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Industrial Crops and Products 31 (2010) 219–224

Contents lists available at ScienceDirect

Industrial Crops and Products

journa l homepage: www.e lsev ier .com/ locate / indcrop

cratch resistance of cellulosic, synthetic, polyurethane, waterborne, andcid-hardening varnishes used on woods

akan Keskina, Musa Atarb, Süleyman Korkutc,∗, Ahmet Tekina

Gazi University, Industrial Arts Education Faculty, Department of Industrial Technology, 06830 Gölbası, Ankara, TurkeyGazi University, Faculty of Technical Education, Department of Furniture and Decoration, 06500 Besevler, Ankara, TurkeyDüzce University, Faculty of Forestry, Department of Forest Industrial Engineering, Beciyorukler Campus, 81620 Düzce, Turkey

r t i c l e i n f o

rticle history:eceived 28 July 2009eceived in revised form 13 October 2009ccepted 17 October 2009

eywords:cratch resistanceoatings

a b s t r a c t

This study was conducted to determine the scratch resistance of cellulosic (C), synthetic (Sn),polyurethane (Pu), waterborne (Wb), and acid-hardening (Ah) varnishes used on wood materials. Testsamples were prepared from Scotch pine, oriental beech, European oak, black poplar, basswood, andblack walnut woods that met ASTM D 358 requirements and were coated according to ASTM D 3023standards with C, Sn, Pu, Wb, and Ah varnishes. The scratch resistance of the samples after the varnishingprocess was determined based on TS 4757. The greatest scratch resistance was obtained for walnut basedon the wood species, whereas the least scratch resistance was obtained for poplar. As for varnish type,the greatest scratch resistance was obtained for synthetic varnish, whereas cellulosoic varnish had the

arnishesayer thickness

ood materials

least scratch resistance. In addition, the greatest scratch resistance was obtained for three layers based onthe layer thickness, whereas the least scratch resistance was calculated for one layer. Based on the woodspecies, varnish type, and layer type, the greatest scratch resistance was found for oak + Pu + three layers,and the least scratch resistance was calculated for basswood + Wb + one layer. Furthermore, differenceswere observed according to varnish type and layer thickness; varnish types were efficient for scratchresistance to the first degree and layer thickness to the second degree. The results showed that a varnish

ers o

application with three lay

. Introduction

Recently, a strong and increasing demand for scratch resistancen coating materials that can be applied to various substrates suchs wood, plastic, metal and glass products has emerged. Woodaterial, which is raw furniture material, is affected by chemical,

hysical, biological, and mechanical factors. The mechanical factorsre friction, scratch, and impact (Berkel, 1972). The protection andifetime durability of the wood material are important with regardo economy and technique (Higley and Kink, 1990).

In a study in which varnishes were applied on three differ-nt softwood species and one hardwood species for comparison,cratch resistance and Janka hardness tests (TS 2479, 1976) wereonducted on 10 specimens each of varnished and non-varnishedarquet materials. The application of varnish had an effect on the

arquet scratch resistance, whereas it had no effect on hardnessGözeneli, 1989).

In another study, two different fine-glass granulometries200 and 325 mesh) were used as fillers for a varnish based

∗ Corresponding author. Tel.: +90 380 5421137; fax: +90 380 5421136.E-mail address: suleymankorkut@hotmail.com (S. Korkut).

926-6690/$ – see front matter © 2009 Elsevier B.V. All rights reserved.oi:10.1016/j.indcrop.2009.10.010

f polyurethane provides a durability advantage.© 2009 Elsevier B.V. All rights reserved.

on a urethane–acrylate oligomer used to cover and protectwood flooring. The varnish was cured with ultraviolet radia-tion. The results showed that the varnish scratch resistanceincreased significantly after adding fine glass (Vargas and Wiebeck,2006).

