impact of impregnation chemical on the bending strength of solid and laminated wood materials

Materials and Design 30 (2009) 796–803

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Materials and Design

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Technical Report

Impact of impregnation chemical on the bending strength of solidand laminated wood materials

Hakan Keskin *

Gazi University, Industrial Arts Education Faculty, Department of Industrial Technology Education, Division of Industrial Materials Technology Education,06830 Gölbasi, Ankara, Turkey

a r t i c l e i n f o

Article history:Received 29 August 2007Accepted 22 May 2008Available online 21 July 2008

0261-3069/$ - see front matter � 2008 Elsevier Ltd. Adoi:10.1016/j.matdes.2008.05.043

* Tel.: +90 3124851124x1088; fax: +90 312485312E-mail address: [email protected]

a b s t r a c t

The aim of this study was to investigate the effect of impregnation chemical on the bending strength ofthe solid and laminated wood materials. For this aim, Oriental beech, European oak, Scotch pine, Orientalspruce and Uludag fir woods impregnated with Imersol Aqua according to ASTM D 1413-99 and produc-ers’ definition. Laminated wood samples were produced from the impregnated wood materials accordingto TS EN 386 in the five ply form (4 mm each) from beech, oak, pine, fir and spruce wood by usingDesmodur-VTKA adhesive. The bending strength values were measured according to TS EN 408. Conse-quently, the bending strength of impregnated + laminated (I + LW) softwoods, pine, spruce and firincreased, respectively by 10.06%, 1.83% and 5.78% whereas the bending strength of impregnated + lam-inated hardwoods, beech and oak decreased, respectively by 4.78% and 9.15% with respect to laminatedcontrol samples (LW). Considering the interaction of wood type and process, the bending strength wasobtained from laminated Oriental beech, whereas the lowest was found for impregnated Uludag fir. Inconsequence, in the massive construction and furniture elements that the bending strength after theimpregnation and lamination (I + LW) is of great concern, beech and pine materials could berecommended.

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1. Introduction

Wood has good insulating properties against heat and sound. Itcan be worked easily and it is available in many texture, color,sizes, and shapes. Due to its properties, wood is being used for vari-ety of aims. In the forest products industry, raw materials shouldbe used economically and reasonably to improve the utilizationof timber. This is a vital issue for the future of the forest resources.

Long and curved forms may not be manufactured from massivewood due to production difficulties and economic reasons. Thelamination technique has been used to produce variety of shapes(curved, tapered and ribbed) of wood members to suit architec-tural and structural aims. Also, short wood pieces can be used forthis purpose and it is possible to eliminate strength reducing char-acteristics due to knots, shakes or drying, because the laminationneed not be thick when seasoned before manufacturing. The prop-erties can be improved by using dried and small thickness of woodwithout degrades. Lamination may be positioned due to strengthcriteria with respect to species, density, grades and defects. Lami-nated timber has less variability in strength and stiffness comparedto massive sawn timber [1].

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3.

LVL is more economic and aesthetic than solid woods. It can beused for production of furniture, cupboard, desk, chair, table, etc.building materials, column and beams [2].

Technological properties of the laminated cedar wood (Cedruslibani A. Rich), Scotch pine wood (Pinus sylvestris L.), beech wood(Fagus orientalis L.) and oak wood (Quercus petrea Liebl.) have moresuperior values, technological properties (6–9%) than the solidwoods, representing their kinds [3].

The bending strength of laminated beech and poplar combina-tion was found 98.66 N mm�2 [4]. It can be used for structuraland non-structural applications [5].

If the wood materials are used without processing by preserva-tives with regard to the area of usage, fungal stains, insect infesta-tion, humidity, fire, etc. damage the wood. As a result of thesedamages, wood require to be repaired, maintained or replaced be-fore its economic life ends [6].

It is reported that pressure treatment caused to a decrease of8–10% in the bending strength of different wood types [7]. It wasassessed that, salty impregnation materials increased the compres-sion strength by 4.6–9.6%, whereas decreased the bending strengthby 2.9–16% [8]. In another study, chromate copper arsenate (CCA)and arsenate copper arsenate (ACA) salts did not caused any signif-icant impact on modulus of elasticity in bending [9].

