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letnik 64tevilka 1-2/2012

UDK 630ISSN 0024-1067

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Sistem ocenjevanja zelenih stavb (LEED): Prouevanje vpliva koliine katalizatorja na utrjevanje UF in MUF


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napovednikLes s koliarskih naselbin na Ljubljanskem barju in njegov razis-kovalni potencialKatarina ufar, Anton Veluek

Analiza ivljenjskega cikla (LCA) objektivno merilo okoljskih zahte

zelenih javnih naroil (ZeJN)Andreja Kutnar, Janez Kr, Nike Kranjc, Mitja Pikur, rtomir Tavzes, Miha Humar

kazalo1 Green building rating system - leadership in energy and

environmental design (LEED): signicance for wood industry

Arijit Sinha, Andreja Kutnar6 Prouevanje vpliva koliine katalizatorja na utrjevanje urea-

formaldehidnega in melamin-urea-formaldehidnega lepila zdiferenno dinamino kalorimetrijoAle Ugovek, Milan ernekNapovednik

uvodnik

raziskave in razvoj

kratke vesti napovednik

Ustanovitelj in izdajateljZveza lesarjev Slovenije.

Urednitvo in uprava

1000 Ljubljana, Karlovka cesta 3, Slovenijatel. 01/421-46-60, faks: 01/421-46-64e-pota: [email protected]

Urednitvo in sodelavci urednitvaGlavni in odgovorni urednik: prof. dr. Miha HumarTehnini urednik: Stane Koar, univ. dipl. in.Lektoriranje: Darja Vranjek, prof. slov. in soc.

Oblikovalska zasnova revijeBotjan Lenjak

TiskLittera Picta d.o.o.

Uredniki svetPredsednik: mag. Darinka Kozinc, univ. dipl. in.

lani: Peter Tomi, univ. dipl. oec., Mitja Strohsack, univ. dipl. iur.,mag. Miroslav trajhar, univ. dipl. in., Bruno Komac, univ. dipl.in., mag. Andrej Mate, dipl. oec., Stanislav kali, univ. dipl. in.,Janez Pucelj, univ. dipl. in., Igor Milavec, univ. dipl. in., Flor ijanCifrek, Edi Iskra, prof. dr. Marko Petri, doc. dr. Milan ernek,Zdenka Steblovnik upan, univ. dipl. in., mag. Majda Kanop, univ.dipl. in., prof. dr. Franc Pohleven, Bojan Pogorevc, univ. dipl. in.

Uredniki odborprof. em. dr. dr. h. c. mult. Walter Liese (Hamburg), prof. dr.Helmuth Resch (Dunaj), dr. Milan Nei (Beograd), prof. dr.Radovan Despot (Zagreb) prof. dr. Vito Hazler, prof. dr. MihaHumar, mag. Jasna Kralj Pavlovec, doc. dr. Manja Kitek Kuzman,Alojz Kobe, univ. dipl. in. les., mag. Darinka Kozinc, dr. NikeKrajnc, strok. svet. Borut Kriej, doc. dr. Joe Kropivek, IgorMilavec, univ. dipl. in. les., prof. dr. Primo Oven, prof. dr. Marko

Petri, mag. Mitja Pikur, prof. dr. Franc Pohleven, mag. MarijaSlovnik, prof. dr. Milan ernek, prof. dr. dr. h. c. Niko Torelli, dr.Sreko Vratua, prof. dr. Roko arni

Letna naroninaPosamezna tevilka 4,50 EURDijaki in tudenti 16 EUR.Posamezniki 35 EUR.Podjetja in ustanove 160 EUR.Obrtniki in ole 80 EUR.Tujina 160 EUR + potnina.Naronina velja do preklica. Pisne odjave upotevamo ob koncuobraunskega obdobja.

Transakcijski raunZveza lesarjev Slovenije-LES, Ljubljana, Karlovka cesta 3,IBAN (TR): SI56 0310-0100-0031-882 pri SKB d.d., Ljubljana

SWIFT: SKBASI2X

Revija izhaja v dveh dvojnih in osmih enojnih tevilkah letno.Za izdajanje prispeva Javna agencija za knjigo RepublikeSlovenije.Na podlagi Zakona o davku na dodano vrednost spada revija Lespo 43. lenu pravilnika med nosilce besede, za katere se plaujeDDV po stopnji 8,5 %.Vsi znanstveni lanki so dvojno recenzirani.Izvleki iz revije LES so objavljeni v AGRIS, Cab International -CD-Tree ter v drugih informacijskih sistemih.


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1. IntodctIon

The construction, characteristics, operation, and demo-lition of buildings are increasingly recognized as a majorsource of environmental impact. Globally, infrastructureand building construction consumes 60 % of the raw ma-terials extracted from the Earth (Bribian et al. 2011). Buil-

Abstract: Due to global warming issues and climate change, sustainability became an important factor in building design.

Since buildings consist of a multitude of products, they have an important and wide-ranging impact on the environment.

Therefore, several environmental assessment methods and accreditation systems for buildings have been developed. In this

paper building rating system Leadership in Energy and Environmental Design (LEED), as the global market leader in the

green building rating systems, is presented. LEED is a commendable and grand eort in moving towards sustainable deve-

lopment by encouraging development of new green built environment and converting existing built environment green.

However, it does have certain pitfalls and challenges, which are discussed with respect to material selection, especially wood

and wood products.

Key words: building design, LEED, wood

Izvleek: Zaradi segrevanja ozraja in podnebnih sprememb je postal trajnostni razvoj pomemben dejavnik pri nartovanju

stavb. Stavbe imajo zaradi tevilnih vgrajenih materialov najrazlineje pomembne vplive na okolje. Zato so bile v preteklosti

e razvite metode in akreditirani sistemi za ocenjevanje okoljskih vplivov stavb. V lanku je predstavljen trenutno vodilni

ocenjevalni sistem na trgu sistemov ocenjevanja zelenih stavb, Leadership in Energy and Environmental Design (LEED). LEED

ima s spodbujanjem razvoja novega zelenega okolja in s preoblikovanjem obstojeega okolja stavb v zeleno pomembno

vlogo in tevilne zasluge pri trajnostnem razvoju stavb. Vsebuje pa tudi nekaj nesmiselnosti in izzivov, ki jih v lanku obravna-

vamo glede na izbor materialov, predvsem lesa in lesnih izdelkov.

