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Dosadanji glavni i odgovorni urednici Prof. dr Sreten Mladenovi (19672001)

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SADRAJ CONTENT J. Radoevi, J. Malina, N. Doli, P. Ljumovi, S. Slavica Matei

Susceptibility to corrosion of welded AlMgSi alloy EN AW 6060............................................................................. 3

Ljiljana Rakovi, Duica Samardi, Bratislav Miloevi Vodorazredivi dvokomponentni poliuretanski premazi u zatiti naoruanja i vojne opreme ................................................ 7

Dritan Prifti, Marjola Prifti Tuffs and kaolins areas evaluation for use as pozzolanic materials .......................................................................................... 17

Mario Nikola Muek, Jelica Zeli The effect of alkali activator on the development of mechanical properties of fly ash based geopolymer..................... 22

Irina Fierascu, Romulus Dima, Radu Claudiu Fierascu Natural extracts for solving the issue of biodeterioration of the artifacts ................................................................................. 26

Borislav Malinovi, Jovo Mandi, Miomir Pavlovi, Milorad Tomi Smanjenje HPK-vrijednosti otpadnih voda anodnom oksidacijom u industriji poludisperzija i disperzija .................... 31

Miodrag Smelcerovic, Novica Djordjevic, Dragan Djordjevic Kinetics of reactive dyes adsorption on the bottom ashes ........... 37

Sreko Manasijevi, Sran Markovi, Radomir Radia Primena novih tehnologija u cilju poboljanja eksploatacionih svojstava klipova sus motora od aluminijumskih legura ............ 45

Miroljub Trifunovic, Novica Grujic, Branislav Nedeljkovic Kompoziti sa matricom na bazi legure CuZn37 za izradu frikcionih elemenata ....................................................................... 51

ive arkoevi, Miodrag Arsi, Marko Rakin, Bojan Meo, Milan Mii

Otpornost na koroziju zavarenih cevi u naftnim buotinama .... 57 Suzana Dorevic, Stana Kovaevi, Ljubia Nikoli, Dragan Dorevi

Zatita pamune pree od naprezanja impregniranjem modifikovanim skrobom ................................................................ 64

Vladislav Matkovi, Miroslav Soki, Branislav Markovi Recikliranje opasnog otpada na bazi nikla iz industrije biljnih ulja ....................................................................................... 71

Violeta D. Miti, Vesna P. Stankov-Jovanovi, Marija D. Ili, Sneana . Jovanovi, Sneana D. Nikoli-Mandi

Uticaj poara na sadraj tekih metala u biljkama i zemljitu... 75 Ljiljana Avramovi, Mile Bugarin, Zoran Stevanovi, Ljubia Obradovi, Marko Jonovi, Radojka Jonovi, Radmila Markovi

Uticaj rudnikog otpada iz RTB Bor na okolne vodotokove ...... 83 Veljko uki

Mogunosti upravljanja graevinskim otpadom u Republici Srpskoj ........................................................................ 87

Reklame .......................................................................................93

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J. RADOEVI et al ... SUSCEPTIBILITY TO CORROSION OF WELDED AlMgSi ALLOY

ZATITA MATERIJALA 54 (2013) broj 1 3

J. RADOEVI1), J. MALINA2), N. DOLI2), Scientific paper P. LJUMOVI1), S. SLAVICA MATEI3) UDC:620.197.3

Susceptibility to corrosion of welded AlMgSi alloy EN AW 6060 In this paper electrochemical studies on welding joints of commercial extruded Al-alloy EN AW 6060 have been performed in order to evaluate corrosion behavior in solution of 3.5 mass.% NaCl. Potentiodynamic techniques like Tafel polarization and cyclic anodic polarization were employed in order to monitor the general corrosion resistance and pitting susceptibility. Results have shown that weld zone has cathodic character compared to the base alloy, so that passive corrosion current is higher, while pitting potential Epit and repassivation potential Erp are lower for specimens made from welded AlMgSi coupons. Key words: Corrosion of welded AlMgSi alloy EN AW-6060; Chloride medium

1. INTRODUCTION In constructions of Al-alloys welding is the most

frequently used joining technique, and the heat input required to weld aluminium alloys is larger than the heat input required to weld steels [1,2]. The larger heat input is caused by the substantially higher thermal conductivity of the aluminium alloys. When welding aluminium alloys, it should be realised that the commercial alloys often show large differences in thermal conductivity. Generally speaking, the thermal conductivity of a lower Mg concentration alloy, e.g. the AA6060 alloy, is much better than the thermal conductivity of a higher Mg concentration alloy, e.g. the AA5083 alloy. Welded alloys of the 6xxx series are more sensitive to hot cracking than the alloys of the 5xxx series. The tendency of solidification cra-cking can be minimised by using a proper compo-sition of the filler metal. For this reason the Al-Mg alloys are frequently welded with the filler metal ER5356 (AlMg5) [1].

The alloy EN AW-6060 (AlMgSi0.5) is heat trea-table corrosion resistant alloy, especially in atmos-pheric conditions. It is suitable for wrought and extru-sion processing, with the possibility of making very complex shapes [3]. The alloy is available in several versions with different amounts of silicon and mag-nesium added in order to optimize different properties such as mechanical characteristics, surface appeara-nce, suitability for anodizing, etc. Aluminium alloy 6060 is commonly used for architectural sections for

Author's address: 1)University of Split; Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, Ruera Bokovia 32, Split, Croatia, 2)University of Zagreb; Faculty of Metallurgy, Aleja narodnih heroja 3, Sisak, Croatia, 3)Head of Environmental protection office at ibensko Kninska county, ibenik, Croatia

Paper received: 7.08.2012.

windows, doors, curtain walls, interior fittings, lig-hting, furniture and office equipment, and structural applications where surface finish is important. Ave-rage hardness and strength can be further improved by adding copper and silicon to aluminium matrix. By heat treatment (whether artificial or natural aging), further improvements of hardness and strength can be achieved [4,5]. Good weldability and deformability in cold rolled state make it an excellent choice for appli-cation in vehicles. However, like other aluminum alloys, in aggressive media it is susceptible to general and pitting corrosion [6].

2. EXPERIMENT

2.1 Material From commercial semi-finished extruded alumi-

nium profiles rectangular in cross section and 2mm thick, test specimens measuring 30 mm x 80 mm x 2 mm were machined and welded with filler metal AlMg5 [4].

Chemical composition of EN AW-6060 identified by optical emission spectrometer [7] was as follow (mass %): Al-98.72, Si-0.49, Mg-0.45, Fe-0.21, Mn-0.02 while mechanical properties were in accordance with the 6xxx series.

Welding procedure used in this experiment was TIG AlMg5. 2.2 Electrochemical testing

Electrochemical measurements were performed in electrochemical cell consisting of three electrodes. Platinum is used as counter electrode, while the referent electrode was saturated calomel electrode (SCE). Rectangular specimens made from basic material and those with weld bead placed in the center of the coupons served as working electrodes, with exposed circular area of 3.14 cm2. Before each measurement specimens were mechanically and che-mically treated. They were sanded with grit sandpaper

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J. RADOEVI et al ... SUSCEPTIBILITY TO CORROSION OF WELDED AlMgSi ALLOY

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400, 500, 600 and 1000. In order to remove the surfa-ce oxide layer and eventually incorporated impurities, the specimens were cleaned for 1 minute in alkaline solution (0.1 M NaOH at 40 C), then rinsed in distilled water, and as quickly as possible placed in the electrochemical cell.

Corrosion properties were studied in 3.5 mas % NaCl solution at room temperature (22 C 2 C). Solution was deaerated by blowing purified nitrogen (5N) into the reactor for 15 minutes before the start of testing, and above the solution during the experi-ments. Electrochemical measurements were carried out using a computer controlled Potentiostat/Galva-nostat (PARSTAT 2273), managed with appropriate software PowerSuite. To study the corrosion behavior of alloy EN AW 6060 and for the determination of electrochemical parameters the following methods are used: open circuit potential (Eocp) monitoring linear potentiodynamic polarization (Tafel polari-

zation) in the potential range 250 mV vs Eocp, scan rate 2 mV/s

anodic cyclic polarization starting from -1.0 V to -0.2 V in the anodic direction and back again, scan rate 10 mV/s

2.3 Metallography Surface morphology was observed by optical mi-

croscope Olympus GX 51 with digital camera Olym-pus DP70. Etching was done according to procedure outlined in [8].

3. RESULTS AND DISCUSSION 3.1. Open Circuit potential (Eocp)

Time dependence of the open circuit potential (Eocp) in deaerated 3.5 % NaCl at room temperature was monitored for a period of 1 h and 1/2 h. It was found that Eocp was stabilized after 15 min at a potential of -800 mV and -778 mV for unwelded and welded EN AW 6060, respectively, Figure 1.

Figure 1 - Variation of open circuit potential (Eocp)

of EN AW 6060 in deaerated 3.5% NaCl as a function of time

This curves show that after a significant evolution of the free potential towards higher values, it stabili-zes around a value of 800 mV and -778 mV for unwelded and welded specimens, respectively. More noble Eocp for specimen with weld bead impose the conclusion that weld material behaves more cathodic when compared to base metal. The indicated values were taken for further experiments, and time for the stabilization of system is set at 30 min. Testing time lasted for couple of hours, therefore it was found that system stabilises after fifteen minutes.

3.2. Linear polarization Characteristic polarization curves recorded in

Tafel region can be observed in Figure 2 while characteristic electrochemical parameters obtained from these polarization curves are shown in Table 1.

Specimens with weld bead have shown the posi-tive shift of Ecorr, suggesting cathodic character of weldment. However, higher jcorr and vcorr were deter-mined for the welded specimen relative to nonwelded one. Characteristic values of Ecorr from Table 1 served as a starting point for the next testing.

Figure 2 - Potentiodynamic polarization curves of alloy EN AW 6060 in deaerated 3.5% NaCl

J. RADOEVI et al ... SUSCEPTIBILITY TO CORROSION OF WELDED AlMgSi ALLOY

ZATITA MATERIJALA 54 (2013) broj 1 5

Table 1 - Electrochemical parameters of alloy EN AW 6060 in deaerated 3.5% NaCl

Specimen Eocp, V Ecorr, V ba, mV/dec. bc, mV/dec jcorr , Acm-2 vcorr, mma-1

EN AW 6060 -0.800 -0.853 90.2 176.3 3.91 1.385 x 10-2

Welded EN AW 6060 -0.778 -0.802 260.2 211.9 5.21 1.847 x 10-2

3.3 Anodic cyclic polarization In order to accurately determine the potential area

in which the sample behaves passively and an area where there is an active dissolution, the measure-ments were carried out with anodic cyclic polariza-tion. From the curves in Figure 3, it is possible to determine the characteristic parameters (Table 2) of materials prone to passivation, i.e. the pitting poten-tial (Epit) at which the breakdown of passive layer starts, and repassivation potential (Erep) where again a passive state is re-established. Ability of repassivation is manifested by gradual reduction of the current polarization, which is known as hysteresis loop (Ehys = Epit Erep): the narrower the loop, the material is prone to repassivation (at the experimental conditions used).

It is visible in Figure 3 that the reverse polariza-tion curves have standard cyclic behavior with area enclosed by hysteresis loop. The lower value of Ehys (52 mV relative to 153 mV) suggests that welded specimen repassivates more easily. However, accor-ding to Epit value, its pitting susceptibility is higher. Evidently, the corrosion behaviour of welded EN AW 6060 was largely controlled not only by its nobler Eocp and Ecorr but also by the microstructural cons-tituents present on the surface of this material.

