PRO LIGNO Vol. 7 N° 4 2011 · omenirii, continua sa fie un material modern, provenit din resurse...

ONLINE ISSN 2069-7430ISSN-L 1841-4737

PRO LIGNO Vol. 7 N° 4 2011www.proligno.ro pp. 71-82

NOI OPTIUNI PRIVIND MATERIALULLEMNOS PENTRU FERESTRE - UN

STUDIU COMPARATIV PRIVINDABSORBTIA DE APA §I UMFLAREA

NEW MATERIAL OPTIONS FOR WOODENWINDOWS - A COMPARATIVE STUDY ON

WATER ABSORPTION / ADSORPTIONAND SWELLING

Maria Cristina TIMARProf.dr.ing. - Universitatea Transilvania din Bra§ov - Facultatea Ingineria Lemnului

Adresa/Address: B-dul Eroilor nr. 29, 50036 Bra§ov, RomaniaE-mail: cristinatimargunitbv.ro

Emanuela BELDEANef lucr.dr.ing. - Universitatea Transilvania din Bra§ov - Facultatea Ingineria Lemnului

Adresa/Address: B-dul Eroilor nr. 29, 50036 Bra§ov, RomaniaE-mail: ebeldeangunitbv.ro

Rezumat:Lucrarea prezinta o parte dintr-un studiu privind

determinarea compararea comportamentului 'capde apa a unor specii indigene exotice folosite inmod curent la o scare mai mare sau mai mica inproductia de ferestre din lemn. Lemnul acetilat,respectiv sortimentul comercial Accoya, un noumaterial reprezentand lemn ameliorat prinmodificarea chimica, a fost inclus in acest studiupentru comparare, ca o posibila alternative ecologicala materialul lemnos tehnologiile actuale de tratare.Au fost determinati coeficientii totali de umflare pedirectiile radiala tangenciala absorbtia de apa inteste de laborator de imersie higroscopicitatepentru 4 specii indigene: brad (Abies alba), pinsilvestru (Pinus sylvestris), larice (Larix decidua),stejar (Quercus robur) 3 specii exotice amazoniene,nou promovate pe plata europeana: Ochoo (Huracrepitans L.), Cambara (Erisma uncinatum W.),Yesquero (Cariniana estrellensis), comparativ cuAccoya. Rezultatele demonstreaza o higroscopicitateredusa o stabilitate dimensionala mai bung pentruAccoya comparativ cu toate speciile indigeneexotice testate.

Cuvinte cheie: lemn; absorbtie de apa; umflare;acetilare; Accoya; specii exotice indigene.

INTRODUCERELemnul, unul dintre primele materiale utilizate

de om, cu o istorie indelungata in cultura §i civilizatiaomenirii, continua sa fie un material modern, provenitdin resurse regenerabile, cu aplicatii diferite in conditiide interior §i exterior, pentru care o durata de viataextinsa §i conservarea aspectului estetic, a integritatiifizice §i proprietatilor mecanice, precum §i

functionalitatea produselor respective sunt cerinteimportante.

Totu§i, este §tiut faptul ca degradarea lemnuluiapare in diferite conditii de utilizare, precum inexterior, neacoperit, deasupra solului, sub actiuneadirecta a factorilor de mediu, ceea ce corespundeclasei de utilizare 3. De aceea, sunt necesare

Abstract:This paper presents part of a research aiming at

determining and comparing the water behaviour ofsome indigene and exotic wood species currentlyused at a larger or more reduced scale in theproduction of wooden windows. Acetylated wood,namely the commercial Accoya, a novel woodenmaterial improved by chemical modification, wasincluded in this study for comparison, as a possiblefuture ecological alternative to the current employedwooden materials and treating technologies. The totalswelling coefficients on the radial and tangentialdirection and the water absorption / adsorption inimmersion and hygroscopicity laboratory tests for 4indigene wood species: fir (Abies alba), pine (Pinussylvestris), larch (Larix decidua), oak (Quercus robur)and 3 exotic Amazonian wood species newlypromoted in the European market: Ochoo (Huracrepitans L.), Cambara (Erisma uncinatum W.),Yesquero (Cariniana estrellensis), wood weredetermined comparatively to Accoya. The resultsprove the reduced hygroscopicity and betterdimensional stability of Accoya wood compared to theall the tested indigene and exotic wood species.

Key words: wood, water absorption / adsorption;swelling, acetylation; Accoya; exotic and indigenespecies.

INTRODUCTIONWood, one of the first materials used by man,

with a long history in the human culture andcivilisation, continues to be a modern ecologicalmaterial from renewable resources with very differentinterior and exterior applications were an extendedservice life and conservation of aestheticalappearance, physical integrity and mechanicalproperties, alongside the functionality of therespective wooden product are importantrequirements.

However, it is well known that wood degradationoccurs under different service life conditions, such asin outdoor, non-covered, above ground applications ofwood under the direct action of climatic factors,

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procedee de tratare adecvate, complexe, care sainclude protectia urmata de acoperirea cu materialede finisare pentru exterior, rezistente la UV §i apa.Totu§i, actiunea cumulate a agentilor biologici, inspecial a ciupercilor de discolorare, mucegai §iputregai, impreuna cu radiatiile UV, apa dinprecipitatii §i continua variatie a umiditatii atmosferice,determine o degradare complexa, interdependenta alemnului §i materialelor de acoperire (Timar §.a.2008).

