Eur. J. Wood Prod. (2012) 70:37-43 DOl 1O.1007/s00107 -0 10-0494-y

OSB as substrate for engineered wood flooring

Costel Barbuta . Pierre Blanchet· Alain Cloutier· Vikram Yadama . Eini Lowell

Received: 26 August 2009 / Published online: 13 November 2010 © Springer-Verlag 2010

Abstract Oriented strand board (OSB) is a commodity sheathing, OSB web stock and ponderosa pine OSB sub­ product subject to market fluctuation.Development of a spe­ strates showed higher distortion. The PYA type I adhesive cialty OSB could lead to a better, and more stable, market led to weak bonding with high-density OSB surface.The re­ segment for OSB. It was demonstrated in a previous study sults of this study demonstrate the potential of OSB panels (Barbuta et al. in Eur. 1. Wood Prod. 2010), that OSB may to be used as substrate for EWF. be designed to obtain a high bending modulus of elasticity in the parallel direction, close to Baltic Birch Plywood (BBP) OSB als Tragerplatte ffir Doppelboden in its strongest direction. This study focused on the use of such specialty OSB in the manufacturing of engineered Zusammenfassung OSB ist ein Massenprodukt, das wood flooring (EWF) prototypes,a product that widely uses Marktschwankungen unterliegt. Die Entwicklung spezieller BBP as substrate in Canada. The performance of these two OSB-Platten konnte zu besseren und stabileren Absatzmog­ prototypes (aspen/birch and ponderosa pine) was studied. lichkeiten flir OSB flihren. In einer frliherenStudie (Barbuta Five types of substrates: BBP, sheathing OSB, web stock et al. Eur. J. Wood Prod. 20 I 0) wurde die Moglichkeit auf­ OSB and the two specialty OSB prototypes were used to gezeigt, OSB herzustellen, dessen Biege-Elastizitatsmodul manufacture EWF. A 3-mm thick sugar maple plank was se­ in Faserrichtung nahezu gleich dem von Birkensperrholz lected as the surface layer for all constructions. A polyvinyl (BBP) in seiner sUirksten Richtung ist. acetate (PVA) type I adhesive was used to bond the com­ In der vorliegenden Studie wird die Verwendung von spe­ ponents. The tests in conditioning rooms showed that BBP ziellen OSB zur Herstellung von Doppelboden (EWF) un­ substrate constructions present the lowest distortion between tersucht, flir die in Kanada liberwiegend BBP als Trager­ humid and dry conditions as well as aspen/birch specialty platte verwendet wird. Die Eigenschaften von zwei Prototy­ OSB, according to ANOVA. The construction with OSB pen (EspelBirke und Ponderosa Kiefer) wurden untersucht. Zur Herstellung der Doppelboden wurden flinf verschiede­ ne Tragerplattentypen verwendet, namlich BBP, OSB flir C. Barbuta . P. Blanchet (181) . A. Cloutier Wand- und Deckenelemente, OSB flir Stege von I -Tragem Sciences du bois et de la foret, Universite Laval, Quebec, QC, und die zwei speziellen OSB-Prototypen. FUr aIle Konstruk­ Canada mm e-mail: [email protected] tionstypen wurde eine 3 dicke Deckschicht aus Zucker­ ahom ausgewahlt. Zur Verklebung der Komponenten wur­ P. Blanchet de Polyvinylacetat (PVA) vom Typ I verwendet. Klima­ Value-added wood products, FPlnnovations, Quebec, QC, Canada tisierungsversuche zeigten gemaB ANOVA, dass sich bei

V. Yadama Prtifkorpem mit BBP als Tdigerplatte sowie bei speziellen Wood Material and Engineering Laboratory, Washington State OSB aus EspelBirken-Mischung die geringsten Formande­ University, Pullman, WA, USA rungen zwischen feuchten und trockenen Bedingungen er­ gaben. Bei den anderen Prlifkorpem ergaben sich groBe­ E. Lowell USDA Forest Service, Pacific Northwest Research Station, re Formanderungen. Der PVA-Klebstoff vom Typ I fUhrte Portland, OR, USA zu einer schlechten Verklebung bei OSB-Oberflachen hoher