(a) EN w 6060

(b) welded EN AW 6060

Figure 3 - Typical anodic polarization curves in deaerated 3.5% NaCl for alloy EN AW 6060

Table 2 - Electrochemical parameters determined from anodic polarization curves in deaerated 3.5% NaCl Specimen Ecorr, mV Epit, V Erep, V Ehys, V Ipass, A

EN AW 6060 -0.853 -0.700 -0.800 0.153 88.5

Welded EN AW 6060 -0.802 -0.750 -0.790 0.052 250.0

Comparison of electrochemical parameters in Table 1 and Table 2 enables to conclude that cathodic character of welded specimen is not the guarantee for its better corrosion resistance.

The reason for such electrochemical behaviour was revealed by metallography.

3.4. Metallography Weld bead and corrosion pits formed on the

surface of alloy EN AW 6060 are shown in Figure 4.

Metallographic analyses revealed microstructural peculiarities of base metal and welded area like surface porosity and heterogeneity, especially in heat affected zone.

Figure 4c illustrates that weld exhibits a smaller grain size than base metal while equiaxed grains in heat affected zone are characterized with numerous particles of secondary intermetallic phases. Their presence on the surface of the alloy favors the

J. RADOEVI et al ... SUSCEPTIBILITY TO CORROSION OF WELDED AlMgSi ALLOY

ZATITA MATERIJALA 54 (2013) broj 1 6

formation microgalvanic cells resulting in pitting corrosion [9].

Figure 4 - Optical micrographs of alloy EN AW

6060: (a) weld bead in plain view; (b) piting after cyclic anodic polarization in 3.5.% NaCl; (c)

particles of Fe-reach intermetallic phases (Barker etching, polarized light, tint-filter); W-weld metal,

BM-base metal; HAZ- heat affected zone

Numerous pits are visible along the fusion line of welded zone in Figure 4b. It is obvious that welding process has lead to melting and mixing of the filler metal with basic material, resulting in additional complexity in the distribution of intermetallic compounds in the microstructure. The former studies with local corrosion of AlMg alloys [8] have shown that particles containing iron, like -Al(FeSi,Mn) as cathodes in local microcorrosion cells.

4. CONCLUSIONS

On the basis of electrochemical and metallo-graphic studies of EN AW 6060 alloy it was found that in 3.5% NaCl both, unwelded and welded specimens are prone to general and pitting corrosion.

Electrochemical tests and values obtained for Eocp and Ecorr have shown that welded specimens have cathodic character compared to the base alloy. However, weld bead on the surface of alloy EN AW 6060 contributes to its heterogeneity, so that higher corrosion rate and pitting susceptibility are recorded for welded specimens.

The results indicated that welded EN AW 6060 is more prone to pitting corrosion due to the presence of intermetallic phases in the heat affected zone of the alloy that favor the formation microgalvanic cells.

5. REFERENCES [1] T. Luijendijk, Journal of Materials Processing

Technology 103 (2000) 29 -35. [2] V. Panchal, A. Patel, N. Shah, Zastita materijala 53,

1 (2012) 15-24. [3] C. Vargel, Corrosion of Aluminium, Elselvier Ltd.,

Amsterdam, 2004. [4] URL:http://www.sallu.me/OOO_Salume/

OOO_%22Salume%22_files/Data_6060.pdf [5] D.Vuksanovic,D.Radonjic,D.Boricic,Z.Cvijovic,Lj.

Pavlovic, Zastita materijala 49, 1 (2008) 51-57. [6] Z. Szklarska-Smialowska, Corrosion Science 41

(1999) 1743-1767. [7] R. Mimica, J. Radoevi, S. Slavica-Matei,

Strojarstvo 53 (2011) 271-275. [8] N. Doli, J. Malina, A. Begi Hadipai, J. Min.

Metall.-B 47 (2011) 79-87. [9] A. Aballe, M. Bethencourt, F.J. Botana, M.J. Cano,

M. Marcos, Corros. Sci. 45 (2003) 161180.

IZVOD

SKLONOST KOROZIJI ZAVARENE AlMgSi LEGURE EN AW 6060 U ovom lanku provedena su elektrokemijska ispitivanja na zavarenim spojevima komercijalne, ekstrudirane Al-legure EN AW-6060 u cilju procjene korozijskog ponaanja u otopini s 3.5% - tnim masenim udjelom NaCl. Potenciodinamike tehnike poput Tafel polarizacije i ciklike anodne polarizacije primijenjene su u cilju promatranja otpornosti na opu koroziju i sklonosti pojavi pitinga. Rezultati su pokazali da zona zavara ima katodni karakter u usporedbi s osnovnom legurom tako da je struja pasivacije vea, dok su piting potencijal Epit i repasivacijski potencijal Erp nii za uzorke izraene iz zavarenih AlMgSi ploica. Kljune rijei: Korozija zavarene AlMgSi legure EN AW-6060; Kloridni medij

Rad primljen: 7.08.2012. Originalni nauni rad

LJ. RAKOVI i ... VODORAZREDIVI DVOKOMPONENTNI POLIURETANSKI PREMAZI ...

ZATITA MATERIJALA 54 (2013) broj 1 7

LJILJANA RAKOVI1, Originalni nauni rad DUICA SAMARDI2 UDC:620.197.6 BRATISLAV MILOEVI2

Vodorazredivi dvokomponentni poliuretanski premazi u zatiti naoruanja i vojne opreme

Vodorazredivi dvokomponentni poliuretanski premazi predstavljaju najnoviju tehnologiju u idustriji boja i lakova. Ekoloki su prihvaljivi, jer se za proizvodnju i primenu u premazima koristi voda umesto organskih rastvaraa. Poznato je, da se u industrijski razvijenim zemljama, ova tehnologija dokazala u zatiti automobila, aviona, energetskih i drugih industrijskih postrojenja. U tom cilju istraivane su mogunosti da se ova tehnologija primeni u zatiti naoruanja i vojne opreme. U ovom radu uraen je nov komponentni sastav premaza i modifikovan tehnoloki postupak izrade, kako bi se ostvarili osnovni zahtevi antikorozionih i maskirnih svojstava u vodorazredivim dvokomponentnim poliuretanskim premazima. Premazi, razvijeni po novoj tehnologiji maskirnih boja (zelena svetla, braon i crna) ispitivani su po standardima odbrane SORS 1564/03 i SORS 8655/11. Pored standardnog ispitivanja, izvreno je i ispitivanje zatitnih sistema sa isto vodorazredivim bojama i konbinovanih zatitnih sistema sa vodorazredivim i bojama na bazi organskih rastvaraa. Dobijeni rezultati ukazuju da su Vodorazredive dvokomponentne poliuretanske pokrivne maskirne boje zadovoljile zahteve kvaliteta pokrivne boje, namenjene za antikorozionu i maskirnu zatitu naoruanja i vojne opreme.Rezultati ispitivanja zatitnih sistema, pokazali su da ispitivani sistemi poseduju zadovoljavajui nivo kvaliteta fiziko- mehanikih karakteristika, hemijske postojanosti i zatitne sposobnosti. Rezultati ispitivanja konbinovanih sistema ukazuju na dobru kompatibilnost ispitivanih vodorazredivih boja i boja na bazi organskih rastvaraa. Kljune rei: Vodorazredivi dvokomponentni poliuretani, umreavanje, maskirni pigmenti, refleksija

1. UVOD Vodorazredivi dvokomponentni poliuretanski pre-

mazi, predstavljaju najnoviju tehnologiju u industriji bo-ja i lakova. Poseduju izvanredna svojstva, podjednaka kao i svojstva dvokomponentnih poliuretanskih prema-za, koji se razreuju organskim rastvaraima, a imaju tu prednost da sadre smanjenu koliinu isparljivih organs-kih jedinjenja. Dananje vodorazredive dvokomponen-tne formulacije poliuretanskih premaza, sadre ispod 220 grama isparljivih organskih jedinjenja po litru proiz-voda, a razvojem ove tehnologije tei se ka njihovoj potpunoj eliminaciji.

Razvoj vodorazredivih premaza i sirovina za proiz-vodnju istih, zapoeo je pedesetih godina prolog veka, uglavnom u industrijski razvijenim zemljama sa poja-vom zakonske regulative za zatitu okoline sredine. Ekoloki su prihvatljivi [1-5], jer se za proizvodnju i pri-menu u premazima koristi voda, umesto organskih ras-tvaraa, koja ima prednosti u nezapaljivosti i neotrovno-sti. Meutim, treba imati u vidu da se fizika svojstva vode i organskih rastvaraa bitno razlikuju. Upravo zbog toga je formulisanje vodorazredivih dvokomponentnih poliuretanskih premaza u odnosu na dvokomponentene

Adrese autora: 1Ni, Nikole Paia 65/14, 2Vojno-tehniki institut, Ratka Resanovia 1, Beograd

Rad primljen: 10.11.2012.

poliuretanske premaze, koji se razreuju organskim rast-varaima, mnogo sloenije, a cena konanog proizvoda vea. U postupku primene, razlike nisu uoene pri nano-enju vodorazredivih poliuretanskih premaza u odnosu na poliuretanske premaze, koji se razreuju organskim rastvaraima.

Izgled filma prevlake uglavnom je uslovljen tehni-kom nanoenja. Kod postuka nanoenja rasprivanje od velike vanosti je da se koriste dizne odgovarajue veli-ine, a oprema za rasprivanje mora imati odgovarajui kapacitet i izlazni pritisak. U sistemima sa osnovnim epoksi premazima na bazi vode ili organskih rastvaraa, vodorazredivim dvokomponentnim poliuretanskim pre-mazima obezbeuje se dobra zatita od korozije, meha-nika otpornost i svetlosna postojanost uz zadravanje boje i sjaja.

Specifikacija kvaliteta pokrivnih prevlaka za zatitu naoruanja i vojne opreme u pogledu maskirnosti, deter-minisana je od strane nacionalnih armija svake zemlje. U okviru toga nijansa-ton i veliina refleksije determi-nisani su sa standardima. Izborom pigmenata sa masker-nim svojstvima u vodorazredivim dvokomponentnim formulacijama poliuretanskih pokrivih premaza, ostva-ruju se propisane vrednosti refleksije i tona. Na taj nain omogueno je utapanje vojnih objekata u okolinu, kako pri vidljivoj, tako i pri infracrvenoj svetlosti.

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1.1. Razvoj i struktura vodorazredivih dvokomponentnih poliuretana

Stvaranje poliuretana zasnovano je na visokoj reak-tivnosti izocijanatne grupe polifunkcionalnog izocija-nata, koja reaguje lako sa hidroksilnim grupama polifun-kcionalnog polimera, uz formiranje stabilnih poliuretana i stvaranje strukture unakrsnim povezivanjem [6]. Pri tome ne dolazi do izdvajanja sporednih proizvoda. Naj-znaajnije je u osnovi izgradnja uretanske veze, reak-cijom adicije, pri emu se vodonik iz hidroksilne grupe adira na azot iz izocijanatne grupe [7].