Ferestrele §i obloanele reprezinta produse finitedin lemn importante pentru clasa de utilzare 3. Dinpacate, lemnul tinde sa piarda pozitia sa pe piatapentru aceste aplicatii traditionale in favoareaplasticului §i metalelor u§oare (aluminiu). Acest lucruse datoreaza operatiilor de intretinere, care constauin curatare, §lefuire, chituire §i refinisareasuprafetelor din lemn, care trebuie facute frecvent, inmod uzual la fiecare 3-5 ani (Timar 2003,http://www.apar. it/Eng I ish/pdfs/Man ual_Wood_eng I.pdf ).

Principalul motiv pentru inlocuirea lemnului cuplastice sau metal este reducerea semnificativa aactivitatilor de intretinere pentru aceste materialerezistente la apa §i la biodegradare §i care nunecesita finisare ulterioara. Totu§i, imbatranireanaturals a acestor materiale (in special PVC) in 20-30 ani, costurile pentru reciclarea acestora, impactulasupra mediului inconjurator, precum §i obtinerea lordin resurse neregenerabile, din ce in ce mai reduse,nu pot fi neglijate intr-o abordare corecta in spirituldezvoltarii durabile (http://www.ironwoods.com/ironwoods_woods_vs_plastics.html).

De aceea lemnul trebuie sa ramana solutiasustenabila pentru ferestre §i alte aplicatii in clasa deutilizare 3 (http://www.swedishtimberproducts.co.uk/index.php). In aceasta privinta, s-au dezvoltat pe planmondial not concepte §i tratamente menite sa creascadurata de viata a produselor din lemn in conditiiadverse de mediu, inclusiv clasa de utilizare 3,precum modificarea chimica a lemnului, tratamenteletermice la temperaturi ridicate, tratamentele cu ra§ini,alaturi de protectia clasica §i finisarea cu produseacceptate din punct de vedere ecologic (Militz §i Hill2005; Hill §.a. 2007, Van Acker §i Peek 2008).

Acetilarea lemnului este un proces demodificare chimica bazat pe reactia grupelor -OHhidrofile din lemn cu anhidrida acetica, ele fiindinlocuite cu grupari acetat hidrofobe cu volum maimare. Acetilarea induce un proces de umflarepermanents a membranei celulare §i o reducere ahigroscopicitatii, modificari ce determine ameliorareaproprietatilor lemnului concretizata in: higroscopicitateredusa, stabilitate diemnsionala merits, resistenta labiodegradare, rezistenta imbunatatita la factorii demediu §i o mai bung performanta in timp a peliculelorde finisare (Rowell 1984, 1991, Timar 2003). Lemnulmasiv acetilat este un sortiment de lemn amelioratprin modificare chimica, proces care a urmat cusucces toti pa§ii de la formularea principiului de baza

corresponding to the biological use class 3 (UC 3).Adequate complex treating procedures that shouldinclude preservation followed by coating withadequate UV and water resistant finishing materialsfor exterior use are, therefore, necessary. However,the cumulative action of the biological agents,especially staining, mould and decay fungi, actingtogether with UV radiation, rainwater, and an almostcontinuous variation of the relative atmospherichumidity, determine a complex, inter-dependantdegradation of both wood and coatings (Timar et al2008).

Windows and shutters represent importantwooden commodities in the use class 3.Unfortunately, wood tends to loose its market positionto plastics and light metals (i.e. aluminium) for thistraditional application. This is mainly because of themaintenance operations, consisting in cleaning,sanding, stopping and re-finishing of the woodensurfaces, needed to be done quite frequently, usuallyevery 3 - 5 years, (Timar 2003,http://www.aparit/English/pdfs/Manual_Wood_engl.pdf ).

The significant reduction of maintenanceactivities for these biological and water resistantmaterials (plastics, aluminium), which do not requirefurther coating, is the main reason for this trend.However, the natural aging of these materials(especially PVC) in 20-30 years, as well as the costsand environmental impact of their recycling, alongsidetheir obtainment from non-renewable resources cannot be neglected in a correct sustainable approach(http://www.ironwoods.com/ironwoods_woods_vs_plastics.html).

That is why wood should remain a sustainablesolution for windows and other applications in the UC3 (http://www.swed ishti m berprod ucts.co. uk/i nd ex. p hp).With this respect new concepts and treatments meantto increase the service life of wooden products inadverse conditions including the use class 3, such aschemical modification of wood, heat treatments, resintreatments alongside classical wood preservation andcoating with environmentally acceptable products arebeing developed worldwide (Militz and Hill 2005; Hillet a12007, Van Acker and Peek 2008).

Wood acetylation is a process of chemicalmodification based on the reaction of hydrophilichydroxyl groups from wood with acetic anhydride, sothat they are replaced by larger volume hydrophobicacetate groups. A permanent cell wall swellingphenomenon and a reduced hygroscopicity count forthe improved properties of the resulting acetylatedwood: reduced hygroscopicity, better dimensionalstability, biological resistance, improved weatheringresistance and better performance of coatings(Rowell 1984, 1991, Timar 2003). Acetylated solidwood is a sort of wood improved by chemicalmodification that succeeded successfully all the stepsfrom the basic principle idea (going back to the1940s), to the laboratory successful research leading

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(Inca din anii 1940), la cercetari de laboratorconducand la tehnologii simplificate, apoi la cercetariin statie pilot pang la aplicarea practice pe scaraindustrials (Kollmann §i Cote 1968, Rowell 2006,2009). Acest succes a fost posibil printr-o activitate decercetare internationala indelungata, intr-un consortiucuprinzand institute de cercetare, universitati deprestigiu §i parteneri industriali, activitate sustinuta §ipromovata in faza de testare §i implementare aprodusului de o large comunitate §tiintifica prin diferiteproiecte europene precum Network on WoodModification (NWM) (Militz §i Lande 2009).