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Dichte. Die Ergebnisse dieser Studie belegen das Potential these adhesives are commonly used in the construction of von OSB-Platten fUr Tragerplatten von Doppelboden. EWF today. He found that epoxy was weaker than the other adhesives. The adhesives PVA type II, polyurethane hot melt and EPI showed the best behaviours in terms of aging per­ 1 Introduction formance and they were not significantly different. Engineered wood flooring strips are unbalanced compos­ Since the introduction of engineered wood flooring (EWF) ite constructions. Their deformation is caused by the specific to the market in the 1970s, the popularity of these products reaction of each layer to changes in moisture content (MC) has grown steadily. According to the Floor Covering Weekly and temperature near the top surface. Blanchet et al. (2006) (2008), in 2007, 37.5% of the wood flooring installed in the used a finite-elementanalysis to study the hygromechanical United States was EWF. In this period, the North Ameri­ behaviour of EWF. The analysis showed that the mechanical can EWF market has been negatively influenced by the eco­ properties of the substrate and its thickness have a signif­ nomic decline. The average square foot price of EWF has icant impact on EWF deformation. Furthermore, they con­ jumped by 6% from 2006 to 2007. The development of low cluded that enhancing the mechanical properties of the core cost components would be of interest to EWF manufactur­ layer does reduce EWF deformation. Blanchet et al. (2006) ers. indicate that the bending modulus of elasticity (MOE) of Generally, EWF has 3 components: a surface layer, the the substrate affects the cupping deformation. The mini­ substrateand a backing layer. The surface layer is manufac­ mum bending MOE in parallel direction, required by the tured from high-quality hardwood. Its thickness determines CSA 0437.0 (CSA 1993) standard for OSB class 0-2 is the number of sandings (i.e., refinishings) it can tolerate. In 5500 MPa. Blanchet (2008) suggests the necessity to in­ EWF, a surface layer thickness higher than 3 mm is con­ crease OSB bending MOE in one direction to reach a per­ sidered to be a high-quality product. The substrate is the formance level comparable to Baltic Birch (Betula pendula) core layer. Its main function is mechanical since it restrains plywood (BBP) currently used for EWF manufacturing in surface layer deformation. This layer makes it possible to Canada. According to the Handbook of Finnish Plywood achieve the desired flooring strip thickness. Generally, the (Anonymous 2002), the BBP bending MOE in parallel di­ substrateis made of wood composite materials, such as high rection should be 11400 MPa. density fiberboard(HDF), plywood or wood sticks. The bot­ The objective of this study was to evaluate the behaviour of EWF made with two specialty OSB panels (100% pon­ tom layer enhances the appearance of EWF backing, but it derosa pine (Pinus ponderosa) and 90%/10% aspen/birch also reduces cupping (Blanchet et al. 2(06). Generally, the (Populus tremuloideslBetula papyrijera) strands) as sub­ use of a backing layer is linked to the use of a HDF or a strate and benchmark them with three other construction laminated solid wood strip as substrate. materials used as substrate in EWF (Sheathing OSB, Web Using the French standard NF B54-011 (AFNOR 1980), stock OSB and BBP). Blanchet et al. (2003b) developed a method for testing en­ gineered flooring strips adapted to North American climate conditions. Flooring strip assemblies were subjected to al­ 2 Material and methods ternatively dry and wet cycles. It was assumed that, in North America, a dry environment of 20DC and 20% RH corre­ 2.1 EWF prototypes manufacturing sponds to winter conditions and a humid environment of