Za industriju boja i lakova, komercijalno su raspolo-ivi derivati veih molekulskih masa polifunkcionalnih izocijanata, jer su u zdravstvenom pogledu bezbedniji od monomernih diizocijanata u uslovima proizvodnje i primene. U procesima dobijanja derivata veih mole-kulskih masa, nastaju razliite strukture: stvaranje adukta, obrazovanje biureta, polimerizacija diizocijanata uz nastajanje izocijanurata.

Razvojem vodorazredivih dvokomponentnih poli-uretana, ukljuuje se i razvoj novih tipova poliizocija-nata [8]. U tom pogledu koriena su dva osnovna pristupa:

- U prvom pristupu predlae se upotreba konvencio-nalnih poliizocijanata, najvie izocijanuratni trimer na bazi HDI-heksametilendiizocijanata, po mogunosti u niskoviskoznoj formi. Ovaj pristup se oslanja na emul-zifikaciona svojstva vodorazredivih poliola, da bi se po-moglo homogeno dispergovanje poliizocijanata. U ne-kim sluajevima, bolje dispergovanje treba ostvariti po-mou razreivanja poliizocijanata organskim rastva-raima ili meanjem komponenti velikom brzinom. Ne-dostatak ovakvom pristupu su poveano uee organ-skih rastvaraa i potreba za specifinom opremom za meanje.

- U drugom pristupu predlae se korienje poliizo-cijanata, koji je funkcionalizovan, da bi se sam mogao dispergovati u vodi. Ovo se moe postii, uvoenjem hidrofilnih bonih grupa, u sastav poliizocijanata [9]; prikazano na strukturi hidrofilno modifikovanog HDI-izocijanurata, slika 1.

O C N CH2 6

C

NC

N

CN

CH2 6 N C O

CH2 6 N C

O

OR

H

O

OO

Slika 1 - Struktura hidrofilno modifikovanog HDI

izocijanurata Poliizocijanatati dobijeni ovim postupkom lako se

disperguju i nisu potrebni dodati napori, koji su prt-hodno opisani. Nedostaci ovom pristupu mogu da budu:

slabija postojanost prema vodi i manja tvrdoa prevlake (suvog filma). Ovo je posledica poveane hidrofilnosti i smanjene funkcionalnosti izocijanatnih grupa [10]. Da bi se prevazili ovi problemi razvijena je nova generacija hidrofilno modifikovanih poliizocijanata, koju karakte-rie smanjeni sadraj hidrofilnih grupa i poveana funk-cionalnost izocijanatnih grupa. Korienjem nove gene-racije poliizocijanata [11] u vodorazredivim dvokompo-nentnim formulacijama poliuretanskih pokrivnih pre-maza, poveava se gustina umreavanja u prevlakama i postojanost u vodi.

Kao reakcioni partneri u dvokomponentnim poliure-tanima, koriste se polifunkcionalne komponente, najve-im delom tipa poliakrilata i poliestra. Kod vodoraz-redivih dvokomponentnih poliuretana, reakcioni partneri su polioli disperzionog tipa ili polioli emulzionog tipa. Polioli disperzionog tipa, esto se pripremaju vieste-penom sintezom, koja ukljuuje polimerizaciju u organ-skim rastvaraima ili u masi, posle toga sledi neutral-lizacija i prenos poliola u vodu, a u nekim sluajevima i otklanjanje organskih rastvaraa. Niska molekulska ma-sa i visok sadraj hidrofilnih grupa (hidroksilne, karbo-ksilne ili druge stabilizirajue grupe), omoguuju do-voljnu meljivost ove disperzije u vodi. Kao rezultat, polioli disperzionog tipa su u obliku koloidne disperzije, manjih veliina estica. Polioli emulzionog tipa, pripre-maju se polimerizacijom u emulziji, a estice su im ne-to vee. Polioli disperzionog tipa mogu se umreavati i konvencionalnim poliizocijanatima. Polioli emulzionog tipa su obino prilagoeni korienju poliizocijanata, ko-ji su dispergovani u vodi, a velikom molekulskom ma-som omogueno je veoma brzo suenje na sobnoj tem-peraturi [12]. Polioli disperzionog tipa u vodorazredivim dvokomponentnim poliuretanskim premazima, formiraju prevlake postojane prema vodi, organskim rastvaraima i vremenskim uslovima, ali sa neto sporijim suenjem.

1.2. Teorijske osnove mehanizma formiranja filma

Nastajanje filma, umreavanjem vodorazredivih dvokomponemntnih poliuretana je neuobiajeno sloen proces i sastoji se od dinamike serije dogaaja, koji su meusobno povezani. Pri spajanju komponenti dvo-komponentnih premaza, kinetika reakcije je veoma brza, reaktanti se moraju meati neposredsno pre primene, inae bi dolo do prevremenog geliranja. Vreme geli-ranja zavisi od specifinosti reaktanata, katalizatora i temperature.

Kod dvokomponentnih poliuretanskih premaza sa organskim rastvaraima, kraj pot-life-a se obino poka-zuje znaajnim poveanjem viskoziteta. Ovde je visko-zitet jednostavna funkcija molekulske mase, a poveanje viskoziteta direktno oslikava meru u kojoj je reakcija uznapredovala.

Pot-life vodorazredivih dvokomponentnih poliure-tanskih premaza je sloena pojava. Znaajan je veliki broj promenljivih, ukljuujui brzinu reakcije poliizo-cijanata sa poliolom i vodom, relativne koncetracije

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reaktanata i koloidno stanje sistema. Zbog heterogene prirode ovog sistema, poveanje molekulske mase, usled reakcije poliola i poliizocijanata u polimerskoj fazi, ne mora da dovede do vidljive promene viskoziteta u kontinualnoj vodenoj fazi. Tako, mera viskoziteta ne moe biti dovoljna da se tano proceni pot-life. Meu-tim, dinamiki porast viskoziteta, koji ovde biva praen obilnom penom, zbog razvoja ugljendioksida, postavlja gornju granicu pot-life-a.

Premaz se mora primeniti pre nego to doe do opsenije reakcije stvrdnjavanja. Za uspostavljanje he-mijske karakteristike filma i razvoja mehanikog inte-griteta tokom stvrdnjavanja, mogue su sledee reakcije izocijanata sa hidroksilnim grupama poliola i vode [13].

R NCO +R NH2 R N C

O

H

N

H

R

R NCO +H2O R N C

O

H

OH R NH 2+ CO2

R NCO +R OH R N C O R

O

H

a)

c)

d)

Slika 2 - Reakcije izmeu izocijanatnih grupa i

jedinjenja sa aktivnim vodonikom

Prikazanim reakcijama slika 2, izocijanata sa hid-roksilnim grupama poliola, formira se film uz stvaranje uretanskih veza unakrsnim povezivanje a). U vodo-razredivim dvokomponentnim poliuretanima, pored stvaranja uretanske veze unakrsnim povezivanjem, reak-cijama izocijanatne grupe sa vodom, formira se polikar-bamidna kiselina, koja se raspada na poliamin i ugljen-dioksid c).

Poliamin reaguje sa drugom izocijanantnom gru-pom, to dovodi do stvaranja poliuree d).

U dvokomponentnim poliuretanima sa organskim rastvaraima, kljuni problem vezan za ovaj mehanizam, je relativna brzina isparavanja rastvaraa, u odnosu na brzinu reakcije umreavanja. Brza reakcija umreavanja i udrena poveana molekulska masa, mogu da izazovu jedan broj potencijalnih problema. Rastvarai mogu da budu zarobljeni i da formiraju mehurie unutar filma. Uz to, ukoliko se molekulska masa isuvie brzo poveava, tokom ranijih stadijuma umreavanja, difuzija reaktivnih grupa moe biti ometana. To spreava kompletnu reakciju i ostavlja nie molekulske mase u filmu. Brza reakcija uslovlava nepokretnost itavog sisitema. Ovaj efekat dovodi do unutranjih stresova i do formiranja potencijalnih defekata. S druge strane, spore reakcije

usporavaju suenje i mogu da izazovu razvoj osobina, koje nisu poeljne.

Na osnovu raspoloivih modela, nastajanje filma u vodorazredivim dvokomponentnim poliuretanima, odvi-ja se isparavanjem vode uz istovremenu koalescenciju estica polimera i reakciju izmeu poliola i poliizo-cijanata [14]. Ovaj proces se komplikuje kompetativnim reakcijama poliizocijanata sa hidroksilnim grupama iz vode. Dok prvom reakcijom nastaju eljeni poliuretani, drugom se formira poliurea i ugljendioksid. Ugljen-dioksid mora da se eliminie iz premaza, pre zavretka formiranja filma, kako bi se izbegli defekti u masi ili na povrini nastalog filma. Neki istraivai su izneli ogra-niene dokaze u redosledu i obimu dogaaja, koji se odvijaju tokom nastajanja filma u vodorazredivim dvo-komponentnim poliuretanima [15].

Meanje disperzija poliizocijanata i poliola, pre pri-mene, inicirae reakcije izocijanat-hidroksilna grupa i izocijana-voda. Ukoliko u ovom momentu doe do koa-lescencije poliizocijanata i hidroksifunkcionalnih es-tica, to e olakati eljenu reakciju izocijanat-hidroksilna grupa. Ovaj efekat se dodatno pojaava, ukoliko poliol enkapsulira poliizocijanat. Hare [16] je naveo, da do ove enkapsulacije dolazi i da reakcija zapoinje u hidro-filnim centrima, na interfejsu poliizocijana-poliol. Reak-cija poliizocijanata sa hidroksilnim grupama poliola je bra od reakcije sa vodom. Meutim, odreena reakcija sa vodom je neizbena. Da bi se obezbedila kompletna reakcija hidrolize, postalo je uobiajeno korienje vika poliizocijanata u odnosu NCO/OH od 1,5.

2. EKSPERIMENTALNI DEO

2.1 Materijali i premazi

Za formulisanje komponentnog sastava, vodorazre-divih dvokomponentrnih poliuretanskih pokrivnih pre-maza, sa maskirnim svojstvima, izvreno je istraivanje i analiza, evropskih proizvoaa veziva za vodorazredive poliuretane, kao i pigmenata sa zadovoljavajuom IC refleksijom, u cilju obezbeivanja maskirnih svojstava premaza. Nakon toga izabrani su najvaniji sirovinski materijali, koji bi bili prihvatljivi za komponentni sastav naznaenih proizvoda.

U toku ispitivanja, vie puta je modifikovan sasatav i tehnoloki postupak, kako bi se ostvarile optimalne performanse istraivanih proizvoda. Materijali, koji su korieni u ovom istraivanju, predstavljaju reprezen-tativne uzorke postojeih proizvoda, poznatih proizvo-aa veziva, pigmenata i ostalog za industriju boja i la-kova. U formulacijama premaza za vodorazredivo dvo-komponentno poliuretansko vezivo, odabrana je OH-funkcionalna poliakrilna disperzija sa umreivaem od meavine niskoviskoznog i hidrofilnog alifatinog poli-izocijanata, na bazti HDI-heksametilendiizocijanata.

IR-spektroskopijom [17], snimljeni su FT-IR spektri OH-funkcionalne poliakrilne disperzije i umreivaa, metodom nanoenja tankog filma na nosa KBr ploice,

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a FT-IR spektri umreenog vodorazredivog poliure-tanskog veziva KBr tehnikom (formiranje pastila od 1mg uzorka i 150 mg KBr). Snimanja su vrena na spek-trofotometru BOMEN Hartman&Braun MB-100 series u oblasti talasnih brojeva 4000-400cm na Tehnolokom fakultetu u Leskovcu, Univerzitet Ni.