It has been reported that among mould pressed and coated par-ticleboard (wersalite) and HPL (High Presssure Laminate) woodmaterials processed with polyurethane varnish and unprocessedMDF (Medium-density fiberboard) with laminated oriental beech,the greatest scratching strength was obtained with Werzalit(5.06 N), whereas the least strength was found for unpro-cessed MDF with polyurethane-varnished laminated orientalbeech (1.72 N). According to these results, Werzalit coated withpolyurethane varnish could be recommended for kitchen workta-bles in residences (Ors et al., 2002). The properties of wood, such asthe anatomical structure, density, specific gravity, surface rough-ness, extractive substances, and color, may affect varnishing results(Baykan et al., 2000). The greatest scratch resistance was obtained

for laminate parquet (5 N), followed by laminated parquet (2.3 N)and wood parquet (0.2 N). Döngel (2005) found that the effects ofwood species on the varnish scratch resistance were not significant,but the effects of varnish type were important. Akgün (2008) foundthat nanolacke UV varnish has better scratch resistance and surface

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20 H. Keskin et al. / Industrial Cro

ardness than conventional varnishes. The test results also showedhat the greatest scratch resistance was obtained with acrylic var-ish, whereas the least scratch resistance was found with cellulosicarnish. The type of wood does not affect scratch resistance, buthe type of covering material does (Özdemir, 2003). The greatestcratch resistance was obtained for particleboard coated with Con-inue Press Laminates (CPL), whereas boards coated with lacqueredaint had the least scratch resistance (Nemli, 2000).

Two-component waterborne polyurethane coatings haveecome increasingly popular over the last several years driveny market demands for higher performance, formaldehyde-free,hermosetting, water-based coatings. Water-dispersible polyiso-yanates have been specifically developed as crosslinkers for usen such coatings in conjunction with hydroxy-functional polyolsacrylics, polyester, or polyurethane dispersions) (Feng et al., 1999).elf-crosslinking acrylic emulsions exhibit increased resistancend offer improved coating quality; this range of acrylic emulsionsffers the coating producer the possibility to formulate coatingsor universal use at a moderate price. Blending this material witholyurethane dispersions improves toughness and scratch andbrasion resistance and broadens the overall application (Ginkel,001).

UV clearcoats have improved scratch resistance over two-omponent polyurethane or dual-cure systems, and coating scratchesistance has been extensively studied in the past few years.lthough many studies have correlated the physical charac-

eristics of the coatings such as viscoelastic properties withcratch resistance, scratch tests do not usually consider thenfluence of substrate or basecoat (Hara et al., 2000). Many dif-erent types of stains and clear coat finishes have been used tochieve depth and clarity, which the users of fine office furni-ure have grown to appreciate and expect. Technologies rangingrom precatalyzed lacquers to UV-curable coatings allow one tohoose the determined characteristics and green solutions for

project without sacrificing aesthetic quality. Physical prop-rty requirements include water and solvent resistance, scratchesistance, and pen imprint, among others (Smith and Kimball,008).

Most kitchen cabinets, some office furniture, and many inte-ior fittings are manufactured using melamine-coated surfaces orood-based panels (e.g., particleboard and MDF). For this rea-

on, properties such as abrasion and scratch resistance are verymportant for end-use applications. The success of the finishedroduct depends upon the decorative surfacing material’s prop-rties and production parameters (Nemli and Usta, 2004). Thebrasion and scratch resistance of laminated board that is coveredith melamine, in which fine aluminium oxide granules have been

dded, is increased (NEVAMAR, 1995).

The aim of this experimental study was to determine the scratch

esistance of cellulose, synthetic, polyurethane, waterborne, andcid-hardening varnishes, which are widely used on wood materi-ls.

able 1roperties of varnishes used in tests.