Kljune besede: dizajn stavb, LEED, les

Arijit SINHA*, Andreja KUTNAR** UDK 728:502.12

GREEN UILDING RATING SSTEM

- LEADERSHIP IN ENERG ANDENVIRNMENTAL DESIGN (LEED):SIGNIFICANCE FR DINDUSTRSistem ocenjevanja zelenih stavb - Leadership in Energy and

Environmental Design (LEED): Pomen za lesno industrijo

* Assistan t Professo r, Depar tment of Wood Science and Engineering, Oregon StateUniversity, 234 Richardson Hall, Corvallis, Oregon, USA;e-mail: [email protected]

** dr., University of Primorska, Andrej Marui Institute, 6000 Koper, Slovenia,ILTRA d.o.o., Celovka cesta 268, 1000 Ljubljana, Slovenia;e-mail: [email protected], [email protected] *corresponding author


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ding represents 40 % of these materials, in other words24 % of these global extractions. In the US, with 4 % ofworlds population the consumption of resources is at astaggering 25 % of total resources available in the world(Teller and Bergman 2010). A majority of these resources(60 % according to USGBC) are consumed in the buildingindustry. In Europe, the per capita mineral extractions

for buildings are approximately 4.8 tons per year (Wadel2009), which is 64 times the average weight of a person.In addition to that, energy consumption during and in useof building is enormous. In the US, the built environmentaccount for 65 % of all energy consumption (USGBC 2010).In the European Union (EU) the corresponding number is42 % (Nelson et al. 2002). Moreover, carbon dioxide (CO2)emissions from the built environment accounts for rou-ghly 35-40 % of total emissions, both in the US as wellas in the EU (Environmental Information Administration2008, Nelson et al. 2002). The increased use of resources,resulting pollution and emissions highlight the need for

a transformation that will enable us to save and conserveenergy for sustainable development.

One strategy for achieving that transformation is most wi-dely known by the term green building. Green buildingcan be characterized as integrated building practices thataim to signicantly reduce the environmental footprint ofa building in comparison to standard practices. Descrip-tions of green building generally focus on a number ofcommon elements, especially siting, energy, water, mate-rials, waste, and health. One of the most salient featuresof green building is integration. Although individual ele-ments can be addressed separately, the green building

approach is more comprehensive, focusing on the envi-ronmental footprint of a building over its life cycle, frominitial design and construction to operations during thebuildings useful life, through end-of-life strategies. Thedesire to integrate the various elements of green buildinghas led to the development of rating and certication sy-stems to assess how well a building project meets a spe-cied set of green criteria. There are many green buildingrating systems such as Buildings Research EstablishmentEnvironmental Assessment Methodology (BREEAM) fromthe UK, HQE (France), Green Star (Australia), DGNB (Ger-many), etc. In the United States the most popular systemis the Leadership in Energy and Environmental Design(LEED).

In the commercial arena in the United States, LEED is themarket leader. It can be argued that the LEED system isalso a global leader in green building. The LEED Internati-onal Roundtable is composed of representatives from 21countries who work to provide global consistency in regi-onal approaches to green building. Each of these 21 co-untries utilizes LEED rating systems that are catered to the

local conditions in their country. Additionally, LEED hregistered projects in 133 countries. In the housing setor LEED is making signicant inroads through relativenewer standard called LEED for homes. Despite BREEAMdominance in the European green building performanmarket, LEED is gaining some traction. Various projeall over Europe are adopting LEED measures. Several b

ildings have been already LEED certied in Italy, EnglanPoland, the Czech Republic, Bulgaria, and Portugal.

2. LadshIp In ny and nIonmntaL dsIn, Ld

The LEED rating system in the United States is adminisred by United States Green Building Council (USGBC). TUSGBC has the responsibility of developing and mofying the LEED standard, while the LEED certication projects is administered through Green Building Certiction Institute (GBCI). As the green building principles wegaining acceptance in the society, LEED provided a de

tion to the green building and formulated a standardmeasurement. LEED aims to facilitate positive results the environment, occupant health and nancial returthrough an integrated design process.

LEED is a voluntary rating system to ensure a superenvironmental performance of a building over its time. Since its inception in 2000, LEED has evolved aimproved through several revisions. LEED 2009 is the crent version, while discussions are currently underwfor LEED 2012. LEED 2009 contains the following specirating systems: 1) New Construction (NC); 2) Existing Budings: Operations and Maintenance; 3) Commercial Int

riors; 4) Core and Shell; 5) Retail; 6) Healthcare; 7) Homeand 8) Neighborhood Development. Each of the ratisystems is composed of 100 points, which are dividamong these ve categories: Sustainable Sites (26); WaEciency (10); Energy and Atmosphere (35); Materials aResources (14); and Indoor Environmental Quality (1Additionally, up to 10 bonus points are possible throuinnovative design and consideration of regional prioritiEach category in LEED 2009, has certain prerequisites thare mandatory for all projects and are not eligible for pints. The points are then distributed across major categries and are assigned in a progressive way for incremen

Figure 1. Level f Ld erii (sBc)slik 1. vi eriirj Ld (sBc)


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function in harmony to achieve that goal, and that is whyLEED has certain prerequisites in each category that needsto be fullled to be considered for LEED certication.

2.1. LEED cEfc

LEED certication is essentially a three step process. Therst stage involves project registration. The project teamhas to prepare all the supporting documents such as LEEDletter templates, etc., and also has to list the project onlinewith GBCI. The second step can be termed as technicalsupport. During this stage the building is being built andany clarications regarding credits and prerequisites canbe sought from the GBCI. The nal step in the process isto complete all the documentation describing prerequisi-tes and credits sought in each category. The documentsare then reviewed by GBCI and upon successful reviewLEED certication is granted to the project. The costs as-sociated with it are quite signicant. Studies says the costranges between 2-5 % of the project cost, that includes

USGBC costs, fess for LEED management, commissioningagent, and energy modeling, and additional constructi-on and innovation costs. However, the certication doesbring a lot of benets to the project. Primary benet isthe recognition for project stakeholders for their buildingquality and environmental stewardship. The certicationis a credible external validation of the sustainability goalsof the project. The project gains prominence and is alsoused by USGBC for marketing purposes and case studies.In certain areas, the project might qualify for a wide arrayof state and local government incentives.