After the impregnation of pine wood samples by hot–cold opentank method with eleven preventives, no significant difference was

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observed in the bending strength except the decreasing effects ofFluotox containing acid florid [10].

It was assessed that, Boron compounds impregnation materialsincreased the modulus of elasticity in bending of LVL, prepared inthe form of five layers from impregnated beech wood veneers,bonded with phenol-formaldehyde, by 9–14% [11].

In this study, solid and laminated Oriental beech, European oak,Scotch pine, Oriental spruce and Uludag fir woods commonly beingused in furniture manufacturing and construction were examinedwith respect to the impacts of impregnation with Imersol Aquaon the bending strength.

2. Materials and methods

2.1. Wood materials

Oriental beech (F. orientalis Lipsky), European oak (Q. petrea Lie-bl.), Scotch pine (P. sylvestris Lipsky), Oriental spruce (Picea oriental-is Lipsky) and Uludag fir (Abies Bornmülleriana Mattf.) woods wereused as test materials. Specific pains were taken for the selection ofwood materials. Accordingly, non-deficient, proper, knotless, nor-mally grown (without zone line, without reaction wood and with-out decay, insect mushroom damages) wood materials wereselected.

2.2. Impregnation chemical

Imersol Aqua used as an impregnation material in this studywas supplied from Hemel–Hickson Timber Products Ltd., Istanbul.Imersol Aqua is non-flammable, odourless, fluent, water-based,complete soluble in water, no corrosive material with a pH valueof 7 and a density of 1.03 g cm�3. It is available as ready-madesolution. It contains 0.5% w/w tebuconazole, 0.5% w/w propiconaz-ole, 1% w/w 3-Iodo-2-propynl-butyl carbonate and 0.5% w/wcypermethrin. Before the application of Imersol Aqua on the woodmaterial, all kinds of drilling, cutting, turning and milling opera-tions should be completed and the relative humidity should bein equilibrium with the test environment. In the impregnationprocess, dipping duration was at least 6 min and the impregnationpool contained at least 15 l of impregnation material for 1 m3 ofwood. The impregnated wood was left for drying at least 24 h [12].

2.3. Adhesive

Desmodur-VTKA (Desmodur-Vinyl Trie Ketonol Acetate) adhe-sive usually has been found preferable for the assembly processin the woodworking industry. It is a one component (withoutany solvent), polyurethane based and moisture cured adhesive. Ithas a pH of about 7 and viscosity of 5500–7500 mPa s at25 ± 2 �C. Its density is 1.11 ± 0.02 g cm�3, the period of solidifica-tion at 20 ± 2 �C with 65 ± 5% relative humidity is 24 h. It is recom-mended that the adhesive should be applied one surfaceapproximately 190 g m�2. It is directly applied to one of the sur-faces and bonding process is conducted at 20 ± 2 �C and 65 ± 5%relative humidity conditions [13].

2.4. Determination of densities

The air-dry and oven-dry densities of the test samples weredetermined according to TS 2472 [14]. For determining the air-dry density, the test samples with a dimension of20 � 30 � 30 mm were kept under the conditions of 20 ± 2 �C and65 ± 5% relative humidity until they reached to a constant weight.The weights were measured with an analytic scale of ±0.01 g sen-sitivity. Afterwards, the dimensions were measured with a digital

compass of ±0.01 mm sensitivity. The air-dried densities (d12) ofthe samples were calculated by the following formula (1):

d12 ¼M12

V12g cm�3 ð1Þ

where, M12 is the air-dry weight, and V12 is the volume at air-dryconditions.

The samples were kept at a temperature of 103 ± 2 �C in thedrying oven until they reached to a stable weight for the assess-ment of oven-dry density. Afterwards, oven-dried samples werecooled in the desiccators containing calcium chloride. Then, theywere weighted on a scale of ±0.01 g sensitivity and their dimen-sions were measured with a compass. The volumes of the sampleswere determined by stereo metric method and the densities (do)were calculated by the following formula (2):

do ¼Mo

Vog cm�3 ð2Þ

where M0 is the oven-dry weight, and V0 is the oven-dry volume ofthe wood material.