Accoya® este denumirea comerciala a lemnuluiacetilat (Pinus radiata) produs actualmente de firmaTitan Wood Limited in Olanda(http://www.accoya.com/index.asp,http://www.titanwood.com/index.asp). Lemnul acetialt este un materialcu o stabilitate dimensionala remarcabila,higroscopicitate redusa §i durabilitate ridicata, calitaticare II recomanda pentru diferite utilizari in exteriorprecum ferestrele (www.coedderwen.co.uk,www.bswaccoya.co.uk). Totu§i, acest material esterelativ nou §i putin cunoscut pe piata in general §ifoarte probabil aproape necunoscut producatorilor dinRomania.

0 alts abordare recenta in productia de ferestreeste utilizarea unor specii noi, mai putin utilizate saucunoscute provenite din exploatari forestieresustenabile, incluzand, pe langa speciile repedecrescatoare, §i specii exotice din padurileamazoniene. Aceste specii sunt promovate deAmazonian Center for Sustainable Forest EnterpriseCADEFOR (Centro Amazonico de DesarrolloForestal). Aceasta este o organizatie non-profit dinSanta Cruz, Bolivia fondata sa asiste sectorulforestier privat amazonian §i comunitatile indigenelocale, pentru a -si realiza potentialul maxim pe piatade export certificate, posibil prin baza de resurseforestiere bogate, politici favorabile de mediu §iobligatia unui managment forestier durabil(http://www.cadefor.org/en/cadefor/cadefor.php).

Unele dintre aceste specii exotice din padurileamazoniene au fost recent introduse pe piataeuropeana §i utilizate pentru diverse aplicatii, inclusivproductia de ferestre din lemn. Aceste specii sunt maiputin cunoscute in Europa de catre cercetatori §iproducatori, informatiile §tiintifice disponibile desprestructura §i proprietatile lor fiind limitate in principal lafi§ele de caracteriyare elaborate de catre CADEFOR(www.cadefor.org/en/especies/ficha.php).

Lucrarea de fata prezinta o parte dintr-un studiumai amplu privind determinarea §i comparareacomportamentului fata de ape a unor specii indigene§i exotice folosite actualmente la o scara mai maresau mai mica in productia de ferestre din lemn.Lemnul acetilat, respectiv sortimentul comercialAccoya, a fost inclus in acest studiu pentrucomparare, ca o posibila alternative ecologica lamaterialele lemnoase utilizate §i tehnologiile actualede tratare. In cadrul cercetarilor experimentale

to simplified technologies, then to the pilot scaleapplication and finally to the industrial production(Kollmann and Cote 1968, Rowell 2006, 2009). Aninternational, long-time research effort within aconsortium of well known research and industrialpartners from Europe sustained and promoted in thetesting and implementation phase by a largerscientific community through different EU projects,such as the Network on Wood Modification (NWM),made this possible (Militz and Lande 2009).

Accoya® is the trade name of the acetylatedwood (Radiata pine - Pinus radiata) producedcurrently by Titan Wood Limited in the Netherlands(http://www.accoya.com/index.asp,http://www.titanwood.com/index.asp). Acetylated wood is a material witha remarkable dimensional stability, reducedhygroscopicity and increased durability, qualities thatqualifies it for different outdoors utilisations includingwindows (www.coedderwen.co.uk, www.bswaccoya.co.uk).However, this material is relatively new and lessknown on the market in general and, most likely,almost unknown to the Romanian wood processors.

Another sustainable approach in the productionof windows is the employment of new, less used orknown wood species from sustainable forestry,including, alongside fast growing species, exoticwood species from the Amazonian forests. Thesewood species are promoted by the Amazonian Centerfor Sustainable Forest Enterprise CADEFOR (CentroAmazonico de Desarrollo Forestal). This is a service-based non-profit organisation located in Santa Cruz,Bolivia founded to assist the Bolivian \ Amazonianprivate forest sector and local \ indigenouscommunities to achieve their full potential in thecertified export market afforded by their rich forestresource base, favourable environmental policy andcommitment to sustainable forest management(http://www.cadefor.org/en/cadefor/cadefor.php).

Some of these exotic wood species from theAmazonian forests are being currently introducedonto the European market and used for differentapplications including the production of woodenwindows. These species are less known in Europe forthe scientists and the industrial processors, theavailable scientific information on their structure andproperties being rather limited to somecharacterization sheets elaborated by CADEFOR(www.cadefor.org/en/especies/ficha.php).

This paper presents part of a research aiming atdetermining and comparing the water behaviour ofsome indigene and exotic wood species currentlyused at a larger or more reduced scale in theproduction of wooden windows. Acetylated wood,namely commercial Accoya, was included in thisstudy for comparison and as a possible futurealternative to the current employed wooden materialsand treating technologies. The total swellingcoefficients on the radial and tangential direction andthe water absorption / adsorption in immersion andhygroscopicity laboratory tests, properties important

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PRO LIGNO Vol.7 N°4 2011www.proligno.ro pp. 71-82

prezentate s-au determinat coeficientii totali deumflare pe directiile radiala §i tangentiala §i absorbtiade ape, in teste de imersie §i higroscopicitate, pentru4 specii indigene §i 3 specii exotice comparativ cuAccoya.