2.2. chLLEgEs LEED cEfcThe USGBC, although a grand and comprehensive eorttowards sustainable design, has certain pitfalls in terms ofhow it rates the materials. While Materials and Resourcesmay not be the most important part of the green buildingschemes as they are currently written, they are signicantnonetheless. There are provisions in LEED and other pri-mary green building programs, which could result in si-gnicant negative impacts on wood and wood productsas a building material (Bowyer 2008). The LEED rating sy-stem rates the material at the same level while being usedin the building. All materials are considered at an equal

footing and their life history does not have an impact onthe rating credits. Materials like, concrete and wood areconsidered equal. However, life cycle analysis have sho-wn that wood has less embodied energy than concreteor steel because it is a biological renewable material (Pu-ettmann et al. 2010), while the raw materials to make ce-ment and then concrete is a product of energy intensivemining (PCA 2002, van Oss and Padovani 2002, Rajendranand Gambatese 2007). Steel is preferred over wood and

level of documented eorts to increase environmentalperformance. The LEED system rates buildings at four le-vels - certied, silver, gold, and platinum (Figure 1), withfollowing credit requirements:

` Certied - 40 - 49 points,

` Silver - 50 - 59 points,

` Gold - 60 - 79 points,` Platinum - 80 points and above.

Figure 2 shows the ve categories that comprises any LEEDrating systems. Each category was designed to meet certa-in sustainability goals pertaining to various aspects of en-vironment, social, and economic wellbeing of the societyas shown in Figure 2. Sustainable sites have project speci-c goals, and the siting of the project plays an importantrole in dening the scope of the project and also shapingthe sustainability goals. Redevelopment of an abandonedbuilding space, for e.g., earns extra credit in LEED becau-se by rehabilitating we are using a built space that already

exists and hence, not creating additional environmentalfootprint. Water eciency category have various provisionthat allows the builders and architect to keep in mind thelocal water issues and then design accordingly. Reuse ofgray water for various applications not requiring potablewater use is valued highly in LEED. Energy category enco-urages looking for alternate renewable sources of energyand not being dependent on fossil generated energy. Thematerial category encourages using materials that can berecycled easily and have less carbon footprint. The Indo-or environment category is designed to create a betterliving space for the inhabitants. The idea overall is provi-

ding a structure for the wellbeing of inhabitants in an en-vironmentally conscious way. All these categories have to

Figure 2. te ielg bei e ruure f Ldrig e.slika 2. Merila vrednotenja v trukturi oenjevalnea

itema LEED.


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concrete, because of its recyclability and recycled content(USGBC 2010). Steel while recyclable, has higher enviro-nmental impacts than wood because the raw materialhas to be mined and then steel has to be extracted in afurnace (IISI 2000). Many exper ts, including Bowyer (2008)consider this viewpoint of steel given more importance,as a serious error from an environmental standpoint.

LEED assigns extra credit for materials that are rapidly re-newable (LEED-NC 2009). The criterion of rapid renewa-bility with respect to wood is a 10-year turn around peri-od. For tress with a rotation time of 10 years or less, thosecredits can be attained. However, for longer rotation cropsvaluable credits cannot be obtained. Wood is a renewa-ble material, with some trees have lesser of rotation cycle,while some trees have higher rotation period. Anotherforest product, Bamboo, for e.g., is a rapidly growing treeas compared to Maple and hence, bamboo ooring ispreferred over Maple ooring in LEED. The scientic back-ground of this preference has been heavily challenged

(Bowyer 2007) and there is ongoing debate, to whetherchange the category of rapidly renewable to renewa-ble (YPFPG 2008). The current version of the LEED stan-dard is undergoing signicant revisions. While it is not yetclear what the nal version of the standard will look like,some of the proposed changes have positive implicationsfor wood products. Among the proposed changes is theallocation of points for materials that meet the criteria ofthe USDA Biopreferred program (Knowles and Sinha 2011).As currently written, this will replace the current credit re-ceived for rapidly renewable materials and will give woodthe credit it deserves as a renewable material.

A challenge that a rating system faces is to ensure thatthe wood coming into the project has been grown andharvested in a sustainable manner. Forest Certicationensures this. Forest Certication has a two-fold objectivein any green rating program. It provides evidence that thewood has been grown and harvested in environmentallyand socially responsible manner, and determines whetherwood might qualify for credits as a renewable material.It will also ensure that wood harvested illegally will not re-ceive any credits. There are many forest certication sche-mes prevalent in the US. Currently, Forest StewardshipCouncil (FSC) is the only one recognized by the USGBC

(LEED-NC 2009). Alternative programs, although similar intheir eorts to promote responsible forest managementare not recognized. With FSC wood being limited, it is dif-cult to earn credits for certied wood under the LEEDsystem. It is one of the most underutilized credits in LEED.However, there is a clear indication that other certicati-on will be given recognition in LEED but not in the samelevel as FSC. Additionally, wood is the only material that

requires external validation or certication, while othcompeting materials in LEED do not (LEED 2009), despsocial and environmental impacts associated with othmaterials (Bowyer 2007, 2008).

3. concLsIon and Ft dIctIon oLd

USGBC through LEED has accomplished a major mistone in formulating a set of standards for each buildito be measured upon for their sustainability goals. LEprovides a credible third party validation of sustainabty claims of the stakeholders and is recognized worldwde. Many government agencies now require every staowned building to be LEED silver certied or equivaleThis is a major testimony of credibility and recognitifor an independent agency such as the USGBC. LEED hbeen the market leader in the commercial sector forwhile, and now focusing their eorts to make inroads inthe residential sector. Wood as building material enjo

a signicant market share in this sector. The policies anattitude of LEED for this sector will have a major eect owood and wood products industry. Currently, LEED onprovides points for FSC certied wood and wood produts and does not consider wood to be rapidly renewabmaterial. This has caused strong reactions from manythe forest industry, which has resulted in LEED evaluting their stance on forest certication on several occsions. Each time this has been brought to a vote of thmembership, strong support has been provided for onaccepting wood from the Forest Stewardship Councilis not likely that this stance will change in the near futu

(Knowles and Sinha 2011). However, LEED is likely to acceother forest certications in the new version LEED 2012

The latest version of LEED, called the LEED 2012 is schedled to release in August of 2012 and it is a step in the rection of performance-based rating systems. Althouit is far from comprehensive performance based systethere are provisions that indicate its inclination towarbeing one.

acnowLdmnt

The authors acknowledge the Target research programe project V4-1139: Carbon footprint of primary wo

products.

Fncs1. Ber J.L. (2007) The green building programs-are they re

green? Forest Products Journal, 57(9): 6-17

2. Ber J.L. (2008) The green Movement and the forest produindustry. Forest Products Journal, 58(7/8): 6-13

3. Bribi I.Z ., cill a.., a.a . (2011) Life cycle assessmof building materials: Comparative analysis of energy and env


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nmental impacts and evaluation of the eco-eciency improve-ment potential. Building and Environment, 46: 1133-1140

4. Builig deig crui (Bdc) (2006) Green Buil-dings and the Bottom Line. Oak Brook, IL.

5. Ieril Ir seel Iiui (IIsI) (2000) Worldwi-de LCI database for steel industry products. IISI, Brussels, Belgium.

6. le c., si a. (2011) Green Building Systems in NorthAmerica: How Do They Compare. Western Forester, 56(5): 2 p.