2.5. Determination of moisture content

The moisture content of test samples before and after theimpregnation process was determined according to TS 2471 [15].Thus, the samples with a dimension of 20 � 20 � 20 mm wereweighed and then dried at 103 ± 2 �C in an oven till they reach toa constant weight. Then, the samples were cooled in desiccatorscontaining calcium chloride and weighed with an analytic scale.The moisture content of the samples (h) was calculated by the fol-lowing formula (3):

h ¼ Mr—Mo

Mo� 100 g g�1 ð3Þ

where Mr is weight of the samples and M0 is the oven-dry weightof the samples.

2.6. Preparation of test samples

The test lumbers, for the preparation laminated wood, with adimension of 50 � 70 � 820 mm were cut from the sapwood partsof solid woods and conditioned until they reached an equilibriumin moisture distribution.

The lumbers were impregnated according to ASTM D 1413-99[16], TS 344 [17] and TS 345 [18] with Imersol Aqua by dippingmethod. The lumbers were dipped in the impregnation poolimmersing 1 cm below the upper surface for 2 h for medium-termdipping. The specifications of the impregnation solution weredetermined before and after the process. Retention of impregna-tion material (R) was calculated by the following formula (4):

R ¼ G � CV

103 kg m�3 ðG ¼ T2 � T1Þ ð4Þ

where G is the amount of impregnation solution absorbed by thesample, T2 is the sample weight after the impregnation, T1 is thesample weight before the impregnation, C is the concentration(%) of the impregnation solution, and V is the volume of thesamples.

Laminated lumbers, with a dimension of 20 � 50 � 820 mmwere produced according to TS EN 386 [19]. For this purpose, ve-neers with 4 mm thickness, were cut from air-density lumberswith a dimension of 50 � 70 � 820 mm by using circular saw ma-chine. The glue was spread to one surface of veneer by using a roll.The spreading rate of glue was approximately 190 g m�2. Thespreading rate was calculated by weighting each veneer before

SW(Solid Wood)

LW(Laminated Wood)

I+LW(Impregnated +

Laminated Wood)

ISW(Impregnated Solid Wood)

Fmax Fmax FmaxFmax

Fig. 1. Cross-section of the bending strength test sample (layer thickness is 4 mm).

798 H. Keskin / Materials and Design 30 (2009) 796–803

and after gluing. The glue line pressure ranged between 0.7 and1.2 N mm�2 depending on the species of wood, and solidified inapproximately 30 min. Laminated lumbers were kept under a tem-perature of 20 ± 2 �C and 65 ± 5% relative humidity until reachingto a constant weight.

Bending strength of test samples, with a dimension of20 � 20 � 400 mm, perpendicular to the fiber and glue line werecut from the drafts having an average humidity of 12% accordingto TS EN 408 [20] as shown in Fig. 1.

A total of 20 treatment groups were obtained with five differentkinds of wood materials. Ten replications were made in each treat-ment group. Thus, a total of 200 samples (5 � 4 � 10) wereprepared.

2.7. Determination of bending strength

Perpendicular to the fiber and glue line (c) bending strengthtests was carried out with the Universal Testing Equipment shownin Fig. 2, according to TS EN 408.

The capacity of the Universal Testing Equipment was 400 N. Thespeed of the test machine was adjusted to 5 mm/min. for breakageto occur in 1–2 min. Bending strength was calculated with the fol-lowing equations:

rb ¼3Fmax � ðL� l1Þ

2bh2 ðN mm�2Þ ð5Þ

where Fmax is the breaking load on the scale (N), L is distance be-tween the lower tension rods (mm), l1 is distance between twoloads (mm), b is the cross-sectional width of test sample (mm), his the cross-sectional thickness of the test sample (mm).

Fig. 2. Test equipment for bending

2.8. Statistical analyses

The impacts of impregnated on the bending strength of lami-nated wood material were analysed by ANOVA (analysis of vari-ance). When the differences between groups were found to besignificant, Duncan test was used to determine the differences be-tween means at prescribed level of a = 0.05. Statistical values (AN-OVA, mean, deviation of standard, variance, minimum, maximumvalues) were calculated by the SPSS 13.00 for Windows computersoftware.