Analizom FT-IR spektra OH-funkcionalne poliakril-ne disperzije, identifikovana je OH-grupa prisustvom trake na 3600-3000cm, koja potie od valencionih vibracija iste. Potvrda prisustva OH-grupe je traka na 800-650cm od deformacionih vibracija van ravni.

U FT-IR spektru umreivaa, karakteristina je in-tenzivna traka na 2275-2250cm, kojom se identifikuju valencione vibracije NCO-grupe. Prisustvo trake u ob-lasti 3700-3300cm potie od valencionih vibracija NH-veza sa razliitim poloajem u makromolekulu. Identifi-kovana je i pojava deformacionih vibracija van ravni NH-veza u oblasti 800-500cm.

Za snimanje FT-IR spektra umreenog vodoraz-redivog poliuretanskogm veziva, komponente su spojene

u odnosu racionalnog umreavanja NCO/OH, nanoene na staklene ploice i posle deset dana suenja i otvrd-njavanja, izvreno je snimanje formiranog filma umre-enog veziva.

Analizom FT-IR spektra formiranog filma uoen je nestanak trake na 2271cm, karakteristine za prisustvo NCO-grupe, kao i pojava novih traka, koje potiu od formiranja uretanske veze na 1730,5cm i urea veze na 1527,9cm. Ovim je izvrena kvalitativna analiza umre-avanja odabranog vodorazredivog poliuretanskog ve-ziva za prihvatljivu primenu.

Iizbor maskirnih pigmenata odreen je na osnovu propisanih vrednosti spektralne refleksije za svaki ton sa gornjom i donjom graninom linijom u dijagramu na i-joj je apscisi naneta talasna duina izraena u nano-metrima (nm), a na ordinati refleksija izraena u procentima (%).

U tu svrhu korieni su podaci iz tehnikih infor-macija proizvoaa i eksperimentalna merenja IC ref-leksije u Vojnotehnikom Instiruru Beograd.

Tabela 1 - Numerike vrednosti IC refleksije maskirnih pigmenata [18-21] Talasna duina (nm) 650 670 700 750 800 850 900 950 1000 Refleksija (%) za zeleni pigment

7,3 7,5 11,9 34,8 38,3 39,2 39,6 39,2 38,6

Refleksija (%) za crni pigment

7,4 7,4 7,6 8,7 9,9 11,6 13,2 14,3 15,0

Refleksija (%) za uti pigment

68,0 67,6 65,0 70,4 80,2 85,0 84,9 88,0 87,0

Refleksija (%) za crveni pigment

40,0 42,0 60,1 62,3 58,0 58,5 60,0 70,2 78,0

Refleksija (%) za braon pigment

14,0 14,5 20,1 23,4 30,0 45,5 50,6 55,7 62,0

Refleksija (%) za plavi pigment

20,0 40,5 80,0 82,0 82,5 82,5 80,0 81,6 80,0

S obzirom da je broj organskih i neorganskih pig-

menata, sa kojima se moe ostvariti odgovarajua spek-tralno-refleksiona kriva ogranien, to je u izradi vodo-razredivih dvokomponentnih poliuretanskih pokrivnih premaza primenjen postupak miksiranja u cilju ostvari-vanja eljenog tona i odgovarajue krive spektralne refleksije.

U komponentnom sastavu vodorazredivih dvokom-ponentnih poliuretanskih premaza, znaajno je i uee pomonih sredstava [22]. Povrinski aktivnim srdstvima za dispergovanje i kvaenje otklonjene su energetske barijere u glavnom sirovinskom sastavu, a time je postignuta optimalna raspodela estica i stabilizacija premaza. Upotrebom pomonih sredstava protiv talo-enja ostvarena je stabilizacija u lagerovanju. Pomonim sredstvima je omoguena bra deaeracija, a tiksotropija

premaza, vana za primenu, podeena je reolokim aditivima.

Na osnovu rezultata eksperimentalnog istraivanja, kroz modifikaciju sastava i tehnolokih faza rada, po-stavljena su nova reenja premaznih sredstava sa oso-binama koje su unapred programirane, prema zahtevima u zatiti naoruanja i vojne opreme. Za dalja eksperi-mentalna ispitivanja po novorazvijenim formulacijama i tehnolokom postupku uraeni su premzi sa sledeim karakteristikama:

Vodorazrediva dvokomponentna poliuretanska pokrivna maskirna boja-zeleno svetla-ton br.1 VOC 82 (g/L) Sadraj suve materije teinski (A+B) 56,5 (%) Gustina (A+B) na 20C 1,33 (g/cm)

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Odnos spajanja komponentni A:B=7:1 Racionalno umreavanje NCO/OH 1,4 Vreme upotrebe spojenih komponenti 2 h. Teoretska izdanost 6,2 (m/kg)

Vodorazrediva dvokomponentna poliuretanska pokrivna maskirna boja-braon-ton br.6 VOC 87 (g/L) Sadraj suve materije teinski (A+B) 57,6 (%) Gustina (A+B) na 20C 1,35 (g/cm) Odnos spajanja komponentni A:B=7:1 Racionalno umreavanje NCO/OH 1,3 Vreme upotrebe spojenih komponentni 2 h. Teoretska izdanost 6,5 (m/kg) Vodorazrediva dvokomponentna poliuretanska pokrivna maskirna boja-crna-ton br.10 VOC 85 (g/L) Sadraj suve materije teinski (A+B) 55 (%) Gustina(A+B) na 20C 1,32 (g/cm) Odnos spajanja komponentni A:B=7:1 Racionalno umreavanje NCO/OH 1,3 Vreme upotrebe spojenih komponenti 2 h. Teoretska izdanost 6,7 (m/kg)

2.2. Ispitivanje kvaliteta po standardima odbrane Uzorci vodorazredivih dvokomponentnih poliure-

tanskih pokrivnih maskirnih boja u tri tona (zelena-svetla-ton br.1, braon-ton br.6 i crna-ton br.10), razvijeni po novoj tehnologiji, izraeni su u laboratoriji fabrike Pomoravlje ad Ni, a ispitivanja su izvrena u Vojno-tehnikom institutu, Sektoru za materijale i zatitu, prema zahtevimaSORS 1564/03 i SORS 8655/11, koji-ma je definisan kvalitet, Dvokomponentnih poliure-tanskih maskirnih boja, na bazi organskih rastvaraa za primenu u sistemima antikorozione i maskirne zatite. Pored standardnih ispitivanja, prema zahtevima nave-denih SORS, izvrena su i preliminarna ispitivanja uzoraka boja u sistemima sa Vodorazredivom dvokom-ponentnom epoksi osnovnom bojom ( koja je isto tako bila predmet razvoja po novoj tehnologiji ), kao i u sis-temima sa bojama na bazi organskih rastvaraa (Dvokomponentnom osnovnom epoksi bojom po SORS 1549 i Dvokomponentnom poliuretanskom maskirnom bojom po SORS 1564). Cilj ispitivanja konbinovanih sistema na bazi novorazvijenih vodorazredivih boja i boja sa organskim rastvaraima, bio je da se oceni kva-litet takvih sistema i mogunost njihove primene u proizvodnji, a posebno u odravanju naoruanja i vojne opreme (na primer za parcijalno ili celokupno obna-

vljanje ve postojee antikorozione i maskirne zatite bazirane iskljuivo na bojama sa organskim rastva-raima).

Priprema uzoraka za laboratorijsko ispitivanje Vo-dorazredivih dvokomponentnih poliuretanskih pokrivnih maskirnih boja uraena je u skladu sa zahtevima SORS 1634/03.

Kao podloga za izradu uzoraka koriene su ploe dimenzije 150 mm x70 mm x 0,7-1 mm na bazi elika 0147, kvalitet prema SRPS CB3.521. Priprema po-vrina podloga izvedena je bruenjem, brusnim papirom P240 do stepena St3 i odmaena medicinskim ben-zinom.

Uzorci boja, pripremljeni su sjedinjavanjem kom-ponenti u odnosu A:B= 70:10 i homogenizovani mea-njem, bez razreivanja vodom. Isti su naneeni na pod-loge 15 minuta posle sjedinjavanja komponentni, ras-privanjem pomou komprimovanog vazduha u uslo-vima okoline T = 18-23C i RV = 50-75%. Ostvarene su debljine prevlaka 50-60 m.

Izraeni su sledei uzori za laboratorijsko ispitivanje:

*Prevlake boje u maskirnom tonu br.1-zelena-svetla (uzorci oznake 1)

*Prevlake boje u maskirnom tonu br.6-braon (uzorci oznake 6)

*Prevlake boje u maskirnom tonu br.10-crna (uzorci oznake 10)

*Tri tipa zatitnih sistema sa prevlakama sledeih boja:

Sistem I- na bazi vodorazredivih boja Vodorazrediva dvokomponentna epoksi osnovna

boja Vodorazrediva dvokomponentna poliuretanska

pokrivna maskirna boja Sistem II- na bazi kombinovanih boja Dvokomponentna epoksi osnovna boja SORS 1549

na bazi organskih rastvaraa Vodorazrediva dvokomponentna poliuretanska

pokrivna maskirna boja Sistem III- na bazi kombinovanih boja Vodorazrediva dvokomponentna epoksi osnovna

boja Dvokomponemntna poliuretanska maskirna boja

SORS 1564 na bazi organskih rastvaraa Ispitivanje svih uzoraka vreno je 7(sedam) dana

nakon njihove izrade.

3. REZULTATI I DISKUSIJA Uzorci prevlaka boja, u sva tri maskirna tona: zelena

svetla-ton br.1, braon-ton br.6 i crna-ton br.10 (uzorci oznake 1,6 i 10), ispitivani su i ocenjeni prema zah-tevima SORS 1564/03 i SORS 8655/11. Rezultati ispi-tivanja prikazani su u tabelama 2 i 3 i na slikama 3,4 i 5.

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Tabela 2 - Rezultati ispitivanja po SORS 1564/03 uzoraka prevlaka vodorazredivih dvokomponentnih poliuretanskih pokrivnih boja maskirnih tonova br.1, br.6 i br.10

Rezultati ispitivanja uzoraka oznake Ispitivana karakteristika Met. ispit. SORS 1634 Zahtev po SORS 1564 1 6 10

Stanje u posudi M 1 homogena suspenzija zadovoljava zadovoljava zadovoljava

Osobine pri razreivanju i nanoenju

M 2, M 8

premaz ujednaene de-bljinei bez nedostataka zadovoljava zadovoljava zadovoljava

Vreme upotrebljivosti, h - ne zahteva se oko 2

Vreme suenja, h potpuno suv

M 9 najvie 24 zadovoljava zadovoljava zadovoljava

Debljina m M 11 50-55 60 50-55 60

Pokrivna mo, m M 12 30 do 40 zadovoljava zadovoljava zadovoljava

Prianjanje i zarez M 14 GT 0 zadovoljava zadovoljava zadovoljava

Tvrdoa, s M 20 najmanje 80 58 48 54

Otpornost na udar M 17 najmanje 4500 > 6000 > 6000 > 6000

Otpornost na abraziju, L/m M 22 0,1 zadovoljava zadovoljava zadovoljava

Elastinost, mm M 23 najmanje 6 > 6,7 > 6,7 > 6,7

Savitljivost, mm M 24 6 zadovoljava zadovoljava zadovoljava

Postojanost prema svetlosti M 32 bez promene izgleda; boja u granicama tolerancije zadovoljava zadovoljava zadovoljava

Postojanost na temperaturne uticaje M 26

bez promene izgleda; tvrdo-a u granicama tolerancije zadovoljava zadovoljava zadovoljava

Postojanost prema vodi posle 168 sati izlaganja M 25

bez promene izgleda, boje, sjaja; tvrdoa u granicama tolerancije

zadovoljava* zadovoljava* zadovoljava*

Postojanost prema mineralnom ulju M 25

bez promene izgleda, boje;sjaj i tvrdoa u grani-cama tolerancije

zadovoljava zadovoljava zadovoljava

Postojanost na te. gor. izooktan/benzen

M 25 bez promene izgleda, boje;sjaj i tvrdoa u grani-cama tolerancije

zadovoljava zadovoljava zadovoljava

* uzorci su zadovoljili u potpunosti zahteve kvaliteta posle 72 sata izlaganja; posle 168 sati izlaganja na pojedinim uzorcima uoena je pojava u vidu sitnih mehura, koji su nestali posle 24 sata suenja uzoraka u laboratorijskim uslovima.