7. Ld (2009) LEED for New Construction and Major Renovation.USGBC, Washington D.C.

8. prl cee aii (pca) (2002) Environmental lifecycle inventory of Portland cement concrete. Appendix: Life cycleinventory of Portland cement manufacture. PCA, Skokie, Ill.

9. pue m.., Berg ., hubbr s., J L., LikeB., oeil ., wger F.. (2010) Cradle-to-gate life-cycle inven-tory of US wood products production: CORRIM Phase I and PhaseII products. Wood and Fiber Science, 42: 15-28

10. jer s., bee J.a. (2007) Solid waste generation inasphalt and reinforced concrete roadway life cycles. Journal of In-frastructure Systems, 13(2): 88-96

11. ie se ree Builig cuil (2010) Green Buildingand LEED core concepts. USGBC Washington DC.

12. sBc (2012) About LEED. http://www.usgbc.org/DisplayPage.

aspx?CMSPageID=1720 (08.01.2012)13. v o h.., pvi a.c. (2002) Cement manufacture and

the environment. Part I: Chemistry and technology. Journal of In-dustrial Ecology, 6(1): 89-105

14. wel . (2009) Sustainability in industrialized architecture:Modular lightweight construction applied to housing. DoctoralThesis. Polytechnic University of Catalonia-Department of Archi-tectural Constructions. Available online at: http://www.tdx.cat/TDX-0122110-180946

15. ypFp (2008) Assessing USGBCs Policy Options for Forest Certi-cation & the Use of Wood and Other Bio-based Materials. A sum-mary report prepared by the Yale Program on Forest Policy andGovernance February 25, 2008.


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Izvleek: Urea-formaldehidna in melamin-urea-formaldehidna lepila so med najpogosteje uporabljenimi lepili na podro

ju lepljenja lesa in lesnih kompozitov. Utrjujejo v kislih pogojih, hitrost utrjevanja pa je odvisna od koliine dodanega kata

lizatorja. V raziskavi je bil prouevan vpliv koliine katalizatorja na utrjevanje komercialnega urea-formaldehidnega in me

lamin-urea-formaldehidnega lepila ter vpliv hitrosti segrevanja na utrjevanje z uporabo diferenne dinamine kalorimetrije

Izdelana je bila tudi simulacija utrjevanja obeh lepil pri izotermnih pogojih.Kljune besede: diferenna dinamina kalorimetrija, katalizator, melamin-urea-formaldehidno lepilo, urea-forma

dehidno lepilo

Abstract: Urea-formaldehyde and melamine-urea-formaldehyde adhesives are the most commonly used adhesives fo

bonding of wood and wood-based composites. They are cured under acidic conditions and their curing rate is therefore de

pendent on the amount of added catalyst. Inuence of the amount of catalyst and of heating rate on curing of commercia

urea-formaldehyde and melamine-urea-formaldehyde adhesive was investigated using dierential scanning calorimetry

Simulation of curing of both adhesives at isothermal conditions was also calculated.

Keywords: dierential scanning calorimetry, catalyst, melamine-urea-formaldehyde adhesive, urea-formaldehyd

adhesive

* univ. dipl. in. les., Univerza v Ljubljani, Biotehnika fakulteta, Oddelek za lesarstvo,Jamnikarjeva 101, 1000 Ljubljana, e-pota: [email protected]

** prof. dr., Univerza v Ljubljani , Biotehnika fakulteta, Oddelek za lesarstvo,Jamnikarjeva 101, 1000 Ljubljana, e-pota: [email protected]

so urea-formaldehidna (UF) in melamin-formaldehid(MF) lepila. Amino smole so produkti reakcije aldehidz molekulami, ki vsebujejo amino ali amidne skupinNajpogosteje uporabljeni komponenti z amino skupinmi sta senina oziroma urea in melamin, medtem konajpogosteje uporabljen aldehid formaldehid. UF lepso najbolj razirjena med aminoplastinimi lepili ter pvladujejo pri izdelavi vezanih, ivernih in vlaknenih plo

Ale UGVEK*, Milan ERNEK** UDK 630*824.

PRUEVANJE VPLIVA KLIINE

KATALIZATRJA NA UTRJEVANJEUREA-FRMALDEHIDNEGA INMELAMIN-UREA-FRMALDEHIDNEGALEPILA Z DIFERENN DINAMINKALRIMETRIJAnalysis of inuence of the amount of catalyst on urea-formaldehyde and melamine-urea-formaldehyde adhesivecuring using differential scanning calorimetry

1. od

Najpomembneja aminoplastina lepila v lesni industriji


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notranjo uporabo (Frihart, 2005) ter v pohitveni industriji.Duromerna lepila na osnovi uree utrjujejo preko polikon-denzacije, pri emer urea reagira s formaldehidom v dvehstopnjah. V prvi stopnji (bazino okolje) nastajajo mono-,di- in tri- metiloluree, v drugi stopnji (kislo okolje) pa na-stopi kondenzacija metiloluree, pri emer najprej nastanetopen in v nadaljevanju netopen zamreen polimer (Piz-

zi in Mittal, 2003). Prednosti UF lepil so zaetna vodoto-pnost, trdnost, ognjeodpornost, dobre toplotne lastnostiin transparentnost v utrjenem stanju ter prilagodljivostna razmere med utrjevanjem. Njihova najveja pomanj-kljivost je slaba vodoodpornost utrjenih lepilnih spojev(Pizzi, 1983). MF lepilo je predstavnik vodoodpornih ami-noplastinih lepil, ki pa je zaradi visoke cene melamina kar3,5-krat draje od UF lepila (Dinwoodie, 1983). Zaradi tegase v praksi porabi precej ve melamin-urea-formaldehi-dnega (MUF) lepila, v katerem je del melamina nadome-en z ureo. Za zagotavljanje zadostne vodoodpornostimora biti razmerje med melaminom in ureo med 50:50

in 30:70 (Pizzi in Mittal, 2003), eprav e majhni delei me-lamina UF lepilom izjemno izboljajo strino trdnost le-pilnega spoja in njegovo odpornost proti vodi (ernek inKutnar, 2009). MUF lepila predstavljajo dober kompromismed kakovostjo MF in nizko ceno UF lepil (Frihart, 2005).Kemizem utrjevanja MUF lepil je podoben tistemu pri UFin MF lepilih, vendar zaradi razlinih razmerij med mela-minom in ureo obstaja ve variacij. Tako UF kot MUF lepiladokonno utrdijo v kislem okolju.