Type of varnish pH Density, g cm−3 Viscosity DINCup

Polyurethane (filling) 5.94 0.98 18Polyurethane (last) 4.01 0.99 18Synthetic – 0.94 18Waterborne (filling)a 9.30 1.015 18Waterborne (last)b 8.71 1.031 18Cellulosic (filling) 2.9 0.955 20Cellulosic (last) 3.4 0.99 20Acid-hardening (last) 8.0 0.99 18

a ASTM D 65.b ASTM D 45.

Products 31 (2010) 219–224

2. Materials and methods

2.1. Materials

2.1.1. Wood materialsOriental beech (Fagus orientalis Lipsky), Scotch pine (Pinus

sylvestris Lipsky), black walnut (Juglans nigra Lipsky), basswood(Tilla grandifolia Ehrh.), European oak (Quercus petreae Liebl.) andblack poplar (Populus nigra Lipsky) were selected as test materi-als because of their wide use in the wood products industry. Thewood samples were selected randomly from timber merchantsin Ankara, Turkey. Special emphasis was given to selection; onlyintact, straight, and knotless materials were selected.

2.1.2. VarnishesExperimental samples were varnished with cellulosic, synthetic,

polyurethane, waterborne, or acid-hardening varnishes accordingto the terms specified in ASTM D 3023 (1998). The varnishes wereobtained from firms in Ankara, Turkey. The amount of varnish usedwas calculated based on solid content and the manufacturer’s direc-tions. Some of the properties of the varnishes used in the tests aregiven in Table 1.

2.2. Methods

2.2.1. Test sample preparationThe wood samples, cut from sapwood, were conditioned at

20 ± 2 ◦C and 65 ± 5% relative humidity for 3 months until theirweights stabilized. Test samples (n = 900) of each wood species with12% average moisture and dimensions of 100 mm × 100 mm werecut according to the procedure described in TS 2470 (1976). Surfacesanding was perfromed with sand paper (silicon carbide, P180C-QB, waterproof, English Abrasives, Atlas Brand, England), and ASTMD 3023 (1998) standard procedures were applied for varnishing.According to this standard, the surfaces were sanded slightly toremove fiber swells, cleaned of dust, and varnished according tothe manufacturer’s definition.

The rough drafts for the preparation of test and control sampleswere cut from the sapwood parts of massif woods with dimensionsof 190 mm × 140 mm × 15 mm and then conditioned at a temper-ature of 20 ± 2 ◦C and 65 ± 3( relative humidity until they reacheda 12% humidity distribution based on ASTM D 358 (1983). Sampleswith dimensions of 100 mm × 100 mm × 10 mm were cut from thedrafts, and a 6.5-mm diameter hole was drilled in the middle forthe scratch resistance test (Fig. 1).

2.2.2. VarnishingTest samples were varnished according to ASTM D 3023 (1998).

The sample surfaces were sanded with abrasive paper to removefiber swellings and dust before varnishing. The producer’s direc-tions were considered for the solvent composition and hardenerratio. Three finishing layers were applied after the filling layer.Spray nozzle distance and pressure were adjusted according to the

/4 mm Amount used, g cm−2 Nozzle gap Air pressure

125 1.8 2125 1.8 2100 – –

67 1.3 167 1.3 1

125 1.8 3125 1.8 3100 1.8 3

H. Keskin et al. / Industrial Crops and Products 31 (2010) 219–224 221

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Table 2Dry-film thicknesses of varnish types (�m).

Wood materials Layer types Varnishes

Sn Pu Wb Ah C

Scotch pine1 L 93.2 94.1 93.2 93.8 92.62 L 115.1 115.5 102.3 127.9 106.93 L 125.7 125.5 105.7 132.4 112.2

Basswood1 L 93.4 94.3 94.1 94.2 89.92 L 113.9 114.9 101.4 127.2 103.53 L 123.9 123.4 103.3 131.4 111.5

Black walnut1 L 92.9 89.6 92.4 88.9 94.42 L 117.4 124.4 113.1 140.7 125.53 L 143.3 130.2 123.9 147.7 127.2