Tabela 3 - Rezultati ispitivanja maskirnih karakteristika uzoraka prevlaka vodorazredivih dvokomponentnih

poliuretanskih pokrivnih boja maskirnih tonova br.1, br.6 i br.10

Rezultati ispitivanja uzoraka oznake Karakteristika Zahtev po SORS 8655

1 6 10

Nijansa vizuelna podudarnost sa odgovarajuom merom maskirne boje-tona po SORS 8655 zadovoljava

zadovoljava zadovoljava

Sjaj 5 za tonove po SNO 8655 3 2 5

IC refleksija (650-1000 nm)

vrednosti prema dijagramu refleksije po SORS 7511 zadovoljava zadovoljava zadovoljava

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Slika 3 - Dijagram IC refleksije prevlake vodorazredivedvokomponentne poliuretanske pokrivne boje

maskirnog tona br. 1

Slika 4 - Dijagram IC refleksije prevlake vodorazredive dvokomponentne poliuretanske pokrivne boje

maskirnog tona br.6

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Izvetaj o isp itivanju refleksije

Slika 5 - Dijagram IC refleksije prevlake vodorazredive dvokomponentne poliuretanske pokrivne boje

maskirnog tona br.10 Tabela 4- Rezultati ispitivanja zatitnih sistema prevlaka na bazi samo vodorazredivih boja (uzorak I) i sistema na

bazi kombinacije prevlaka vodorazredivih i boja sa organskim rasvaraima ( uzorak II i III) Rezultati ispitivanjazatitni h sistema oznake

Ispitivana karakteristika Met. ispit.

SORS 1634 Zahtev sistem I sistem II sistem III Kompatibilnost osnovnog i pokrivnog premaza -

bez raslojavanja i povrinskih nedostataka zadovoljava zadovoljava zadovoljava

Izgled prevlake M 13 bez povrinskih nedostataka zadovoljava zadovoljava

Debljina prevlaka sistema m M 11 do 140 110-130 110-120 110-120 Prianjanje (''reetka'' 2 mm) M 14 GT 0 zadovoljava zadovoljava zadovolava

Elastinost, mm M 23 5 zadovolava zadovolava zadovolava

Savitljivost, mm M 24 6 zadovoljava zadovoljava zadovoljava

Otpornost na udar, br. kugl. M 20 4500 zadovoljava zadovoljava zadovoljava

Postojanost prema vodi M 25 bez promene izgleda, prianjanja posle 168 h zadovoljava zadovoljava zadovoljava

Postojanost prema meavini izooktan/benzen M 25

bez promene izgleda, prianjanja posle 24 h zadovoljava zadovoljava zadovoljava

Postojanost prema dizel gorivu M 25 bez promene izgleda, prianjanja posle 24 h zadovoljava zadovoljava zadovoljava

Postojanost prema motornom ulju M 25

bez promene izgleda, prianjanja posle 96 h,

t=100C zadovoljava zadovoljava zadovoljava

Postojanost prema dekontami-nantima, 2 % i 10 % Ca(OCl)2

M 25 bez promene izgleda, prianjanja posle 24 h zadovoljava zadovoljava zadovoljava

Postojanost prema neorganskim elektrolitima, (10 % CH3COOH, 2 % NaOH, 5 % NaCO3)

M 25 bez promene izgleda, prianjanja posle 24 h zadovoljava zadovoljava zadovoljava

Postojanost u vlanoj atmosf., RVv 100 %, t=(382) M 27

bez promene izgleda, prianjanja, posle 168 h zadovoljava zadovoljava zadovoljava

Postojanost u slanoj magli 5 % NaCl, t=(35) M 28

bez promene izgleda, prianjanja, posle 168 h zadovoljava zadovoljava zadovoljava

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Uzorci tri zatitna sistema: Sistem I- na bazi vodo-razredivih boja, Sistem II i Sistem III- na bazi kom-binovanih boja, ispitivani su i ocenjeni prema krite-rijumima, koji se primenjuju u osvajanju i razvoju novih kvaliteta zatitnih sistema za antikorozionu i maskirnu zatitu naoruanja i vojne opreme.

Rezultati ispiivanja zatitinih sistema prikazani su u tabeli 4.

Pri nanoenju vodorazredivih boja, postupkom ras-privanja, nisu uoene razlike u odnosu na boje sa or-ganskim rastvaraima. Rezultati izmerenih debljina pre-vlaka pokazuju da je ostvarena visoka nadgradnja filma, nanoenjem samo u jednom sloju. Vizuelno je konsta-tovana kompaktnost filma i homogena jednolina mat povrina, izmerene vrednosti sjaja do 5%.

Rezultati IC refleksija prevlaka vodorazredivih dvo-komponentnih poliuretanskih pokrivnih boja, maskirnih tonova br.1, br.6 i br.10 pokazuju da su ostvarene zadovoljavajue krive spektralnih refleksija, a time je zadovoljen osnovni uslov u pogledu maskirnosti. Ostva-rena je visoka pokrivna mo, ve sa debljinom prevlake od oko 30 m, to poveava ekonominost i sniava cenu kotanja materijala. Vrednosti, koje su dobijene merenjem mehanikih osobina prevlaka ispitivanih Vo-dorazredivih dvokomponentnih poliuretanskih boja ne zaostaju za vrednostima mehanikih osobina prevlaka Dvokomponentnih poliuretanskih boja na bazi organskih rastvaraa, iako je suenje i otvrdnjavanje i kod jednih i kod drugih na sobnoj temperaturi, a ne na povienoj, to ima prednosti u utedi energije. Rezultati pokazuju da su prevlake vodorazredivih boja postojane na uticaj tenih goriva, mineralnog ulja, vode, poviene temperature i svetlosti uz zadravanje boje i sjaja.

Na probnim uzorcima sa zatitnim sistemima: Sis-tem I- na bazi vodorazredivih boja i kombinovanim Sis-temima II i III-na bazi vodorazredivih i boja sa organ-skim rastvaraima, ostvarena je dobra kompatibilnost izmeu osnovne i pokrivne prevlake. Ova ispitivanja su potvrdila mogunost primene Vodorazredivih dvokom-ponentnih poliuretanskih pokrivnih maskirnih boja i preko postojee antikorozione zatite sa bojama na bazi organskih rastvaraa. Kod merenja debljina prevlaka Sistema I, II i III, konstatovane su ujednaene vrednosti, to ukazuje da se pri primeni, u reolokom pogledu, vodorazredive boje i boje na bazi organskih rastvaraa podjednako ponaaju.

Rezultati uporednih ispitivanja zatitnih sistema, ukazuju da su u sistemima sa vodorazredivim bojama ostvarene dugotrajne performanse (adhezija, mehanika zatita i hemijska postojanost), neobhodne za primenu ovih sistema u tekim uslovima eksploatacije.

4. ZAKLJUAK Ispitivani uzorci Vodorazredivih dvokomponentnih

poliuretanskih pokrivnih maskirnih boja, zelena svetla-ton br.1, braon-ton br.6 i crnaton br.10 (izraeni u laboratorijskim uslovima), zadovoljili su zahteve kva-

liteta pokrivne boje po SORS 1564/03 i SORS 8655/11, namenjene za antikorozionu i maskirnu zatitu naoru-anja i vojne opreme.

Rezultati ispitivanja probnih uzoraka tri tipa zatit-nih sistema, na bazi uzoraka ispitivanih vodorazredivih boja, pokazuju da ispitivani sistemi poseduju zado-voljavajui nivo kvaliteta fiziko-mehanikih karakte-ristika, hemijske postojanosti i zatitne sposobnosti u primenjenim uslovima ispitivanja. Rezultati dobijeni kod probnih uzoraka, kombinovanih zatitnih sistema ukazuju na dobru kompatibilnost ispitivanih vodo-razredivih maskirnih boja i boja na bazi organskih ras-tvaraa, to ukazuje na mogunost njihove ire primene u proivodnji i odravanju naoruanja i vojne opreme.

Dobijeni rezultati bili bi polazna osnova za potvdu reproduktivnosti i standardnosti kvaliteta Vodoraz-redivih dvokomponentnih poliuretanskih pokrivnih mas-kirnih boja u industrijskoj proizvodnji za realne uslove primene na sredstvima naoruanja i vojne opreme.

LITERATURA [1] S. Caki, .Lanjevac, M.Rajkovi, Lj.Rakovi, J.

Stamenkovi: Reticulation of queous polyuretane systems, Zatita materijala, 52 (2011), 1, 43-49.

[2] V.Alar, I.Stojanovi, I.Mihali: Zatita ugljeninog elika vodorazredivim premazima, Zatita materijala, 52 (2011), 3, 201-207.

[3] I. Sojanovi, V. Alar, I. Juraga, Analiza zatitnih svojstava premaza na vodenoj bazi na etalnim podlogama, Zatita materijala, 53 (2012), 3, 195-201.

[4] M. Jai, Uporedna svojstva uretan-alkidnih i vodo-razredivih premaza za povrinsku obradu drveta u eksterijeru, Zatita materijala, 53 (2012), 1, 45-51.

[5] E.Almeide, S.Dulcinea, J.Uruchurtu: Corrosion per-formance of waterborne coatings for structural steel, Progres in Organic coatinngs, 37 (1999), 131-140.

[6] H.Kittel,Lehrbuch der Lacke und Beschichtungen Verlag W-A Colomb, Berlin Oberschwandorf, (1973), 534-556.

[7] Lj.Rakovi, Osnovi polimernog inenjrstva, Tehniki fakultet u Leskovcu, Univerzitet Ni,(1995),72.

[8] C.A,Hawkins, A.C.Sheppard, T.G. Wood, Recent advance in aqueous Two-Component sistems for hea-vydaty metal protection, Progres in Organic Coating, 32 (1976), 253-261.

[9] W.Kubitza, H.Gruber, J.Probs, USA Patent 5075370, (1970).

[10] S.Caki, Dokorska disertacija, Selektivna kataliza izocijhanat-hidroksilne reakcije Mn(III) Kompleksom sa meovitim ligandima u dvokomponentnim poliure-tanskim premazima, Tehnoloki fakultet u Leskovcu, Univerzitet Ni, 2004.