MATERIALE 8I METODAIn acest studiu experimental s-au utilizat:

Accoya (lemn de Radiata pine acetilat) de la Titanwood, patru specii indigene relativ frecvent utilizate inproductia de ferestre: brad (Abies alba), pin (Pinussylvestris), larice (Larix decidua), stejar (Quercusrobur) §i trei specii exotice din padurile amazoniene,recent introduse la o scare mai redusa in productia deferestre de pe piata europeana: Ochoo (Huracrepitans L.), Cambara (Erisma uncinatum W.) §iYesquero (Cariniana estrellensis). In Tabelul 1 estedata o lista a speciilor utilizate, cu coduri §i catevadate din literature privind proprietatile fizice,durabilitatea naturala §i impregnabilitatea.

in the behaviour and fiability of windows andprotective coatings, were determined for 4 indigeneand 3 exotic wood species comparatively to Accoyawood.

MATERIALS AND METHODSAccoya wood (acetylated Radiata pine) from

Titan wood, four indigene wood species relativefrequently used for the production of windows: fir(Abies alba), pine (Pinus sylvestris), larch (Larixdecidua), oak (Quercus robur) and three exotic woodspecies from the Amazonian forests, recentlyintroduced at a low scale in the production of windowsfor the European market: Ochoo (Hura crepitans L.),Cambara (Erisma uncinatum W.) and Yesquero(Cariniana estrellensis) were included in thisresearch. A list of the wooden species this paper isreferring to with their given codes and some availableliterature data on some of their physical properties,natural durability and impregnability are presented inTable 1.

Tabelul 1 / Table 1Specii lemnoase utilizate in teste ri date din literature privind proprietatile lor / Wood species used in

the tests and some literature data on their propertiesNr.crt.

Specii lemnoase /Wood species

Cod /Code

Densitate laU=12-15% /

Density at 12-15% MC[g/cm3]

Coeficienti totali decontragere / Total

shinkage coefficients

Coeficienti totali deumflare (calculati) / Total

swelling coefficients(calculated)

Durabilitate /Permeabilitate

Durability /Permeability(see Note)Ra Tg Ra Tg

0 Radiata pine(Pinus radiata)

- 0.45 - 0.58 1.9...2.7 3.5...5.5 1.9...2.7 3.6...5.8 *4-5F, SH, SHA,ST/2-3H, 1S

1 Accoya wood'(Acetylated Radiatapine)

Ac 0.8 1.5 'Foarte durabil,1F/'Very durable, 1F

2 Fir 2(Abies alba Mill)

B 0.35 - 0.45 -0.75

2.9...3.8 7.2...7.6 2.9...3.9 7.7...8.2 *4F, SHH, SHA,ST/2-3 H; 2v S

3 Pine 2(Pinus sylvestris)

P 0.33 - 0.52 -0.89

3.3...4.5 7.5...8.7 3.4...4.7 8.1...9.5 *3-4F, SH, SA, ST/3-4 H; 15

4 Larch 2(Larix decidua)

L 0.44 - 0.59 -0.85

3.3...4.3 7.8...10.4 3.4...4.4 8.4...11.6 *3-4F, SH, SA, ST/4 H; 2v S

5 Oak 2(Quercus robur)

S 0.43 - 0.69 -0.96

4...4.6 7.8...10 4.1-4.8 8.4...11.1 *2F, SA, MT/4 H; 1 S

6 Ochoo'(Hura crepitans L.)

EX1_0

0.55 3.9 5.7 4.05 6.04 "Durabilitateredus6,susceptibil laalb6streara /Destul depermeabil/Low durability,

susceptible toblue stain/Rather permeable

7 Cambara'(Erisma uncinatumW.)

EX2_C

0.57 4.2 9.1 4.38 10.01 5Durabilitateredus6 /Permeabil5Low durabilityPermeable

8 Yesquero'(Carinianaestrellensis)

EX3_Y 0.68 4.4 7.2 4.60 7.755Permeable

Note: Literature data from EN 350/2 (natural durability and impregnability)* and the following references:I http:// www. accoya .com /pdf/Web_PDF_brochure.pdf2 Wagenfuhr, Holzatlas, 2000, http://www.fachbuch-leipzig.hanser.de3 www.cadefor.org/en/especies/ficha.php



Materialul lemnos conditionat la 20-23°C §i 50-55% umiditate relativa a fost prelucrat cu atentie inpiese de mici dimensiuni cu fete plane §i dimensiunide (20 x 20 x 30) mm pe cele trei directiifundamentale (radial -Ra, tangential -Tg §ilongitudinal - L), avand inelele anuale din sectiuneatransversals paralele cu fetele tngentiale. Fiecareepruveta a fost codificata (specia §i numarul) §imarcata in 5 puncte de masurare pe o fatatangentiala §i una radials, dupa cum se observa inFig. 1. Aceste puncte au fost utilizate pentru adetermina dimensiunile epruvetelor pe directiile Ra §iTg ca medie a 5 masurari, cu precizie de 0.01 mm.

The wooden material conditioned at 20-23°C and50-55 % RH was carefully processed into small testsamples with smoothly planned faces withdimensions of (20 x 20 x 30) mm on the threefundamental directions (radial -Ra, tangential -Tg andlongitudinal - L), having the annual rings in the cross-section parallel to the two tangential faces. The testsamples were then coded (species code and number)and 5 measuring points were marked, as shown inFig. 1, on one tangential and one radial face of eachtest sample. These points were used for determiningthe dimensions of the samples on the Ra and Tgdirections as the average of 5 measurements withprecision of 0.01 mm.

b.Fig. 1.