European oak1 L 94.6 89.8 91.5 94.4 90.82 L 119.2 111.6 112.1 121.7 120.13 L 136.5 128.1 124.7 143.4 126.8

Oriental beech1 L 93.6 93.1 96.1 94.8 94.42 L 116.2 124.7 114.9 138.8 124.53 L 135.9 131.5 125.9 146.5 127.2

Black poplar1 L 97.3 94.4 88.2 88.3 90.72 L 125.3 117.5 101.1 125.2 103.9

Fig. 1. The test sample (sizes given in mm).

roducer’s definition, and the nozzle was moved parallel to theample surface at a distance of 20 cm. Varnishes were applied at0 ± 2 ◦C and 65 ± 3% relative humidity.

.2.3. Determination of non-volatile matter contentNon-volatile matter content (NV) was determined according to

S 6035 EN ISO 3251 (2005), by the formula:

V = m2 − m0

m1 − m0× 100 (1)

here m0 is the empty cap weight (g), m1 represents the cap weightith test sample (g), and m2 is the cap weight with the remnant

g).The test samples were kept at 80–100 ◦C for 60 min according

o ASTM D 1005-95 (2001). The thickness of the varnish layers waseasured with a comparator that had a sensitivity of 5 �m.

.2.4. Determination of scratch resistancePatterns of scratch resistance were determined based on TS 4757

1986). The scratch tester created a scratch on the sample sur-ace that could be seen with the naked eye using a diamond bitradius, 0.090 ± 0.003 mm). The diamond bit was placed parallelo the horizontal plain using a spirit level, and the experimentalample was connected to a supporting disc with a pressure screwhat works at a speed of 5 ± 1 rotation/min. When the supportingandle with the diamond bit touched the sample, it was broughto a horizontal position, and the experiment started after makingdjustments with a sensitivity of ±0.01 N. The experiment startedith a 5-N applied force, and if no trace resulted on the sample

urface, the applied force was decreased in 0.5-N steps until a con-inuous scratch was formed. If a continuous scratch was formedith 5 N, then the force was decreased to 2 N by 0.5-N steps, toN by 0.25-N steps, and to 1 N by 0.1-N steps. The experimentas concluded when a dotted scratch was formed. After clean-

ng the sample surface with a soft cloth and alcohol, the surfaceas checked by eye under 100-lx lamps. The value of the contin-ous scratch mark before the appearance of dotted scratches wasccepted as the sample scratch resistance.

.2.5. Statistical analysesBy using six different types of wood materials, five varnish types,

nd three different layer thicknesses, and with 10 samples for each

ombination of parameters, a total of 900 (6 × 5 × 3 × 10) preparedamples were produced. A multiple analysis of variance (MANOVA)as used to determine the scratch resistance of the cellulosic, syn-

hetic, polyurethane, waterborne, and acid-hardening varnishes.hen the differences between groups were significant, Duncan’s

3 L 138.2 126.9 106.4 127.8 111.7

Sn, synthetic; Pu, polyurethane, Wb, waterborne; Ah: acid-hardening, C: cellulosic;1 L, one layer; 2 L, two layers; 3 L, three layers.

Multiple Range test was used to determine the differences betweenmeans at the level of ˛ = 0.05. Statistical values were calculated withSPSS 15.00 (SPSS Inc., Chicago, IL, USA).

3. Results and discussion

3.1. Dry-film thickness

The mean dry-film thickness values for each varnish type aregiven in Table 2.

Based on the varnish types, the highest dry-film thickness valuewas obtained for acid-hardening varnish, whereas cellulosic var-nish had the lowest dry-film thickness value.

3.2. Scratch resistance

The mean scratch resistance values according to wood species,varnish type, and layer thickness are shown in Table 3.