20DC and 80% RH corresponds to summer conditions. The constructions used in this study are presented in Fig. 1. Blanchet et al. (2003a) present a comparative study on the The geometry of the EWF strip considered was 85 mm wide, use of four types of adhesives in EWF manufacturing: urea 12 mm thick and 610 mm long. The EWF prototypes were formaldehyde (UP), melamine-urea formaldehyde (MUF), produced using five different materials as substrate: Baltic type III polyvinyl acetate (PVA) and polyurethane (PUR). plywood, sheathing grade OSB, web stock OSB, specialty These adhesives were used to bond a 4 mm thick, 65 mm aspen/birch OSB and specialty ponderosa pine OSB. The wide and 600 mm long sugar maple wear layer over a set physical and mechanical properties of these substrates are of cross-grain 8 mm thick, 22 mm width and 65 mm long presented in Table 1. These properties were determined ac­ sticks. The PUR adhesive gave the best results, followed cording to ASTM standard D 1037-06a (ASTM 2006). by UP, MUF and PVA. The authors explained these results A combination of three optimum parameters was selected by the molecular reaction between the isocyanate groups in for the manufacturing of the two types of specialty OSB the PUR adhesive and the moisture in the wood. Blanchet panels (aspen/birch and ponderosa pine) as determined by CW08) compared four other cold-set adhesives: polyvinyl Barbuta et al. (2010): 6.5% phenol-fOIroaldehyde resin con­ acetate (PVA) (type I), epoxy, polyurethane hot melt, and tent, steep density profileand a percent weight-base between emulsion polymer isocyanate (EPI). Except for epoxy, all of the layers of 0.45/0.1010.45.

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Surfacelayer mended for the installation of EWE The edges of the

Adhesive 610 mm x 1220 mm (2' x 4') assemblies were sealed with a bead of silicone in order to limit edge effects. In order Composite substrate to determine the MC of the surface layer and the substrate, 3 supplementary EWF strips for each type of substrate were prepared by sealing the edges and backs of the strips with aluminum foil to reproduce non-homogeneous water vapour transfer. The flooring strips were subjected to a three-week cycle of alternating dry (20°C and 20% RH) and wet con­

Fig. 1 Cross-section diagram of an engineered wood flooring strip ditions (20°C and 80% RH). The cupping distortions of the Abb. 1 Querschnitt eines Doppelbodenelements EWF were measured over the width of the strip with a dial gauge as described by Blanchet et al. (2003b). EWF dis­ Table 1 Physical and mechanical properties of the substrates used in tortion measurements were made during each cycle at the the construction of the EWE MOE/I: bending modulus of elasticity de­ following intervals: 0, 1,2,3,5, 7,14 and 21 day(s). In ad­ termined parallel to grain of surface layer; MORlI: modulus of rupture dition, the MC of both the surface and the substrate layers determined parallel to grain of smface layer; IB: internal bond was monitored. At each interval, 4 samples of 12.5 mm by Tab. 1 Physikalische und mechanische Eigenschaften der fur die Her­ steHung der DoppelbOden verwendeten Tdigerplatten. MOEl/: Biege­ 65 mm for each type of substrate were cut from the sup­ Elastizitatsmodul in Faserrichtung der Deckschicht. MORlI: Biegefes­ plementary strips. The surface layer was separated from the tigkeit in Faserrichtung der Deckschicht, IB: Querzugfestigkeit substrate by cutting between the two layers with a band saw. The MC was determined according to ASTM standard Type of substrate Density MOElI MORII IB 3 kglm MPa MPa MPa D4442-07 Method A (2007). Because the specialty OSB panels were manufactured at Baltic plywood 640 9080 75 1.965 an interval of four months, this test was divided into two Sheathing grade OSB 645 4850 28 0.305 parts. First,the aspen/birch prototypes were tested and then

Web stock OSB 665 4500 29 0.345 the ponderosa pine prototypes. Considering the fact that

Aspen/birchOSB 670 8135 69 0.495 temperature and relative humidity in the conditioning room