Aspecte metodologice / Methodological aspects:a - forma i dimensiunile epruvetelor de Incercare / form and dimensions of test samples; b -

dispozitiv de masurare / measuring device; c - aspectul unor probe dupa testul de higroscopicitate /aspect of some test samples after the hygroscopicity test.

c.

Pentru experimentari s-au pregatit cafe 20 deepruvete din fiecare specie care au fost impartite in 2grupe. Epruvetele numerotate de la 1-10 au fostfolosite pentru determinarea coeficientilor totali deumflare pe directie radials §i tangentiala (aRa, am in%) §i absobtiei de apa (WA72, %) printr-un un test deimersie totals in apa de 72h la 20°C. Epruvetelenumerotate de la 11-20 au fost folosite intr-un test dehigroscopicitate in doua etape. Pentru acest scopprobele aduse la stare anhidra prin uscare in etuva la103 ± 2°C au fost cantarite §i masurate §i apoi puseintr-o camera climatica la 20 ± 2°C §i 30 ± 2%umiditate relativa, unde au fost pastrate pang auajuns la umiditatea de echilibru (EMC 30, %).Cantaririle periodice ale probelor (la 24 h pentruprimele 3 zile §i apoi la intervale de 7 zile) au aratatca starea de echilibru a fost atinsa dupa 28 zile. Dupaaceasta perioada conditiile din camera climatica aufost schimbate la 20 ± 2°C §i 90 ± 2% umiditaterelativa, testul continuand in mod similar in noileconditii de umiditate relativa (RH 90%) pans s-a atinsnoua stare de echilibru (EMC 90, %) dupa alte 28zile. In acest moment testul s-a considerat terminatiar probele au fost masurate din nou pentru a calculacoeficientii partiali de umflare a0-90,Fia, a0-90,Tg in %.Date le rezultate din cantaririle periodice au fostfolosite pentru a trasa diagramele comparative aleabsorbtiei de apa in testul de higroscopicitate pentru

A number of 20 test samples were prepared foreach of the wood species and were divided into 2groups. The samples numbered 1-10 were used fordetermining the total swelling coefficients on theradial and tangential directions. (aRa, am in %) and thewater absorption (WA72, %) after a total waterimmersion test of 72h at 20°C. The samplesnumbered 11-20 were used in a two stepshygroscopicity test. For this purpose the test samplesbrought in anhydrous state by drying in an aircirculating oven at 103 ± 2°C were weighed andmeasured and then placed in a climatic chamber at20 ± 2°C and 30 ± 2% RH, where were kept until thecorresponding equilibrium moisture content (EMC 30,%) was reached. The periodical weighting of thesamples (every 24 h for the first 3 days and then at 7days intervals) showed that equilibrium was reachedin 28 days. After this period the conditions in theclimatic chamber were changed to 20 ± 2°C and 90 ±2% RH, the test being continued similarly under thesenew conditions until a new equilibrium state under thenew relative humidity conditions (EMC 90, %) wasreached (after another 28 days). At this point the testwas considered finished and the test pieces weremeasured again in order to calculate the partialswelling coefficients a0-90,Fia, a0-90,Tg in %. The datafrom the periodical weighting of samples served todraw comparative diagrams of water adsorption

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speciile considerate.

REZULTATE I DISCUTIIRezultatele din testul de imersie totala in apa

sunt ilustrate grafic in Fig.2. Este evident ca lemnulacetilat Accoya este mult mai stabil diemnsionaldecat celelalte specii testate avand coeficeintii totalide umflare cei mai mici de 0.83 % pe directie radialasi 1.45% directie tangentiala, ceea ce corespundeunui coeficeint de anizotropie (raport intre umflareatangentiala cea radial5) de 1.75. Aceste valori suntin concordanta cu cele prezentate de producator:contragere tangentiala totala 1.5% si contragereradiala totala 0.8% (http://www.accoya.com/pdf/Web_PDF_brochure.pdf).

Coeficientii de umflare totala ai speciilorindigene au variat intre -4 -5% pe directie radiala-8 - 10% pe directie tangentiala, in timp ce coeficientiide anizotropie, e, calculati ca raport intre umflareatangentiala cea radiala au avut valoari in jur de 2,ceea ce este uzual, exceptand lemnul de pin pentrucare aceasta valoare a fost mai scazuta (1.66).

Rezultatele pentru cele trei specii exoticetestate nu au fost foarte diferite: coeficientii deumflare totala au variat intre 3.90 - 5.30% pe directieradiala - 6 - 10.2 % pe directie tangentiala. Totusi,la speciile Ochoo (Hura crepitans L.) §i Yesquero(Cariniana estrellensis) anizotropia umflarii a fost mairedusa, valorile coeficientilor de umflare radialatangentiala fiind mult mai apropiate (4.6 si 6.0 pentruOchoo si 3,28 si 4,98 pentruYesquero),correspunzand unor valori e de 1.29 si respectiv 1.57.Coeficientul de anizotropie pentru Cambara (Erismauncinatum W.) a fost mai apropiat de valoarea uzualade 2 (e = 1,93). Trebuie subliniat in acest context ca,pe lang5 coeficienti de umflare totala cat mai redusi,un coeficient de anizotropie redus este considerat caun indicator calitativ favorabil pentru materialullemnos pentru ferestre.