The greatest scratch resistance was obtained for black walnut(1.109 N), and the least scratch resistance was obtained for blackpoplar (0.493 N). The greatest scratch resistance according to var-nish type was obtained with synthetic varnish (0.974 N), whereascellulosic varnish had the least scratch resistance (0.355 N). Basedon layer thickness, the greatest scratch resistance was measuredwith three layers (0.961 N), whereas the least scratch resistancewas obtained with one layer (0.581 N).

The mean scratch resistance values based on the combinationof the wood material and varnish type are given in Table 4.

According to the combination of the wood species and varnishtype, the greatest scratch resistance was obtained for Europeanoak + synthetic, whereas basswood + cellulosic varnish had the leastscratch resistance.

The mean scratch resistance values according to the combina-tion of the wood material and layer thickness are shown in Table 5.

According to the combination of the wood material and layer

thickness, the greatest scratch resistance was obtained for Euro-pean oak + three layers, whereas the least scratch resistance wascalculated for black poplar + one layer.

The mean scratch resistance values according to the combina-tion of the varnish species and layer thickness are given in Table 6.

222 H. Keskin et al. / Industrial Crops and Products 31 (2010) 219–224

Table 3Average scratch resistance according to the species of woodmaterial, type of varnish, and layer thickness (N).

Types of material Scratch resistancea

Wood materialsb

Black walnut (Bw) 1.109 AEuropean oak (Eo) 1.039 BOriental beech (Ob) 0.8733 CBasswood (B) 0.5932 DScotch pine (Sp) 0.5051 EBlack poplar (Bp) 0.4927 E

Varnishesc

Synthetic (Sn) 0.9739 AWaterborne (Wb) 0.9336 BPolyurethane (Pu) 0.8640 CAcid-hardening (Ah) 0.7179 DCellulosic (C) 0.3549 E

Layer thicknessd

3 layers (3 L) 0.9603 A2 layers (2 L) 0.7656 B1 layer (1 L) 0.5807 C

Comparisons were made between each control and its test.a Homogeneity groups: the same letters (A, B, C, D and E)

in each column indicate that there is no statistical differencebetween the samples according to the Duncan’s multiply rangetest at P < 0.05.

b LSD0.5: 0.01755.c LSD0.5: 0.01602.d LSD0.5: 0.01241.

Table 4Average scratch resistance values according to the combination of wood materialspecies and varnish types (N).

Type ofprocess

Na Type ofprocess

Na Type ofprocess

Na

Eo + Sn 1.400 A Ob + Pu 0.9127 G Sp + Sn 0.5307 LMBw + Wb 1.347 B Ob + Ah 0.8027 H Sp + Wb 0.5127 MEo + Wb 1.297 C Sp + Pu 0.7633 HI Bp + Pu 0.4487 NBw + Pu 1.285 C B + Sn 0.7467 IJ Sp + Ah 0.4153 NOOb + Sn 1.230 D B + Wb 0.7447 IJ Bp + C 0.3853 OBw + Sn 1.223 D Bp + Sn 0.7127 J Ob + C 0.3780 OEo + Pu 1.133 E Bp + Wb 0.6573 K Sp + C 0.3037 PBw + Ah 1.126 E B + Pu 0.6420 K Eo + C 0.3013 PEo + Ah 1.066 F B + Ah 0.6380 K Bp + Ah 0.2593 QOb + Wb 1.043 F Bw + C 0.5667 L B + C 0.1947 R

a Different letters in the columns refer to significant differences among woodspecies at the 0.05 confidence level (LSD0.5 = 0.03925); rpm, revolutions per minute;Bw, black walnut; Eo, European oak; Ob, oriental beech; B, basswood; Bp, blackpoplar; Sp, Scotch pine; Ah, acid-hardening; Pu, polyurethane; Sn, synthetic; Wb,waterborne; C, cellulosic.

Table 5Average scratch resistance values according to the combination of wood materialand layer thickness (N).