[11] Bayer Material Science AG, Coatings, Adhe-sives&Speialties, Leverkussen, Deuschland.

[12] D.Fiori, Two-component water reducible polyuretane coatings, Progres in Organic Coatings, 32 (1997), 65-71

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[13] Grupa autora, Monografija, Korozija i zatita mate-rijala, In, drut. za koroziju Beograd. (2012),378 str.

[14] D.I.Fischer, Aqueous 2-Pack-PUR-Systems based on OH-funcional Dispersions and Polyisocyanates, Tech-nical seminar II BASF AG, Ludwigschafen, (1997).

[15] P.B.Jacobs, P.C.Yu, Two-Component Waterborne Poliuretane Coatings, Journal of Coatings, Tehnology, 65 (1993), 45.

[16] C.H.Hare, Protective Coatings, Fundamentalis of shemistry and Composition, Technology Publishing Co, Pittsburgh, PA,p.263.

[17] S.Milosavljevi, Strukturne instrumentalne metode, Hem. fakultet Bgd.(1994),49-132.

[18] Standard odbrane, Refleksija mask. mater. u UV, V i BIC podrujeEM spektra,SORS 7511/02

[19] Standard odbrane,Opti propisi za proveru maskirnih karakteristika SORS 8655/11

[20] Ferro Corporation, Performance Pigments and Color, Cleveland, Ohio USA.

[21] BASF, Peformance Chemicals for Coatings, Plastics and Speciaties, Ludwigschafen, Germany.

[22] Cognis, Technical Data Sheets, Additives Germany.

ABSTRACT

WATERBORN TWO-PACK URETHANE COATINGS FOR PROTECTION OF WEAPON AND MILITARY EQUIPMENT Waterborn two-pack urethane coatings represent innovative technology in paints and coatings industry. Since the water is replacing volatile organic solvents in production and application processes, their ecological acceptance is unquestionable. It is well known that this technology is approved as superior for corrosion protection in energetic and industrial plants as well as in automotive and aircraft industries of developed countries. With such idea, the possibility of application of this technology for protection of military equipment has been investigated. In work presented in this paper, the new component formulation was designed and technology parameters were modified in manner to confirme the predefined requests for anticorrosive and camouflage properties of waterborne two-pack urethane coatings. Coatings developed according to approved scheme of camouflage painting (light green, brown and black) were submitted to laboratory testing according to military standards SORS 1564/03 and SORS 8655/11. Besides the standardized testing of single coatings, the protective properties of complex, hybrid coatings systems, composed with both, waterborne and conventional paints, were tested. Results implicate that waterborne two-pack urethane finish coatings satisfy the quality requests for finish coatings for anticorrosion and camouflage protection of military equipment. Results of protective paint systems composed of waterborne coatings show their satisfactory level of physical-mechanical properties, chemical stability and protective ability. Test results of hybrid systems, combined of, waterborne and conventional paints approve their good compatibility, Key words: waterborn two-pack urethane, camouflage pigments, spectral reflectance refleksija Paper received: 10.11.2012. Scientific paper

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DRITAN PRIFTI1, Scientific paper MARJOLA PRIFTI2 UDC:666.5:553.6

Tuffs and kaolins areas evaluation for use as pozzolanic materials Various tuffs and kaolins were evaluated for use in cement as pozzolanic additives. These materials were analyzed for chemical and mineralogical composition, reactive Si content and also were used for the production and testing of blended cements. The JOMEN tuffs, that seem to exist in significant reserves, already appear to be problematic due to their low reactive SiO2 content. The kaolin samples that were studied included those from the KORTHPULA, VIG and DEJAI areas. The search for suitable tuffs materials is now focused on the JOMEN area. The KORTHPULA kaolin had a high reactive silica content and could be considered as a potential pozzolanic additive. About the kaolins, the above conclusions were based on spot surface samples; the suitability of the kaolins as pozzolanic additives will need to be verified based on samples of core drilling that is planned for the near future. Key words: tuff, kaolin, pozzolanic additives, cement.

INTRODUCTION Pozzolanic materials are natural substances of si-

liceous or silica-aluminous composition or a combi-nation thereof. Pozzolanic materials do not harden in themselves when mixed with water but, when finely ground and in the presence of water they react at normal ambient temperature with dissolved calcium hydroxide ( Ca(OH)2) to form strength-developing calcium silicate and calcium aluminate compounds [5-7]. Pozzolanic materials like Kaolin and Tuffs consist essentially of reactive silicon dioxide ( SiO2) and aluminium oxide ( Al2O3). The remainder con-tains of iron oxide ( Fe2O3) and other oxides. Various tuffs and kaolins were evaluated for use in the cement as pozzolanic additives [2-4]. Evaluation of these materials included:

a) Chemical and mineralogical analyses. b) Determination of reactive SiO2 content. c) Production and testing of blended cements

(Blaine, H2O%, strength). Ignition loss is usually determined by tests in a

laboratory furnace. [1,8].

Tuffs: Almost all of the examined tuff areas were

rejected due to either quality of the material and/or potential local and mining conditions/problems (including low reserves availability). The JOMEN tuffs, that seem to exist in significant reserves, already appear to be problematic due to their low reactive SiO2 content [8]. However, if there are formations in the vicinity different than those already examined, further testing is recommended.

Author's address: 1Cement Factory Antea Cement Sh.A ,Boka e Kuqe, Burizan, Kruj, Albania, 2Municipality of Tirana, Albania.

Paper received: 15.10.2012.

The search for suitable pozzolanic materials for the BEZHAN and PUKE areas should continue only after the investigation of geological and local mining conditions is completed

Kaolins: Minerals of the kaolin group differ in content of

SiO2 as well as by the crystallographic structure and optical properties [ 8 ]. The kaolin samples that were studied included those from the KORTHPULA, VIG and DEJAI areas that were closer to the plant. The KORTHPULA kaolin had a high reactive silica content that satisfies the EN 197-1.

However, since the laboratory cement produced with that had a high water demand due to the presence of clays, further testing is needed when used for concrete manufacturing. The cement produced with the VIG kaolin had a satisfactory strength and a low water demand. Hence, if the reactive silica of the VIG kaolin content exceeds that required by the EN 197-1 it could be considered as a potential pozzolana [6,9,11].

MATERIALS AND METHODS

Materials used in this study were selected tuffs and kaolins samples from different areas closer and far from the plant. The methods used for analyzing all these samples are X-Ray fluorescence and Wet Chemical Analysis [8]. Samples were prepared for measurement in the X-Ray Fluorescence apparatus in the form of tablets as follows. Upon arrival at the laboratory samples initially is made the determination of moisture and then pass on crusher to reduce the fines below 5 mm. Then we mix the sample well and weight respectively 12 g and 6 g of the same material and put in the Polab-APM apparatus for sample preparation in the form of tablets. After preparing the

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samples in the form of tablets we clean them with air and then introduce to the XRF measurement apparatus and make measurements of each material according to the respective calibration curves. Once the measurement is finished we take the results for each element and based on these results we judge on the quality of each material. For the wet chemical analysis we have followed the European Standard EN 196-2 [8].

RESULTS AND DISCUSSION

I. Tuffs Tuff samples from the areas listed in the

following table along with their XRF chemical analyses, were evaluated for use in cement as pozzolanic additives. The reactive silica content of selected tuff samples determined according to EN 197-1 is also reported [1,6]. The chemical analysis and the reactive silica content are presented in table 1.

Table 1 - Tuffs chemical analysis and the reactive silica content

Location Nr SiO2 Al2O3 Fe2O3 CaO MgO K2O Na2O SO3 LOI SUM SiO2 react

1 74.34 12.07 1.21 0.62 0.19 4.39 3.00 0.00 4.34 100.14 2 73.46 11.82 2.04 0.35 1.40 7.08 0.00 0.00 2.99 99.14 3 67.39 12.35 2.23 2.18 1.53 7.52 0.00 0.00 4.04 97.24 7.804 69.92 13.64 2.54 0.30 1.83 8.12 0.00 0.00 3.86 100.22 5 72.55 12.26 2.16 0.46 2.17 6.76 0.00 0.00 3.42 99.79 6 70.44 12.95 2.42 0.42 2.27 7.50 0.00 0.00 3.70 99.70 7 56.81 18.58 3.88 1.74 0.77 5.55 3.37 0.00 7.66 98.37

GRAMSH 8 54.36 20.81 4.78 1.26 1.06 4.11 2.34 0.01 10.02 98.73 avg 67.41 14.31 2.66 0.92 1.40 6.38 1.09 0.00 5.00 99.17

9 62.22 15.49 4.11 3.09 2.52 1.46 2.10 0.00 7.92 98.90 10 64.26 13.59 3.34 1.96 3.11 1.56 1.23 0.00 9.49 98.55 47.4511 63.14 13.34 3.73 1.92 3.64 1.41 0.93 0.00 9.28 97.39 12 62.16 13.98 3.82 2.59 3.55 1.43 0.86 0.00 9.56 97.94 13 70.03 12.36 2.13 1.60 1.51 2.42 1.11 0.00 9.11 100.27 14 66.03 12.88 2.64 1.96 1.97 1.94 0.96 0.00 11.14 99.53 15 66.95 13.07 2.53 1.68 1.68 2.10 1.90 0.00 8.97 98.87 16 66.78 12.97 2.35 2.30 1.30 2.20 1.78 0.02 8.59 98.28 17 68.58 12.82 2.33 1.62 1.19 2.23 1.97 0.00 7.99 98.75

VRAP 18 67.57 13.62 2.59 2.15 1.06 2.04 2.46 0.00 7.27 98.76 avg 65.77 13.41 2.96 2.09 2.15 1.88 1.53 0.00 8.93 98.72

19 40,08 7,94 3,85 16,50 7,53 2,57 0,00 0,13 22,16 100,76

20 57,70 15,36 5,17 1,16 5,98 5,06 0,00 0,03 7,86 98,33 21 55,12 14,16 5,91 3,26 5,62 4,89 0,00 0,02 9,95 98,92 22 62,17 13,20 5,95 1,25 3,78 4,81 0,00 0,04 6,81 98,00 23 46,26 11,84 4,90 9,70 6,46 2,52 1,76 0,06 16,29 99,78 24 51,43 14,16 5,67 5,75 4,57 3,02 1,82 0,05 12,17 98,64 4,6025 53,81 15,70 6,35 2,72 4,17 2,59 2,83 0,01 9,82 98,00 26 53,84 12,39 4,84 5,94 5,92 4,81 0,00 0,01 12,11 99,85 27 57,84 6,92 3,07 13,20 2,46 1,85 0,00 0,01 14,70 100,05

JOMEN (GJIROKASTER)

28 36,36 6,25 2,05 26,32 1,98 1,87 0,00 0,00 26,2 101,05 avg 51,46 11,79 4,78 8,58 4,85 3,40 0,64 0,04 13,81 99,34

29 84,52 6,27 2,96 0,20 0,73 1,52 0,00 0,00 4,28 100,49

30 69,17 12,30 5,80 0,02 1,40 3,77 0,00 0,00 6,13 98,58 3,46

MUZINE (DELVINE) 31 86,52 5,06 239 0,11 0,53 1,33 0,00 0,00 3,87 99,81 avg 80,07 7,88 3,72 0,11 0,89 2,20 0,00 0,00 4,76 99,63

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32 91,99 3,18 1,52 0,31 0,50 0,72 0,00 0,07 1,96 100,24