Ponderosa pine OSB 675 9050 72 0.950 are not perfectly stable,each type of specialty OSB substrate was compared separately with the other substrates. The vari­ ations of the conditions in the conditioning room arethe re­ A 3 mm-thick sugar maple plank was selected as the sur- sult of the opening of the chamber door for each measure­ . face layer for the production of EWE Prior to gluing, all ment (Blanchet et al. 2005). the panels and all the maple planks were stored in a con­ In order to assess long-term delamination of the sub­ ditioning chamber at 20°C and 50% RH, until a constant strate,10 samples (50 mm wide x 83 mm long) of each type mass was obtained. At the end of the conditioning period, of substrate were subjected to an oven delamination test. The the substrates were sanded to ensure a uniform thickness samples were subjected to four successive 8-hour cycles in and an appropriate gluing surface. Sanding was performed a moist environment (20°C and 80% RH), followed by 16 in a three-belt sander with 100,120 and 150 grit aluminium hours in an oven at 70°C. Glueline and substrate delami­ oxide paper. The production of EWF strips involved cold­ nations were quantified by a linear measurement of the de­ press gluing of the surface layer and substrates with a type I lamination plane with a verniercalliper. The delaminations PYA (polyvinyl acetate) adhesive provided by Hexion Spe­ length for each sample were added and recorded at the end cialty Chemicals (XB-90K5-LF). Press time was 30 minutes of each cycle. at 1.72 MPa (250 psi). Gluing was achieved in such a way 2.3 Data analysis as to ensure that the substrate panel surface layer orientation was perpendicular to the grain of the sugar maple surface Analysis of variance (ANOVA) using Statistical Analysis layer. Because the PYA adhesive is a water-based product, System (SAS) software 9.1 was conducted to determine the another conditioning period at 20°C and 50% RH was re­ performance of EWF strips,focusing on the maximum de­ quired to ensure a uniform MC across the product. Follow­ formation amplitude between the two environmental cycles. ing the machining of tongues and grooves, the surface layer This amplitude was determined by calculating the difference was sanded to a final EWF strip thickness of 12 mm. between the highest summer cupping value and the lowest winter cupping value. Long term delamination of the sub­ 2.2 Testing strate was evaluated using an ANOVA on the total values of delamination after four cycles. Comparisons were per­ The flooring strips were glued onto 12.5 mm-thick Duroc formed to detect differencesbetween the specialty OSB pan­ cement panels with Bostik Best urethane adhesive recom- els and the other substrates.

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0.2 ...... 0.2 ...... +------r----.--._--.------,------i20°C,20%RH 20°C,20%RH

E 0.0 E 0.0 +-----..-----,---tE'----,------r----i E 10 30 5 30 40 -;; -0.1 -.------+------1 g> -0.1 -M------+------l c 'i5.. '§: -0.2 -I\-��:::::::::;;;;;�;:::_��------� 0- :::l <3 -0.2 U -0.3 +-�"."..-==___=_-__jf------_! -0.3 +--�c::::::::::�b",_4------____l 20°C,80%HR -0.4 ..1...... •A ...... , 20°C, 80%RH -0.4 J.. .• ...... · . ...· ..· ...... ·• .. · ...... ••.. •...... ·.· ...... · ...... • .. · ...... ··f ...... 1 Conditioning time (days) Conditioning time (days) -+- Sheating grade aSB ---- Web stock aSB -Ir- Apen/birch aSB � BBP -+- Sheathing grade aSB ____Web stock aSB -Ir- Ponderosa pine aSB � BBP

Fig. 2 Average EWF distortion as a function of conditioning time (days) and substrate type including aspen/birch specialty OSB Fig. 3 Average EWF distortion as a function of conditioning time Abb. 2 Durchschnittliche Schiisselung des Doppelbodens in Abhtin­ (days) and substrate type including ponderosa pine specialty OSB gigkeit der Klimatisierungsdauer (Tage) und des Trtigerplattentyps ein­ Abb. 3 Durchschnittliche Schiisselung des Doppelbodens in Abhiin­ schlieBlich del' speziellen OSB aus Espe/Birke gigkeit der Klimatisierungsdauer (Tage) und des Tragerplattentyps ein­ schlieBlich del' speziellen OSB aus Ponderosa Kiefer