3. Result and discussion

3.1. Peculiarities of impregnation solutions

The pH value and density of Imersol Aqua, used for the impreg-nation process did not change either prior or after the impregna-tion. This may be due to the use of fresh solution in eachimpregnation process.

3.2. Retention quantities

Results of retention test were summarized by using descriptivestatistics such as the maximum, minimum, mean, standard devia-tion and variance. Descriptive statistical values of tested retentionamounts of test samples are presented in Table 1.

ANOVA of the impact of impregnation method on retention ofimpregnated and laminated wood materials is given in Table 2.

According to ANOVA, differences between groups were found tobe significant (F4;45 = 1213.932, P < 0.05). Duncan test was used todetermine the differences between means at prescribed level ofa = 0.05 and results of Duncan are displayed in Table 3.

According to Duncan test results, highest retention amount wasobtained in beech and the lowest was in oak wood samples. Thehighest retention amount obtained in beech could be attributableto the impact of permeability. The lowest retention amounts werefound in oak. This may be due to tyloses in oak.

3.3. Oven-dry density

Statistical values for the oven-dry density of test samplesimpregnated with Imersol Aqua by using medium-term dippingmethod and laminated with Desmodur-VTKA adhesive are givenin Table 4.

strength (dimensions in mm).

Table 1The quantities of retention of massive wood materials (km�3)

Impregnation method Statistical values Oriental beech European oak Scotch pine Oriental spruce Uludag fir

Medium-term dipping (SW) x 211.417 65.159 74.310 92.833 83.062Sd 7.940728 3.993300 5.654022 3.389350 3.428832v 70.06129 17.71827 35.51997 12.76411 13.06321Min 199.506 59.206 68.106 87.032 79.325Max 223.254 72.152 86.995 98.329 90.035

SW: solid wood, Min: minimum, Max: maximum, Sd: standard deviation, v: variance.

Table 2ANOVA indicating the impact of wood types and impregnation method on retention

Source SS DF MS F value SIG*

Between groups 144823.930 4 36205.982 1213.932 0.000Within groups 1342.142 45 29.825Total 146166.070 49

*P < 0.05. SS: sum of squares, DF: degrees of freedom, MS: mean square, SIG:significance.

Table 3Retention amounts as a result of Duncan test

Wood material (SW) Subset for a = 0.05

1 2 3 4 5

European oak 65.159Scotch pine 74.310Uludag fir 83.062Oriental spruce 92.833Oriental beech 211.417Signature 1.000 1.000 1.000 1.000 1.000

Means for groups in homogeneous subsets are displayed.Uses harmonic mean sample size: 10.

Table 5ANOVA indicating the impact of wood types and process on the oven-dry density





ANOVA of the impact of impregnation method on oven-dry den-sities of impregnated and laminated wood materials are presentedin Table 5.

According to ANOVA, differences between groups were found tobe significant (F19;180 = 342.676, P < 0.05). Duncan test was used to

Table 4Oven-dry densities of wood materials (g cm�3)

Process Statistical values Oriental beech European

SW x 0.650 0.639Sd 0.02165290 0.030417v 0.00052094 0.001028Min 0.616 0.576Max 0.675 0.668

ISW x 0.663 0.658Sd 0.0161443 0.017552v 0.0002896 0.000342Min 0.632 0.631Max 0.686 0.695

LW x 0.673 0.666Sd 0.0143391 0.021221v 0.0002284 0.000500Min 0.649 0.638Max 0.698 0.701

I + LW x 0.685 0.676Sd 0.0138711 0.014922v 0.0002137 0.000247Min 0.668 0.659Max 0.718 0.702

SW: solid wood, ISW: impregnated solid wood, LW: laminated wood, I + LW: impregnated

determine the differences between means at prescribed level ofa = 0.05 and results of Duncan test are displayed in Table 6.

As seen from the Table 6, Impregnated + laminated beech wood(BI + LW) samples have the highest oven-dry density. In contrast, firmassive wood (FSW) samples have the lowest oven-dry density inall groups.