Pri industrijskem lepljenju lesa sta bistvenega pomenaoptimalna temperatura in as stiskanja lepljencev, saj jecilj lepljenja v im krajem asu zagotoviti zadostno tr-

dnost lepilnega spoja. Utrjevanje UF ali MUF lepil pospei-mo z dodatkom katalizatorja, ki znia pH vrednost lepila, zdovajanjem toplotne energije ali s kombinacijo obeh, kar

je v praksi najpogosteje. Ker je pH vrednost UF in MUF le-pil med 7,0 in 8,5, ta lepila pa dokonno utrdijo pod kislimipogoji, je poleg temperature lepljenja bistvenega pome-na e koliina dodanega katalizatorja (Gao in sod., 2009).Dodatek katalizatorja mora biti optimalen, saj v primeru

nezadostne koliine pride do prepoasnega utrjevanja,pri emer je za zadostno utrditev potrebna vija tempera-tura. Ta lahko privede do hidrolize lepila in posledino ni-

jih trdnosti lepilnega spoja. Do hidrolize lahko pride tudi vnasprotnem primeru, ko je dodatek katalizatorja previsok,saj je poleg hitrosti utrjevanja pospeena tudi reakcija hi-drolize (Xing in sod., 2005).

Za doloanje optimalne temperature utrjevanja ami-noplastinih lepil z razlinimi delei katalizatorja je zelouporabna metoda diferenne dinamine kalorimetrijeoz. Dierential Scanning Calorimetry (DSC) (Cai in sod.,2010; Gao in sod., 2009; Myers, 1990; Poljanek in sod.,2006; Xing in sod., 2005). Z DSC metodo namre spremlja-mo fazne prehode oziroma kemine spremembe medutrjevanjem vzorca na podlagi toplote, ki jo vzorec oddaali sprejme med segrevanjem, ohlajanjem ali ohranjanjemkonstantne temperature. V primeru materiala, pri kateremse med procesom utrjevanja izloa voda ali kakno drugotopilo, je zaradi potencialnega prekrivanja eksotermnih

in endotermnih signalov najprimerneja uporaba visoko-tlane DSC merilne celice, ki zagotavlja izhajanje hlapnihproduktov pri vijih temperaturah (Cerc Koroec in sod.,2004; Szesztay in sod., 1996). Namen raziskave je bil oka-rakterizirati utrjevanje UF in MUF lepila v odvisnosti odkoliine dodanega katalizatorja in z uporabo kinetinegamodela Model-free kinetics simulirati potreben as zautrjevanje obeh lepil pri doloenih izotermnih pogojih.

2. matIaLI In mtod

V raziskavi sta bili uporabljeni komercialni lepili slovenskihproizvajalcev in sicer UF lepilo Lendur - 200 (Nafta Len-

dava d.o.o.) in MUF lepilo Meldur H97 (Melamin Koevjed.d.). Lepili sta bili uporabljeni pred iztekom skladine-ga asa. Kot katalizator je bil uporabljen amonijev klorid(NH

4Cl), raztopljen v vodi (NH

4Cl

aq). Meanice lepil z razli-

nimi dodatki NH4Cl

aqso bile pripravljene tako, da je bil de-

le vode, v kateri je bil katalizator raztopljen, vedno enak.Koncentracija NH

4Cl

aqse je spreminjala glede na eleno

koliino dodanega katalizatorja lepilu. Dele (w) NH4Cl

preglei 1. prirv leili ei F leil Leur 200 klizrje nh4cl


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torja se obmoje eksotermnega signala premika proti njim temperaturam, kar najlaje analiziramo s primerjatemperatur pri katerih eksotermni signal dosee svoj mksimum (T

max). Tako lahko ugotovimo, da so razlike v T

med dodatki katalizatorja do 1 % dobro opazne, medteko je razlika med 1 % in 1,5 % minimalna (Preglednica Eksotermnega vrha pri UF lepilu brez katalizatorja ni b

zaznati, je pa opazen intenziven endotermen signal ndoseeno temperaturo 170 C, kar je predvidoma povezno s hidrolizo lepila. Entalpija eksotermnega signala (

je sorazmerna z dodano koliino katalizatorja. To lahpojasnimo z nianjem vrednosti pH lepilne meanice posledino vianjem reaktivnosti funkcionalnih skup(Xing in sod., 2005). Priporoljiva optimalna koliina ddanega katalizatorja UF lepilu Lendur - 200 je glede rezultate 1 %.

Eksotermni signali, zaznani med procesom utrjevanMUF lepila Meldur H97 z razlinimi dodatki katalizatorse raztezajo na bistveno irem temperaturnem obmju, prav tako so Tmax v primerjavi z UF lepilom vije (Sl2). T

maxpri utrjevanju lepila Meldur H97 je odvisna od k

liine dodanega katalizatorja in se z njegovim vianje

glede na maso (m) lepila (UF/MUF) je znaal med 0 in 1,5% (Preglednici 1 in 2).

DSC meritve so potekale z visokotlano DSC napravo (HPDSC 1) proizvajalca Mettler Toledo. Masa vzorcev lepil vzatesnjenih 40 ml aluminijastih lonkih s prebodenimpokrovkom je znaala med 10,14 in 10,41 mg in je bila

izmerjena s tehtnico Mettler Toledo XS205. Meritve so po-tekale v duikovi atmosferi pri nadtlaku 50 bar s imer smose izognili izparevanju vode na temperaturnem obmojumed 25 C in 200 C. V prvem delu raziskave, v kateremsmo prouevali vpliv dodatka katalizatorja, je bila hitrostsegrevanja 10 C/min na temperaturnem obmoju med25 C in 200 C. V drugem delu raziskave je bil dodatekkatalizatorja konstanten (1,00 %), hitrosti segrevanja pa sobile 5 C/min, 10 C/min in 20 C/min. Vse meritve so bileponovljene dvakrat.

Analiza meritev je bila opravljena s pomojo programaSTARe Software 10.0 (Mettler Toledo) in uporabo kineti-

nega modela Model-free kinetics (MFK) za simulacijoutrjevanja lepilnih meanic pri izotermnih pogojih. Za iz-raun entalpije eksotermnih signalov je bila uporabljenabazna linija Spline.