Absorbtia de apa dup5 testul de imersie totalain apa 72 h la 20°C a fost diferita pentru speciilestudiate, dup5 cum se observa in Fig. 2 (jos). Stejarul(Quercus robur) §i Cambara (Erisma uncinatum W.)au avut cele mai mici valori ale absorbtiei de apa(-35-37 %). Accoya, bradul, pinul, laricele Ochooau avut absorbtii de apa medii (-61-77 %), in timp ceYequerro a absorbit circa 143 % apa fata de stareainitiala absolut uscata. Aceste diferente in caracterulhidrofil permeabilitate intre speciile investigate suntde asteptat ca consecinte ale caracteristicilorspecifice anatomice chimice ce le diferentiaza.

dynamic in the hygroscopicity test for the consideredwood species.

RESULTS AND DISCUSSIONThe results of the total water immersion test are

illustrated by the graphs in Fig.2. It is obvious thatAccoya wood is much more dimensionally stable thanthe other wood species tested having the lowest totalswelling coefficients of 0.83 % on the radial directionand 1.45% on the tangential direction, correspondingto a coefficient of anisotropy (ratio between tangentialand radial swelling) of 1.75.These values are in verygood accordance with the data presented by theproducer: tangential total shrinkage 1.5% and radialtotal shrinkage 0.8% (http://www.accoya.com/pdf/Web_PDF_brochure.pdf).

The total swelling coefficients of the indigenespecies tested varied in the range of -4 -5% on theradial direction and -8 - 10% on the tangentialdirection, while the coefficients of anisotropy, e,

calculated as the ratio between tangential and radialswelling were around the value of 2, which is usual,excepting the pine wood for which this was lower(1.66).

The results for the three tested exotic specieswere not very different: the total swelling coefficientsvaried between 3.90 - 5.30% for the radial directionand -6 - 10.2 % for the tangential direction. However,Ochoo (Hura crepitans L.) and Yesquero (Carinianaestrellensis) demonstrated a reduced anisotropy ofswelling, the radial and tangential swelling coefficientsbeing much closer (4.6 and 6.0 for Ochoo and 3,28and 4,98 for Yesquero), corresponding to e values of1.29 and 1.57 respectively. The anisotropy coefficientfor Cambara (Erisma uncinatum W.) was close to theusual value of 2 (e = 1,93). It has to be highlighted inthis context that, alongside reduced total swellingcoefficients, a reduced coefficient of anisotropy isseen as a quality for the wooden material forwindows.

The water absorption after the total waterimmersion test of 72 h at 20°C was different for thestudied wood species as shown in Fig. 2 (bottom).Oak (Quercus robur) and Cambara (Erismauncinatum W.) presented the lowest water absorptionvalues (-35-37 %). Accoya, fir, pine, larch and Ochoogave medium water absorptions (-61-77 %), whilstYequerro absorbed around 143 % water reported tothe initial oven dry state. These differences in termsof hydrophilic character and permeability between theinvestigated wooden species are an expectableconsequence of their specific anatomical andchemical features.

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T


PRO LIGNO Vol.7 N°4 2011www.proligno.ro A pp. 71-82

Test de imersie totala in apa / Total water immersion test12,0

Exotic species Indigene species

10,0

Ra Tg8,0

6,0

4,0

2,0

0,0

ex1_0 ex2_C ex3_Y Fir Pine Larch Oak

Specii lemnoase / Wood species

Test de imersie totala in apa / Total water immersion test180,0

160,0

---- c* 140,0co -2o_ c003 120,0

13a) ,

12- 100,0MI 0

ii i 80,0o 60,0

.c2 ze.41 co 40,0

20,0

0,0

Exotic species

72 h / 20°C

ex1_0 ex2_C ex3_Y

Acc0ya

Indigene species

I hFir Pine Larch Oak


Fig. 2.Comportamentul comparativ al speciilor lemnoase testate in test de imersie totala in apa: coeficienti

totali de urnflare (sus) .Fi absorb(ie de apa (jos) / The comparative behaviour of the tested woodspecies in a total water immersion test: total swelling coefficients (top) and water absorption (bottom)

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30,0

25,0

5,0

0,0

Test de hi rosco icitate / Hvaroscopicity testRH 30 % / RH 90 °A)

!t2Aex1_0-A-

-A- ex2_Cex3_Y-A-

-S-Accoya

I I I I I

0 10 20 30 40 50

Durata testului / Test duration [zile /days]

60 70

30,0

25,0

Test de higroscopicitate / Hygroscopicity testRH 30 % / RH 90 °A,

0

- A-Accoya- E-Fir_B- 0-Pine P- 6- Larch_L

- 6-0ak_S

10 20 30 40 50 60 70

Durata testului / Test duration [zile / days]

Fig. 3.Dinamica absorbtiei de apa in cele doua etape ale testului de higroscopicitate: Accoya comparativ cu

speciile exotice (sus) ,Fi cele indigene (jos) / The dynamic of water adsorption in the two stephygroscopicity test: Accoya wood compared to exotic species (upper) and common indigene wood

species (bottom)

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Diferentele de higroscopicitate §i dinamicaabsorbtiei de vapori de apa intre speciile studiate aufost foarte bine reflectate in testul de higroscopicitatein doua etape, dupa cum se observa in diagrameledin Fig.3. Forma generala a curbelor ilustreazacaracterul higroscopic al materialului lemnos §i celedoua etape ale testului. Atunci cand materialullemnos anhidru a fost introdus in camera climatica laumiditate relativa de 30% a aparut o absorbtie rapidade vapori de apa in prima zi §i apoi mult mai redusa'Dana and s-a atins o stare de echilibrucorespunzatoare unei umiditati atmosferice relativede 30% (EMC 30, %). Cand conditiile din cameraclimatica s-au schimbat prin cre§terea umiditatiirelative la 90%, probele au absorbit din nou foarterapid apa din atmosfera §i au evoluat apoi mai lent inacest sens 'Dana la o noua stare de echilibru,corespunzatoare unei umiditati atmosferice relativede 90% (EMC 90, %).