3.4. Air-dry density

Statistical values for the air-dry density of test samples impreg-nated with Imersol Aqua by using medium-term dipping methodand laminated with Desmodur-VTKA adhesive are given in Table 7.

ANOVA of the impact of impregnation method on air-drydensities of impregnated and laminated wood materials is givenin Table 8.

According to ANOVA, differences between groups were found tobe significant (F19;180 = 436.908, P < 0.05). Duncan test was used todetermine the differences between means at prescribed level ofa = 0.05 and results of Duncan test are displayed in Table 9.

oak Scotch pine Oriental spruce Uludag fir

0.537 0.403 0.3852 0.0180177 0.01914288 0.017235130 0.0003607 0.00040716 0.00033005

0.506 0.382 0.3490.569 0.444 0.409

0.559 0.416 0.4024 0.0149415 0.01451206 0.022697133 0.0002480 0.00023401 0.00057240

0.536 0.398 0.3530.578 0.446 0.429

0.567 0.426 0.4016 0.0170906 0.01587324 0.027631324 0.0003245 0.00027995 0.00084832

0.544 0.401 0.3630.592 0.452 0.441

0.573 0.437 0.4188 0.0190157 0.01247437 0.019171854 0.0004017 0.00017290 0.00040842

0.548 0.424 0.3950.604 0.465 0.452

+ laminated wood, x: mean.

Table 7Air-dry densities of wood materials (g cm�3)

Process Statistical values Oriental beech European oak Scotch pine Oriental spruce Uludag fir

SW x 0.685 0.668 0.571 0.430 0.410Sd 0.01567163 0.01835320 0.01167946 0.021378494 0.009798469v 0.00027288 0.00037426 0.00015156 0.000507822 0.000106678Min 0.651 0.633 0.554 0.405 0.399Max 0.706 0.688 0.592 0.472 0.434

ISW x 0.693 0.684 0.593 0.444 0.420Sd 0.01570222 0.01604369 0.01863759 0.014229898 0.007194442v 0.00027395 0.00028602 0.00038595 0.000224988 0.000005756Min 0.672 0.654 0.562 0.422 0.405Max 0.724 0.709 0.621 0.472 0.432

LW x 0.699 0.688 0.609 0.452 0.432Sd 0.01564896 0.01879388 0.02050463 0.018338211 0.012983066v 0.00027210 0.00039245 0.00046715 0.000373656 0.000187289Min 0.672 0.651 0.572 0.425 0.408Max 0.721 0.712 0.634 0.482 0.458

I + LW x 0.713 0.694 0.620 0.462 0.441Sd 0.01335065 0.01700264 0.02691486 0.020098756 0.016890530v 0.00019804 0.00032121 0.00080495 0.000448844 0.000316989Min 0.692 0.668 0.583 0.433 0.419Max 0.733 0.715 0.665 0.492 0.476

Table 6Oven-dry densities as a result of Duncan test

Process 1 2 3 4 5 6 7 8 9 10

FSw 0.385FISw 0.402 0.402SSw 0.403 0.403FLw 0.401 0.401SISw 0.416 0.416FI + Lw 0.418 0.418SLw 0.426 0.426SI + Lw 0.437PSw 0.537PISw 0.559PLw 0.567PI + Lw 0.573OSw 0.638BSw 0.650 0.650OISw 0.658 0.658 0.658BISw 0.663 0.663OLw 0.666 0.666 0.666BLw 0.674 0.674OI + Lw 0.676 0.676BI + Lw 0.685Signature 0.057 0.113 0.106 0.199 1.000 0.156 0.054 0.111 0.070 0.059

Means for groups in homogeneous subsets are displayed. Uses harmonic mean sample size: 10, subset for a = 0.05, B: Beech, O: Oak, P: pine, S: spruce, F: fir, SW: solid wood,ISW: impregnated solid wood, LW: laminated wood, I + LW: impregnated + laminated wood.

Table 8ANOVA indicating the impact of wood types and process on the air-dry density

SOURCE SS DF MS F Value SIG*




As seen from the Table 9, Impregnated + laminated beech wood(BI + LW) samples have the highest air-dry density. In contrast, firwood (FSW) samples have the lowest air-dry density in all groups.