3. ZLtatI

Utrjevanje UF in MUF lepil je v veliki meri odvisno odtemperature segrevanja in dodatka katalizatorja. NH

4Cl

namre reagira s formaldehidom, pri emer se tvori klo-rovodikova kislina, ki znia pH vrednost lepilne meanicein posledino sproi utrjevanje (Gao in sod., 2009). Vplivdodatka NH

4Cl na utrjevanje komercialnega UF lepila Len-

dur - 200 je prikazan na Sliki 1. DSC termogrami (0 %, 0,25%, 0,5 %, 1% in 1,5 %) prikazujejo potek utrjevanja na tem-peraturnem obmoju do 200 C. Del termograma med25 C in 35 C je odstranjen zaradi zaetnega uravnavanjatoplotnega toka v vzorcu in je za razumevanje utrjevanjanepomemben. Iz termogramov je razvidno temperatur-no obmoje eksotermnega signala, ki predstavlja zamre-evanje UF lepila oziroma formacijo metilenskih povezav(Chow in Steiner, 1975). S poveevanjem delea kataliza-

preglei 2. prirv leili ei mF leil melur h97 klizrje nh4cl

slik 1. dsc ergri vliv kliie nh4cl

urjevje F leil Leur 200


11/1464(2012) t 1-2

medtem ko je razlika med lepilno meanico z 0,25 % in1,5 % zgolj dobrih 20 C. Kot pri UF lepilu Lendur - 200 jetudi v primeru MUF lepila Meldur H97, razlika v T

maxmed

lepilnima meanicama z 1 % in 1,5 % dodatkom kataliza-torja minimalna (Preglednica 3). Glede na rezultate T

maxje

priporoljiva optimalna koliina dodanega katalizatorjaMUF lepilu Meldur H97 1 %.

Oblika eksotermnega signala ima en izrazit vrh, ki pa seponekod prekriva s predhodnim in manj izrazitim signa-lom. Manj izrazit signal bi lahko pripisali formaciji meti-lenskih povezav urea-urea, medtem ko drugi, izrazitejisignal, povezujejo prav tako s formacijo metilenskih pove-zav, vendar v tem primeru melamin-melamin (Cai in sod.,2010). O enem izrazitem eksotermnem signalu med utr-

jevanjem MUF lepila poroata tudi Tsou in Shiah (2003),medtem ko sta Pizzi in Panamgama (1995) zaznala peteksotermnih signalov. Ne glede na izrazitost signalov vnaem primeru je mogoe na podlagi termogramov utr-

jevanja pri vsaj treh razlinih hitrostih segrevanja () izde-

lati simulacijo potrebnih asov utrjevanja (t) pri doloenitemperaturi (T

0).

Metoda MFK omogoa oceno ak-tivacijske energije (E

) kot funkcije

stopnje utrjenosti () na podlagirazmerja med in potrebnimi tem-peraturami za doseganje elene pri doloeni . Poimenovanje me-tode MFK temelji na dejstvu, da zaizraun t

pri T

0ne potrebuje po-

datka o modelu oziroma redu ke-mijske reakcije (Menczel in Prime,2009). Izraun temelji na enabi,

ki je bila kasneje preoblikovana za uporabo podatkov izprogramov segrevanja

in pri kateri J predstavlja integral glede na dejansko tem-peraturo vzorca T(t

) in R plinsko konstanto (Vyazovkin,

2006).

Na Sliki 3 je prikazano utrjevanje UF lepila Lendur - 200 z1 % dodatkom NH

4Cl pri treh razlinih (5 C/min, 10 C/

min in 20 C/min). Z vianjem je oblika eksotermnega si-gnala vija, izraziteja in oja, T

maxpa se via (Preglednica 6).

pojavi pri nijih temperaturah. Oitna razlika v Tmax

je opa-

zna med lepilom brez dodanega katalizatorja in ostalimilepilnimi meanicami, saj je razlika med T

maxpri lepilu brez

in lepilu z 0,25 % dodatkom katalizatorja skoraj 40 C,

slik 2. dsc ergri vliv kliie nh4cl

urjevje mF leil melur h97

preglei 3. liv kliie klizrj nh4cl t

xi h

slik 3. dsc ergri vliv iri egrevj urjevje F leil Leur 200 ri 1 % kunh

4cl


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S pomojo metode MFK lahko na podlagi utrjevanja lepilapri treh razlinih simuliramo potrebne t

pri izotermnih

pogojih, da zagotovimo doloeno . Tako je npr. za 90 %utrditev UF lepila Lendur - 200 pri 120 C potrebnih 4,8 se-

kunde (Preglednica 4), za 90 % utrditev MUF lepila MeldurH97 pri enakih pogojih pa celo minuto (Preglednica 5).

Na Sliki 4 je prikazano utrjevanje MUF lepila Meldur H97 z1 % dodatkom katalizatorja pri treh razlinih (5 C/min,10 C/min in 20 C/min). Med MUF termogrami je e oi-tneja razlika v obliki eksotermnih signalov kot pri UF le-pilu. Viden je en izrazit eksotermni signal, ki ponazarja za-mreenje in pri vijih temperaturah prehod v endotermnisignal, ki nakazuje na hidrolizo lepila. T

maxse z vianjem

via (Preglednica 6).

Na sliki 5 je grano ponazorjena primerjava simulacijepoteka utrjevanja UF in MUF lepil pri 120 C. Simulacijepoteka utrjevanja lepil v praksi sluijo za doloanje opti-

malnega asa lepljenja. Na prikazanem primeru je oitnda bi bil za lepljenje lesa z MUF lepilom potreben bistvno dalji as kot pri lepljenju z UF lepilom.

4. ZaLJUtrjevanje UF in MUF lepil je odvisno predvsem od temperature lepljenja in koliine dodanega katalizatorja, kznianjem pH vrednosti lepilne meanice sproi reakcNamen raziskave je bil prouiti vpliv koliine katalizato(amonijev klorid) na potek utrjevanja dveh komercialnaminoplastinih lepil: UF lepilo Lendur - 200 in MUF lepMeldur H97 z diferenno dinamino kalorimetrijo.

