks in wood ora bad fixture of the tenon in the mortise member. Onthe other hand, degraded coatings could increase therisk of decay by allowing rainwater absorption into thewood and delaying wood drying, thus prolongingconditions suitable for fungal attack.Thus, these results may be due to a fluctuation inmoisture content in the samples, which unfortunately


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greit a cepului n scobitur. Pe de alt parte,peliculele de finisare degradate ar putea crete risculde putrezire, prin facilitarea absorbiei apei de ploaien lemn i ntrzierea procesul de uscare, prelungindastfel condiiile adecvate pentru atacul ciupercilor.Astfel, aceste rezultate se pot datora fluctuaiei

coninutului de umiditate din probe, care, din pcate,nu a putut fi controlat n timpul testului i care esteconsiderat de o deosebit importan i de alicercettori (Brischke 2008, Schauwecker 2010,Clausen i Lindner 2011).

n concluzie, se poate spune cefectul pozitival tratamentului de bio-protecie observat la evalurileanterioare (Timar i Beldean 2007, Timar .a.2008),s-a pierdut n timp, dup 7 ani de expunere nexterior.

could not be controlled during the test and was foundextremely important by other researchers (Brischke2008, Schauwecker 2010, Clausen and Lindner2011).

Concluding, it could be said that even if apositive effect of the bio protection treatment applied

could be noticed at previous evaluations (Timar andBeldean 2007, Timar et al.2008), this was lost in timeafter 7 years of outdoors exposure.

0

1

2

3

4

Crapaturiinlemn/Crack

sin

CW

Nefinisat / Uncoated Finisat / Coated S1 Finisat / Coated S2

FAG / BEECH

Fata superioara expusa / Upper exposed face - 7 years

M

R

0

1

2

3

Aderentapeliculei/Adhe

ofthecoatingA

Finisat / Coating S1 Finisat / Coating S2

FAG / BEECH

Fata superioara expusa / Upper exposed face - 7 years

M

R

a b

Fig.7.Influena tipului de tratament asupra degradrii non-biologice a feelor superioare ale probelor din

testul L-joint dup7 ani expunere: crpturi n lemn (a) i aderenpeliculde finisare (b).M- probe martor frbioprotecie, R- probe tratate cu produs biocid de referin/

Influence of type of treatment on the non- biological degradation of upper faces of the L-joint test

samples after 7 years exposure: cracks in wood (a) and adherence of coating films (b).M- control samples without bio-protection, R- samples treated with the reference biocide.

Dup 7 ani de expunere n exterior, cele maimulte din probe au dezvoltat crpturi extinse. Acestlucru a fost previzibil, avnd n vedere instabilitateadimensionala lemnului de fag i faptul c, nu a fostaplicat nici un tratament pentru a reduce umflarea icontragerea probelor prezentate n aceast lucrare.Cu toate acestea, se poate observa un efect pozitival tratamentului cu produsul biocid pe bazde Cu-Cr,n reducerea crpaturilor, att pentru probelenefinisate ct i pentru probele finisate din lemn defag (Fig.7a). Cuprul este un fungicid cu spectru largde aciune, n timp ce cromul servete ca inhibitor lacoroziune i ca agent de fixare, conducnd lacreterea rezistenei la splare, mbuntindu-seastfel durata de viaa lemnului (Cooper .a.1993).n plus, reaciile complexe de fixare a cuprului nlemn sub influena cromului hexavalent ar puteaimplica o modificare a caracterului hidrofil alsuprafaei lemnului conducnd la o absorbie mailent a apei n lemn, aa cum arat i MaldasKamden (1998a, 1998b) pentru lemnul tratat cu CCA.

Probele cu crpturi minime dup 7 ani deexpunere, au fost cele bio-protejate i finisate cu

Most of the samples developed extensivecracking after 7 years of outdoors exposure. This wasexpectable considering the dimensional instability ofbeech wood and the fact that for the test samplespresented in this paper no treatment to reduceswelling and shrinking was applied. However, it couldbe noticed a positive effect of the treatment with theCu-Cr biocide product in reducing the cracking of bothuncoated and coated beech wood samples (Fig.7a).Copper is broadly toxic to fungi, while chromiumserves as a corrosion inhibitor and as a fixation agentleading to a leaching resistance, thus improving thewood service life (Cooper et al 1993). Moreover, thecomplex reactions of copper fixation on wood underthe influence of CrVImight have implied a modificationof the hydrophilic character of wooden surface leadingto a slower absorption of water in wood, as shown byMaldas and Kamden (1998a, 1998b) for CCA treatedwood.

The samples with minimum cracking after 7years of exposure were those bio-protected and


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vopsea alchidic alb (RS2). Aceleai probe auprezentat pelicule de finisare mai puin degradate i oaderen nc destul de bun a acestora (Fig. 7b),dei este de ateptat ca aceast situaie s seschimbe n curnd, datorit dezvoltrii ciupercilor demucegire sub peliculi efectului lor negativ asupra

aderenei, aa cum este ilustrat n imaginilemicroscopice din Fig.4

CONCLUZIIn aceast cercetare s-a utilizat un test L-joint

(mbinare L) modificat, n care au fost expuse probedin lemn de fag martor i tratate (bio-protejate ifinisate). Tratamentele aplicate au fost exclusivtratamente simple de suprafa, constnd ntr-untratament cu un produs biocid de referinpe bazdeCu-Cr, urmat apoi de finisare cu dou tipuri demateriale peliculogene: o lazur alchidic semi-transparentmaro, i o vopsea alchidicalb.