Type of process Na Type of process Na

Eo + 3 L 1.2980 A Bp + 3 L 0.6960 GBw + 3 L 1.1180 A Ob + 1 L 0.6816 GBw + 2 L 1.0260 B Sp + 3 L 0.5800 HEo + 2 L 1.0080 C B + 2 L 0.5640 HOb + 3 L 0.9304 C Bp + 2 L 0.5096 IOb + 2 L 0.9124 D Sp + 1 L 0.4896 IBw + 1 L 0.8680 D Sp + 2 L 0.4458 JB + 3 L 0.7804 E B + 1 L 0.3476 KEo + 1 L 1.2980 F Bp + 1 L 0.2724 L

a Different letters in the columns refer to significant differences among woodtypes at the 0.05 confidence level (LSD0.5 = 0.0304), Bw, black walnut; Eo, Europeanoak; Ob, oriental beech; B, basswood; Bp, black poplar; Sp, Scotch pine; 1 L, onelayer; 2 L, two layers; 3 L, three layers.

Table 6Average scratch resistance values according to the combination of varnish type andlayer thickness (N).

Type ofprocess

Na Type ofprocess

Na Type ofprocess

Na

Wb + 3 L 1.222 A Sn + 1 L 0.9337 E Wb + 1 L 0.5167 IPu + 3 L 1.110 B Sn + 2 L 0.8897 F As + 1 L 0.4913 ISn + 3 L 1.098 B Pu + 2 L 0.8807 F C + 3 L 0.3850 JWb + 2 L 1.062 C As + 2 L 0.6757 G C + 1 L 0.3603 JAs + 3 L 0.9867 D Pu + 1 L 0.6013 H C + 2 L 0.3195 K

a Different letters in the columns refer to significant differences amongwood species at 0.05 confidence level (LSD0.5 = 0.0277), Ah, acid-hardening; Pu,polyurethane; Sn, synthetic; Wb, waterborne; C, cellulosic; 1 L, one layer; 2 L, twolayers; 3 L, three layers.

According to the combination of the varnish type and layerthickness, the greatest scratch resistance was obtained for water-borne + three layers, whereas cellulosic + two layers had the leastscratch resistance.

The results of the MANOVA for wood species, varnish types, andlayer thickness are shown in Table 7.

The difference between the groups regarding the effect of vari-ance sources on scratch resistance was significant (˛ = 0.05). Thepost hoc test results are given in Table 8.

The greatest scratch resistance was obtained for Europeanoak + polyurethane + three layers, whereas the poorest scratchresistance was measured for basswood + waterborne + one layer(Fig. 2).

4. Discussion

According to wood species, the greatest scratch resistance wasobtained for black walnut (1.109 N), whereas black poplar had theleast scratch resistance (0.493 N). In terms of their scratch resis-tance, black walnut had the highest resistance, followed in orderby European oak, oriental beech, basswood, Scotch pine, and blackpoplar. The porosity of the black walnut wood may be the reasonfor this greater resistance. It has been reported that the porosityaffects the internal binding force among varnish molecules (cohe-sion) (Christiansen, 1990; Kaygın and Akgün, 2008).

According to varnish type, the greatest scratch resistance wasobtained for synthetic varnish (0.974 N), whereas the least scratchresistance was measured for cellulosic varnish (0.355 N). Syntheticvarnish was followed, in order, by waterborne, polyurethane, acid-hardening, and cellulosic varnishes. A high scratch resistance may

result from the technical specifications of synthetic varnish.

For the combination of the wood species and varnish types,the greatest scratch resistance was obtained for Europeanoak + synthetic (1.40 N), whereas basswood + cellulosic had theleast scratch resistance (0.195 N). The most important factors

Table 7Results of the multiple analysis of variance.

Source Freedom Sum ofsquare

Means ofsquare

F-value P < 0.05 sig.