Ugotovljeno je bilo, da se z veanjem delea katalizatozniuje potrebna temperatura za utrjevanje obeh aminplastinih lepil oziroma se nia temperatura maksimumeksotermnega signala, ki karakterizira reakcijo utrjevan

Priporoena optimalna koliina katalizatorja je bila tako

preglei 4. siulij rebeg urjevj F leil Leur 200 z 1 % k nh4cl ri

lei izeri gji z egje elee je urjei

slik 4. dsc ergri vliv iri egrevj urjevje mF leil melur h97 ri 1 % ku nh

4cl

slik 5. siulij urjevj ri 120 c z F leilLeur 200 i mF leil melur h97 z 1 % k nh

4cl


13/1464(2012) t 1-2

primeru UF kot MUF lepila 1 %. Prouevan je bil tudi vplivhitrosti segrevanja UF in MUF lepila z 1 % dodatkom ka-talizatorja na utrjevanje. Z vianjem hitrosti segrevanja se

je viala temperatura maksimuma eksotermnega vrha, napodlagi omenjenih podatkov pa so bile izraunane simu-lacije utrjevanja obeh lepil pri izotermnih pogojih. Ugoto-vljeno je bilo, da pri 120 C MUF lepilo Meldur H97 za 90 %utrjenost potrebuje skoraj 13-krat toliko asa kot UF lepiloLendur - 200.

ZahaLa

Prispevek je nastal z DSC opremo nabavljeno v okviru te-meljnega raziskovalnega projekta J4-2177 Razvoj okoljuprijaznih lepil iz obnovljivih rastlinskih polimerov, aplika-tivnega raziskovalnega projekta L4-2144 Premazi iz ute-koinjenega lesa in raziskovalnega programa P4-0015Les in lignocelulozni kompoziti, ki jih nancira Javnaagencija za raziskovalno dejavnost RS.

5. II1. ci X., iel B., w h., Zg s. y., wg X. (2010) A study on

the curing and viscoelastic characteristics of melamineureafor-maldehyde resin in the presence of aluminium silicate nanoclays.Composites: Part A, 41: 604-611

2. cer re ., u mer L., Bukve p. (2004) Termi-na analiza fenolformaldehidnih oblikovnih mas: spremljanje za-mreevanja s heksametilentetraminom. V: Glavi P. (ur.), Brodnjak-Vonina D (ur.). Jubilejni 10. Slovenski kemijski dnevi 2004, Maribor,23. in 24. september 2004. Maribor, 1-10.

3. c s., seier p. . (1975) Catalytic, exothermic reactions ofurea-formaldehyde resin. Holzforschung, 29(1): 4-10

4. diie J. m. (1983) Properties and performance of woodadhesives. V: Wood adhesives - Chemistry and technology. Pizzi A.(Ur.), Marcel Dekker, New York and Basel, 1-57

5. Frir c. . (2005) Wood adhesion and adhesives. V: Handbookof wood chemistry and wood composites. Rowell R. M. (Ur.), CRC

Press: 215-2786. Z., wg X., w h., Liu Z. (2009) DSC characterisation ofurea-formaldehyde (UF) resin curing. Pigment & resin technology,38(1): 3-9

7. meze l J. d., prie . B. (2009) Thermal analysis of polymers,Fundamentals and applications. John Wiley & Sons, Hoboken, NewJersey, 696

8. mer . . (1990) Formaldehyde liberation and cure behavior ofurea-formaldehyde resins. Holzforschung, 44(2): 117-126

9. pizzi a. (1983) Aminoresin wood adhesives. V: Wood adhesives -Chemistry and technology. Pizzi A. (Ur.), Marcel Dekker, New Yorkand Basel, 59-104

10. pizzi a., mil . L. (2003) Handbook of adhesive technology. M.Dekker, New York and Basel, 1024

11. pizzi a., pg L. a. (1995) Diusion hindrance vs. wood-

induced catalytic activation of MUF adhesive polycondensation.Journal of applied polymer science, 58: 109-115

12. pljek I., ebeik ., rj m. (2006) Characterization ofphenol-urea-formaldehyde resin by inline FTIR spectroscopy. Jo-urnal of applied polymer science, 99(5): 2016-2028

13. szez m., Lzl hevig Z., ng p., t F. (1996) DSCcharacterisation of Urea/formaldehyde condensates, II. Experien-ces with high pressure DSC cell. Holz als roh- und werksto, 54:399-402

14. erek m., ur a. (2009) Aminoplastina lepila. Les, 61(2): 47-53

15. tou c., sia t. (2003) Reaction kinetics behavior of melamine-urea-formaldehyde wood adhesives by dierential thermal analysisand its application. Taiwan journal of forest science, 18(4): 339-348

16. zvki s. (2006) Model-free kinetics, Staying free of multi-

plying entities without necessity. Journal of thermal analysis andcalorimetry, 83(1): 45-51

17. Xig c., deg J., Zg s. y., iel B., cluier a. (2005) Dif-ferential scanning calorimetry characterization of urea-formal-dehyde resin curing behavior as aected by less desirable woodmaterial and catalyst content. Journal of applied polymer science,98: 2027-2032

preglei 5. siulij rebeg urjevj mF leil melur h97 z 1 % k nh4cl ri

lei izeri gji z egje elee je urjei

preglei 6. liv iri egrevj tx


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ZA PRIPRAV PRISPEVKV1. PrisPEvkiRevija Les objavlja izvirne in pregledne znanstvene ter strokovneprispevke s podroja lesarstva, pohitvene industrije in z lesarstvompovezanih podroij (arhitekture, oblikovanja, okolja, gradbenitva, et-nologije ). Vsi objavljeni prispevki so recenzirani. Za vsebino prisp-evka so odgovorni avtorji. O obliki in datumu objave lanka odloaurednitvo.

2. obsEg PrisPEvkovPrispevki morajo biti pripravljeni v skladu s temi navodili. Znanstvenilanki naj ne presegajo 18.000 znakov s presledki, po dogovoru zurednikom lahko le pregledni znanstveni lanki obsegajo 27.000 zna-kov s presledki. Priporoena dolina strokovnih lankov je 9.000 zna-kov s presledki. Za angleke prevode povzetkov so odgovorni avtorji.Urednitvo revije Les zagotovi lektoriranje slovenskih tekstov. Tekstovprispevkov, zgoenk in disket avtorjem ne vraamo. Na zahtevo av-torja vraamo slikovno gradivo.

3. JEzikV reviji Les objavljamo znanstvene prispevke v slovenskem alianglekem jeziku, strokovne pa le v slovenskem jeziku.

4. PovzEtEkZa izvirne in pregledne znanstvene lanke, morajo avtorji pripravitipovzetek v angleini in slovenini. Pri tujejezinih avtorjih, bo zaslovenski povzetek poskrbelo urednitvo. Povzetek mora podati

jedrnato informacijo o vsebini prispevka. Okvirno naj zajema 1.000znakov s presledki.