33 71,60 14,49 2,50 0,14 1,54 3,68 0,00 0,00 5,.32 99,28 34 77,64 11,58 1,91 0,16 0,75 1,48 0,00 0,00 5,31 98,82 35 66,92 17,79 2,61 0,10 0,88 2,09 0,00 0,00 7,78 98,16 38,84 36 72,37 13,87 2,79 0,26 1,05 1,74 0,00 0,00 7,01 99,08 37 91,79 3,41 1,54 0,17 0,42 0,75 0,00 0,00 1,79 99,86 38 63,46 2,94 1,38 17,13 0,83 0,82 0,00 0,00 14,59 101,14 39 85,09 5,63 2,34 0,40 0,99 1,67 0,00 0,00 2,75 98,88

DOMNIE SHKODER

40 73,53 4,32 2,00 9,82 0,80 1,03 0,00 0,24 7,60 99,33

avg 77,16 8,58 2,06 3,16 0,86 1,55 0,00 0,03 6,01 99,42 41 62,76 10,36 5,65 5,06 3,37 1,53 0,60 0,00 8,70 98,02 16,68 42 71,39 8,30 4,15 3,11 2,33 130 0,54 0,00 7,75 98,86

DUMREA (BELSH) 43 56,45 11,98 6,50 5,17 4,49 1,80 0,43 0,00 11,05 99,85 avg 52,75 8,90 3,89 14,24 2,51 1,49 0,47 0,03 15,17 98,91

44 49,45 10,16 5,32 13,37 3,60 1,84 0,56 0,00 15,21 99,51 13,07 45 44,13 10,63 4,53 16,79 3,26 1,76 0,47 0,10 18,35 100,02 46 50,33 5,66 2,01 20,64 1,30 0,84 0,00 0,10 20,67 101,55 47 41,57 6,22 2,25 27,17 1,58 1,02 0,00 0,08 20,18 100,07 48 40,52 5,90 1,97 27,69 1,36 0,93 0,00 0,02 20,95 99,34 49 58,11 10r88 2,64 9,20 1,35 2,36 1,60 0,00 13,70 99,85 50 29,30 5,84 1,94 35,01 1,54 0,96 0,00 0,09 26,05 100,73 51 70,95 12,82 1,94 1,45 0,80 3,19 2,14 0,00 6,79 100,09 52 38,06 8,91 4,86 23,56 3,96 1,72 3,00 0,03 15,44 99,54 53 29,33 5,83 1,94 35,13 1,54 0,95 0,00 0,09 26,02 100,83 54 58,34 11,51 2,24 6,31 1,20 2,57 1,66 0,03 16,68 100,54 55 45,91 19,02 4,06 10,38 2,85 039 0,00 0,03 17,85 100,49 56 22,78 6,29 1,88 38,67 1,41 1,08 0,00 0,05 28,05 100,21 57 63,37 11,31 2,44 6,75 1,22 2,78 2,20 0,00 10,98 101,05 58 59,98 11,87 2,82 7,47 1,62 2,35 1,41 0,01 11,18 98,72

CAKRAN

59 69,12 12,41 1,67 1,49 0,62 3,16 2,09 0,00 7,66 98,21 avg 48,20 9,70 2,78 17,57 1,83 1,74 0,95 0,04 17,24 100,05

60 64,59 9,88 4,42 5,40 236 1,39 0,87 0,01 8,91 97,84 61 39,69 10,07 3,98 18,57 3,22 1,05 0,00 0,23 18,10 94,91 62 42,12 9,79 6,45 0,85 3,10 1,31 0,68 0,11 11,74 76,16 63 54,27 12,77 6,46 3,51 4,04 1,52 0,00 0,29 14,94 97,80 64 54,12 12,10 12,21 1,17 3,46 1,58 0,00 0,16 12,43 97,23

BEZHAN

65 55,64 13,27 6,78 2,20 3,94 1,64 1,79 037 12,89 98,51 avg 51,74 11,31 6,72 5,28 335 1,42 0,56 0,20 13,17 80,35

66 19,54 5,07 1,90 42,24 3,25 0,25 0,00 0,02 36,74 109,01 67 15,07 4,22 1,70 45,08 4,97 0,04 0,00 0,04 40,85 111,97 68 44,47 7,88 7,25 10,34 15,72 0,00 2,09 0,01 11,79 99,55 69 16,75 2,82 0,99 48,62 1,87 0,00 0,00 0,01 40,25 111,31 70 3,91 1,16 0,50 46,36 0,37 0,03 0,08 0,04 36,85 89,30 71 59,37 11,47 8,67 1,71 5,19 0,93 2,54 0,03 7,58 97,49 72 49,18 8,18 7,49 6,91 12,96 0,88 0,00 0,00 12,46 98,05

HELMES

73 22,86 3,05 2,92 29,78 3,25 0,17 0,06 0,00 30,27 92,36 avg 28.89 5.48 3.92 28.87 5.94 0.29 0.59 0,0 I8 27.09 101.12

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Only two of the examined tuff samples, namely from the VRAP and DOMNIE areas, had a reactive silica content exceeding that required by the EN

197-1. Testing of a laboratory cement produced with the VRAP tuff showed a high late strength [6,9,10].

Table 2 - VRAP tuff laboratory cement analysis

Nr %VRAP Blaine H2O% In. Setting Time Fin. Setting Time 1-d 2-d 7-d 28-d

1 0 3330 23.4 100 150 10.2 18.1 29.7 44.72 20 5000 30.6 180 230 13.5 21.8 36.0 49.3 Both of the above together with the SHKODER

area tuffs have been rejected as potential quarries due to inadequate reserves and non-favorable mining conditions/problems. The GRAMSH, JOMEN/GJI-ROKASTER, MUZINE, DUMREA and CACRAN tuffs had a low reactive SiO2 and could not be used as pozzolanic additives according to EN 197-1 [6]. Preliminary examination of the HELMES samples indicated that the quality of the raw materials from this area was rather low, since most of the samples had low a SiO2 and a high carbonate content. Even though the reactive silica content in one of the JOMEN tuff samples came up low, the present

investigation should focus on this area due to its considerable reserves and favorable mining conditions.

II. Kaolins Kaolins from the Korthpula (react. SiO2=41.6),

Vig and Kaster areas were also examined as alternative pozzolanic sources. The strength of the respective laboratory cements was acceptable but the water demand of the cement produced with the Korthpula kaolin was high and that could cause problems in concrete [6 - 10].

Table 3 - KAOLINS laboratory cement analysis

Nr Location Blaine H2O% In. Setting Time Fin. Setting Time 1-d 2-d 7-d 28-d

1 - 3330 23.4 100 150 13.5 21.8 36.0 49.32 Korthpula 4430 33.4 140 200 10.9 15.8 26.5 35.83 Vig 4580 26.8 180 240 9.0 15.4 27.1 36.24 Kaster 4540 26.8 160 210 10.8 15.6 28.5 39.3

CONCLUSIONS

Tuffs: Almost all of the examined tuffs areas were rejected due to either quality of the material and/or potential mining conditions/problems and low reserves potential. The search for suitable pozzolanic materials is now focused on the JOMEN area due to its considerable reserves and favorable mining conditions despite its low reactive silica and additional tests and sampling is necessary. Further, it is recommended to clarify the potential of the areas of BEZHAN and PUKE.

Kaolins: The KORTHPULA kaolin had a high reactive silica content and could be considered as a potential pozzolana. However, the water demand of the respective blended cement was high and that could be a drawback when used for concrete manufacturing. The lab cement produced with the VIG kaolin had a low water demand and a satisfactory strength. Hence, the VIG kaolin could be

used as pozzolana in case its reactive SiO2 comes out higher than the min. limit of the EN 197-1. The above conclusions were based on spot surface samples; the suitability of the kaolins as pozzolanic additives will need to be verified based on samples of core drilling that is planned for the near future.

REFERENCES

[1] Kurt E.Peray New York, N.Y 1979. Cement Manufacturers Handbook. pp. 3-5.

[2] S.Muralidharan,A.K.Parande,V.Saraswathy,K.Kumar,N.Palaniswamy, Efect of silica fume on the corrosion performance of reinforcements in concrete, Zatita materijala, 49, 4 (2008) 3-9.

[3] A. Pecani imento, Tirane 2010, pp.25-53

[4] A. Pecani -- imento dhe teknologjia e prodhimit te saj, Qershor 1990, pp. 28-37

D. PRIFTI, M. PRIFTI TUFFS AND KAOLINS AREAS EVALUATION FOR USE AS POZZOLANIC ...

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[5] J. Marku, The incorporation of fly ash as supple-mentary cementing material in concrete, Zatita materijala, 51, 3 (2010) 159-165.

[6] EN 197-1, June 2000 Cement Part 1: Composition, Specifications and Conformity Criteria for Common Cements. pp. 9-16

[7] J. Marku, K. Vaso, Optimization of copper slag waste content in blended cement production, Zatita materijala, 51, 2 (2010) 77-81.

[8] EN 196.02 Methods of testing cement- Part 2: Chemical analysis of cement, pp. 2441

[9] EN 196.03 Methods of testing cement- Part 3: De-termination of setting times and soundness, pp 6-22

[10] EN 196-6 Methods of testing cement: Determina-tion of fineness, 11-19

[11] Walter H. Duda, Cement Data Book, Volume 1: International Process Engineering in the Cement Industry, 317

IZVOD

TUFOVI I KAOLINI IZ RAZLIITIH OBLASTI ZA UPOTREBU KAO POCOLANSKI MATERIJALI Razni tufovi i kaolini bili su razmatrani za upotrebu u cementnoj industriji kao pocolanski aditivi. Ovi materijali su analizirani na hemijski i mineraloki sastav, sadraj reaktivnog Si, a takoe, su korieni za proizvodnju i testiranje raznih meavina cementa. Tufovi iz JOMENSKE oblasti, koji postoje u znaajnim rezervama, problematini su zbog niskog sadraja reaktivnog SiO2. Uzorci kaolina, koji su prouavani, uzeti su iz oblasti KORTHPULA, VIG i DEJAI. Potraga za odgovarajuim tuf- materijalima je sada fokusirana na JOMEN oblasti. Kaolin iz KORTHPULA ima visok sadraj reaktivnog Si i moe se smatrati kao potencijalni pocolanski aditiv. Navedeni zakljuci o podobnosti kaolina, kao pocolanskog aditiva iz ovih oblasti, na osnovu uzoraka sa povrine zemljita, morae da se verifikuju na osnovu uzoraka uzetih sa veih dubina, koji su planirani za blisku budunost. Kljune rei: tuf, kaolin, pocolanski aditiv, cement. Rad primljen: 15.10.2012. Originalni nani rad

M. N. MUEK, J. ZELI THE EFFECT OF ALKALI ACTIVATOR ON THE DEVELOPMENT OF...

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MARIO NIKOLA MUEK* Scientific paper JELICA ZELI UDC:628.44:504.3.054

The effect of alkali activator on the development of mechanical properties of fly ash based geopolymer

The alkali activation of fly ash is a physical-chemical process of mixing fly ash with alkaline activators in order to produce materials with high mechanical properties - geopolymers. Three types of geopolymers were synthesized. The same fly ash was used in all the samples, but the alkali activator has been changed: water glass (sample A), sodium hydroxide (sample B) and combination of water glass and sodium hydroxide (sample C). After preparation, all samples were thermally cured in the laboratory oven at the temperature of 85 C for 24 hours. Mechanical strengths were measured after 3, 7 and 28 days, and during that period of 28 days all the samples were hermetically sealed and stored at room temperature. The results obtained indicate that, geopolymer, synthesized by mixing fly ash with the combination of water glass and sodium hydroxide as alkaline activator, developed the highest compressive strengths during all period of interest, about 21.23 MPa at the age of 3 days and 21.28 MPa at the age of 7 days, which then reached 22.52 MPa after 28 days of curing at room temperature. Key words: geopolymers, alkali activator, compressive strengths

INTRODUCTION The alkali activation of fly ash (FA) is a physical-

chemical process of mixing glassy component of FA with certain alkaline activators. The mixture is cured under certain temperature to make solid materials. The alkaline solution most often used is a sodium silicate solution, although potassium silicate solutions and other alkaline solutions have also been used (Palomo et al., 1999). The final structure and physical properties of FA based geopolymers depends heavily on the chemical composition of the starting material, nature and concentration of alkali activator. Palomo et al. also found that different fly ashes activated with NaOH cured at 85 C for 24 h produced material with compressive strength between 35-40 MPa, and about 90 MPa if some water glass was added to the NaOH solution (SiO2/Na2O = 1.23).