Pentru evaluarea i cotarea fenomenelorcomplexe de degradare biologic i non-biologic alemnului de fag i a peliculelor de finisare aprute nzona mbinrii (cep) i pe feele exterioare aleprobelor, dup 7 ani expunere n exterior, deasuprasolului, s-au utilizat aprecierea vizual direct istudiul microscopic.

Principalele fenomene de degradare au fostdiscolorarea produs de ciupercile de mucegire ide albstreal, putrezirea n zona cepului i crpturimari n lemn. Efecte caracteristice aciunii factorilorde mediu au fost evidente pentru probele nefinisate:asperizarea suprafeei, schimbarea culorii, crpturi,fisuri, n timp ce probelew finisate au prezentatdegradri ale peliculelor de finisare: degradarepunctiform, crpturi, scderea aderenei,delaminare i exfoliere.

Tratamentele de suprafa aplicate au avutdoar o influen limitatasupra apariiei fenomenelorde degradare. Cele mai bune rezultate au fostobinute pentru probele tratate cu biocid i ulteriorfinisate cu vopsea alchidicalb. Totui, este evidentc tratamentul lemnului de fag, pentru utilizri nexterior, ar trebui s implice principii i tehnici maiavansate de tratare dect protecia superficial ifinisarea, continund s rmn o provocare ncercetare.

n final se poate afirma c testul L-jointmodificat, asociat cu sistemul complex de evaluare icotare utilizat pentru evaluarea nedistructiv aprobelor, i-au dovedit utilitatea i versatilitatea naprecierea fenomenelor complexe de degradare alemnului i a peliculelor de finisare prin expunere nexterior i obinerea de date utile pentru corelarea lor.

n partea a doua a acestei lucrri se vaprezenta gradul de degradare n corelaie cu risculde umezire, alturi de date cumulative reprezentndevoluia n timp a fenomenelor de degradare, precumi rezultatele evalurii distructive dup 7 ani deexpunere n exterior.

further coated with the alkyd white paint (RS2). Thesame samples presented the less degraded coatingand still a fairly good adherence of the coating film(Fig. 7b), though it is expectable that this situation willchange soon due to the mould fungi developing underthe coating film and their negative effect on its

adherence as illustrated by the microscopic pictures inFig.4.

CONCLUSIONSA modified L-Joint test, within which control and

treated beech wood samples were exposed wasemployed in this research. The treatments appliedwere exclusively simple surface treatments consistingin a preservative treatment with a reference Cu-Crbiocide product and further coating with two coatingmaterials: a brown, semi-transparent, alkyd lasure anda white alkyd paint.

Direct visual assessment and microscopy wereemployed to evaluate and rate the complex biological

and non-biological degradation of beech wood andcoatings on the inner joint area and external faces ofthe test samples, after 7 years of outdoors, aboveground exposure.

The main degradation phenomena werediscolouration by mould and staining fungi, decay inthe tenon area and extensive wood cracking.Characteristic weathering effects were obvious for theuncoated samples: roughened surfaces, colourchanging, cracking and checking, whilst the coatedones showed degradation of the coating films: spot-wise degradation, cracking, adherence loss, flakingand exfoliation.

The surface treatments applied had only a

limited influence on the occurring degradationphenomena. The best results were obtained for thesamples treated with biocide before finishing with thealkyd white paint. However, it is obvious thattreatment of beech wood for exterior uses shouldimply more advanced treating principles andtechniques than surface preservation and coating,remaining a challenging research topic.

Finally it can be stated that the modified L-jointtest associated with the complex rating schemeemployed for the non-destructive samples evaluationproved their utility and versatility in assessing thecomplex degradation phenomena of wood andcoatings in outdoors exposure and getting input datafor their correlation.

A further development in assessing degradationin correlation with the risk of wetting will be presentedin the second part of this paper, alongside cumulativedata showing the in-time evolution of degradation andresults of destructive evaluation after 7 years ofoutdoors exposure.


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MULUMIRIAutorii sunt recunosctori specialitilor de la BFHHamburg Germania, pentru ghidarea primilor pai ndomeniul evalurii testelor n teren i ncurajareaacestui proiect de cercetare pe termen lung. Deasemenea este apreciat sprijinul financiar acordat

prin reeaua tematic Wood Modification (FP5) iAciunea COST E37, pentru un stagiu STSM (2003)i doucursuri intensive (2004, 2006).

ACKNOWLEDGEMENTThe authors remain grateful to the specialists fromBFH Hamburg Germany for guiding our first steps infield tests evaluation and encouraging this long-termresearch project. The financial support of theThematic Network on Wood Modification (FP5) and

COST Action E37 for a STSM (2003) and two trainingschools (2004, 2006) is also acknowledged.

BIBLIOGRAFIE / REFERENCES

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an accelerated outdoor L-joint performance test. European Journal of Wood and Wood Products, 61(2):125-132.***SR EN 335:2007. Durability of wood and wood- based products - Definition of use classes - Part 1: General.***SR EN 330:1997. Wood preservatives. Field test method for determining the relative protectiveeffectiveness of a wood preservative for use under a coating and exposed out-of-ground contact. L-jointmethod.***CEN/TS 12037:2003. Wood preservatives. Field test method for determining the relative protectiveeffectiveness of wood preservative exposed out of ground contact: Horizontal lap-joint method.***SR EN 252:1995. Field test method for determining the relative protective effectiveness of a product forwood preservative in ground contact.http://www.wolman.de/en/infocenter_wood/from_tree_to_wood/wood_species/beech/index.phphttp://www.erlauusa.com/Outdoor_Furniture.htmlhttp://www.wood-database.com/lumber-identification/hardwoods/european-beech/http://www.timberwood.ro/products.html,

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