5. kLJunE bEsEDEKljunih besed je lahko najve 8. Predstaviti morajo podroje raziska-ve, podane v lanku. Napisane morajo biti v slovenskem in anglekem

jeziku. Razvrene naj bodo v abecednem redu slovenskih besed.

6. nasLov LankaNaslov lanka naj bo kratek in razumljiv. Pri izvirnih in preglednihznanstvenih lankih, naj bo zapisan v slovenskem in anglekem jezi-ku. Za naslovom sledijo ime/imena avtorja/avtorjev (ime in priimek).

7. nasLov avtorJa/avtorJEv

Pod imeni avtorjev naj bodo zapisane otevilene intitucije odkoder prihajajo avtorji prispevkov. Za vodilnega avtorja navedimo enaslov, telefonsko, faks tevilko in elektronski naslov.

8. PrEgLEDnicE, grafikoni in sLikEPreglednice in slike naj bodo jasne; njihovo mesto mora biti ned-voumno oznaeno, njihovo tevilo naj racionalno ustreza vsebini.Slike in preglednice morajo podpirati tekst. Vsi naslovi slik oziromapreglednic morajo biti navedeni v slovenskem in anglekem jeziku.Za angleke naslove preglednic in slik so odgovorni avtorji. Naslovepreglednic piemo nad preglednico, naslove slik pa pod slike.

Preglednica 1. Vpliv irine branik na gostoto smrekovega lesa

Slika 1. Pokodba hinega kozlika (foto: J. Puhar)

9. LitEratura in viriPri znanstvenih prispevkih uporabljeno literaturo citiramo med

besedilom, pri strokovnih pa ne. Ve avtorjev istega dela citiramo ponaslednjih naelih: delo do dveh avtorjev (Priimek in Priimek, leto)npr. (Cankar in Preeren, 1984)]; delo ve kot dveh avtorjev (Priimekprvega avtorja in sod., leto), na primer (Kova in sod., 2002). V ko-likor ime avtorja kake trditve navedemo v tekstu, je dovolj e polegzapiemo le letnico objave. V primeru da eno trditev podkrepimo zdvema ali ve viri, jih razvrstimo po letnici objave in loimo s podpiji(Cankar, 1992; gajner in sod., 1998). Standarde navajamo le s kraticostandarda in letnico izdaje, na primer (SIST EN 113, 1996). Zakonodajo

navajamo s kratico, ki nastopa v uradnem listu (BPD 98/8/EC, 19(ZKem, 2006).

Kot vire navajamo le javno dostopno literatura. Citiranje interporoil, ekspertiz, neobjavljenih podatkov ni zaeleno. Literaturo udimo po abecednem redu. Imena avtorjev piemo odebeljeno:

lanek: kovai J., preeren m. (2000) Relevantne lastnohrastovine. Les, 52: 369-373

Knjiga: iardon h.w. (1997) Handbook of copper compoun

and applications. M. Dekker, New York, 325 Poglavje v knjigi: kai y. (1991) Chemistry of Extractives. V: Wood aCellulosic Chemistry. Hon DNS (Ur.), Shiraishi N (Ur.), Marcel DekkNew York, 215-255

Zakonodaja: Biocidal Products Directive 98/8/EC (1998) Ocial Jonal of the European Communities L 123:1-63

Standard: EN 113 (1996) Wood preservatives; Determination of ttoxic values against wood destroying basidiomycetes cultured agar medium.

Internetni vir: Pri dokumentih dostopnih le prek interneso elementi navedbe: avtor (e je znan), naslov dokumenleto, organizacija (e je znana), datum zadnje spremembe

je znan), URL naslov, datum (dan ko smo dokument prebrPredstavitev Drutva inenirjev in tehnikov lesarstva Ljubljana. (20DIT Ljubljana. http://www.ditles.si /index1.htm (3.12.2007)

12. Latinska iMEna taksonovLatinska imena rodov, vrst in intraspecinih taksonov piemokurzivi italic (Picea abies (L.) Karst.)13. forMat in obLika PrisPEvkalanek naj bo pisan v formatu WinWord (.DOC ali .RTF), na A4 fmatu, font Arial, velikost 11. Naslovi poglavij naj bodo odebeljeProsimo, da tekst piete enostolpino in ga ne delite na okvire.Zaradi pozicioniranja naj bodo risbe in fotograje vkljuene v teter e dodatno (!) priloene kot slikovne datoteke (glej toko 15).Prispevke poljite v elektronski obliki (disketa, CD, DVD) na nasurednitva (Karlovka 3, 1000 Ljubjana) ali po e-poti na naslov [email protected]. obLikovanJE grafikonove se le da, ne uporabljajte MS Excela, ker ne moremo nadzovati parametrov grakona (debelina rt, rafure, velikost grafa it

priporoamo profesionalne programe za risanje grakonov: OrigSIGMA plot Zaradi pravilnega poloaja naj bodo vsi grani ementi vstavljeni tudi v tekst. Ozadje grakona mora biti belo!V kolikor gre za stolpien diagram s samo eno vrsto stolpcev, bodo le-ti beli s rno obrobo; rafure v tem primeru niso potrebne3D grakoni niso zaeleni; e je mono, uporabljajte 2D grakone.

15. obLikovanJE sLikovnEga graDiva Slikovno gradivo lahko digitaliziramo v urednitvu, medtem morajo za digitalizacijo diapozitivov poskrbeti avtorji sami. Slika, rejena z digitalnim fotoaparatom mora imeti loljivost vsaj 2,1 m

jona pikslov (irina naj bo vsaj 8,4 cm - 1 stolpec - pri 300 DPI).

Slike naj bodo skenirane pri loljivosti 300 dpi.

Vse slike morajo biti priloene (!) v originalnem TIFF, JPEG ali ustrnem granem zapisu. Zaradi pravilnega poloaja naj bodo vst

ljene tudi v tekst. Vse fotograje naj bodo podnaslovljene in datirane z letnico.

Risbe naj bodo izdelane v enem izmed raunalnikih risarskih pgramov (Corel DRAW, FreeHand itd.). Upotevati je potrebno mmalno debelino rte, k i znaa 0,25 toke oziroma 0,15 mm. Slabih fokopij in risb, narejenih s svinnikom, ne sprejemamo. e je mogose izogibajte risanju v Wordu (zlasti raznih FLOW diagramov s fucijo Draw), ker se pri razlinih fontih oblika sesuje in je ni mogorestavrirati niti izpisati. Najvekrat nastopijo tudi teave pri izvozPDF datoteko. Za morebitne nasvete se obrnite na urednitvo.

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