Table 2 Average cupping distortion values as a function of substrate type was noted (0.263 and 0.287 mm, respectively). These con­ Tab. 2 Durchschnittliche Schiisselung in Abhangigkeit del'jeweiligen stituted the best substrate group in terms of cupping. In the Tragerplatte second group, the sheathing grade OSB and web stock OSB Type of substrate Average (nun) Groupa exhibit average cupping values of 0.453 and 0.430 mm re­ spectively. Sheathing grade OSB 0.453 A Figure 3 presents the average cupping deformation as Web stock OSB 0.430 A a function of conditioning time for substrates made from Aspen/Birch OSB 0.287 B sheathing grade OSB, web stock OSB, ponderosa pine spe­ BBP 0.263 B cialty OSB and BBP. The ANOVA indicates that at least one type of substrate is significantlydifferent from the others. In aAccording to Waller-Duncan test the means with the same letter are order to classify flooringstrips in terms of substrate, a multi­ not significantly different at 5% probability level ple comparison test was carried out using the Waller-Duncan test (Table 3), which highlighted three different groups at 3 Results and discussions the 0.05 probability level. As in the preceding case, the BBP substrate exhibits the best average value for cupping (Fig. 3). 3.1 Engineered wood flooring distortion Although the average bending MOE value obtained for OSB produced with ponderosa pine strands was 9050 MPa, there Figure 2 presents the average EWF cupping deformation as are significant differences between the measured amplitude a function of conditioning time (days) for substrates made of cupping values for this type of substrate and the BPP sub­ from sheathing grade OSB, web stock OSB, aspen/birch strate. This may be due to the poor dimensional stability of OSB and BBP. The ANOVA results show that at least one panels made from ponderosa pine strands. This dimensional type of substrate exhibits properties that are differentin rela­ instability is tied to the use of small-diameter ponderosa pine tion to the others. The Waller-Duncan multiple comparison logs (100 mm to 200 mm) with a high proportion of juve­ test highlighted two different groups (Table 2) at the 0.05 nile wood. Fahey et al. (1986) demonstrated that ponderosa probability level. The best average cupping value was ob­ pine juvenile wood exhibits significant longitudinal shrink­ tained for BBP. This type of plywood is made of seven plies age when compared to mature wood. of birch. This slow-growth species produces wood of an ex­ The different reaction of each EWF layer to changes in cellent quality. The average parallel modulus of elasticity moisture content and the different Me in the surface layer for this type of plywood is 9080 MPa, whereas the average and the substrate (Fig. 4),generate tensile, compression and measured value for specialty OSB produced with a mixture shear stresses. When these stresses become too high, sub­ of aspen and birch strands is 8135 MPa (Table 1). Despite strate delamination can occur. The observation of ponderosa these values, no significantdifference between the measured pine OSB and aspen/birch OSB substrates in a climatic cupping values for the BBP substrate and those for the OSB chamber highlighted this type of delamination (Fig. 5). The substrate made from a mixture of aspen and birch strands number of delaminations and their depth negatively impact

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Table 3 Average cupping values as a function of substrate type 70 ------Tab. 3 DurchschnittIiche SchUsselung in Abhangigkeit der jeweiligen -+- AB aSB --II- PP aSB --6- wsaSB -)(-SG aSB ___BBP 60 Tragerplatte E S 50 +------=���------Type of substrate Average (mm) Groupll 40 +------���------=-=�------

Web stock OSB 0.369 A 30 Sheathing grade OSB 0.322 B 20 t--�----�======���=-�=--- Ponderosa pine OSB 0.321 B 10 +------=--=��------BBP 0.273 C O +---�--��--�--�--��--�--��--. 4 a According to Waller-Duncan test the means with the same letter are 2 3 not significantly different at 5% probability level Cycle

Fig. 6 Substrate delamination as a function of substrate and condi­ 14.00..------.------tioning cycles (AB OSB-aspenlbirchOSB, PP OSB-ponderosa pine OSB, WS OSB-web stock OSB, SG OSB-sheathing grade OSB and BBP-Baltic birch plywood) Abb. 6 Delaminierung der jeweiligen Tragerplatten in Abhangigkeit der KIimatisierungszyklen (AB OSB - OSB aus EspeIBirke, PP OSB - OSB aus Ponderosa Kiefer, WS OSB - OSB fUr I-Stege, SG OSB­ OSB fUr Wand- und Deckenelemente, BBP Birkensperrholz)