Din curbele pentru diferite specii lemnoase sepoate observa clar ca Accoya se situeazaintotdeauna in pozitia cea mai de jos, ceea cedemonstreaza higroscopicitatea sa redusa ca urmarea modificarii chimice. Aceasta curba indica, deasemenea, o umiditate de echilibru redusa pentruacest tip de lemn ameliorat, respectiv EMC 30 = 1.42% §i EMC 90 = 6.08%, comparativ cu valorile EMC 30variind intre 4.44-5.44% §i EMC 90 variind intre18.62-22.81%, inregistrate pentru celelalte speciiexotice §i indigene incluse in acest test.

In graficele din Fig. 4 (jos) sunt detaliate maimulte informatii privind diferentele de higroscopicitateale speciilor lemnoase testate, reflectate in valorileumiditatilor de echilibru corespunzatoare celor douaconditii de umiditate atmosferica realiyate in test(umiditate relativa de 30% §i de 90 % la 20 °C). In Fig4 (sus) sunt prezentate valorile coeficientilor partialide umflare ao_go pe directie radiala §i tangentiala,determinati la sfar§itul testului de higroscopicitate. Dinnou este evidenta cea mai bung stabilitatedimensionala a lemnlui acetilat Accoya (ao-9o,Ra= 0.42± 0.10, a0-90,T9= 0.78 ± 0.23, e = 1.86) in comparatiecu celelalte specii testate.

The differences in terms of hygroscopicity anddynamics of water vapours adsorption between thespecies were very well reflected in the two-stephygroscopicity test, as shown by the diagramspresented in Fig.3. The general shape of the curvesillustrates the hygroscopic character of the woodenmaterial and the two phases of the test. When theanhydrous material was introduced into the climaticchamber at RH 30% a rapid water adsorptionoccurred in the first days and then much slower until afirst equilibrium stage corresponding to theequilibrium moisture content at RH 30% (EMC 30)was reached. When the conditions in the climaticchamber were changed by increasing the RH to 90%,the samples adsorbed again very rapidly water fromthe atmosphere and evolved then slower in thisrespect until a new equilibrium state, corresponding toEMC 90 was reached.

Looking at the curves for the different woodspecies, it can be very clearly observed theindividualised lower position of the curve for Accoyawood, which proves its significantly reducedhygroscopicity as a consequence of chemicalmodification. This curve also indicates the reducedequilibrium moisture content for this type of improvedwood, respectively EMC 30 = 1.42 % and EMC 90 =6.08%, compared to values varying between 4.44-5.44% for EMC 30 and 18.62-22.81% for EMC 90registered for the other exotic and indigene woodspecies included in this experiment.

More detailed information on the differencesbetween the hygroscopicity of the tested woodspecies reflected in the values of the equilibriummoisture content reached in the two atmosphericconditions (RH 30% and RH 90 % at 20 °C) arepresented in the column graph in Fig. 4 (bottom). Thevalues of the partial swelling coefficients ao_90 on theradial and tangential direction, determined at the endof the hygroscopicity test are also presented Fig 4(top). The best dimensional stability of Accoya wood(ao_90,Ra= 0.42 ± 0.10, ao-9o,Tg= 0.78 ± 0.23, e = 1.86)compared to the other tested wood species is againobvious.

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14,0

2,0

0,0

Test de higroscopicitate / Hygroscopicity test

Exotic speciesAC

C

O

ya

1 Ra Tg

Indigene species

ex1_0 ex2_C ex3_Y Fir Pine Larch Oak


Za)

242 81E .1) ,--,

vCD z (515,0w E 2.0i E 111"a2 1 0, 0

E 42D .3

Lu0- 5,0

30,0

25,0

20,0

0,0

Test higroscopicitate / Hygroscopicity testRH 30 % /RH 90%

Exotic species AC

C

O

ya

EMC 30 EMC 90

Indigene species

ex1_0 ex2_C ex3_Y 1111 Fir Pine Larch Oak


Fig. 4.Accoya vs. Specii exotice .Fi indigene in testul de higroscopicitate in daub' etape (umiditate relativa

30% / 90%): coeficienri parriali de urnflare a0.90 (top) .Fi umiditate de echilibru 30, 90 (jos) / Accoya vs.exotic and indigene wood species in a two step hygroscopicity test (RH 30% /RH 90%): partial

swelling coefficients a0.90 (top) and equilibrium moisture content EMC 30, EMC 90 (bottom)

REZUMATLemnul este o resursa valoroasa §i sustenabila

ce trebuie sa i§i mentina §i consolideze pozitia pepiata pentru aplicatii traditionale §i moderne. Totu§i,

CONCLSIONSWood is a valuable and sustainable resource that

should keep and consolidate its place on the marketin various traditional and novel applications. Adequate

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pentru o bung performanta in timp a prodselor dinlemn se imopun tratamente initiale adecvate §i masuride intretinere.