The air-dry and oven-dry densities of impregnated samples in-creased with respect to un-impregnated samples. As a matter offact, it was observed that, the retention amount was higher inlong-term dipping than short-term dipping. This may be due to

more penetration of impregnation solution into the wood withthe extension of time. In a similar research, it was reported thatin the impregnation of Scotch pine and beech the retention anddensities increased with the increase in impregnation period[21]. Besides, this might be because of the lamination process. In-deed, lamination processes’ increasing the bending strength inwood material is declared [3].

3.5. Bending strength

Results of bending strength test were summarized by usingdescriptive statistics such as the maximum, minimum, mean, stan-dard deviation and variance. Descriptive statistical values of testedbending strength of test samples are presented in Table 10.

As well as that, average values of the interaction between thewood material type and process and the results of ANOVA andDuncan test results regarding the impacts of wood type and pro-

Table 10Bending strength results of wood materials (N mm�2)

Process Statistical values Oriental beech European oak Scotch pine Oriental spruce Uludag fir

SW x 123.489 112.084 97.486 80.569 74.346Sd 2.15827016 1.86393400 1.47785834 1.481337517 1.881747807v 5.17570010 3.86027773 2.42673921 2.438178711 3.934416456Min 119.658 108.536 95.564 78.002 70.234Max 126.992 114.658 99.652 83.657 76.993

ISW x 119.412 98.918 102.739 83.198 76.275Sd 1.62192740 0.98888426 1.63011147 1.667830735 1.344919332v 2.92294276 1.08654676 2.95251490 3.090732622 2.009786678Min 116.215 97.345 99.567 80.652 73.662Max 122.204 100.635 105.561 85.951 78.635

LW x 126.529 116.295 98.259 84.661 78.601Sd 4.74805071 3.77803451 1.32047802 2.89790601 2.840879406v 25.0488728 15.8594942 1.93740245 9.33095711 8.967328667Min 120.235 110.332 95.602 80.802 75.371Max 132.466 124.029 99.723 89.402 85.471

I + LW x 120.319 105.641 108.155 86.212 81.033Sd 2.92511911 4.23885495 5.09445915 2.22513392 2.98869638v 9.50702426 19.9643237 28.8372378 5.50135662 9.92478450Min 115.602 100.601 101.007 83.918 76.209Max 125.673 112.527 120.228 90.617 85.127

SW: solid wood, IMW: impregnated solid wood, LW: laminated wood, I + LW: impregnated + laminated wood, x: mean.

Table 11ANOVA indicating the impact of wood types and process on the bending strength




Table 9Air-dry densities as a results of Duncan test

Process 1 2 3 4 5 6 7 8 9 10 11

FSw 0.411FISw 0.420 0.420SSw 0.430 0.430FLw 0.430 0.432FI + Lw 0.441 0.441SISw 0.444 0.444SLw 0.452 0.452SI + Lw 0.462PSw 0.572PISw 0.593PLw 0.609PI + Lw 0.620OSw 0.668OISw 0.684 0.684BSw 0.685 0.685OLw 0.689OI + Lw 0.693BISw 0.694BLw 0.699 0.699BI + Lw 0.712Signature 0.237 0.175 0.127 0.190 0.209 1.000 1.000 0.184 0.051 0.107 0.089

Means for groups in homogeneous subsets are displayed. Uses harmonic mean sample size = 10, subset for a: 0.05, B: beech, O: oak, P: pine, S: spruce, F: fir, SW: solid wood,ISW: impregnated solid wood, LW: laminated wood, I + LW: impregnated + laminated wood.


cess on the bending strength are displayed in Tables 11 and 12,respectively.

As seen from the Table 11, differences between groups werefound to be significant (F19;180 = 361.839, P < 0.05). Duncan testwas used to determine the differences between means at pre-

scribed level of a = 0.05 and results of Duncan test are given in Ta-ble 12.

According to Duncan test results, considering the interaction ofwood type and process, the highest bending strength was obtainedin laminated beech (BLW = 126.529 N mm�2) whereas the lowestwas in un-impregnated fir wood (FSW = 74.346 N mm�2).