3.2 Oven-generated delamination

Figure 6 presents the average length of substrate delamina­ tion as a function of substrate and conditioning cycles. The 50 analysis of variance showed that the effect of the substrate Conditioning time (days) on delamination was highly significant at 0.01 probability level. Waller-Duncan test results on the substrate delamina­ -+-SMS __AB aSB -.-PP aSB -*""WS aSB -*-SGaSB -BBP I I tion after four cycles highlighted three different groups at 0.05 probability level (Table 4). The BBP substrate is the Fig. 4 Average moisture content as a function of conditioning time (days) and layer type (SMS-sugar maple surface layer, AB most delamination-resistant one in an oven test. Only one OSB-aspen/birch OSB substrate, PP OSB-ponderosa pine OSB sample out of ten exhibited delaminations. In the second substrate, WS OSB-web stock OSB substrate, SG OSB-sheathing group, the ponderosa pine OSB substrate showed a com­ grade OSB substate and BBP-Baltic birch plywood substrate) parable performanceto aspenlbirch OSB. The delamination Abb. 4 Durchschnittliche Holzfeuchte in Abhangigkeit der Klimati­ sierungsdauer (Tage) und des Schichttyps (SMS - Deckschicht aus values for commercial OSB panels (third group) are nearly Zuckerahorn, AB OSB - OSB aus EspeIBirke, PP OSB - OSB aus twice as high as those of specialty OSB panels. Since the Ponderosa Kiefer, WS OSB - OSB fUr I-Stege, SG OSB - OSB fUr wood strand bonding in an OSB panel is achieved by ad­ Wand- und Deckenelemente, BBP Birkensperrholz) hesive droplets, delamination occurs more easily within an OSB panel substrate than in a BBP substrate where the plies are bonded with a continuous glueline. Surfacelayer Figure 7 presents the average value of the glueline de­ lamination as a function of substrate and conditioning cy­ Delamination cles. All the OSB substrates exhibited glueline delamina­ tions. BBP substrate behavedas expected with almost no de­ Substrate laminations. The presence of glueline delamination for OSB substrates suggests incompatibility between the PYA adhe­ sive and the surface layers of the panels or an inappropri­

Fig. 5 Ponderosa pine OSB substrate delamination ate surface preparation. This incompatibility may be due to Abb.5 Delaminierung der OSB-Tragerplatte aus Ponderosa Kiefer the low penetration of the adhesive in the high density panel surface layer. The analysis of variance indicates a highly sig­ nificanteffect of substrates on glueline delamination at 0.01 EWF cupping values. The presence and high number of de­ probability level. The Waller-Duncan test (Table 5) shows laminations in the OSB substrate made from ponderosa pine that the ponderosa pine OSB substrate exhibits the higher strands explain the non-significant difference between this average value for glueline delamination. This lower com­ type of substrate and the sheathing grade OSB substrate. patibility between the PYA adhesive type I and ponderosa

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Table4 Average substrate delamination as a function of substrate type Anderson (1951) found that the quantity of extractives in at the end of four cycles Tab. 4 Durchschnittliche Delaminierung der jeweiligen Tragerplatte the heartwood of ponderosa pine is between 12% and 15%. nach 4 Zyklen These extractives could negatively interact with the adhesive and affect bonding quality. Type of substrate Average (rnrn) Groupa

Sheathing grade OSB 58.90 A 4 Conclusion Web stock OSB 58.40 A Aspenlbirch OSB 27.41 B In this study, five EWF prototypes were manufactured and Ponderosa pine OSB 21.88 BC evaluated. The five types of substrates were Baltic Birch BBP 0.34 C Plywood,sheathing grade OSB, web stock OSB, specialty aspen/birch OSB and specialty ponderosa pine OSB. Re­ a According to Waller-Duncan test the means with the same letter are not significantly different at 5% probability level sults highlighted the influence of the substrate mechanical and physical properties on the performance of EWF strips. EWF made from Baltic Birch Plywood substrate presented 60 �------the lowest dimensional changes,and therefore the lower av­ --.-AB OSB __PP OSB ----.-WS OSB � SG OSB ___BBP E 50 +------erage cupping values (0.263 and 0.273 mm). However,non­ g significant differences between the Baltic Birch Plywood c 40 +------7L------­ o substrate and the aspen/birch OSB substrate (0.287 mm) � c 30 +------��------were noted. The results for the OSB substrate made from 'E C\'I small-diameter ponderosa pine logs were similar to those � 20+------��====���-=------for the sheathing grade OSB (0.321 and 0.322 mm),but dif­ � 10 +------��------­ c ferent from those of the Baltic Birch Plywood substrate. The � type I PYA adhesive led to weak bonding with high-density 2 3 4 OSB panel surface layers. Gluing practices should be revis­ Cycle ited accordingly. This work demonstrates the potential of OSB substrate Fig. 7 Glueline delamination as a function of substrate and condi­ tioning cycles (AB OSB-aspenlbirch OSB, PP OSB-ponderosa pine use in EWF constructions. Additional research on the char­ OSB, WS OSB-web stock OSB, SG OSB-sheathing grade OSB and acterization of EWF mechanical behavior is needed to deter­ BBP-Baltic birch plywood) mine the nature and distribution of the stresses that lead to Abb.7 Delaminierung der Klebfuge in Abhangigkeit der Tragerplatte delamination in the glueline. The delaminations observed in und der Klimatisierungszyklen (AB OSB - OSB aus Espe/Birke, PP OSB - OSB aus Ponderosa Kiefer, WS OSB - OSB fill' I-Stege, SG OSB panel prototypes are also present in Baltic Birch Ply­ OSB - OSB filr Wand- und Deckenelemente, BBP Birkensperrholz) wood substrates but at the lowest level. It should be possi­ ble to improve internal bond of these specialty OSB panels to prevent delaminations. An in-depth study of this type of Table5 Average glueline delamination as a function of substrate type at the end of four cycles fracture would help to define the relationship between this Tab.5 Durchschnittliche Delaminierung del' Klebfugen nach 4 Zyk­ type of fracture and the properties of EWF components. len in Abhangigkeit der jeweiligen Tdigerplatte