Productia de ferestre este un domeniu unde laora actuala lemnul §i plasticul sunt in competitie. Inaceasta privinta, o stabilitatea dimensionala mai bunga materialelor lemnoase la variatia umiditatiiatmosferice sau contactul direct cu apa §i reducereaabsorbtiei de apa in stare de vapori sau lichida suntproprietati cu efect pozitiv pentru a asigura o maibung performanta in timp a ferestrelor §i a straturilorde finisare.

In acest studiu au fost comparate patru speciicomune indigene §i trei specii exotice, nou introdusepe piata europeana, cu lemnul acetilat Accoya, inceea ce prive§te umflarea §i absorbtia de apa in testede imersie totala in apa §i higroscopicitate.

Rezultatele au demonstrat o mai bungpreformanta a lemnului Accoya comparativ cu speciileindigene §i exotice considerate ca rezultat almodificarii chimice a polimerilor din membranacelulara. Prin urmare, acetilarea lemnului trebuieconsiderate o tehnologie alternative de tratare pentruo performanta ridicata a produselor din lemn.

AccoyaTM este rezultatul a peste 70 ani decercetari §i dezvoltare a acetilarii lemnului, pornind dela ideea §i experimentele initiale, 'Dana la o tehnologiecare a a reu§it sa parcurga cu succes toate etapelede la cercetare, de la laborator 'Dana la lansareacomerciala a unui nou material lemnos cuperformante deosebite §i sustenabil, care deschidenot oportunitati pentru producerea de ferestre dinlemn cu durabilitate §i performanta superioara fata dealte materiale.

initial treatments and maintenance are, however,necessary for a good in time performance.

The production of windows is a field where woodand plastics are in competition nowadays. With thisrespect a better dimensional stability of the woodenmaterial in response to the variation of atmospherichumidity or the direct water contact and a reducedwater adsorption/absorption are properties favourablefor a better in-time performance of wooden windowsand protective coatings. Four commonly usedindigene wooden species and three exotic species,newly introduced in the European market, werecompared in this study with acetylated Accoya woodin terms of swelling and water uptake in totalimmersion and hygroscopicity tests.

The results proved the better performance ofAccoya wood compared to the considered indigeneand exotic species as a result of the chemicalmodification of the cell wall polymers. Woodacetylation should be considered, therefore, as analternative treating technology for high performancewooden products.

AccoyaTM is the result of more than 70 years ofresearch and development on wood acetylation, fromthe first idea and initial experiments to a technologythat succeeded from laboratory research to thecommercial launch of a novel high performance,sustainable wooden material, which createsopportunities for joinery products that will very likelyoutlast and outperform others.

BIBLIOGRAFIE / REFERENCESHILL, C.A.S., JONES, D., MILITZ, H., ORMONDROYD, G.A. (Eds). (2007). Proceedings of The ThirdEuropean Conference on Wood Modification, Cardiff, ISBN 184-220-096-8.KOLLMANN, F.P., COTE W.A. (1968). Principles of wood science and technology, vol.1, Solid wood, SpringerVerlag, New York, 97-133.MILITZ, H., HILL, C. (Eds) (2005). Wood modification: Processes, Properties and Commercialisation., Proc.2nd European Conference on Wood Modification, Goettingen.MILITZ, H., LANDE, S. (2009). Challenges in wood modification technology on the way to practicalapplications, Wood Material Science & Engineering, Vol. 1, pp. 23-29, ISSN 1748-0280 (electronic) 1748-0272(paper).ROWELL, R.M. (1991). Chemical modification of wood. In: Hon and Shiraishi Ed. Wood and CellulosicChemistry, Marcel Dekker Inc., pp. 703-755.ROWELL, R.M. (2006). Acetylation of wood - Journey from analytical technique to commercial reality, ForestProducts Journal, vol 56, no.9, pp. 4-12.ROWELL, R.M. Ed. (1984). The Chemistry of Solid Wood, Advances in Chemistry Series, 207, WashingtonD.C., pp. 175-207.ROWELL, R.M., IBACH, R., MCSWEENY, J., NILSSON, T. (2009). Understanding Decay Resistance,Dimensional Stability and Strength Changes in Heat Treated and Acetylated Wood. In: Proceedings of ECWMStockholm, pp. 489-502, ISBN 978-91-86319-36-6.TIMAR, M.C., BELDEAN, E., ZELENIUC, 0., LICA, D. (2008). Outcomes of a modified L-joint test in Romania- opportunities for a complex evaluation of the performance of wood in outdoor above ground conditions - In:Proceedings of COST Action E37 Final Conference, Bordeaux 2008, pp. 107-117. ISBN 9789080656505.TIMAR, M.C. (2003). Ameliorarea lemnului, Ed. Univ. Transilvania, Brasov, ISBN 973-635-141-6.VAN ACKER, J., PEEK, R.D. (Eds.) (2008). Socio-economic perspectives of treated wood for the commonEuropean market, Proceedings of COST E37 Final Conference, Bordeaux.

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WAGENFUHR, R. (2000). Holzatlas, 5 Auflage, Fachbuchverlag Leipzig im Carl21390-2.http://www.apar.it/English/pdfs/Manual_Wood_engl.pdfhttp://www.accoya.com/index.asphttp://www.titanwood.com/index.aspwww.coedderwen.co.ukwww.bswaccoya.co.ukhttp://www.ironwoods.com/ironwoods_woods_vs_plastics.htmlhttp://www.swedishtimberproducts.co.uk/index.phpwww.cadefor.org/en/especies/ficha.phpwww.tropix.cirad.fr/africa/acajou.pdf

Hanser Verlag. ISBN 3-446-

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