Factor A 5 56.516 11.303 1915.2047 0.0000Factor B 4 43.385 11.346 1922.4812 0.0000A × B 20 15.286 0.764 129.5029 0.0000Factor C 2 21.627 10.813 1832.2156 0.0000A × C 10 3.893 0.389 65.9567 0.0000B × C 8 11.668 1.458 247.1249 0.0000A × B × C 40 15.469 0.387 65.5262 0.0000Error 810 4.780 0.006

Total 899 174.624

Factor A = wood materials (Scotch pine, oriental beech, European oak, black poplar,basswood, black walnut); Factor B = varnish type (acid-hardening, polyurethane,synthetic, waterborne, cellulosic); Factor C = layer thicknesses (1 L, one layer; 2 L,two layers; 3 L, three layers).

H. Keskin et al. / Industrial Crops and Products 31 (2010) 219–224 223

Table 8Results of the Duncan test.

Type of process Na Type of process Na Type of process Na

Eo + Pu + 3 L 1.700 A Ob + Pu + 1 L 0.908 JKL Ob + Ah + 1 L 0.468 STUEo + Wb + 3 L 1.700 A B + Sn + 3 L 0.900 JKL Bw + C + 3 L 0.460 STUVBw + Pu + 3 L 1.650 AB Bw + Sn + 2 L 0.900 JKL Sp + Wb + 1 L 0.460 STUVBw + Wb + 2 L 1.600 B Bp + Sn + 2 L 0.890 KL Sp + C + 1 L 0.454 TUVEo + Sn + 1 L 1.600 B Ob + Pu + 2 L 0.880 KL B + Ah + 2 L 0.452 TUVEo + Ah + 3 L 1.500 B Bp + Sn + 3 L 0.870 LM Bw + C + 2 L 0.440 TUVOb + Sn + 3 L 1.480 C Sp + Pu + 3 L 0.860 LM Bp + Ah + 3 L 0.440 TUVBw + Wb + 3 L 1.480 C Bw + Wb + 1 L 0.840 LM Sp + Wb + 2 L 0.438 TUVBw + Ah + 3 L 1.480 C Bw + C + 1 L 0.800 MN Bp + Pu + 2 L 0.420 TUVWBw + Sn + 1 L 1.470 CD Bw + Pu + 1 L 0.754 NO Ob + C + 2 L 0.412 UVWEo + Wb + 2 L 1.450 CD Sp + Pu + 2 L 0.750 NO Bp + Pu + 1 L 0.386 VWXBw + Pu + 2 L 1.450 CD Eo + Wb + 1 L 0.740 NO Sp + Ah + 1 L 0.384 VWXEo + Sn + 3 L 1.400 D Eo + Ah + 1 L 0.738 NO B + Pu + 1 L 0.382 VWXBw + Sn + 3 L 1.300 E Ob + Wb + 1 L 0.730 NO Bp + Sn + 1 L 0.378 VWXOb + Wb + 2 L 1.250 EF Bp + Wb + 2 L 0.720 O Bp + C + 2 L 0.358 WXYBw + Ah + 2 L 1.200 FG B + Sn + 2 L 0.716 O Eo + C + 1 L 0.326 XYZEo + Sn + 2 L 1.200 FG Bw + Ah + 1 L 0.698 OP Sp + Ah + 2 L 0.322 XYZEo + Pu + 2 L 1.200 FG Sp + Pu + 1 L 0.680 OP Eo + C + 2 L 0.318 XYZB + Wb + 3 L 1.200 FG Sp + Sn + 3 L 0.640 PQ B + C + 3 L 0.300 YZcOb + Sn + 2 L 1.150 G Sp + Wb + 3 L 0.640 PQ Eo + C + 3 L 0.260 csOb + Wb + 3 L 1.150 G B + Sn + 1 L 0.624 PQ Ob + C + 1 L 0.242 csgOb + Sn + 1 L 1.060 H Bp + C + 3 L 0.590 QR Sp + C + 2 L 0.237 csgiBp + Wb + 3 L 1.040 HI B + Pu + 2 L 0.584 QR Sp + C + 3 L 0.220 sgiöOb + Ah + 3 L 0.980 IJ Bp + Pu + 3 L 0.540 RS Bp + Wb + 1 L 0.212 sgiöB + Ah + 3 L 0.980 IJ Sp + Ah + 3 L 0.540 RS Bp + C + 1 L 0.208 sgiöB + Pu + 3 L 0.960 JK Eo + Pu + 1 L 0.498 ST Bp + Ah + 1 L 0.178 giöüOb + Ah + 2 L 0.960 JK B + Ah + 1 L 0.482 STU Bp + Ah + 2 L 0.160 iöüEo + Ah + 2 L 0.960 JK Sp + Sn + 2 L 0.482 STU B + C + 2 L 0.152 öOb + Pu + 3 L 0.950 JK Ob + C + 3 L 0.480 STU B + C + 1 L 0.132 ü