This may be a result of lamination and impregnation process. Inliterature, it is stated that the lamination process was increased thebending strength [3]. In one another study, it was determined thatboron compounds was increased the bending strength and modu-lus of elasticity in bending values for some wood materials [11].

The bending strength determined with regard to the woodtypes and process is given in Fig. 3.

Among the impregnated + laminated wood (I + LW) materials,the highest bending strength value was obtained in beech (BI + LW)

50

60

70

80

90

100

110

120

130

Oriental beech European oak Scotch pine Oriental spruce Uludag fir

Process

Ben

ding

Str

engt

h (N

.mm

-2) Sw ISw Lw I+Lw

SW: Solid wood, ISW: Impregnated solid wood, LW: Laminated wood, I+LW: Impregnated + laminated wood

Fig. 3. Bending strength determined with regard to the wood materials and process.

Table 12Mean comparisons of the bending strength due to wood species and impregnation process

Process 1 2 3 4 5 6 7 8 9 10 11 12 13 14

FSw 74.34FISw 76.27 76.27FLw 78.60 78.60SSw 80.57 80.57FI + Lw 81.03 81.03SISw 83.19 83.19SLw 84.66 84.66SI + Lw 86.21PSw 97.48PLw 98.26OISw 98.92PISw 102.74OI + Lw 105.64PI + Lw 108.15OSw 112.08OLw 116.29BISw 119.41BI + Lw 120.32BSw 123.49BLw 126.53Signature 0.135 0.072 0.074 0.053 0.256 0.229 0.297 1.000 0.052 1.000 1.000 0.484 1.000 1.000

Means for groups in homogeneous subsets are displayed. Uses harmonic mean sample size = 10, subset for a = 0.05, B: beech, O: oak, P: pine, S: spruce, F: fir, MW: solid wood,IMW: impregnated solid wood, LW: laminated wood, I + LW: impregnated + laminated wood.


and the lowest value in fir (FI + LW). This may be a result of theimpregnation material, lamination process and densityeffectiveness.

For the combination of the impregnated solid wood (ISW) mate-rials, the highest bending strength value was obtained in beech(BISW) and the lowest value in fir (FISW). This may be due to thehigher density of beech than other tested wood materials.

In the laminated wood (LW) materials, the highest bendingstrength value was obtained in beech wood samples (BLW) andthe lowest value in fir (FLW). This may be a result of laminationprocess and density effectiveness.

Among the massive wood (SW) materials, the highest bendingstrength value was obtained in beech wood samples (BSW) andthe lowest value in fir (FSW). This may be due to the higher density,celluloses and hemicelluloses of Oriental beech wood than othertested wood materials. It was reported that the hardwoods havemore cellulose and hemicelluloses than softwoods [22].

4. Conclusion

It has been determined that the bending strength of impreg-nated + laminated (I + LW) softwoods; pine, spruce and fir in-

creased, respectively by 11.34%, 7.01% and 8.98% whereas thebending strength of impregnated + laminated hardwoods, beechand oak decreased, respectively by 2.63% and 6.09% with respectto solid wood control samples (SW), representing their kinds. Thissituation can be attributable to the higher resistance of softwoodsagainst the chemical substances. It was reported that the softwoodwoods, having less hemicelluloses are more resistant to chemicaleffects than hardwood woods [22].

Consequently, the bending strength of impregnated + laminated(I + LW) softwoods, pine, spruce and fir increased, respectively by10.06%, 1.83% and 5.78% whereas the bending strength of lami-nated + laminated hardwoods, beech and oak decreased, respec-tively by 4.78% and 9.15% with respect to laminated controlsamples (LW). These may be due to positive effects of Imersol Aquaon the structure of the softwood material.

Considering the interaction of wood type and process, the bend-ing strength was obtained from laminated Oriental beech, whereasthe lowest was found for impregnated Uludag fir.

In consequence, in the massive construction and furniture ele-ments that the bending strength after the impregnation and lami-nation (I + LW) is of great concern, Oriental beech and Scotch pinematerials could be recommended.


References

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impact of impregnation chemical on the bending strength of solid and laminated wood materials

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