Type of substrate Average (rnrn) Group

Ponderosa pine OSB 47.7 A American Society for Testing and Materials (2006) Standard methods Aspen/birch OSB 27.5 B of evaluating the properties of wood-based fiberand particle panel Sheathing grade OSB 22.3 B materials. ASTM D 1037-06a. ASTM, Philadelphia, pp 120-149 American Society for Testing and Materials (2007) Standard test meth­ Web stock OSB 2.2 C ods for direct moisture content measurement of wood and wood BBP 0 C base materials. ASTM D 4442-07. ASTM, Philadelphia, pp 450- 455 a According to Waller-Duncan test the means with the same letter are Anderson AB (1951) Some practical applications of wood chemistry not significantly different at 5% probability level research. For Prod J 1(1):72-74 Anonymous (2002) Handbook of Finnish plywood. Finnish Plywood Forest Industries Federation, Lahti, pp 67 pine OSB substrate can be explained by the presence of ex­ Anonymous (2008) Statistical report '07. Floor Cov Wkly 57(29) tractivesin ponderosa pine. Extractives are soluble in neutral Association Fran�aise de Normalisation (AFNOR) (1980) NF B 54- 011 Norme fran�aise homologuee, Fabrication et classement des solvents, such as water,alcohol, ether and benzene. They are parquets contrecolles a parement en bois feuillus durs. Saint­ found in higher concentrations in the bark and heartwood. Denis La Prairie, France, pp 9 (in French)

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Barbuta C, Blanchet P, Cloutier A, Yadama C, Lowell E (2010) Blanchet P, Gendron G, Cloutier A, Beauregard R (2005) Numerical Tailor made OSB for special application. Eur J Wood Prod. prediction of engineered wood flooringdeformation. Wood Fiber doi: 10. J 007/s001 07-0 10-0477-z Sci 37(3):484-496 Blanchet P, Cloutier A, Gendron G, Beauregard R (2006) Engineered Blanchet P (2008) Contribution of engineered wood flooring compo­ wood flooring design using the finite element method. For Prod J nents to its hygromechanical behaviour. For Prod J 58(7/8): 19-23 56(5):59-65 Blanchet P, Beauregard R, Erb A, Lefebvre M (2003a) Comparative Canadian Standard AssoCiation (CSA) (1993) Test methods for OSB study of four adhesives used as binder in engineered wood parquet and waferboard CSA 0437 Series-93, pp 85 flooring. For Prod J 53(1):89-93 Fahey TD, Max TA, Ay er Sachet JK (1986) Factors affecting grade Blanchet P, Beauregard R, Cloutier A, Gendron G, Lefebvre M (2003b) change of Ponderosa pine lumber in the Desert Southwest. For Evaluation of various engineered wood flooring constructions. For Prod J 36(6):36-40 Prod J 53(5):30-37

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