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B + Wb + 2 L 0.910 JKL Sp + Sn + 1 L

a Different letters in the columns refer to significant differences among wood tyriental beech; B, basswood; Bp, black poplar; Sp, Scotch pine; Ah, acid-hardeningayers; 3 L, three layers.

ffecting this result are the binding force between the varnish layernd the wood surface (adhesion) and the internal binding forcemong the varnish molecules (cohesion) (Hammond et al., 1969).

For the combination of the wood species and layer thickness, thereatest scratch resistance was calculated for European oak + threeayers (1.312 N), whereas the least scratch resistance was obtainedor black poplar + one layer (0.273 N). Increased layer thicknesss efficient for scratch resistance, but this efficiency can change

ith varnish type. For the combination of varnish type and layerhickness, the greatest scratch resistance was obtained for water-orne + three layers (1.222 N), whereas the least scratch resistanceas calculated for cellulosic + two layers (0.319 N). The cohesion

ffect of oils, which are used in the production of acid-hardeningarnishes, may have resulted in the greatest scratch resistancemong all sample groups (Sönmez and Budakcı, 2004). When allf the tested factors were considered, the greatest scratch resis-ance was obtained for European oak + polyurethane + three layers

ig. 2. Scratch resistance according to wood species, varnish type, and layer thick-ess.

0.470 STU B + Wb + 1 L 0.118 ü

the 0.05 confidence level (LSD0.5 = 0.068), Bw, black walnut; E, European oak; Ob,olyurethane; Sn, synthetic; Wb, waterborne; C, cellulosic; 1 L, one layer; 2 L, two

(1.70 N), whereas basswood + waterborne + one layer (0.118 N) hadthe poorest scratch resistance. The effects of European oak densityand hardness on the scratch resistance of the varnish layer weresignificant. Furthermore, the binding force between the varnishlayer and the black walnut surface (adhesion) was an additionalfactor in this result. Applying polyurethane varnish in three layersincreased the internal binding force among the varnish molecules(cohesion), so the cohesive force affected the varnish scratch resis-tance. Because of its low density, basswood had the least scratchresistance compared with other samples on which the same var-nishes and layer thicknesses were used.

An increase in layer thickness does not always lead to improvedscratch resistance; the result is dependent on the type of var-nishing material. Thus, three layers of polyurethane varnish hadthe least scratch resistance for European oak. In contrast, twolayers of polyurethane varnish had the greatest scratch resis-tance for the same wood. This result was probably due to theeffects of low internal binding force and low adhesion among thepolyurethane varnish molecules (cohesion). Consequently, it can bestated for wooden parquets that scratch resistance against mechan-ical effects, such as friction, scratching, and impact is significant,especially in tight places such as an office, classroom, or corri-dor. Varnishing with three layers of polyurethane or waterborneon European oak can provide an advantage in this respect. Forwooden parquets in which the scratch resistance is not so impor-tant, acid-hardening varnish can be applied. Three layers of varnishare preferred in these applications, but to prevent economic losses,two layers of synthetic varnish on oriental beech or European oakis also an option.

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