MATERIALS AND METHODS

Materials A type F (as defined in ASTM C618) fly ash from

the Croatian power plant Plomin 2 (Plomin) was used in the present study. The chemical analysis of fly ash is given elsewhere (Muek et al., 2012). Technical - grade sodium silicate solution (a type S, water glass, 3Na2O 3SiO2) and sodium hydroxide, p. a., (Kemika) were used as alkaline activator.

Author's address: University of Split, Faculty of Ch-emistry and Technology, Teslina 10/V, 21000 Split, *muky@ktf-split.hr

Paper received: 27.11.2012.

Instrumentation The FTIR spectra of geopolymers were made on

KBr pastille on a Perkin Elmer Spectrum One in the range from 4000 to 450 cm -1.

Toni Technik hydraulic press modular system was used for the compressive strength measurements.

Synthesis of geopolymers

Three types of geopolymers where synthesized. Certain amounts of fly ash were mixed with alkali activators. The same fly ash was used in all the samples, but the alkali activator has been changed: water glass (sample A), 16 M NaOH solution (sample B) and 16 M NaOH solution and sodium silicate solution (sample C). In samples B and C solution/ash ratio was 0.40. To provide good workability extra water was added. After adding all the components, geopolymer paste started to form. The mixture was mixed for 10-15 minutes and poured into poly-propilene cylindrical containers along with constant stirring. Containers were hermetically sealed to prevent moisture evaporation. The fresh pastes were heat cured at 85 C for 24 h in an oven. After 24 h, the geopolymer samples were removed from the oven and kept at room temperature for 28 days.

In the sample A, the fly ash was activated with a water glass solution to prepare paste specimens. In order to provide good workability, the solution/ash ratio was 0.72. Total water in system was only water from sodium silicate which itself contained w = 67.75 % of water. No extra water was added. After mixing,

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the fresh pastes were cast immediately into metallic moulds (4 x 4 x 16 cm) that were later kept in a hermetically sealed tin mould to prevent moisture evaporation. They were exposed to heat curing in a laboratory convection oven at 85 C for 24 h. After removing from the oven, the alkali-activated fly ash (AAFA) specimens were covered with plastic to protect the samples from excessive water loss, and kept at room temperature for 28 days, respectively.

The compressive strength of all paste specimens prepared, was determined after 3, 7 and 28 days in accordance to the Croatian standard HRN EN 196-1:2005.

RESULTS AND DISCUSSION

FTIR analysis of geopolymer samples The FTIR spectra for geopolymer system (sample

C), as well as the spectrum for the original FA, are plotted in Fig. 1. These spectra reveal the differences between the original FA and geopolymeric materials formed. The main broad band at 1087.07 cm-1 in the original FA, corresponding to asymmetric stretching vibrations of SiOSi and AlOSi (Vempati et al., 1994; Mollah et al., 1994) becomes sharper and shifts towards lower frequencies ( ~ 1023 cm-1) as a result of the formation of new reaction products associated with ongoing alkali activation.

3 days

7 days 28 days

Wavenumber / cm-14000,0 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 600 450,0

%T

3456,05

1648,29

1023,11

797,79

563,03 463,17

1448,58694,15

Fly ash

Figure 1 - FTIR spectra for the original FA and sample C after 3, 7 and 28 days of curing

in the air at room temperature.

The bands located at ~ 795 cm-1 and ~ 463 cm-1 are ascribed to bending vibrations of SiOSi and OSiO bonds implying to the presence of quartz which is hardly affected by alkaline activation of FA (Bakharev, 2005; Lee & van Deventer, 2002). The bands located at ~ 694 cm-1 and ~ 563 cm-1 are specifying the presence of mullite.

In all geopolymeric materials, new bands appeared in the regions of ~1650 cm-1 and ~ 3456 cm-1 that were attributed to bending vibrations (HOH) and stretching vibrations (OH, HOH). Water is needful for process of geopolymerisation as it implicates the destruction of solid particles and the hydrolysis of dissolved Al3+ and Si4+ ions. Bond at ~ 1450 cm-1 assigned to the stretching vibrations of O

CO bond occurred in all AAFA samples implying to the presence of the sodium bicarbonate.

This observation of changes in the FTIR spectra of the AAFA materials indicate that the geo-polymerisation reaction occurred leading to the formation of the main reaction product, an amorphous aluminosilicate gel in all samples examined.

Effect of alkali activator on development of mechanical properties

The compressive strength, of all geopolymer pastes formed, was determined after 3, 7 and 28 days of curing in the air at room temperature. The values of compressive strengths measurements increased over the whole period of interest, as it can be seen from the Fig. 2. The sample C showed maximum

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compressive strength during all period of interest, about 21.23 MPa at the age of 3 days and 21.28 MPa at the age of 7 days, which then reached 22.52 MPa after 28 days of curing at room temperature.

The increase in the 28-days compressive strength measurements was also found in the samples A and B, although, their values are significantly lower than those obtained for sample C.

Figure 2 - Development of the compressive strengths for all the samples during the period of 28 days.

The mixture of sodium hydroxide with sodium

silicate solution was found to affect significantly the compressive strength of geopolymers. Similar effect was found by Panias et al. (2007). According to the authors, sodium hydroxide acts on the dissolution process, as well as on the bonding of the solid particles in the final structure. Sodium silicate solution controls the soluble silicate concentration and the predominant silicate species in the geo-polymeric system, improving the mechanical strength of the produced materials.

CONCLUSIONS

The geopolymerisation reaction occurs in all alkali activated samples prepared. The usage of alkali activator reflects on the values of compressive strength measured during all period of interest.

The sample C showed maximum compressive strength, 22.52 MPa, after 28 days of curing at room temperature. It is evident that the mixture of sodium hydroxide with water glass as alkaline activator is needful to gain geopolymeric materials with higher compressive strength that can find their applications as construction materials.

Acknowledgments The present study was financially supported by

the Ministry of Science, Education and Sports in the Republic of Croatia under the Project 011-1252970-2252.

REFERENCES [1] Bakharev T. (2005): Geopolymeric materials

prepared using class F fly ash and elevated temperature curing, Cem. Concr. Res. 35 (6) 1224-1232.

[2] Lee W.K.W., van Deventer J.S.J. (2002): Structural reorganization of class F Fly Ash in alkaline silicate solutions, Colloids Surf. A 211 (1) 49-66.

[3] Mollah M.Y.A., Hess T.R., Cocke D.L. (1994): Surface and bulk studies of leached and unleached fly ash using XPS, EDS, SEM and FT-IR techniques, Cem. Concr. Res. 24 (1) 109-118.

[4] Muek M.N., Zeli J., Jozi D. (2012): Microstructural characteristics of geopolymers based on alkali-activated fly ash, Chem. Biochem. Eng. Q. 26 (2) 89-95.

[5] Palomo A., Grutzeck M.W., Blanco M.T. (1999): Alkali-activated fly ash, A cement for the future, Cem. Concr. Res. 29 (8) 1323-1329.

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[6] Panias D., Giannopoulou I.P., Perraki T. (2007): Effect of synthesis parameters on the mechanical properties of fly ash-based geopolymers, Colloids Surf. A 301 246254.

[7] Vempati R.K., Rao A., Hess T.R., Cocke D.L., Lauer H.V. (1994): Fraction and characterisation of Texas lignite Class F fly ash by XRD, TGA, FTIR and SFM, Cem. Concr. Res. 24 (6) 1153-1164.

IZVOD

UTICAJ ALKALNOG AKTIVATORA NA RAZVOJ MEHANIKIH KARAKTERISTIKA LETEEG PEPELA NA GEOPOLIMER Alkalna aktivacija leteeg pepela predstavlja fizikalno-kemijski proces mijeanja leteeg pepela sa alkalnim aktivatorima kako bi se proizveo materijal visokih mehanikih vrstoa - geopolimer. Sintetizirane su tri vrste geopolimera. Kod svih sinteza koristio se isti letei pepeo, dok se mijenjala samo vrsta alkalnog aktivatora: vodeno staklo (uzorak A), natrijev hidroksid (uzorak B) i kombinacija vodenog stakla i natrijevog hidroksida (uzorak C). Nakon sinteze, svi uzorci su podvrgnuti toplinskoj obradi u trajanju od 24 sata u laboratorijskoj pei na temperaturi od 85 C. Mehanike vrstoe su testirane nakon 3, 7 i 28 dana njegovanja. U tom periodu od 28 dana svi uzorci su hermetiki njegovani pri sobnoj temperaturi. Geopolimer sintetiziran mijeanjem leteeg pepela sa kombinacijom vodenog stakla i natrijevog hidroksida, kao alkalnog aktivatora, je razvio najvie mehanike vrstoe tijekom cijelog perioda ispitivanja: 21.23. MPa nakon 3 dana, 21.28 MPa nakon 7 dana i, konano, 22.52 MPa nakon 28 dana njegovanja pri sobnoj temperaturi. Kljune rijei: geopolimeri, alkalni aktivator, mehanike vrstoe Rad primljen: 27.11.2012. Originalni nauni rad

I. FIERASCU et al NATURAL EXTRACTS FOR SOLVING THE ISSUE OF .

ZATITA MATERIJALA 54 (2013) broj 1 26

IRINA FIERASCU1, ROMULUS DIMA2, Scientific paper RADU CLAUDIU FIERASCU3 UDC:620.197.2 :729

Natural extracts for solving the issue of biodeterioration of the artefacts The biodeterioration of the artefacts is a worldwide problem. Each cultures cultural heritage is practically an act of identity; the way it is preserved is an important indicator of the degree of civilization of that community. All the artefacts (organic, inorganic or mixed) are exposed to various environmental conditions (temperature, pH, humidity, aerobic or anaerobic conditions, etc) that can lead to mould growth. The growth of microorganisms on the artefacts deteriorates theme in various ways (crusts, patina, staining, discoloration, mechanical damage, fouling, soiling, etc.) and leads to tremendous economic and aesthetic loss. The fungal species found in the environment that contaminates objects (Aspergillus, Penicillium, Cladosporium, Aureobasidium, Mucor, etc.) are commonly referred to as environmental mould. The aim of this investigation is the v